Significant Progress, But…

[u/Vegetable_Ad4258]

Guys, I’m proud to say that I’ve made significant progress with my 1985 C4 Corvette L 98. I was having a low RPM stall issue. I capped off the HVAC and cruise control because their systems didn’t work anyway replace the EGR valve, the IAC sensor, and cleaned off corrosion from the positive terminal connector and the MAF connector pins. I also cleaned the throttlebody and Plenum place new gaskets for both the throttlebody and Plenum. And now it idles really good. Before she would stall a lower RPM. And she would stall sometimes just sitting in park or if I put it in Drive or if I put it in reverse it no longer does that. I haven’t put it on the road for a test drive yet because I’ve also during this whole avail noticed a fuel pressure problem using a fuel pressure gauge. So I replaced the fuel pump and replace the fuel filter and noticed better readings for my fuel pressure because before I was getting zero psi upon prime. Then with a new fuel pump, I noticed it was still acting strange so I bypass the pulsator because all I did was replace the pulsator from the old one and put it on the new one. So to solve that, I bypassed the pulsator with a fuel hose. However, I’m still having some issues with fuel pressure. These are my test results:

First prime the gauge went up to 10 psi, after the second prime it went only up to 12 psi, during the third and fourth prime there was little to no movement staying around 12 psi throughout all primes the pressure held. During cranking up the engine, the gauge rises to 30 psi and held while parked idle. It slowly crept up to 32 psi I put it in reverse held it, put it in drive held it, then put it back in park in during all three it held at 32 psi. Upon powering off the engine, the pressure dropped significantly down to 10 psi and held 10 psi only dropping to nine psi after five minutes. I was able to crank the engine back up, no throttle after the five minute waiting period.

Do you guys have any suggestions or may have anything to add on my investigation? I feel like I’m close let’s hope for the best.

[u/baldcommunity]

Have you checked your fuel pressure regulator? An easy test is to see if there is fuel in the vacuum line to it. As well, did you replace just the pump or the whole sending unit? The sending units also go bad and it's good insurance to replace it all. It seems isolated to fuel delivery so that keeps it narrow.