Hello,
I have a fuel pressure problem that is driving me NUTS! The vehicle is a 2001 Chevy Blazer (4.3 Vortec V6) The car will not start and I haven't had a car because of this for almost two weeks! I have verified spark is fine and timing is fine. So, I checked fuel pressure at test port near distributor and it reads zero when priming pump. Nothing! I put in a brand new, good quality Delphi fuel pump and a brand new fuel pressure regulator. Same results: no pressure at test port.

The fuel filter was recently replaced 9,000 miles ago (and the tank was dropped and cleaned at the time, as well) I take very good care of my car. But to be sure, I removed the fuel filter and put the fuel pressure gauge at the threaded fitting (where the filter normal screws in) straight into the gauge (a dead-end test). This would check the raw value of the pumps PSI not going through the rest of the system. It read 88 psi. I understand this is a proper value.

I then added a straight through pipe where the filter would go and added the gauge hanging off that (like a T connection) So basically as stock but with no filter and a gauge to read at that area. When the pump primed, it read 64 psi, but at the test port area by the distributor still reads zero! How can this be? This makes NO sense because it should be taking the raw 88 psi value, then go through the fuel pressure regulator and drop it down to 64 feeding the excess back to the tank. But if you have no pressure at the test port, then it cant be getting to the FPR! BUT, it's reading 64 psi priming down where the filter is. I dont get it. If there was a blockage where the fuel wasn't getting to the FPR, then it would read about 88 because the fuel isn't reaching the FPR!

There is no kink in any lines and the car ran completely fine before this. Any help would be appreciated and if you need me to test anything, just let me know. I will not let this car get the best of me.

Thanks,
John

 

It sounds like your FPR is working properly and that you may have a plugged fuel pressure test port. Have you tried pulling the Shrader valve out and cleaning it, then repeating the pressure test at the port?

And as far as the no start is concerned, you may have clogged injectors/poppets. You can pull the upper plenum and reinstall the fuel lines to pressurize the system. Then cycle each injector while you have it directed into a clear glass jar to watch it's spray pattern.

 

CAREFULLY check fuel volumn. I think its one quart in 30 sec. There is a fuel pump overide hole next to the fuel pump relay.

 

Okay, I tried so many tests and things today that I'd have to write too much to get into it. I'll try to simply where I'm at now.

Starting from the rear: There is a new quality Delphi fuel pump installed. The fuel filter is removed and a pipe is put in its place to make sure filter wasn't the cause. I blew around 100 psi down the fuel line from the manifold to the fuel filter area. Nothing came out, no blockage. When tested at the fuel filter area, the pump puts out 80 to 85 psi, so the pump should be fine. (this is with pump isolated from the rest of the system going straight into the gauge - dead end.) With the entire system put together and tested (priming pump) at the filter area, I get about 55 or lower psi. I also get that at the test port now. I removed the shrader valve from the test port to make sure it wasn't causing a problem. 55 is lower than it should be, but also, the pressure drops 10-15 psi really quickly indicating a leak somewhere. I am on my SECOND fuel pressure regulator because I thought it was the issue. The new FPR's I installed were of different manufacturers so I doubt its the FPR even though it certainly appears that way. To get two bad FPR's is statically VERY low. When I installed the first one, I put in two brand new fuel injectors (because I had two spares) and cleaned out the rest of them to like new condition. I pressure tested the poppets individually and cleaned them out with B12 Chemtool. They are all like new. I have spent TONS of time on this thing cleaning all the normal carbon on the inside of the intake (you literally could eat off of it now) and replacing all kinds of new parts so this is really frustrating.

Can someone post very clear procedures how to test the FPR without having to remove it. Please explain step by step like I am a fourth grader because I dont want to screw this up. I have got to get my stupid car running. My neighbor had to drive me to the store because I ran out of food at the house and couldn't drive to the store. This is getting ridiculous.

I highly doubt I have leaky injectors as this car never had any issues before this all of the sudden happened. So I'm not sure what else could be leaky besides the FPR. There are no leaks around any pipes from fuel tank all the way to intake so this leak HAS to be under the plenum. Some part of the spider? Also, I looked down the (what I think is PCV port, rear drivers side of plenum) and also the pressure sensor hole with a powerful mag light. I did not see any fuel puddling up and did not hear liquid squirting or any other weirdness.

Maybe taking a bat to the windows and sheet metal might help. Because thats about the only thing I haven't done and I'm about itching to do it!!

Thanks guys!

 

Here's where we are today: First and foremost, I found out my stupid fuel pressure test gauge from harbor freight was not giving me correct readings. It's not the raw gauge itself, its all the fittings that go to it that dont work. I went and looked at the reviews of that product and others had the same problem. DO NOT BUY THEIR FUEL INJECTION PRESSURE TEST KIT, ITEM 97706. It has LOTS of fittings to fit just about anything which is nice but if it doesn't work you cant not troubleshoot!! That stupid kit put me like 2 or 3 days behind because I trusted it was correct. I have since fixed that problem.

So, I took the plenum back off and found what I expected: no leak of any kind. There was no puddling at all, it was bone dry. I pulled each poppet out of its hole and manually ran the fuel pump. (To help others, there is a tiny, single connector next to the fuel pump relay in the main fuse box. Connect 12v to that and your pump will run as long as it sees 12v at that connector. You should fuse the jumper wire to that connector at 10 amp. Super handy instead of turning the key to prime.)

While I was running the pump, I could hear the fuel going through the system, the gauge was reading 64 psi, the injectors didn't spew a drop, the FPR didn't leak through that nipple, no leaks at all. When I stopped the pump, the pressure gauge fell to nothing within a few seconds.

I happened to have another new FPR so I put that in and got the exact same results as above. There are no fuel line leaks from the top of the tank all the way up to the intake. And no components under the plenum are dripping. So this tells me its not an external leak but something INTERNAL. By that I mean that pressure is leaking back to the tank. It seems to be the only thing that makes sense. Is it possible the spider body can internally leak? There are only 6 total o-rings in it (aside from the injector o-rings) and all 6 have been replaced. You have two on each fuel rail tube and two on the FPR. (All the injector o-rings have been replaced too.)

So if its internal, what are the options? You could have an FPR thats not leaking through that nipple but releasing pressure inside itself back to the tank. I really, really doubt I have TWO bad FPR's that are NEW out of the box. The pump is a brand new, premium Delphi. Is it possible the pump is letting pressure go? Maybe that little flexible tube inside the tank that's DIRECTLY coming off the pump body that goes to the roof of the pump canister assembly thing isn't perfectly sealed. Dropping the tank to do the fuel pump was a BITCH!!! I really, really do NOT want to do that again. How can I test just the pump without dropping the tank?

Any other things I have missed? Any ideas?

Thanks guys!

 

Have you verified that the return line is clear of any blockages? I encountered a 318 fuel injected that wouldn't run. Had a blockage in the return line, after it was cleared the truck ran like a top

 

Taking a look at a '97 TSM, it states your next step is to block the fuel pressure line by pinching the flexible hose (between the tank and the in-line filter). If I am understanding it correctly, you'll turn the key on (you'll need someone else to do this) and then pinch the line immediately after the pump shutting off with a suitable tool.

You're supposed to still have the pressure gauge hooked up at the test port. See if the pressure holds steady between 55-61 psi. If it does, then you may have a partially disconnected fuel pulse dampener (Pulsator).

 

I dont think 2001's have a fuel pulse dampener, do they??

Is it possible the fuel injector spider housing (the black plastic box that holds all of the injectors) can be internally leaky sending pressure (fuel) back to the tank?

 

In the TSM's for both my '97 & '98 it states:

"Fuel pressure that continues to fall is caused by one of the following items: 1)The in-tank fuel pump check valve not holding; 2) A partially disconnected fuel pulse dampener (pulsator); 3) The fuel pressure regulator valve leaking; 4) The Central SFI injector and poppet valves leaking."

That's about the best help I can offer without just throwing guesses out there. If you don't have a TSM, subscribe to alldatadiy.com (basically an online
TSM) and follow the test procedures for your year vehicle in case they are different than what I have. I would get either the TSM or the subscription (or both) anyway if you do your own work. Takes a lot of guessing out of processes.