I finished my rebuild a couple of weeks ago and I am having a starting and idleing problem. I will try to go over everything and not leave anything out.

We finish rebuild and we are priming the oil pump and notice an oil leak at the drivers side turbo oil feed at the block. I get that resolved and spin car over with PTU unplugged and no leak.

I go to start the car, just to see if it will start and it fires up instantly. I am grinning from ear to ear. All I need to do is finish the exhaust and get a battery box since I relocated it. Buddies come over and I start the car serveral times and let it run for 30 seconds are so each time. The last time I started it with no problems I let it run for about 1 minute, bring it up to about 2K RPM and shut her off.

I finish the exhaust, bring the car off of the jack stands and she will start and then dies immediatly and then will not start until she sits for a while. Got to a point where she would not start at all. Fuel was going into the vaccuum side of the fuel dampner, so it was replaced and did not solve the problem.

We have tried MAF, ECU, PTU, coil packs, checked injectors for leakege, vaccuum leaks, and added fresh fuel. It seemed like it was flooding so we connected a fuel pressure gauge and adjusted the pressure with the Nismo regulator. If we drop the pressure down to 15 - 20 psi the car will start and not rev up until the pressure is brought back up to 40+ psi.

The injectors were bought used but sent off to RC engineering to be tested and everything was fine. New ECU harness, fuel temp sensor, engine temp sensor, coolant temp sensor, plugs, fuel pressure regualtor and fuel dampner.

This project has been going on for almost 2 years and I am trying to complete before the wife has our first child. I just need to get this problem licked. I am begging for any suggestions at this point.

Thanks,

Greg

 

Did you check the ECU codes?

 

They are 55.

 

First and foremost, thank you for the incredible lack of information about your 300ZX. Fuel system problems on 90-93 TTs and 90-92 NAs will be VERY different than those of 94+ TTs and 93+ NAs, despite the differences between NA and TT 300ZXs. I can help you much if I don't know sh*t about your car. Anyway...

I'm gonna go in order of easiest to hardest to diagnose, since that's how you should always do it to prevent doing more work than you have to...

I know you had RC Engineering do work on the injectors and all, but did you, yourself, test the resistance of the injectors? If you have early-style (pre-94) injectors, they could very likely be dead (especially if you're using gasoline with ethanol content and it was sitting in the injectors for a while). If you have shorted injectors (0 ohms, or very low resistance), the injectors would be dumping excess fuel into the engine. Running low fuel pressure would balance out (kinda) the low resistance, thus allowing the car to start. So first and foremost, check the resistance of the injectors, it's not hard to do and it's better to know.

Second, there is a very important ground that many people forget about. It's on the bell housing of the transmission... did you connect it? It can cause this problem (perhaps it was making some contact at first, but when you finished everything it shook loose and is now not grounding anything). It should be on the passenger's side top of the transmission.

Finally, how old is your fuel pump control unit? These are problematic on earlier 300ZXs, and can also cause symptoms like this. I do not know, offhand, how to diagnose this (nor can I search it for you since tt.net is down at the moment - if I remember correctly, you have to take the cover off it and visually inspect it... when it goes bad, it fries a circuit, and you'll see the burn marks), so you'll have to figure that out for yourself. If you didn't know, the fuel pump control unit is underneath your headlight aiming kit behind your driver's seat (which is under the panel directly behind the seat on 2+0s, and I have no idea where it is on 2+2s).

So check those three things and come back with results.

 

i kinda like this suggestion. for some reason i could see it being up on the jackstands and the ground grounding to the jack stands hangin on them or pinned or soemthing wich is why it ran when sitting up on them....but also you would probably see this hanging and i doubt its that long of a ground. but shaking loose is a good explination to.

 

To specify the ground they're talking about goes from the battery negative terminal...bolts to the firwall...then on down to the top of the bellhousing of the trans. The cable isnt long enough for you to see (if it wasnt bolted to the trans.) looking under the car without the car being up on jacks. its only about 18"-24" long give or take. When the battery was re-routed you may have forgotten about those grounding points. also, did you change out the fuel filter? I'm sure you did you just didnt mention. still we lack some details to assist you any further.

 

Thanks for the reply. To tell you more about the current setup of the car. It is a 1990 TT had 148K miles when I pulled the motor for a rebuild. The rebuild included Wiesco pistons .20 over, Eagle rods, JWT 400 Cams, Nismo 555 (old style) injectors, Doolz intake, JWT 530BB, AshSPEC ECU, and new ECU harness.

The injectors were not sitting in gas for any lenth of time. Other than priming the oil pump and then fixing the oil leak. I will check the resistance still though.

I did install the ground there at the tranny that you mention. I also added a second 4 gauge ground from the tranny to the tranny crossmember. I will check these connections also.

I had no clue about the fuel pump control unit, so I will check that also.

Again, thanks for your suggestions. This is more info that I have gotten then on tt.net or 3zc.

 

Yes, I have changed out the fuel filter, regulator, dampner, verified the hoses are connected correctly. I replaced just about everything on the engine while the car was being rebuilt. The only thing I didn't replace was the valve on the back drivers side of the plenum. Everything else is new or I tried a known good one off of my running NA.

 

I believe I previously suggested just by-passing the control unit by hardwiring the pump to the battery. If you try this it will eliminate the controller as a possible problem.

On the newly built motor, have you double checked your ignition and cam timing?

 

Another possibility is the route of the fuel lines (and it may have contributed to your dampener problem). The feed and return line on the driver's side of the engine (from the fuel filter to the hardline and from the hardline back to the gas tank) could be crossed (I did this the time before last that I pulled my engine). The two lines should not cross each other (they run parallel to each other into the fuel rail). If they form an X, the lines are routed improperly (which would cause your pump to be feeding into the return side, thus going backwards in your dampener causing your dampener issues). I'll see if I can take a pic of what I'm talking about tonight, but they're the two longer fuel lines; the line from the filter into the hardline and its counterpart.

 

fuel pressure relise the presse at the fuel filter .... try that ?

 

Try what... jibberish? j/p

 

Injectors tested fine. I also checked the ground straps and they were tight also.
I did not get a chance to check the fuel pump control unit or by-pass it. I will try that tomorrow.

With the JWT 400 cams is there anything I need to do? When I was researching them, I don't remember reading have to upgrade springs or doing anything with the cam gears.

 

Adjustable cam gears? Are you sure the cam timing is correct? Only running with low fuel pressure is like delaying the injector pulse, aka retarding the timing of when the fuel sprays. Could be a sign that your intake cams are off time.

I know it's a shot in the dark, but unless you're positive about the cam timing, it's a possibility.

 

What is confusing is that it started several times with no problems. The very first time I started it and started right up without having to spin over any. After about 7-8 starts it started having problems. I think I am going to check the timing belt anyways. After I look at the fuel pump control unit.

 

Have you pulled the plugs to make sure they aren't fouled out or damaged in any way?

 

They are black and wet with fuel. I am going to pickup some cheap coppers tomorrow and see what happens.

 

sounds fowled. should be tan at most. mabye a gray comming over them. not black though. nor wet, that means they arent burning crap. hope that means its the plugs and not no spark through the coil packs.

 

Now leaning towards leaky injector o-rings or timing issues.

 

2nd CanyonCarver. If the plugs are wet you're getting fuel, so it can't be a malfunctioning Fuel Pump Control Unit. Sounds like you're either getting too much fuel or spark at the wrong point (if at all).

Check the ignition timing and ignition. To check if your spark plugs are firing at all, take one out at a time, put it in the ignition coil (with the coil connected to the harness), touch the threads of the plug to a ground and try cranking the car (don't touch the spark plug). If you can see a spark, then you have timing or fuel issues.

(Sorry if you already knew how to do that - I generally try to explain everything to keep time down [so you don't have to ask] and also for future searchers who might not know how to do it.)

 

I am going to pick up some cheap copper plugs tomorrow, just to see if the plugs are the problem. I have already checked the o-rings around the injectors and everything was dry. I pulled the fuel rail and pressurized the system and their were no leaks.

I called JWT and spoke with a "Clark" about if there was anything I needed to do with the mild cams. He stated they install the same as stock. He seemed very knowledgeable with the Z32 and tried to help me diagnose the problem. He was saying that the coolant temp sensor may be thinking the engine is cold and dumping to much fuel in. I have tried a different sensor and that did not help.

I guess if the plugs don't fix it I need to check my timing belt and make sure everything is still in time. That is about the only thing I or anybody else can come up with.

 

then started running bad, and you pulled the plugs and they are black and wet, that means your spark is good and your fuel is good, guess what that leaves? AIR, i don't think your engine is getting good air, either exhaust is partially blocked or your intake is clogged. shouldn't be too hard to check either or both. Ill place my money on clogged cats. Cheers!

 

Running brand new test pipes and when the car was started the first few times they were on there. The catback was dropped from my running NA and put on to the TT in the same evening.

We have also diconnected the intake piping at the throttle bodies and it would not start. This could be because of the plugs though. The local NAPA has some cheap Champion coppers I am going to through in today and see what happens.

Wish me luck!

 

But don't fprget, it all has to come together, in the correct amounts, at the right TIME too.

 

Well, Ash was in town and came over to help me diagnose the problem. He thinks the timing belt is off on the crank. We checked compression on all cylinders and they were anywhere from 70 - 85 PSI. It only took him about 10 minutes to diagnose and that included pulling the plugs.

I plan on pulling everything tomorrow and resetting the timing belt. I will let you know how it goes.