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Bad Fuel Pump?

9K views 9 replies 4 participants last post by  gocartone 
#1 ·
Well a while back I posted about getting a running rich code a couple times, and I thought I had fixed that by taking off the third cat as the code hasn't come back yet, but now my truck is starting to idle goofy again.

I went for a drive with it yesterday, got it all warmed up, and then it stalled when I pushed in the clutch rolling up to a stop sign (idle dropped to low). Started it back up and it was idling about 4-500rpm, just barely running. I did some WOT bursts with it and drove it for another 15 miles and it started running normal (idling at ~700-800rpm). About 5 miles after that it started to jump up to 2000rpm whenever I pushed in the clutch, I did some more WOT bursts, but it didn't seem to come down. It came down to ~1200rpm when I got home and parked it, but that's still high. Another thing I noticed the other night (doesn't do it all the time) was that the idle droped when I turned the defrost OFF, to the point that it was almost dying.

When I got home I shut it off and turned the key on to hear the pump fire up, and it has a high pitch squeel to it that it didn't used to have. It has been sounding off for a while now, but sounds worse now. It also bleeds off pressure over night (pretty sure it's the pump anyway), so I'm guessing it would be best just to replace it anyway.

What else could cause the idle to vary like that? I don't think a bad pump would make the idle jump up like it did, I could see making it drop or stall but not idle high. I think I might order one up and throw it in during spring break, I just don't want to go through the trouble and have it still idle like shit.

Also, there is no power loss at all, in town MPG seem to suck but that could be my driving, highway MPG is still where it's always been.

Thanks
 
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#4 ·
Yup, just trying to find out if it could be the fuel pump I guess. The pitch changes when I hit the tank, it's fairly loud when I turn the key on and when its running, so I'm 99% sure the pumps on its way out.
 
#5 ·
Fuel pump is probably heading for the door if it sounds like a pig on a treadmill set to highest settings. But, you are probably experiencing sensor problems as well.
 
#6 ·
Could be vacuum too: At 1/4 throttle aroud 1300-1600rpms with a load on it there is a squeel from somewhere underneath it sounds like. It's been doing that for about a year now though and the idle thing just started happening. I love tracking down little shit like that, that's why it hasn't been fixed ha :rant: I've checked pretty much all the hoses for that a few times with no luck, maybe the leak has got worse and is messing with the idle I guess.
 
#7 ·
The electric fuel pump usually works or not. There is nothing but a magnetically driven impeller so there is little chance of it slowing down. But, being a machine, it might. I'd guess that pressure testing the system would answer that problem.

Let's see; the signal from the catalytic converters go to the same computer that controls the idle (not the distributor adjustment or idle screws) so....is there a chance you caused your own problem?
 
#8 ·
No sensors before or after the 3rd cat, so no. It was having a problem not idling high enough once and a while before I took out the 3rd cat, and it had a running to rich code pop up twice (cleared it once, came back two weeks later, cleared it the same day I took out the cat 3-4 weeks ago, hasn't been back since).

The code was P0172 1/1 Fuel System Rich, which has a long list of shit it could be-

Intermittent condition, restricted fuel supply line, fuel pump inlet strainer plugged, fuel pump module, O2 sensor heater operation, O2 sensor, EVAP system operation, O2 sensor signal circuit shorted to voltage or open, TPS voltage greater than 0.92 volts with throttle closed, throttle position sensor sweep, MAP sensor operation, ECT sensor operation, engine mechanical problem, fuel filter/pressure regulator, PCM

I've seen pumps go bad before they quit before, if it was from the actual motor or just the in tank filter plugged I'm not sure.

I love problems like this, hasn't done it since that day, although it has randomly done it before then. The fuel pressure regulator and all that crap is on the pump, so hopefully replacing the pump will fix it. Ever since I bought it the regulator has leaked pressure back into the tank (pretty sure anyway, loses pressure after a few hours but no gas leaks anywhere), so buying the pump will fix that and the pump that's about to shit out, and hopefully the random messed up idle.
 
#9 ·
Don't go throwing money at the problem by replacing parts. You'd feel silly replacing the pump to discover nothing changed.
 
#10 ·
"Ever since I bought it the regulator has leaked pressure back into the tank (pretty sure anyway, loses pressure after a few hours but no gas leaks anywhere), so buying the pump will fix that and the pump that's about to shit out, and hopefully the random messed up idle."

New pump is going to kill two problems for sure. I've checked for fuel leaks everywhere so I'm 99% sure it's the regulator leaking, and I know the pump sounds bad compared to what it used to sound like. Just trying to figure out if it's going to help at all towards the idle problem or not.
 
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