2000 Blazer 4.3L 4 dr 132000 miles.
Idles gotten a bit rough, truck has been harder to start lately, cranks for a while before firing. lean codes for bank 1 and 2 come and go. I changed my plugs, problem persists!

On a whim, I checked my fuel pressure today at the Schroeder valve under the hood. Here are the numbers.

Initial Key on engine off:55psi

Key on engine running: around 50psi, fluctuating rapidly +/- 1.5psi

Highest pressure I was able to achieve cycling key from on to off was around 60psi.

My question is the leak down. The gauge held steady last year, but now drops off fast. will drop down to 0psi 30 seconds after pump shutoff.
Short of isolating the pump at the filter, as I haven’t the attachment for the gauge right now, where is a leak like that most likely to be? Pump, injectors, or FPR? In my searching, I didnt see anyone mentioning a system that leaks THAT fast. Thanks for the help!

 

My 'guess' is that its the pump, but that is all it is, a guess. Isolating the fuel pump will tell you for sure whether or not the pump is at least contributing to the problem.

 

yea. Test the fuel pressure at the inlet of the fuel filter with a pressure gauge. It needs to ping above 55 (60 is ideal) and hold the pressure. if its low,the pump is the problem,if it holds fine then id say it would be a leaky regulator.

 

Im searching for the thread that details the parts needed for the adapter kit/shut off valve to isolate the pump.

 

Bottom of the fuel pressure tech article.

 

New info:

I noticed my check engine light hasnt been coming on when I put the key in the run position, so I hooked my scanner up and alas! Ive also got a P0301, misfire in #1 cyl. Also of note, my 02 sensors are reading differently, one was at something like .02 and the other was at something like .08, though I could be wrong. They were definately different, though. Im going to pull the #1 plug and smell it for gas. Could a leaking injector be the culprit of all of this, save for the odd CEL malfunction?

 

Freeze frame data:

tps% 13.7
rpms 1581
load% 17.2
maf gr/se 28.95
map kpa 59
coolant temp 194
st ftrm1 4.6
lt ftrm1 23.4
st ftrm2 4.6
lt ftrm2 25.0
st ftrm3 10.9
lt ftrm3 -71.7
lt ftrm4 50.7
st ftrm4 5.4
veh. speed 22
fuel system 1 closed
fuel system 2 closed

From my actron cp9180.

Ive no idea what these fuel trim numbers mean, but it obviously doesnt look right...

 

Maximum fuel pump output pressure on the OP's 2000 4.3L must be between 75psi and 108psi. It must remain above 55psi for 10 minutes after the pump shuts off.

 

New development: Removal of the throttle body allowed me a small peak of the fuel leak inside my plenum. Looks like the FPR is leaking into #5 and #6, shes clean as a whistle in back! Im just going to replace the whole spider assembly, doesnt pay to do all the removal for a FPR just to possibly have to do it again soon for the injectors. Ive got the upgraded injector kit, mounting bracket, and gaskets, but I have a few questions.

1-What size are the nuts that hold the fuel lines are near the distributor/firewall? My wrenches are all too long to fit back there to even check for fit, Ive got to buy some stubby ones.

2-Am I to assume that these new injector's just slide right down where the poppets were, without any sort of clip to hold them in place? My parts guy couldnt find anything about new clips, or O-rings, but if the poppets are held in place by those black clips, it stands to reason that the new ones should also need some method to keep them secured.

Your continued help and advice are greatly appreciated Captain Hook and swartlkk, and everyone else. Thanks guys.

 

1. Stubby open end to hold the line, and a line wrench to loosen the fitting. IIRC 15mm, but better double check

2. The new injector nozzles snap into the ports similar to the old poppet nozzles, but don't snap them in until you have all of them routed correctly, (they're a bitch to remove once snapped in). Read the instructions carefully, some of the lines cross and routing must be correct. The lines are stiff, don't kink them.