I've been trying to run down a miss on a 383 SuperRam setup, and we've been encountering lots of variations in data logging and trying to burn a custom prom. I think I've stumbled onto something thought that may be related.....

Just for grins and piece of mind, and after installing the 3rd set of plugs as well as plug wires in the first 1100 miles on the new engine, I decided to check that the fuel pressure was still set at 43PSI.

I hooked up a test gauge to the Shrader valve, and turned on the key. It immediately jumped to 43, then dropped off to 40 as the fuel pump shut off.

The interesting part was how quickly the pressure dropped after that:
5 secs after pump shut off: 40PSI
15 seconds: 35 PSI
45 seconds: 30 PSI
1 1/2 minute: 25 PSI
8 minutes: 20 PSI
25 minutes: 15 PSI

Sounds like the pressure is bleeding off very quickly, isn't this too quickly? I noticed when I put in the 3rd set of new plugs yesterday that at least 2 cylinders seemed to be running pretty rich while several others looked fine.

I'm looking for thoughts/suggestions on this. The injectors are 24# Holley's that ran about 20 minutes in a 454 HO I had before I switched to 30's in that old big block MPFI setup. BUT --- the "new" injectors set on a shelf for 3 years in the original Holley clamshell package. Maybe they are dirty and that's causing the leak down? I did use all new O-rings on both top and bottom when I installed then with the 383 swap back in May.

I look forward to suggestions/ideas from the wealth of knowledge here on these boards.

- Vern

P.S. - Yeah, I've done the searching, and plan to do the "pinch each fuel line and see when it still drops" test tomorrow evening after work. Just looking for other ideas. I'm not looking forward to having to pull that SuperRam to swap injectors or my Holley AFR....

 

Try pinching the return line then see if the fuel pressure drops.

A bad FPR will bleed pressure off at an abormally fast rate, although I am not sure if it is that fast.

 

If you will do a search for slohand, you will see that he has been having a problem with the Holley AFPR bleeding down almost instantly. He contacted Holley about it and was informed by their technician that they were designed to do that. Sounds like to me, he is now in the process of switching to a different brand AFPR.

 

i dont think that the holley afpr was bad

it would mean the diafram was messed up some how

 

Well - Trickster - you were right on the money with this one. AGAIN!!!

It's the Holley AFPR, and Holley still says they're designed to do that. So, I don't have a fuel pressure or leaking injector problem - I just thought I might have. I clamped off the supply line, and the pressure still dropped very quickly. So the pump backflow valve was not the problem. Pressurized it again, and clamped off the return line, and she held the pressure just fine. So the injectors are not a problem either. It was just the Holley AFPR doing it's "safety thing" and depressurizing the fuel rail for me. Somehow I'd almost bet the "safety thing" is more of a cost based thing, but I could be wrong. Maybe it's "liability conscious" instead....

Regardless, I eliminated this from my list, so THANKS TO ALL!!!!

Have a Great Day, My Friends.


- Vern