Help! Im lost

[jamison]

Hey guys I havent been on here for a while... I have a 1990 C4 with and automatic transmission. My car is having trouble starting after it has been warmed up. It starts fine cold and if I turn it off for a minute once its warm it will start right up. But if it sits for a few minutes it seems something gets hot and causes it not to start. To clarify it will turn over, just not start. Ive already done a bit of research and found out my fuel pressure regulator went and flooded my car including the intake plenum and throttle body. I put in a new regulator and i'm back up to 39psi and its holding pressure just fine. I don't have any leaky fuel injectors. Ive replaced the fuel filter and checked to make sure the return line was clear. I just replaced the cap, rotor, coil, ICM, and the ECM. And its still having the same issue. When the car is turning over it is getting spark but it acts like its flooded even though its not. I'm starting to think a something got damaged from the fuel that flooded into my intake. So I tried the manifold air temp sensor because it could be going faulty when warm and causing my timing to become retarded. But that wasn't it either. So now I am pretty much lost here... I don't know if there are any sensors that could be bad to cause it not to start when hot? Oh also to inform you I have a diagnostic scanner and no codes are showing up.

Any help here would be much appreciated. Thanks!

 

[ex-x-fire]

When it doesn't start, make sure you have injector pulse(noid light).
Do a check on the coolant temp sensor.

 

[jamison]

Injectors and coolant temp sensor checked out.

Im thinking the MAP sensor might be failing. Is there anyway to check it?

 

[vetteoz]

have you pulled the codes to see if anything showing up?

 

[ex-x-fire]

Ohm the injectors when its hot.

 

[boomdriver]

Hey guys I havent been on here for a while... I have a 1990 C4 with and automatic transmission. My car is having trouble starting after it has been warmed up. It starts fine cold and if I turn it off for a minute once its warm it will start right up. But if it sits for a few minutes it seems something gets hot and causes it not to start. To clarify it will turn over, just not start. Ive already done a bit of research and found out my fuel pressure regulator went and flooded my car including the intake plenum and throttle body. I put in a new regulator and i'm back up to 39psi and its holding pressure just fine. I don't have any leaky fuel injectors. Ive replaced the fuel filter and checked to make sure the return line was clear. I just replaced the cap, rotor, coil, ICM, and the ECM. And its still having the same issue. When the car is turning over it is getting spark but it acts like its flooded even though its not. I'm starting to think a something got damaged from the fuel that flooded into my intake. So I tried the manifold air temp sensor because it could be going faulty when warm and causing my timing to become retarded. But that wasn't it either. So now I am pretty much lost here... I don't know if there are any sensors that could be bad to cause it not to start when hot? Oh also to inform you I have a diagnostic scanner and no codes are showing up.

Any help here would be much appreciated. Thanks!

Ignition module ....disassemble the distributor and look for damaged wires inside going to the module, and at the cap/dist housing edge where the rubber insulator block sits. Wires on the cap & coil. Clean all the pins and plug-ins on the dist base.
Wires inside often get pinched or broken. The module can be tested at most parts stores and cheap to replace. Use a WAD of dielectric grease under the module when re-installing. This is for heat sink and might be part of your problem.

 

[John Robinson]

The one thing you have not checked or replaced is the TPS. I had one that did not code but was telling the ECM the engine was flooded and so the ECM shut down the fuel.

[FONT=&quot]Hope this sheds some light on the tps for you[/FONT][FONT=&quot] [/FONT]

[FONT=&quot] [/FONT]​

[FONT=&quot]

[/FONT]

[FONT=&quot]Throttle Position Sensor (TPS)
Copied from 1993 Service Manual[/FONT]​

[FONT=&quot]The Throttle Position sensor (TPS) is a potentiometer connected to the throttle shaft on the throttle body. It is a potentiometer with one end connected to 5 volts
from the ECM and the other to ECM ground. A third wire is connected to the ECM to measure the voltage from the TP sensor. As the throttle valve angle is changed (accelerator pedal moved), the voltage output of the TP sensor also changes. At a closed throttle position, the voltage output of the TP sensor is low (approximately .5 volt). As the throttle valve opens, the output voltage should be approximately 5 volts.

By monitoring the output voltage from the TP sensor, the ECM can determine fuel delivery based on throttle valve angle (driver demand). A broken or loose TP sensor can cause intermittent burst of fuel from the injectors and cause an unstable idle, because the ECM detects the throttle is moving.

If the TP sensor circuit is open, the ECM will set a DTC 22. If the TP sensor circuit is shorted a DTC 21 will be set. A problem in any of the TP sensor circuits will set either a DTC 21 or 22. Once a DTC is set, the ECM will use a default value for TP sensor, and some vehicle performance will return.

A personal note, when my TPS failed it DID NOT set a code other than to tell me the ECM was bad.


[/FONT]

 

[jamison]

I think I found what is wrong. After warming the car up again today and trying somethings out. I heard a bubbling/hissing type of sound while the motor was off. So i traced the sound to my rear crossover tube on the fuel rails. The O-ring on the fuel pressure regulator is shot and letting gas very slowly out. This is the first time ive ever heard it before so im wondering if it was doing this for a while and it finally went. I'm guessing the O-ring went when my fuel pressure regulator went and was pushing 75psi, which was probably too much for the O-rings. But hopefully this is whats wrong.

 

[boomdriver]

I think I found what is wrong. After warming the car up again today and trying somethings out. I heard a bubbling/hissing type of sound while the motor was off. So i traced the sound to my rear crossover tube on the fuel rails. The O-ring on the fuel pressure regulator is shot and letting gas very slowly out. This is the first time ive ever heard it before so im wondering if it was doing this for a while and it finally went. I'm guessing the O-ring went when my fuel pressure regulator went and was pushing 75psi, which was probably too much for the O-rings. But hopefully this is whats wrong.

That might contribute but its not enough to starve the motor for fuel. It would have to be leaking like a garden hose.
If anything, the regulator might be leaking internally and allowing most of the pressure to return to tank. This happens inside so the pressure shows up about right, (40+) and holds pressure but most of it leaks past the valve back into the return system. You could pull the return line and see if the flow was excessive back to tank.

You have to take the Fuel regulator apart and examine the disc/spring/seat assy to see if that was leaking past or if the valve was seated properly. If you suspect an internal leak from a burr or misaligned valve/seat, some very gentle polishing of the matching surfaces with 1000 or 1500 gt paper might knock down any burrs or edges that are preventing a good seal.
Its just as easy to buy another regulator with the internals and a mounting block.

 

[jamison]

Ok I pulled everything off down to the fuel rails and found out the regulator mounting block is shot. The crossover tube that is leaking was doing so because the housing that is supposed to be holding the O-ring is gone. The mounting block looks as if it has been eaten away. So now I need a new mounting block for the fuel pressure regulator.

Do you know of anywhere i can get one?

 

[joe paco]

Jamison: I'm curious. The photo of your 90 shows a concave rear with rectangular lenses, either a 91 or later, or a 90 Z1R. Am I confused?

 

[jamison]

It's an Aftermarket rear bumper. I bought the car with it like that. It's just a stock 90 with the l98 motor.