ChevPasmore
Newbie
Fuel pressure was at 12psi steady when I checked 2 weeks ago. If I recall the PSI should be between 9-13psi. I thought the throttle body was the same for the 5.0 and 5.7 engines. The 7.4 ( 454 ) I believe was different. But I could be wrong. All the information I have is that the engine came out of a 1995 Silverado, but kept the harness of the 1990. So I am assuming they slapped the intake + tbi on from the 1990 to the 95 to keep the sensors in the same location ( not sure if they are different or not ), Maybe everything on the engine is from the 95 and they didn't swap out the ECM/Prom. I will be tearing the glove box apart and will get the 4 digit code tomorrow. If it is not "calibrated". How do I go about that? I just want this damn thing to run haha. I have a 2000 quad cab dually 4x4 GMT400 that I daily but still would like this one operational.what does "fuel pressure is good" mean? what psi is it? Just because injectors are firing and the spray pattern looks good, does not mean they are good or correct. Pull out the ECU and open the small cover, the memcal will have a 4 digit code on it. Post that here and we can see what calibration is in it.
I got my first TBI vehicle was 20, 1989 Caprice ex-cop car w/ 5.7L. For starters it "ran good", but as I discovered after a year or so of owning it, it had been fixed improperly. For starters someone put a 4.3L TBI on it with 4.3L injectors. Putting the correct injectors in it made a huge difference in how it ran. Then I changed the fuel pump (this was before I got a fuel pressure gauge) and upgrade to a TPI pump, again huge difference. fastfpward about 4 years I moved to an area where annual emissions testing was required and car failed miserably. At this point I fonally invested in a fuel pressure gauge and a datalogger. Here's what I found:
- fuel pressure was 8-9 psi (technically in spec)
- the BLM were maxed out, so it was running lean
I made the fuel pressure regulator adjustable and got the pressure up to 13 psi. Made a big improvement on how it ran but still had maxed out BLM's. As a hail marry i went to the wrecker and got some injectors out of a 5.7L and threw them in. BLM'S immediately went to 128 +/- 2. Perfect. Passed enissions testing with flying colours. Car made better power, smoother idle/exhaust tone than it EVER had since I bought it. This why I always verify these things and how a fuel pressure gauge and scanner/datalogger are required for proper EFI troubleshooting.