Hey everyone, I have an 97 Z28 that after you park and let it sit for a couple of minutes it is hard to start. Sometimes it won’t start unless I put it in the clear flood mode by holding the pedal to the floor. I checked fuel pressure and after a couple of seconds it starts to drop slowly. I tested the IAC and it is within ohm range. It has new plugs, wires, and ignition coil. I put 2 bottles of the Seafoam injector treatment in it thinking it could be leaking injectors. Is there a way to test the fuel pressure regulator? Thanks in advance.

 

after car runs and you shut it off, pull the vacuum nipple off the FPR. If any sign of fuel in it...the FPR is bad. Symptom, prolonged cranking.

If fuel and FP check out, move on to ignition.

 

Put a test gauge on the Schrader valve to check fuel pressure.Turn key to “RUN”. Fuel pump should prime for 2 to 3 seconds and shut off. At moment of shut off, pressure should be at least 40 PSI. Then, fuel pressure should hold, or drop slowly. If pressure drops quickly, could be:

- faulty check valve in pump
- leaking injector(s)
- leaking line, including flex line in tank
- leaking fuel pressure regulator (either torn diaphragm (leak to vac line), or shutoff not sealing

To to a quick check if no fuel pressure gauge, cycle the key rapidly back and forth between RUN - OFF - RUN several time. On last cycle, continue to turn key to “START”. If engine starts quicker, you have one of the above problems.

The fact it starts quicker in “clear flood” (accel pedal on floor) would tend to indicate leaking injector(s), or fuel pressure regulator.

 

Thank y’all for the reply. I will try this and let y'all know.

 

Hey everyone, I pulled the vacuum line off of the fpr, and there was no signs of fuel. Is there a way for me to check for leaking injectors ? Their Bosch 30lb injectors and the factory clips don’t work on them and the fuel rail won’t come up enough for me to see if they are leaking. Thanks in advance.

 

The fuel pressure test I described in post #3 is the first step in looking for leaking injectors. Guess you missed that.

If the pressure holds after the pump shuts off, the injectors are not leaking. If the pressure drops rapidly, you have one (or more) of the four causes listed. Then we take additional steps. Unfortunately, lifting the injectors and looking for drips is the best way to check.

 

I did see your post on #3. I checked the fuel pressure and it went up to 40 psi then dropped slowly. I still think it could possibly be a leaking injector.

 

Should have included that info in your initial response.

 

So anymore ideas ?

 

Is the coolant temp sensor in the water pump accurate?

4th Gen LT1 F-body Tech Articles

If the PCM thinks the engine coolant temperature reads lower than it actually is, it may set the starting A/F ratio too rich.

 

It has a 160 thermostat. My scanner is showing 180 degrees operating temperature. I can’t remember, does the PCM receive the temperature from the block or the one on the water pump?

 

PCM reads 2-wire sensor in water pump housing, gauge reads 1-wire sensor in driver side head. That's all explained in the link I included.

The scanner indicates 180°F at the time you attempt to restart the warm engine, and have delayed start? If so, that is not the cause of the problem.

Who tuned it for the 30 #/HR injectors? What mods do you have that required larger injectors? Are these genuine Bosch injectors, or are they the Chinese counterfeits from eBay, for less than $100/set?

 

PCM for less tuned the car. The mods are LE aluminum heads, Lunati Cam 227/235, Long tube headers. I bought the injectors 2 years ago on eBay, rebuilt genuine ones I believe.

 

From the posts I've seen here and on several other LT1 related forums over the last 10 years or so, the pcm-for-less tunes are no longer reliable. I would question the injectors.

 

Yes I have heard the same things, unfortunately wasn’t active on any forums at the time of the build. I would look at getting new injectors. Do y’all have any recommend brand of injectors?