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What are the specs for fuel pressure?

Fuel pressure readings:

Prime x3: 9 psi
Idle: 26 psi
(I was in a bit of a rush when I did this...today I'm going to hook it back up and watch the gauge for about an hour after I shut it off, since most of my problems come when it's been off for about 30-45 minutes)

I don't know the specs yet, but I have a sneaking suspicion that these numbers are awfully low.

Since I didn't have the money right away for the pressure tester, here's what I did in my spare time:

-Cleaned all points where the battery cables go. Replaced the terminals on the battery end of the cables. Checked the cables for corrosion and all looks well. In the midst of doing this, I also found that both connections on my starter were beginning to loosen up.
-Checked all vacuum lines manually, then with carb cleaner. A few of the boots are showing signs of age, but they're still intact. Wrapped the worst ones with electrical tape for temporary piece of mind.
-Pulled and cleaned ALL electrical connectors under the hood, including injectors, and at the fuel tank.
-Cleaned the MAF
-Replaced the MAP (Pulled it to check it and it fell apart, looked inside since it was open and it was pretty gunked up and the wires were crap.
-Pulled and cleaned electrical connections on my coils and ICM.
-Checked all 6 plugs, all look normal with correct gap.
-Tested for spark from coils, all were normal
-Cleaned the IAC valve
-Tested the Fuel Pressure Regulator...no smell of gas from the vacuum after immediate shutoff.

After all this, I'm still getting a bad misfire (if it starts), and it only seems to be getting worse.

So, assuming my pressure IS low, here's a list of my thoughts:

-Replace alternator; it needs replaced anyways, it's been slowly getting worse...had it tested, don't remember the numbers but I was told it would need to be replaced soon (this was back in February or something)

-Fuel filter; haven't replaced it since I've owned it, and who knows how long it's been on there.

-Fuel pump; don't wanna bite the bullet and pay to have it done, but I don't have the means to do it myself...seeing as it was a northern car, there's quite the collection of rust on the lines and I know I'd end up snapping at least one. Local shop said $200 for labor...sound about right?

-Fuel pump relay?; Don't know about this one....don't have a multimeter to test it either. I had an issue with the FPR on a previous car, but don't know if that could be the cause here.

Thoughts please?

CJCroel wrote:What are the specs for fuel pressure?

From my '95 FSM:

48-55psi with the pump running for VIN K
3-10 psi less when idling
Should increase when FPR vacuum line is disconnected.

Check the fuel pressure regulator for evidence of gasoline in the vacuum line. If that is OK, you probably have a bad fuel pump or a nearly clogged filter (not likely).

It's for some reason priming @ 20 psi now..still idling around 26-28. Watch the video...you'll hear the noise when I remove the vacuum from the FPR. Notice how the gauge doesn't change? What's with that?

The numbers are way too low. Looks like you need a new fuel pump.

yeah, that is just plain not enough pressure. DO NOT run the car possible. especially with ANY sort of load. as Bill said, probably the pump, but you may want to go over the lines to be sure its not a kink or leak of any sort.

bill buttermore wrote: Should increase when FPR vacuum line is disconnected.

So why didn't mine? There was no evidence of gas when the vacuum was removed from the FPR, but the gauge didn't move when I took it off...

I was really hoping it wasn't my pump...all of my under-body (including the fuel lines) are rusted and I know they'd snap...shop wants 200 for the labor only, and of course they'd overcharge me for the part...and then they'd want to replace the lines...

CJCroel wrote:

bill buttermore wrote: Should increase when FPR vacuum line is disconnected.

So why didn't mine? There was no evidence of gas when the vacuum was removed from the FPR, but the gauge didn't move when I took it off...

Well, I don't know for sure but here is a guess. The FPR is designed to decrease the fuel pressure from 53 to 43 psi when sufficient vacuum is present. You are starting with, what..20 psi? So, you are not within the range where the FPR will affect the pressure.

If it were my car, at this point, I would install a new pump.

bill buttermore wrote:If it were my car, at this point, I would install a new pump.

Ok...that's what I was afraid of. I appreciate all the help everyone has given me...now here's the fun part.

I'd rather do this myself...is there a step-by-step in the Chilton's manual? I don't have one yet (shame on me). Basically I have an idea of what to do, but want to make sure I'm doing everything right. I think the main issue I'm going to have to deal with is that dreaded rust. How hard are fuel lines to replace? The reason I'm asking all of these questions is because I'm on a reeeeeallly tight budget and it would be pretty much impossible to have it done.

Thanks again!

to be honest, ive never paid attention to my 97, but on my 92s the fuel lines are all plastic. if you see rusty lines, you probably just need to replace the sending unit at the same time as the pump. most parts stores will have both together.

Yeah, that was the plan. I'd really rather use an AC Delco, but that's wayyyy too expensive...and I've read other threads here where people used the cheaper one @ rockauto.com, so that's what I'll probably do. It's the pump/sending unit for $120 (which is great, because then my gas gauge will finally work)

Well, after worrying about where the money will come from, I bit the bullet and applied for a line of credit through the credit union I have the car loan through. I'll have a $1000 card coming my way soon. In the meantime, I'm making a list...because I'm doing a once-over and repairing and replacing. Here's what I've got:

1) Fuel pump/sender ($120 - rockauto.com)
2) Labor for pump replacement ($230 - Christian Brother's Auto)
3) Alternator ($120 - rockauto.com) (acdelco, of course)
4) Battery (~$100)
5) 180* t-stat ($9.99 - intense)
6) Trans flush & coolant flush (together, about $200 @ Christian Bros)
7) Possibly buying the hose to put my CAI where the evap container goes (~$35)
8) Contact lens exam and 3 month supply of contacts ($160) (it's needed, my glasses are fubar)

What else can you think of? Car had a good tune-up about 10 months ago, including intake cleanout, new plugs & wires (about 30k miles ago)... Should I consider replacing my O2 sensor?

Once again guys, thanks for all your help!

CJCroel wrote:Should I consider replacing my O2 sensor?

How old are they?


Also you may be able to do the coolant flush and trans fluid change and save some major bucks by doing it yourself.

I don't know how old the O2 sensors are...I've never replaced them, so hard to tell really.

I'm considering doing the coolant flush myself, but I don't have the means to do the trans. work myself.

While I'm STILL waiting for the money to show up to get it fixed...I poked my head under the hood yesterday (temp gauge was climbing and I wanted to ensure it was the extreme heat and not lack of coolant) and I noticed that I could very clearly hear the injectors...I've never heard them with such clarity before. What's up with that?

She's left me stranded twice now, and I've fortunately been able to restart her after relieving the fuel pressure and waiting a few minutes (I still don't get why it does this when it's hot)...it's getting worse, and I really wish I could expedite this *dang* line of credit thing. I'm going to be talking to a friend today, and hopefully borrowing his Envoy until this problem is fixed.

Oh, and I also want to thank everyone for their ongoing help. This place has been the best thing I've found!

It wouldn't be a bad idea to change your O2 sensor. They're only $40 from Rock Auto for a Denso.

Noisy injectors could be a sign that they're dirty. I remember once in our minivan it got so bad that you could hear it from INSIDE the car. We had to get them professionally cleaned.
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