Need Help figuring out starting issue

[DuoWing]

I'm hoping someone can give me some direction on where to start and what to look for. Anyway I've got my 280Z turbo project that I've been working on. I mess with it here and there, but I'm having trouble with it. I can't get it to start from a cold start very easily. Most of the time I'll be sitting there cranking and cranking. Finally it'll start maybe after stopping and cranking a few more times. Generally it seems that once it starts it'll either immediately die or it will idle, if I give it very light throttle it will start to rev up. Too much throttle and it will nearly die or die. After about 30 seconds to 1 minute the car seems to straighten out and things seem to start acting better. I can drive the car around, rev it(there seems to be a very slight hesitation if I open the throttle real quick(not sure if this is a normal Z thing?) and it revs up fine. Pops on revving down. It will idle all day long and seems fine although idle was a little high, but timing may be off. Need to check that. I can get in and drive the car around. Stalled it out by accident and it started right back up. Once it straightens out I can shut the car off and it'll start right back up with no issues. It just seems once I let it cool all the way down I have to go through this crap again.

 

I'm using two different ECUs:

1986 Z31 Turbo with a Nistune Board

1988 Z31 N/A with Nistune

 

They seem to run generally the same, regardless of ECU. Prior to this swap I had the engine running essentially perfect in my 83' 280ZX Turbo on the Z31 ECU conversion. Since the swap all the gaskets were replaced, oil pump, water pump, head was swapped to a rebuilt P90 with the type "A" N/A cam. Still have my old P90a around. N42 egr-less intake manifold, but I'm still running the Air Regulator. Pallnet fuel rail with pressure gauge, an aftermarket rising rate Fuel Pressure Regulator(set at 40 psi could this cause too much fuel?), and Walbro fuel pump. The fuel tank was professionally removed, blasted, cleaned, and coated. I did change out the CHTS with a new one from Courtesy Nissan because it at some point hit the ground and I figured a bang like that would probably cause an issue.

 

I've done a Maxifuse conversion, have an MSD Blaster II coil, using a remanned ignition box from my 83. I was going around all my wiring and checking everything, shaking wires, checking for any hot wires. I had found that two wires coming from my Fuel Pump Relay were actually getting pretty hot. I re-soldered those wires and they stay cool. This seemed to actually improve my throttle response on the car. The Fuel Pump Relay still seems to be getting warm, don't know if this is normal for these relays to be warm? Z31 ECU is only giving codes for Knock Sensor, Fuel Pump Circuit, and Fuel Temp Sensor. I was getting these codes when I had the setup in my 280ZXT and it was running fine. Z31 FSM shows that the fuel pump circuit code can be related to the idle control valve which my car doesn't have.

 

ECU real time diagnostics would sometimes on startup flash for Ignition and Fuel Pump Circuitissue. I used the other self diagnostics mode and the ECU is seeing the TPS, and Start switch no problem.

 

Removed the oil cap from the valve cover and the car started to idle worse, but it didn't idle terribly. So maybe this could be a vacuum leak I've yet to find? Went through and one by one disconnected the injector connectors. Each injector when disconnected made a definite difference.

 

One final thing is I've checked the compression after the new head/headgasket was put on. I was finding for some reason compression was lower in cylinders 1 and 2. I haven't yet tried to adjust the valves, but I did check the lash and found that these two cylinders my .007(I believe that's the proper clearance?) blade wouldn't fit between the rocker arm and the cam lobe on these two cylinder. I'm really hoping there's not an issue with the head or the headgasket. The car doesn't smoke when running either.

 

So guys, any other suggestions? Anything else I should check? Any other information you guys need that I may have left out? I'm really trying to get this figured out as it's driving me crazy.

Edited September 24, 2010 by DuoWing

[DuoWing]

Well I went and checked all the valve lash cold today and found something interesting. The adjustments were all over the place. Cylinder 1 was about .008-.009, Cylinder 2 was .005, I had one that was at .011, .012, etc. The exhaust valves were something else. 3 of them were .008 and 3 were .012. I didn't have the book with me so I couldn't remember what to adjust the exhaust valves to, but I went through and adjusted all the intake valves to .008 and tightened/torqued them down. I went and had to buy a pack of metric crowfeet for just the 17mm. Hopefully I'll find a use for the rest eventually. Anyway I'm hoping once I've got this taken care of, I'll try and get the car running and warmed up and check my ignition timing. I remember I set it correctly a while back, but I want to say I may have set it before I realized I had forgotten to install the CHTS. So maybe my timing is way off as well. I figure once I've got all that done and had the car warmed up I'll have to do a compression check and then recheck if those cylinders are still showing lower by squirting some oil in there.

 

My spark plugs were all completely black. They looked like they had been fuel soaked, so I need to clean them off or just grab another set of plugs as that may help my issue. Another odd thing I noticed is that ever since I got my aftermarket pressure regulator it seemed like it would never hold pressure. The pump would prime it'd jump to 40psi on the rail gauge and then slowly drop back to 0. Then the other day I noticed after priming it would drop to about a little under 20psi. I think 15-20, and 2 days later it was showing that it was still holding pressure. Maybe there's another fuel issue to check into?

 

As far as valve lash goes, I was looking in my Haynes guides and saw that in the S30 book they show cold lash as .008 for Intake and .010 for Exhaust. The S130 guide shows .007 for intake, and .009 for exhaust, but they both show the same lash values for hot adjustment.

 

Well as said if you guys can provide any help, that would be much appreciated.

[stav2201]

Are you saying your fuel pressure is constantly at 40psi? thats to high. Sounds like your running super rich. Have you checked to see if all of your sensors are working. A bad CHTS of MAF could be causing the problems you having

[ktm]

Another odd thing I noticed is that ever since I got my aftermarket pressure regulator it seemed like it would never hold pressure. The pump would prime it'd jump to 40psi on the rail gauge and then slowly drop back to 0. Then the other day I noticed after priming it would drop to about a little under 20psi. I think 15-20, and 2 days later it was showing that it was still holding pressure. Maybe there's another fuel issue to check into?

 

What brand? It is common for Aeromotive's FPR to not hold pressure after shutting down. Mine bleeds off quickly.

[DuoWing]

I can't remember what brand it is. I picked it up at summit. I think it was a generic brand or it may have been a summit branded one. There's really no logo on the FPR. Will the fact that it bleeds off quickly though cause starting issues?

 

This was it: http://www.summitracing.com/parts/PFS-10670/

 

Professional Products? It was the only thing they had in stock that worked for me and I was kind of desperate at the time trying to get the car running. I don't know if I should look for another regulator or not. It seems to work fine when the car is running though. It's supposed to be rising rate.

Edited September 26, 2010 by DuoWing

[DuoWing]

Alright, well I went ahead and finished adjusting all my valves. All the intake set on the tighter side of .008in and all the exhaust set on the tighter side of .010in. I bolted everything back up. I didn't change out the plugs yet because I didn't want to foul out another set yet. I went and hooked up my 86' Turbo ECU and tried to start the car. Still generally the same issue, although I did manage to get the car to start up a little bit easier this time and it seemed like it was doing alot better with throttle right away. Pretty quickly it smoothed out and seemed to be idling alright. Timing is a bit advanced, by about 4-5 degrees. So I'll need to turn that back as I can adjust the timing maps, etc through Nistune. Hooked up my vacuum gauge, and the needle was hovering right around 17inHG of vacuum. It wasn't perfectly steady, but the needle wasn't bouncing or vibrating that indicated at least to me anything being wrong. Revving/throttle response was a lot smoother after adjusting the valves. Fuel pressure is sitting around 35psi if I remember correctly. Should I adjust the regulator down to 30psi at idle like the FSM says since I'm still using stock injectors for the time being?

 

I think my compression gauge is junk because every cylinder read 95psi. I know not that long ago I was getting much higher readings than that using a completely different gauge. Anyway while the car was running, I shut it off and restarted it a few times just to check again. Kept restarting fine once the car seems to get warmed up a little and straightens out. My Tach was showing 1000 RPM at idle. Nistune was showing about 775-825 which I assume because of the advanced timing. Anyway I was desperately hoping to find a vacuum leak and started spraying carb cleaner or starter fluid, I forget which all around. I was not finding anything near the valve cover gasket, nor the intake/exhaust gasket, nothing around the head, the brake booster, etc. Finally I noticed that when I sprayed a bunch right around the throttle body to Intake Manifold the car would really start bogging down. As the fluid cleared out the idle would come back up, and I did it several times. I then sprayed all around the engine again really loading it up just to make sure and only found that spot. So maybe, I've finally found my issue. So it's either a throttle body gasket, the block off plate I made for where the cold start injector went, or that gasket for the little nub that comes off the throttle body for the air regulator.

 

Where do you guys get new throttle body gaskets. I don't see any on MSA's site.

 

Well hopefully this and my new set of plugs will finally clean this mess up.

[DuoWing]

Made a new throttle body gasket, I can't seem to find a vacuum leak now. So that's a plus, but the car still seems to be the same. About 16-17inHG of Vacuum at idle. It seems to vary depending on the day. Still starting and running issues. Unhooked all the injectors and sat there cranking the car. The tach was reading a dead steady 400rpm and my vacuum gauge was reading a steady 3inHG while cranking. Let the car warm-up and then pulled the plugs and did a compression test.

 

1 - 135

2 - 130

3 - 135

4 - 135

5 - 135

6 - 130

 

This is a little disheartening, but the motor has yet to be run on the road and actually get up to full hot operating temp. So maybe those numbers will come up once the car has gotten hot instead of warm. I squirted oil in cylinders 1 and 2 and redid the test and got 140 for cylinder 1 and 135 for cylinder 2. I didn't bother squirting oil in the other cylinders.

 

My MAF may possibly be dieing or something with my wiring.

 

While idling I started pulling the injector plugs again. I noticed it seemed like upon disconnecting injector number 5 the engine would barely change, or it was such a slight change that it was barely noticeable. Need to go get noid lights now to test and see if the injector is being triggered. Every other injector when disconnected at least made a noticeable difference in the idle. I then went ahead and tried pulling spark plug wires one at a time all made a noticeable difference except number 5. Which either was no difference or just a very slight difference. If 5 is barely firing could this have an effect on my vacuum and cause enough of a difference in the idle? When I had injector 5 unplugged I tried revving the engine and it seemed to make no difference. I tried restarting the motor with plug wire 5 unplugged and it seemed to make no difference in the way it started up.

 

It seems to me that the engine itself has nothing wrong, but that it's more in the electrical or the injection. I guess I'll have to pull the injectors now and test them all. Perhaps the injectors from sitting for awhile got something in them that caused them to start clogging? Maybe it's time to just get a larger set of injectors? SVO injectors?

 

Idle fuel pressure is about 30psi.

 

I'm just getting really frustrated with this. I don't know why I'm having so many issues.

[DuoWing]

Well I'm about at a loss here. I'm thinking it's gotta be a vacuum leak I've failed to find, or something with my wiring. I pulled the rail up today and hooked up the old 280Z pump to it, left the pressure regulator connected along with the return line to the tank. I stuck the feed for the pump in a fresh tank of gas and connected it to the battery. Pump pressurized the rail up to 40psi which is the max my regulator is set at without vacuum on it. Used an old coffee can and a cut fuel injector connector from the 280Z harness and hooked that up to the battery. Went one by one connecting the different injectors. They were all spraying in kind of a cone pattern. Should it be in a straight line, but either way the spray looked all pretty much the same amongst all 6 injectors. They didn't spray intermittent or anything.

 

So the injectors check out, there's not a head/headgasket/valve issue as far as I can tell. At least judging by the compression tests. The fuel pump seems to be fine as the rail pressure seems to hold steady. Spraying starter fluid all over the place hasn't seemed to reveal any other problems. I've got spark at all the plug wires at least when hot and running I do. The only codes the Z31 ECU is giving me is Fuel Pump, Fuel Temp Sensor, and Knock sensor. These were codes I'd get when running my 280ZXT. Maybe I'll have to pull the stock unmodified 87T ECU out of my Z31 and see if that makes a difference. I know the car pretty much won't start with the MAF unplugged and even if it does it won't rev past 2000 or 2500RPM I forget which, but revs fine when plugged in. I'll have to try starting it with the CHTS unplugged next. I guess I'll just have to get out the multimeter and just start testing things.

 

Any other suggestions? I just can't figure out why it seems to run fine once warm.