Some of those pressures are low enough to cause problems but lets start with the classic test. pressure at key on/no start and then the pressure at ten min still with key on.

You seem to be getting inconsistent results so do this three times, bleeding the pressure to zero in between attempts.

Then we will devise a driving test.

George

 

Ok, will do. Will post updates later today hopefully.

 

Good afternoon George, I attached photos, not sure what order I attached them in,



but, as usual the photos have text on them to explain which each one is. Let me know how you would like me to proceed. Thank You.

 

You have a fuel pressure problem. Now lets find out if its in the tank or the intake. Follow the instructions in the FPT sticky for doing these same reading at the output of the fuel filter:

HOW TO: Check regulated fuel pressure, pump max output, & leakdown - Blazer Forum - Chevy Blazer Forums

George

 

Ok, I had to rig some stuff up in place of getting the proper fittings order so was a little trial and error but from what I can tell, with the gauge purged key on and left on (pump was only on for the prime but left key on for GP, it hit around 102 - 104 Lbs. left the key on and I think I had a small bleed but not enough to see or feel a drip but over 10 minutes +/- some seconds for getting my decrepit *** up and down between key operation and watching the gauge lol and the pressure dropped to 60.5 but as that article said it stayed above 55 Lbs. and if I get the right fitting in a timely manner I would imagine it probably only has about 1-2/3's the loss. How do you want me to proceed? P.S. I did finally just call the distributor, and they are supposedly just sending out a replacement Delphi pump just in case this one is causing a problem, supposedly gets here tomorrow at some point. I probably wouldn't bite the task of replacing it until the weekend maybe.

 

Would I be incorrect in thinking I would see the pressure needle going haywire when I am driving and get a fit of the problems I was describing or is the pressure really sensitive enough that a pound drop would cause these weird intermittent problems. I have since discovered if it's not doing it bad at idle I can make it replicate the problems when I go from moving in reverse and drive at lower speed, especially when I first touch the accelerator off idle and also when I hold the break while accelerating or flooring it from a dead stop. All I am sure of at this point is this is my only vehicle right now and it is murdering my wallet with the mileage its getting. before the tune up I was down to 13-14 MPG leading up to doing the tune up which is why I figured I'd just do it especially since the wires were in such shotty shape before that and this problem getting increasingly worse i would get 15.5-15.9 MPG pretty consistently. sorry not sure if any of that knowledge helps out or not.

 

Thats a good strong pump with a good initial charging pressure, That said, thats quite a bit of loss during the 10 min bleed down but is in within spec and should be plenty to run the truck properly. Its almost 20 psi higher that the reading at the intake/shrader after the leakdown. This suggests a leak in the intake or with an injectors(s). There are a couple of different ways to go with this:

1. If there is an accessable section of rubber hose in the return line to the tank after the intake manifold, pinch that off carefully without damaging the hose like with a fuel line clamp and then see if the 10 min leakdown at the shrader improves. If so then its the fuel regulator. If not then its a leak in the lines in the intake plenum or injector(s). If its the regulator then you can replace that, if not then...
2. There are ways to test the injectors for even fuel output using a scanner or dedicated box to pulse them all and measure the pressure drop. Most here dont have that capability but it would offer more information. If not...
3. Youll have to open up the intake plenum and look for clean shiny areas indicating a leak in the plumbing. If you could not do 1) before you can do it now. Some pull the injectors out to look for leaks after charging the manifold at key on but that can be destructive because things can break and everything my not go back as required.
4. Replace the regulator and/or spider using the parts cannon. Unfortunately there is a lot crappy parts out there and failure rates can be high. With new AC Delco spiders not available the preferred choice these days appears to be an echlin unit buts its pricey and there is not a lot of experience here with that unit.

Note that if you are going to open up the intake manifold you may want to consider handling the LIM gaskets while your in there.

George

 

Pressures in the 40's are too low for the truck to run correctly, especially if these are the original injectors. What year is this truck?

George

 

Ok, I will look for the return, not sure where it comes out at on this but Ill hunt it down and try that, so with the return blocked, do you want me to drive it and see if the problems go away or take more test port pressure readings? it was a lot of drop but I am certain a fair amount was contributed to the rig I had to use to adapt everything leaking ever so slightly.

 

its a 2000 with 161K and as far as I am aware it's the original injectors. Lol should I scrap it all and stick a quadrajunk on it? lol at least those are much easier to remove when needed than what I've heard the spiders are lol