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Z31/300zx ECU/MAF to 280ZXT problems


edwin

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Need help please. I attempted to do this swap and I think I did everything right.

 

First It won't start. I had no spark and flooded my plugs. Figured it out. Fixed that. changed my plugs.

Car runs...

But know no matter how the ecu is tuned I am running rich. or is it something else. What am I missing...

Right know the FPR is at zero psi.

I triple check and my MAF it's working correctly. The thermo-switch is fine. everything that tells the ecu what to do is working.

 

My plugs are black and I have oil spitting out of my exhaust.

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I think I saw a similar post on another forum...?

 

I don't believe that your car will run with no pressure at the fuel injectors. You need pressure, quite a bit, to squirt the gas out of the little holes at the end of the injectors, when the ECU tells them to open.

 

How do you know the FPR is at zero psi? Do you mean the regulator is set to zero or do you mean the fuel pressure is measured at zero?

 

Zero psi fuel injection doesn't make any sense.

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Or the bottom of the manifold has so much fuel pooled in it that it's running on fumes and residue.

Seen JeffP's car do that for 5 minutes with no fuel pressure whatsoever.

 

An aside: What gauge are you using. Cheap gauges are never reliable as a measure of fuel pressure. They are more for show than anything reliable. Where is the gauge and where did it come from?

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Or the bottom of the manifold has so much fuel pooled in it that it's running on fumes and residue.

Seen JeffP's car do that for 5 minutes with no fuel pressure whatsoever.

 

An aside: What gauge are you using. Cheap gauges are never reliable as a measure of fuel pressure. They are more for show than anything reliable. Where is the gauge and where did it come from?

 

Hey guys, thanks

The fuel pressure regulator is set at zero. It is positioned at the end of the rail. I have a Pallnet fuel rail and a gauge he supplied

for it. Maybe my FPR is bad. I will open up the manifold and suck up any residue.

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5 minutes worth of puddled fuel. That's a puddle. Didn't think of that. I did think cold start valve stuck open though. Do you have one connected? You mentioned the thermotime switch.

 

You didn't actually say that the gauge showed zero psi. When the car is running, the gauge needle on the rail is at zero?

 

And you have the FPR adjustment stud backed all the way out?

 

You should either start the car or run the fuel pump and turn the FPR adjustment stud in to increase fuel pressure. If the FPR and gauge are working, the gauge needle will move up. This would be a good test of whether or not your gauge and FPR actually work correctly and that your fuel lines are connected right.

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5 minutes worth of puddled fuel. That's a puddle. Didn't think of that. I did think cold start valve stuck open though. Do you have one connected? You mentioned the thermotime switch.

 

You didn't actually say that the gauge showed zero psi. When the car is running, the gauge needle on the rail is at zero?

 

And you have the FPR adjustment stud backed all the way out?

 

You should either start the car or run the fuel pump and turn the FPR adjustment stud in to increase fuel pressure. If the FPR and gauge are working, the gauge needle will move up. This would be a good test of whether or not your gauge and FPR actually work correctly and that your fuel lines are connected right.

 

It's at zero at idle and the gauge needle moves when I increase pressure. So I assume the FPR and gauge is working.

Cold valve is not stuck open. I had my manifold welded up and I don't have one anymore. So Thermotime swicth shouldn't be an issue? or will it still send a signal to the ECU? causing other injectors to spit out more fuel. I don't think so but I had to ask.

Maybe my FPR should be at the front of the rail? I hear it don't matter...

Thanks again!!!

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That really only leaves injectors opening for way too long, or a bad gauge, from my limited knowledge. If the gauge is mounted right on the rail as the pictures I've seen of the Pallnet rail show, then the pressure you see is what should be at the injectors. It sounds like your setup is plumbed correctly. Might be worth connecting another gauge to the inlet side of the rail to verify that the gauge on the rail works right.

 

In your first post you mentioned tuning the ECU. Is the 300ZX ECU tunable? How are you tuning it? That information might help someone understand your issue. I don't know anything about them.

 

I would post a picture of your rail, gauge, FPR and MAF setup and tell people how you're tuning the 300ZX ECU.

 

Good luck.

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These cars will run for 5 min on puddled fuel.

 

The stock ecus on 280zx will fuse the injector drivers and continuously hold the injectors open if you jump start the car with the polarity wrong.

 

After this has happened, I've seen more than one dealership mechanic run the car with the fuel pump off and/or injectors disconnected because of the puddling caused by the fused drivers.

 

It can and has happened.....just not sure it has happened here but it could have.

 

Years later, at Blue Streak's ecu rebuilding facility, I ran into my fair share of fused injector drivers on these ecus.

Edited by HowlerMonkey
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These cars will run for 5 min on puddled fuel.

 

The stock ecus on 280zx will fuse the injector drivers and continuously hold the injectors open if you jump start the car with the polarity wrong.

 

After this has happened, I've seen more than one dealership mechanic run the car with the fuel pump off and/or injectors disconnected because of the puddling caused by the fused drivers.

 

It can and has happened.....just not sure it has happened here but it could have.

 

Years later, at Blue Streak's ecu rebuilding facility, I ran into my fair share of fused injector drivers on these ecus.

 

Fused injectors wow never could of thought of that. How do I fix that? I know for sure I jump started the car so it is posible.

I tune the ECU well not me... Bernard tuned the ecu for me with Nistune. He has done it many time so I feel it is 98% correct. And he has tried many things to get it not to run so rich. I feel it's more a mechanical error.

Any other thing I should check? Thanks

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Is it oil, or is it sooty goopy solventized gasoline that looks like oil?

 

My question was never answered, other than an ASSumption that the 'gauge reads right'...

 

Likely something is incorrectly wired, and the ECU is in "Limp Home" mode---does it rev above 2200rpms?

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