2003 Blazer

About two weeks ago I noticed that after the truck had sat for awhile, it wouldn't start right away like it did before. It has never NOT started, but a few times it took two tries and it seems to "stumble" when starting more often than not. There is no problem if the truck hasn't been sitting for awhile.

I read the forums here a lot, so I knew that the first step I should take is check fuel pressure and leak down. At the test connector in the engine bay, my latest test was key on, engine off, 60 PSI. After ten minutes the pressure dropped to 52 PSI. Because of this, I decided to test the pressure at the fuel filter outlet. I rigged up the gauge using the parts that came with it, using the rubber hose, clamps, and a schrader fitting from one of the adapters. The key on engine off pressure was 80 PSI, and after ten minutes the pressure dropped to 58 PSI. The results of the direct to filter test may be off a little, there was a tiny leak at the hose where it connected to the fuel filter. If I have to I will do this test again to get more accurate readings.

From these numbers it seems that the running pressure is borderline okay, but there is a problem with leakdown. If the direct to filter test results are accurate, it seems I might have a leak somewhere in the plenum. But it is really close to the lower limit that I'm still not sure if I'm right. Is my next step to pull the plenum and check things out there?

I realize that we have a fuel diagnosis thread here, but the diagnostic table images aren't loading for me. I have an electronic factory service manual but the steps in the diagnostic table are a lot different from what I have read in threads here.

 

That kind of suks your in the twilight zone. The presure drop at the filter is too fast but I think its wrong. It only takes a coulple of drops of fuel to knock the pressure down at that point. Try to make the connection dead dry at the filter with your rig and bleed it a couple of times from the gage See if it holds.

 

I figured since the leakdown test at the filter was within spec (barely) that the small leak wouldn't be too much of a big deal since the reading would actually be higher if the tester hose was losing pressure. I will repeat the test again though so I can get the readings more accurate. Done for tonight though, might not be until next weekend.

Twilight Zone is right, I'm still not certain one way or another if it's the pump or leaking under the plenum.

 

I had a hard time getting it plumbed to the fuel filter, too. You pretty much have to bring everything to home depot with you and build it in the store!

 

Okay, here's the updated readings, no leaks this time:

First I tested again at the port in the engine compartment. Key on, engine off, pressure was 60 PSI with pump running. Dropped to 54 immediately after it shut off, 1-2 seconds later rose to 59 PSI. After ten minutes, pressure was 55 PSI.

At the fuel filter, pressure was 81 PSI with pump running, after ten minutes the pressure dropped to 55 PSI.

With these borderline readings, it's looking like the issue is with the pump, correct? Like I said in the first post, the truck has always started, only occasionally has it not started immediately. With the readings barely within spec, that's probably why it's only an intermittent issue, I think.

Does all this sound right to you guys?

 

eh like u said its borderline. If you drive it everyday does it start right up and drive ok? If so,id say forget it and just drive it. Now if its giving you issues everytime now id say its time for a pump. Im sure you know what brand to buy,youve been here long enough lol.

 

Yeah it's not every time, maybe 1 out of 4? At least now I know that I probably will have to drop the tank in the future, if I'm correct in my conclusion.

I've done the job before on my old 2000 Jimmy four door, so I kind of know what to expect. The current truck is an 03 Blazer two door. Any advice/tips on replacing the pump on a two door?

Of course it will be an ACdelco pump.

 

I agree, you've got a pump "on the edge" of failure. 2 door pumps are way easier than 4 door. Let the tank down just far enough to disconnect the 3 lines and the electrical connectors from the fuel pump module. Remove the rubber section from the steel filler neck and pull out the tank. Good idea to hose the top of the tank down before removing the module.

 

I think I read here that two door models do not have a vent hose directly attached to the tank like on four door models, is that correct? (The fitting that is prone to breakage on four door trucks)

 

Correct, the vapor line is attached to the pump module on 2 door. 4 door has an additional vapor fitting toward the front of the tank and it breaks off if you're not careful when you drop the tank down.