duowing

Hey guys it's been a while and time for a check in! I read through threads every so often, just haven't really been active on here. Anyway my Z is still coming along and here's a new problem I'm running into. Every so often, primarily at high RPM/load/freeway speeds if I start to get on it it will start sputtering, cutting out real bad. If I keep on it easy it runs fine. My fuel pump which is supposed to be a Walbro 255lph inline pump, but could be an ebay knockoff is getting really loud lately. I took off the filter I had between the tank and the pump, but that made no difference. I'm running a rising rate fpr I got through Summit. Unfortunately I didn't think to test by pulling the vacuum line off the regulator.

Anyway when I turn the key to ON and the system primes it primes at 36-37psi which is right where I set the regulator to be at. At idle once started the pressure will go down to about 26-27psi which follows the L28ET specs pretty accurately. When revving the car up though my fuel pressure doesn't seem to rise like it should. I don't know if this is regulator or pump related. If I go drive around and then check my pressure gauge will be showing about 21-22psi at idle and again if I rev the car up at idle it will rev fine, but the fuel pressure will not rise like it's supposed to. If I turn the car off wait a moment then turn it back on the fuel pressure will be back to 26-27psi at idle until i start driving around.

I don't know if this is a pump related issue, maybe the relay is going bad(it gets warm, but not hot), or maybe the regulator is causing issues. Unfortunately like I said I didn't think to pull the vacuum line to the regulator so I'll have to check that. Anyway with the pump being as loud as it is lately I'm thinking that's the culprit. Any suggestions from you guys? Also what's a good pump to go with? I'm thinking maybe a Mallory or MSD. It seems like everyone uses the Walbro, but at the same time I seem to see a lot of mixed opinions on them. Could just be mine's a knockoff like I said.

theramz

You might be losing vacuum somewhere. That would explain the lack of rise.

duowing

Went and played around with the car a bit more. Did a real quick drive, but didn't get on the highway and fuel pressure was fine. Drove around more, took a quick run on the highway and now the fuel pressure was low again. While car was running I pulled the vacuum line off the pressure regulator and pressure jumped up, but was lower than what I have the regulator set at. Even the priming process was priming lower than what I have the regulator set at for pressure. I went and kept adjusting the regulator to get the set pressure back to about 36-37psi then left the car for a while. Came back about 2 hours later when everything should be nice and cold and flipped the key to ON to prime it. Now the pressure was showing close to 45psi. So that at least tells me that the regulator seems to be ok, or at least mostly fine. Definitely is sounding like the pump to me, or I'm still thinking maybe an issue with voltage when it gets hot? I have a Bosch 044 inline pump on the way so I'm going to try that. I also think I still have the stock regulator that came with my 280ZXT so if I'm still having issues I'll try that out as well. I think I may need to get a hold of another Fuel Pump Relay for testing also.

duowing

Swapped to a new pump and it still seems to be doing the same thing. At first my tach was freaking out and jumping all over the place and the car was sputtering if I got on it. As long as I just drove calmly it was fine. I started feeling around and the wire to the fuel pump relay that provides the Green pump wire with 12v was definitely getting warmer/hotter than any of the other wires. So I disconnected it from under the dash and I'm going to try running a wire straight from my maxifuse blocks to the fuel pump relay so it's still fused, but getting pretty much a direct path. Also I found my ECU or Harness was definitely having issues as if I'd shake/wiggle it the car would sputter and almost die. I have to figure that out. At least as a start I de-pinned some Z31 ECU connectors I had and pulled all the pins out of the 280ZXT harness connectors and swapped them all over to the Z31 ECU connectors. So hopefully the newer connectors that hold the pins tighter will make a difference there and be my issue. I need to figure out how to mount the ECU better, the way it sits right now lets it move around/vibrate too much.

NismoPick

About a month after I did my Z31T ecu swap, I started having random hesitation probs. I ran the diagnostic codes and got a bunch of sensor trouble codes... racked my brain trying to check / fix them. Then one day on the freeway my a/f gauge just started to wig out so I grabbed the wire to pretty much yank it out and it started working again. So I wiggled the ecu plugs and the car magically settled down. That's when I found out about the 280zxt's common faulty ecu plug grounding wires. I chopped them out and soldered in 89 Z31 ecu plugs.

duowing

If I'm not mistaken you're talking about that smaller ECU plug I think that has the two found wires that go into that crush connector to that larger ground wire that has that covering over it? From what it looked like is that the Z31 still had that same exact setup.when I depinned the Z31 connectors I noticed those two ground wires ran together into that one larger covering. I took it apart and saw the two ECU wires were crushed together to connect to that larger wire. I'm thinking it could just be a case of the fact that the Z31 plugs have those extra plastic inserts to hold the pins in place and make a better connection. I also noticed that just when removing the pins from the 280 connwctors that they had a lot of forward to back play inside the connector which i could easily see why so many people have the issue of needing to reseat the plugs or shake the harness every so often. When you did wire in your connector did you make any changes to that ground setup?

NismoPick

Yes, that's the one. I did chop out that stock crimp that combines the ground wires and replaced it with a better crimp. I soldered all connections and used electrical shrink wrap, then electrical tape. I also wired in a pigtail for my a/f gauge so it's not tapped into the side of the O2 wire, it has it's own direct connection.
I think I have a pic of my new ecu plugs floating around this site too.

duowing

I'll probably end up doing this same thing if it starts acting up again. I was actually thinking of taking that connection and soldering in some extra ground wires directly to the pins before it runs into that larger multi ground crimp point and then running those two to a separate ground that then would run to my star ground setup I'm making in addition to keeping it the original way. At least to add more grounds to the ECU.

duowing

Well either today was a better or day or I'm making some progress...I drove the car for a while and encountered no hiccups or issues with it running. I even tried shaking the ECU and the harness a bit and I seemed to be fine. The car's idle didn't change or it didn't sound like it was going to die. So it could have simply been reseating the connections, or that the Z31 connectors are providing a better connection. After a while though my fuel pump did start getting loud, but even freeway driving, highger RPMs and getting on it the car wasn't sputtering. Got back to where I park the car and just as it's always been the power wire feeding the Fuel Pump Relay was again getting pretty warm/hot along with the relay itself. I really don't know why. I'm just assuming then that it's something with that connector, maybe it's dirty/corroded and not making a good enough connection at the relay. Also fuel pressure was lower as usual. I really should have got out the multimeter and checked what voltage the pump was getting. That's next on my list.

Also I believe that the Z31 ECU supposedly regulates the voltage that goes to the pump, but I'm thinking that shouldn't be of concern for us who have done the swap because I'm pretty sure that the way we have it wired the ECU is only controlling whether the relay is on or off letting battery voltage to pump.

duowing

Well another long drive today and the car seems to be running pretty darn well. I wasn't getting the sputtering or cutting out like I have so maybe it really is the Z31 connectors. Fuel pump still starts getting loud after a while. Swapped the old green style relay for a Tyco 20/30amp relay. Still getting pretty hot after a while. Checked the voltage at the battery and was seeing 14-ish volts. Alternator is doing it's job, checked the wire going into the relay and was seeing 13.8-13.9v. Wire coming out of relay going towards pump was a little lower, and then all the way back at the pump I'm seeing 13-to maybe 13.2v. Pressure at idle is sitting at maybe just above 20psi. A few things I thought is since I never put the intake manifold's heat shield back on maybe it's causing a problem and heating up the fuel and such making the pump work harder? I need to dig the heat shield out and bolt that on to see. Other than that maybe the relay just isn't doing the job? I'm almost wondering if I should try bypassing the relay and wiring the pump straight to fusible links?

NismoPick

13V+ seems fine to me... if it were below 12.6 (good battery voltage), then I'd be worried.

As for the heat shield,
Are you running an intercooler?
Do you do a lot of city driving (stop, go, idle), or mostly freeway?

duowing

My driving varies, but the trips I've been taking involve a good bit of everything. Some higher speed back roads, city driving, and then a good trip up and down the freeway. Also I'm just not sure why the pump after a while starts to get so loud. Generally a lot of my driving sticks to freeway/back roads when I drive my Z normally. Forgot to add currently no intercooler. I've just been working on keeping the boost and setup relatively stock until I pretty much had it running perfectly.

I found a post via jeffp over on Z31Performance.com discussing a similar thing. Basically saying that these old relays along with even newer 30amp relays plus the old wiring are not really enough to support most larger/aftermarket pumps. He was saying having issues with things like the 20amp green relays and seeing a 1v drop across the relay contacts. He PMed me back on HybridZ and was basically restating the same thing, and saying to look for a rather large relay that earlier Infinitis with ABS had. He was saying that these relays will be more than sufficient for my needs for something like the fuel pump.

theramz

Hot wires mean high resistance. You should be getting 35 psi at idle. If you are choking off the flow to 20 psi it will cause the pump to overload too. Are you sure your pump is for efi?

duowing

I'm planning to go take the car for a drive soon. Yes the pump is meant for EFI. I'm using the Bosch 044 Fuel Pump which is supposed to be able to push more fuel than a Walbro 255lph. I just finished rewiring my car with larger 50amp Bosch Relays that were used in a Nissan Quest for the ABS system as well as I ran all new 10 gauge wire for the pump, and a 10 gauge wire from pump negative straight to ground. So I'm hoping the heavier duty wiring fixes my issue.