280ZT Fuel/Wiring Issues?
10-01-2009, 10:41 AM
#1
NisTuner
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280ZT Fuel/Wiring Issues?
I made a post about this over on HybridZ, but I figure I'll ask you guys too. I can get my 280Z to run but I've been having issues. The fuel pump will prime with the key ON then about 20 seconds or less after it shuts off the pressure in the lines drops to about 0. I thought the Pressure Regulator was bad. I bought an adjustable fuel pressure regulator at Summit. No difference, same thing. So I removed the original 76' Fuel pump, modded the old fuel pump bracket and put my Walboro pump in.
So I have the feed from the tank into a Fram G3 Fuel Filter, then into my Pump, pump to steel line that runs to the engine bay, into my engine bay fuel filter to pallnet rail. Then from my pallnet rail to my Regulator, and then from the regulator return to the metal return line, finally back into the tank. I see no problem with this setup, but it's doing the same thing. If I clamp off or partially clamp off the return line it will help it start. Oh I also removed the factory fuel damper as it seemed to be doing nothing for me.
I'm beginning to think it's a wiring issue. A few things I've noticed:
Even though I can get the car to start, it doesn't always want to start.
When connected to my Nistune ECU via my laptop, upon turning the key to Start to try and crank it loses connection. This can be do to other issues, but I know the ECU is fine as I tested it on my Z31.
If the car doesn't start and I let the key off of Start back to ON the Fuel Pump will re-run it's 5-second prime. My Z31 doesn't seem to do this. I flicked the key to start and let off so it wouldn't start and I didn't hear the Fuel Pump re-run again. So I'm almost wondering if there's an issue with my wiring or the ignition barrel in switching. From ON to Start may not be continuously holding a constant power.
Finally the one other thing I noticed. When I was was watching the pressure gauge on my rail and had another person crank the car. I noticed that the fuel pressure wasn't immediately registering, like it was after a few cranks when all of a sudden the pressure shot up and the car started. Any input on this? Should my car be re-priming when going from Start back to ON? This doesn't sound right to me.
On a side note, the Walboro is ridiculously quiet compared to the factory 76' or even my factory ZXT pump.
So I have the feed from the tank into a Fram G3 Fuel Filter, then into my Pump, pump to steel line that runs to the engine bay, into my engine bay fuel filter to pallnet rail. Then from my pallnet rail to my Regulator, and then from the regulator return to the metal return line, finally back into the tank. I see no problem with this setup, but it's doing the same thing. If I clamp off or partially clamp off the return line it will help it start. Oh I also removed the factory fuel damper as it seemed to be doing nothing for me.
I'm beginning to think it's a wiring issue. A few things I've noticed:
Even though I can get the car to start, it doesn't always want to start.
When connected to my Nistune ECU via my laptop, upon turning the key to Start to try and crank it loses connection. This can be do to other issues, but I know the ECU is fine as I tested it on my Z31.
If the car doesn't start and I let the key off of Start back to ON the Fuel Pump will re-run it's 5-second prime. My Z31 doesn't seem to do this. I flicked the key to start and let off so it wouldn't start and I didn't hear the Fuel Pump re-run again. So I'm almost wondering if there's an issue with my wiring or the ignition barrel in switching. From ON to Start may not be continuously holding a constant power.
Finally the one other thing I noticed. When I was was watching the pressure gauge on my rail and had another person crank the car. I noticed that the fuel pressure wasn't immediately registering, like it was after a few cranks when all of a sudden the pressure shot up and the car started. Any input on this? Should my car be re-priming when going from Start back to ON? This doesn't sound right to me.
On a side note, the Walboro is ridiculously quiet compared to the factory 76' or even my factory ZXT pump.
10-01-2009, 10:48 AM
#2
#1: Why did you remove the fuel damper? It keeps the fuel from pulsing due to fuel pump surges, and it probably has a one way check valve to keep the fuel from rolling back when the pump is off.
#2: Have you removed the return line after the FPR to see if it leaks out fuel when the motor is off?
#2: Have you removed the return line after the FPR to see if it leaks out fuel when the motor is off?
10-01-2009, 10:55 AM
#3
NisTuner
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I removed the fuel damper mainly because of the way I had put the pump. I couldn't figure out a good place to put the damper. Also I didn't remove the damper until I had put in the Walboro, and with the Walboro pump in it's acting exactly the same way as when I had the damper and the factory pump. I have had fuel in the return line. I know when I was using the factory regulator I'd be able to clamp off that line and it seemed like it would hold the pressure. Primarily why I thought it was bad. People on HybridZ were saying they were using an Aeromotive FPR very similar to mine and saying they seem to have the same issue of it bleeding off very quickly. It seems like as long as the pump is running the regulator seems to do it's job. I was trying to find out if the old damper acted like a check valve, but I haven't heard an answer on that. I do know that the one we took out just blowing through it, you could blow both ways through it. So if it had a check valve, it's no longer good.
I saw through a search someone referring to it as a check valve/damper, but no responses. I'm not sure.
I saw through a search someone referring to it as a check valve/damper, but no responses. I'm not sure.
Last edited by duowing; 10-01-2009 at 11:03 AM.
10-01-2009, 12:36 PM
#6
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Just a note: the check valve and fuel damper are separate components. The check valve is on/in/part of the stock pump outlet, and the damper is the little canister-looking thing with a bolt head on one end, and line inlet and outlet, right near the stock pump. Pages 2 and 3 of the EFI bible have nice diagrams of them (free at xenons30.com, and elsewhere like Blue's tech tips I think, maybe geocities zGarage, etc.).
I know I need a new check valve, and I saw the part numbers on one of the z boards, and even wrote them down on a PostIt note. And now I can't find the note. Oh well, something to do this winter I guess. Mine had gotten stuck while sitting (drained) for 6 years while I rebuilt the car. Stupidly, I blew compressed air *back* through the line, so I now have a check valve on Perma-Open. Probably didn't do the damper any favors, either. Oops.
FWIW, the Walbro pump I used on the EFI/turbo conversion of my truck actually has kind of a loud whining sound, and my stock 280Z pump is fairly quiet. If your stock pump was loud, maybe it was starting to go (just a guess). I'd also note that my Walbro in the truck does not have a check valve, so I have to let the pump run for a few seconds before starting it. Given I screwed up the check valve on my Z, I have to let the pump run a few seconds on that, too. My Z pump will run in the On key position, even if the engine isn't running. I haven't diagnosed yet if that's a side effect of the upgraded alternator installation or just an electrical problem to be fixed (bad relay perhaps). Again, something to do this winter, I guess. That list is getting a bit long.
Finally, if your system won't hold pressure after shut off, even if you pinch both the feed and return lines firmly closed, maybe you've got a leaking cold start valve and/or injector(s).
cheers,
Dave
I know I need a new check valve, and I saw the part numbers on one of the z boards, and even wrote them down on a PostIt note. And now I can't find the note. Oh well, something to do this winter I guess. Mine had gotten stuck while sitting (drained) for 6 years while I rebuilt the car. Stupidly, I blew compressed air *back* through the line, so I now have a check valve on Perma-Open. Probably didn't do the damper any favors, either. Oops.
FWIW, the Walbro pump I used on the EFI/turbo conversion of my truck actually has kind of a loud whining sound, and my stock 280Z pump is fairly quiet. If your stock pump was loud, maybe it was starting to go (just a guess). I'd also note that my Walbro in the truck does not have a check valve, so I have to let the pump run for a few seconds before starting it. Given I screwed up the check valve on my Z, I have to let the pump run a few seconds on that, too. My Z pump will run in the On key position, even if the engine isn't running. I haven't diagnosed yet if that's a side effect of the upgraded alternator installation or just an electrical problem to be fixed (bad relay perhaps). Again, something to do this winter, I guess. That list is getting a bit long.
Finally, if your system won't hold pressure after shut off, even if you pinch both the feed and return lines firmly closed, maybe you've got a leaking cold start valve and/or injector(s).
cheers,
Dave
10-02-2009, 08:47 AM
#7
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It'll hold a steady 40psi while the pump is going, like the regulator is working with the engine off and the pump priming. As soon as the pump stops/turns off then the fuel pressure will bleed down. As I mentioned two other members running an Aermotive adjustable FPR which is very similar to the one I have on a Z31 and another on a 280Z say their cars do the same thing. Maybe I need to put a check valve in place if the Walboro doesn't have one? I had always heard the check valve was in the pump.
The other thing basically what I was saying is that it almost to me seems like the ECU is losing connection for a moment when I flip from ON to Start. Because when I go back from cranking it will re-run the 5-second prime which is odd as I don't remember it doing anything like that on my 280ZX. Basically too when I start cranking it seem like the gauge on my rail won't show a build of pressure until I've been trying to crank for a few seconds. I would have thought that it would kick the fuel pump on immediately once you start cranking. I'll have to check the wiring, I'll have to pull up the rail and see if I have a stuck open injector. Since this is a turbo car, there's no cold start valve.
The other thing basically what I was saying is that it almost to me seems like the ECU is losing connection for a moment when I flip from ON to Start. Because when I go back from cranking it will re-run the 5-second prime which is odd as I don't remember it doing anything like that on my 280ZX. Basically too when I start cranking it seem like the gauge on my rail won't show a build of pressure until I've been trying to crank for a few seconds. I would have thought that it would kick the fuel pump on immediately once you start cranking. I'll have to check the wiring, I'll have to pull up the rail and see if I have a stuck open injector. Since this is a turbo car, there's no cold start valve.
10-02-2009, 11:31 AM
#9
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ECU codes are nothing different than I've always had with my 280ZXT. Fuel Temp Sensor, and a Fuel Pump Circuit. I had this described as the ECU is looking for a specific feedback resistance and isn't seeing it. Matt at Nistune said this is nothing to really worry about. When the car is running it runs and idles fine so I don't think the pump is suspect. Same code I had with the ZXT. Never really had a fuel issue with that car. After reading through the FSM this sounds like it's more due to the fact that the Fuel Pump isn't wired exactly the same way as it would be in the Z31.
10-02-2009, 11:51 AM
#10
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Oops, my bad. I forgot about the "turbo" part, and didn't realize it was w/o a cold start valve. One less piece to monkey with, though!.
Does start to sound more like the electrical logic behind the pump. Have you temped up a hardwire of the pump to test that? Can you set up a voltmeter to see it while you cycle through On to Start, and see if the pump is getting power that way? If not, then it should be simple, if tedious, to just test the relays and switches in order in your schematic. One of them may not be getting the message that "Start" is OK to send power to the pump.
BTW: I found that posting about the check valve replacement. Short version is Bosch 1 583 386 011 check valve for an old Volvo is the same as the Nissan valve. I haven't ordered that valve to try it first hand, though, and some one else in the thread said they thought it was expensive. I can't vouch for it's price or fitment, but it's what I might try this winter if I can't fix/clean mine.
cheers,
Dave
Does start to sound more like the electrical logic behind the pump. Have you temped up a hardwire of the pump to test that? Can you set up a voltmeter to see it while you cycle through On to Start, and see if the pump is getting power that way? If not, then it should be simple, if tedious, to just test the relays and switches in order in your schematic. One of them may not be getting the message that "Start" is OK to send power to the pump.
BTW: I found that posting about the check valve replacement. Short version is Bosch 1 583 386 011 check valve for an old Volvo is the same as the Nissan valve. I haven't ordered that valve to try it first hand, though, and some one else in the thread said they thought it was expensive. I can't vouch for it's price or fitment, but it's what I might try this winter if I can't fix/clean mine.
cheers,
Dave
10-02-2009, 09:35 PM
#11
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That would be to replace the check valve in your factory pump right?
Anyway I'm going to go check my connection at the ignition switch and see if I'm losing power at some point for a split second. I don't believe there's anything wrong with the relay, as it seems like it operates correctly otherwise. Immediately when I turn the key to ON the pump cycles and starts it's 5-second prime, and you'll immediately see the pressure jump from 0 to 40psi. So we'll see.
Anyway I'm going to go check my connection at the ignition switch and see if I'm losing power at some point for a split second. I don't believe there's anything wrong with the relay, as it seems like it operates correctly otherwise. Immediately when I turn the key to ON the pump cycles and starts it's 5-second prime, and you'll immediately see the pressure jump from 0 to 40psi. So we'll see.
10-03-2009, 02:32 PM
#12
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Well I was messing with the wiring and checking it a bit, and that seems to be ok other than the voltage drop that occurs when going from ON to Start, and I was moving the key very slowly I never noticed a point at where it dropped voltage. I clamped off the fuel line right after the rail, but before the regulator kind of as a way to see if maybe I was losing pressure via a check valve not being there or the injectors. I clamped the line, apparently not all the way so it was completely tight and flicked the key to ON so it would start the prime, then immediately back as I didn't want to try to build up a huge amount of pressure. My pressure was mostly holding and bleeding off very slowly. I think basically the line wasn't clamped all the way like I said. The second I pulled the vice grips off the line the pressure on my gauge shot to 0.
10-04-2009, 06:18 PM
#13
I would use the stock pressure regulator unless you are trying to boost match it. I bought a cheap adjustable regulator a while back for like $20 on ebay. It's very easy to adjust, but doesn't hold pressure at all when the fuel pump is off. I let the system prime before every start.
10-04-2009, 07:23 PM
#14
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Well see the stock regulator was giving me the same issues. So it was making me think it was bad. What I bought is an adjustable that has a 1:1 boost reference or something like that so that it will increase pressure under boost.
Actually adjusts exactly the same way as that. Like you mentioned along with a couple on hybridz, so far it seems like none of these after market regulators are any good at holding pressure when the pump is off.
Actually adjusts exactly the same way as that. Like you mentioned along with a couple on hybridz, so far it seems like none of these after market regulators are any good at holding pressure when the pump is off.
10-10-2009, 11:36 PM
#15
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I think I may have solved the issue. I'm not exactly sure and the car still doesn't fire up immediately, but I'm sure there's plenty of crap to still work out, but it seems to start up now when turning the key to Start.
Anyway while the car was running I was trying to figure out where a wiring issue might be, shaking wires and crap before trying to test the Ignition Switch again. I have coming from my battery a wire with an inline fuse that was there from the previous owner. I ended up using this to be the constant power for my fuel pump relay from the battery. I figured an inline fuse would be a good extra little protection. Anyway I noticed that the Fuse was pretty warm. So I looked at the fuse and I could see that it was looking kinda messed up inside. I checked the wire from the relay to the fuse holder and that was fine no matter how much I wiggled. I think it was the actual contacts on the fuse. I fixed this and put a new fuse, and tightened up another wire to the FPR and this seems to have fixed the problem.
Anyway while the car was running I was trying to figure out where a wiring issue might be, shaking wires and crap before trying to test the Ignition Switch again. I have coming from my battery a wire with an inline fuse that was there from the previous owner. I ended up using this to be the constant power for my fuel pump relay from the battery. I figured an inline fuse would be a good extra little protection. Anyway I noticed that the Fuse was pretty warm. So I looked at the fuse and I could see that it was looking kinda messed up inside. I checked the wire from the relay to the fuse holder and that was fine no matter how much I wiggled. I think it was the actual contacts on the fuse. I fixed this and put a new fuse, and tightened up another wire to the FPR and this seems to have fixed the problem.
10-12-2009, 10:31 AM
#16
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Bah. Well the issue is better, but still isn't quite right. I cleaned up some of the ground points for the battery as well, but it's still kind of random. It's either a wiring or fuel pump issue, but I'm thinking it's wiring.
It seems like it's starting better than it did, but I'm noticing the way it does it is odd. Sometimes the car will start right up with no issues. Other times it will start quickly, sometimes it will take a bit of cranking, and other times not at all. I was watching the pressure gauge when I had a friend turn it. The gauge right on start, started building pressure, then for a moment started to pulse like it dropped pressure, started to build, then dropped, then went up and started. Then we turned the car off and tried again and this time it built pressure immediately and started right up. Tried a few times, it would build pressure and start right up, then it would go back to taking a bit of cranking. It's really odd.
Does anyone know a good way to test the ignition barrel itself? I think the ignition barrel is actually the same in the 280ZX so I may take both of them apart and test them, switch them and see if that helps. It could be the way I wired it up, but it seems odd that everything seems to work fine/idle fine, etc when running or in the ON position, but has issues in the start position.
I guess it could possibly be the relay, but it seems like it it was the fuel pump relay or any other relays that I'd notice a pulsing or inconsistency when it came to the 5-second prime when the key is in the ON position.
It seems like it's starting better than it did, but I'm noticing the way it does it is odd. Sometimes the car will start right up with no issues. Other times it will start quickly, sometimes it will take a bit of cranking, and other times not at all. I was watching the pressure gauge when I had a friend turn it. The gauge right on start, started building pressure, then for a moment started to pulse like it dropped pressure, started to build, then dropped, then went up and started. Then we turned the car off and tried again and this time it built pressure immediately and started right up. Tried a few times, it would build pressure and start right up, then it would go back to taking a bit of cranking. It's really odd.
Does anyone know a good way to test the ignition barrel itself? I think the ignition barrel is actually the same in the 280ZX so I may take both of them apart and test them, switch them and see if that helps. It could be the way I wired it up, but it seems odd that everything seems to work fine/idle fine, etc when running or in the ON position, but has issues in the start position.
I guess it could possibly be the relay, but it seems like it it was the fuel pump relay or any other relays that I'd notice a pulsing or inconsistency when it came to the 5-second prime when the key is in the ON position.
11-15-2009, 02:35 PM
#17
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Alright, I posted a quick thing about this in the post ***** thread.
Anyway, I was messing with my car. I pulled the little spade connector off the male end at the starter. Used a screwdriver to try and jump the terminals to start it with the key in the ON position. My fuel pump seemed to be doing better or I should say actually holding pressure, I still seemed to have no luck, but also I really don't know if this was triggering the Start signal for the ECU. I assume it was seeing as the pump was running. My battery quickly died though, so that could be part of it. Do you guys know if that wire needs to be on the male connector at the starter for the ECU to get the start signal?
Also I changed out the electrical switch for the key barrel. After I was done, when I'd put the key to the start position it wasn't triggering the starter so maybe this switch has gone bad. I have a few more tests to go try though. Any thoughts on other things to test?
Anyway, I was messing with my car. I pulled the little spade connector off the male end at the starter. Used a screwdriver to try and jump the terminals to start it with the key in the ON position. My fuel pump seemed to be doing better or I should say actually holding pressure, I still seemed to have no luck, but also I really don't know if this was triggering the Start signal for the ECU. I assume it was seeing as the pump was running. My battery quickly died though, so that could be part of it. Do you guys know if that wire needs to be on the male connector at the starter for the ECU to get the start signal?
Also I changed out the electrical switch for the key barrel. After I was done, when I'd put the key to the start position it wasn't triggering the starter so maybe this switch has gone bad. I have a few more tests to go try though. Any thoughts on other things to test?
11-15-2009, 02:45 PM
#18
ECU wiring, or CAS. I still have a hesitation when starting my 280zxt. As soon as I get my 280zt wired up I'll know if it acts the same.
I pretty much gave up on my 280zxt starting issue. All the probs I was having (minus that) went away when I cut & spliced in the Z31 ecu plugs. The next step would have been swapping in a Z31 CAS. Direct swap except you need longer bolts & matching nuts to bolt it into the dizzy housing.
I pretty much gave up on my 280zxt starting issue. All the probs I was having (minus that) went away when I cut & spliced in the Z31 ecu plugs. The next step would have been swapping in a Z31 CAS. Direct swap except you need longer bolts & matching nuts to bolt it into the dizzy housing.
11-15-2009, 03:45 PM
#19
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Are you saying the ECU wiring or the CAS is where it gets the start signal or are you saying those are things to look into?
When this setup was in my 280ZXT I actually never had any starting issues. Which is why it's odd that I seem to be having issues now. It actually overall ran very well except for that fact that I had a leak somewhere or my boost controller wasn't set properly and my boost would spike then bleed off.
There's very few wires to actually connect, and even when I put the car to the ON position it triggers the fuel pump 5-second run cycle with no issues, the lights on the ECU flash as they're supposed to, I can connect my Laptop to the Nistune board with no issues. So it seems fine, just when it comes to starting.
I think I'm going to disconnect the fuel pump and put a test light in place on the power wire for the pump. This way I can watch and see if it's pulsing or feeding the pump a constant power.
When this setup was in my 280ZXT I actually never had any starting issues. Which is why it's odd that I seem to be having issues now. It actually overall ran very well except for that fact that I had a leak somewhere or my boost controller wasn't set properly and my boost would spike then bleed off.
There's very few wires to actually connect, and even when I put the car to the ON position it triggers the fuel pump 5-second run cycle with no issues, the lights on the ECU flash as they're supposed to, I can connect my Laptop to the Nistune board with no issues. So it seems fine, just when it comes to starting.
I think I'm going to disconnect the fuel pump and put a test light in place on the power wire for the pump. This way I can watch and see if it's pulsing or feeding the pump a constant power.
11-15-2009, 07:20 PM
#20
The CAS is the optical trigger for spark. So if there's any issues w/ the unit or wiring, that can cause probs too. The round harness plug can have connection probs too.
11-15-2009, 07:24 PM
#21
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I know what you mean about the 280ZX plugs. I'm gonna go back tomorrow with a battery charger and mess with the car a little more. Still seems odd that once it's running it doesn't have any issues, but maybe that's the thing. It just happens to work and runs or it happens to not be working. Maybe the CAS got banged around when we pulled the Dizzy off to change the head.
11-17-2009, 10:24 PM
#22
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Hmm, I'm glad you mentioned the CAS. I haven't messed with it, but I do have a spare used one that Hoov sent me when I bought a Z31 rotor plate from him. Anyway I really don't think there's an issue with my wiring as there's very little wiring to do in this swap and everything seems to work fine. I was reading up on the CAS and apparently it pretty much dictates everything. Depending on what the CAS is showing the ECU determines when to turn the fuel pump on and off, fire the injectors, etc. So I'll start there by checking the wiring harness and the CAS.
I remember when I got my car together we found the rotor in the distributor was banged up, the little metal piece that sits on top of the rotor was all bent and messed up. Makes me think that the distributor got banged around or something when it was removed.
I also think my distributor may have had a Z31 crank angle sensor in it. I remember when I was doing the swap I started looking through the car and found a box with a crank angle sensor in it and a couple of rotor plates. One of them was a Z31 rotor plate and for some reason I want to say that the part matched up for the Z31 CAS.
I remember when I got my car together we found the rotor in the distributor was banged up, the little metal piece that sits on top of the rotor was all bent and messed up. Makes me think that the distributor got banged around or something when it was removed.
I also think my distributor may have had a Z31 crank angle sensor in it. I remember when I was doing the swap I started looking through the car and found a box with a crank angle sensor in it and a couple of rotor plates. One of them was a Z31 rotor plate and for some reason I want to say that the part matched up for the Z31 CAS.
Last edited by duowing; 11-17-2009 at 10:32 PM.
11-18-2009, 11:43 AM
#24
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The wheel in the dizzy hasn't changed since the swap and it ran/started up with almost no issues when I had it in my 280ZX. I had a little bit of a miss at idle, and had a boost leak, but other than that everything seemed good.
Anyway I messed with it for a few minutes as I had some time. I put a test light on the fuel pump power line and was cranking the car by crossing the terminals at the starter. The test light was staying lit up, pulsing a little bit, but not turning off/on. I would think that this seems about right. I plugged the fuel pump back in and was watching the pressure gauge while cranking and the pressure seemed to be staying around 40-ish psi where it normally would be while cranking. Where before it would start to pressurize, drop, or take a few moments of cranking before it would start building pressure, etc.
One other thing I'm still not sure of, was when using at least the key barrel, when I would go to crank, then let off the ECU would then trigger the 5-second fuel prime again. I don't know if this is right or if the ECU is losing power during the cranking cycle. My battery, and my POS jumper box started dieing after a few moments of cranking, so that's not helping either.
Anyway I messed with it for a few minutes as I had some time. I put a test light on the fuel pump power line and was cranking the car by crossing the terminals at the starter. The test light was staying lit up, pulsing a little bit, but not turning off/on. I would think that this seems about right. I plugged the fuel pump back in and was watching the pressure gauge while cranking and the pressure seemed to be staying around 40-ish psi where it normally would be while cranking. Where before it would start to pressurize, drop, or take a few moments of cranking before it would start building pressure, etc.
One other thing I'm still not sure of, was when using at least the key barrel, when I would go to crank, then let off the ECU would then trigger the 5-second fuel prime again. I don't know if this is right or if the ECU is losing power during the cranking cycle. My battery, and my POS jumper box started dieing after a few moments of cranking, so that's not helping either.
11-19-2009, 02:48 PM
#25
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The starter can suck all the power from a weak battery leaving everything else with near zero volts. The fuel pump also draws alot of volts necessitating the prime. This may explain the prime you get and the drop because the battery can't recover after the start. The fuel pump is supposed to run constantly while the fpr regulates a constant pressure (rising in your case). The pressure bleeds off when the pump turns off because the fpr is slightly open. The check valve keeps the fuel from going to its lowest level with gravity thereby keeping the fuel rail full. Newer cars like the 300zx and later hold pressure indefinitely.
All this may only be partially correct but it is my theory on it.
All this may only be partially correct but it is my theory on it.
