I finally picked up a fuel pressure gauge kit yesterday to check pressures. Car had been running terrible again and lean O2 sensor codes 44 and 64 had popped up simultaneously. At first i thought it might be the Idle Air Control Valve as it said in FSM that it could set those codes.

Now that I checked pressure here is what I found. Last night my first readings with key on only 15psi. Started vehicle and had innitially 35psi, this is below the 41-43 range it should be. as the engine ran for a few minutes it dropped and engine sputtered and ran rough with pressuresdropping to 12-15psi and engine died out. Could not get it above 20 at various rpm's. My first thought was that the screen in the regulator was plugged. So since I had a new one I changed it, but screen looked ok and it seem to hold vaccuum and left new one on. I also ruled out relay as I had intial pressure when I turned key on. Had a problem with a couple injectors leaking after putting rails back on, so took the left side back off and used extra vaseline on o-rings and reassembled and left set 'til this morning to check pressures.

Turned key on this morning and had 15 psi twice before starting. Started and went to 20 psi. remained steady for a couple of minutes than began droping and engine sputtered and died. The fuel filter has about 3000 miles on it, don't feel that is a problem. So that leaves the fuel pump and strainer. It was supposedly a fairly new pump less than 5000 miles high output Granatelli pump. Obviously I am not getting enough pressure to the regulator and volume, so is that where the problem might be now?? Any othe ideas that I am overlooking??

Thanks,

Scott

 

Could the pump have low voltage and cause it to run less pressure? Will a bad relay cause lower current to go to the pump?

Thanks,

Scott

 

Update - Put new filter in but all I can get for pressure is 35 lbs. I may pull pump back out and put a piece of hose on that pulsator. Not sure if I could be losing 6 lbs through that or not. Did not take it out on the road to check.

scott

 

After talking to Jon Banner again as I could not get my pressure upto the 43 psi, Pump was putting out 70psi so he said it had to be in the regulator, even though it was new from NAPA and oem replacement. I bought a Aeromotive #13106 for the LT1. Bolts right in and the cover fits on ok to. after checking for leaks I started it came right upto 44psi on my gauge. I backed it down to 43, but now I am wondering if the setting they had it for may have been correct and maybe my gauge is just off a pound. Running my first tank of fuel through to check mileage and it appears on the computer to have improved. Not sure what things can be done to tweak it to get a little better mileage yet.