fuel pressure guage

[playsdixie]

my 85 vette starts hard cold then is fine....I bought a fuel pressure guage to check....pressure is 38 # with key on....now, how long should the system keep that pressure?....everything is pointing to the cold start injector....would that throw a code"""????

 

[Hib Halverson]

38 psi is in the "good" range for fuel pressure. One the pump goes off, does the pressure hold or drop very, very slowly?

When you say "everything points at the cold start injector", how did you arrive that that conclusion?

Did you run the Cold Start Valve test on page 6E3-31 of the Service Manual or are you "guessing"?

 

[playsdixie]

fuel pressure holds for 15-20 minutes....service manual is being shipped. with117,ooo miles, just thinking I could use a new set of injectors. going to run a test this weekend to see if I can eliminate fpr or fuel pump leakage...
also going to use the paper clip to see what code it throws at that 1st startup of the am...after the long crank, it starts with the service light on....if I restart it, light is out and car is fine all day....pretty sure it's going to be a leaking injector.. thanks for the help.

 

[playsdixie]

codes

pulled the codes....34 &54....fuel circuit low voltage....any ideas?

 

[Hib Halverson]

Based on what you've posted, it's unlikely you have a fuel pressure problem but DTC54 is a fuel pump electrical fault so there may be a problem somewhere in the fuel pump's electrical circuitry. The Service Manual you have coming has a whole page of troubleshooting data for that code.

34 is a MAF sensor fault.

I'd solve those two codes first before I'd assume you have a cold start valve problem.

You don't have any leaking injectors because your fuel pressure holds. I there were leaking injectors, fuel pressure would drop quickly.

 

[playsdixie]

Based on what you've posted, it's unlikely you have a fuel pressure problem but DTC54 is a fuel pump electrical fault so there may be a problem somewhere in the fuel pump's electrical circuitry. The Service Manual you have coming has a whole page of troubleshooting data for that code.

34 is a MAF sensor fault.

I'd solve those two codes first before I'd assume you have a cold start valve problem.

You don't have any leaking injectors because your fuel pressure holds. I there were leaking injectors, fuel pressure would drop quickly.

installed a new fuel pump and cleaned the maf....car starts in an instant and no codes......after 100,000 figured it could us a new one. also cleaned the throttle body thoroughly....it was very bad...also found a small vac leak removing the vac line from the throttle body...good advice for any c4 owner....if cars running rough, and you havn't started by cleaning the tb....you've missed the first step..... thanks so much for all the help...