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Anisognathus

Engine shuts off Intermittently, no fuel, pump good.

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89 GL, intermittently shuts off, with no predictability and won't restart.  I Figured out that if I tapped the fuel pump it would start up again and go fine (On a six hour trip, it would stop about every 2 hours)  The pump was getting power, so I put in a new pump, and presto, no problems for about a month, then all of the sudden it started happening again, three times this week already.  And still if I tap the pump mount, it starts right back up and will run fine for a couple days.  During all of this time the car has been doing this thing when I fill up at the gas station, I get back in the car and start it up and it immediately dies after starting, I figure it is connected somehow.  Gas seems clean, (no rust or anything visible from filter)  and the wiring looks and tests good to the pump. I am at a loss right now.  Can anyone help me put the puzzle together???

  

   

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Was the replacement pump a new off the shelf pump or a "new to you" pump from a salvage yard ?

 

I ask because it seems the problem is stil the pump.  You might try changing the filter out to see if that helps, but all signs still point back to the pump based on what you've described.

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I don't want to complicate the issue too much, but last night I added an inline fuel filter before the pump, because I was worried that something coming from the tank was ruining the fuel pumps.  And the car immediately had a severe 'chugging' going on, the engine seeming to be starved of fuel, then not, then starved...etc.  and tapping on the pump, as before, does not resolve it.  I removed the filter, but the problem persisted. So I went to put the filter back, undoing the lines and making sure to tighten the lines(I thought maybe it was sucking air in), and it ran great, in fact I drove it for an hour and a half on the freeway and then parked it for about 10 minutes, and when I went to drive it again, it started this chugging again.  Eventually I unplugged the pump, started the car, releasing the pressure, then plugged it back in and it drove perfect the 1 1/2 hours home. I'd like to believe that this is related to my original issue and that the problem has something to do with pressure.  Does this make any sense??  I am completely stumped.

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And important to add is that the 'chugging' would end in the engine dying eventually.  So I let it idle, listening to it almost die then idle back up to normal, then back down...etc., and I felt the pump and listened during all this and it was working steadily and only shut off after the engine died, not before. 

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You should check to see if the pump conections are corroded. Also while your down there put some wires direct to the battery to see if it stays on. If it does its good if not its bad. Next if its not the pump change both fuel filters if its a carb/ 1 if fuel injected check wiring and relays. If none of those change ECM if it has one. Also if it has a carb you can wire the pump direct to the battery and use a toggle switch if you don't want to mess around.

Edited by turbosubarubrat

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Pump is good, based on the fact that is works perfectly when I connect the green plugs under the hood (trouble code test plugs).  I did clean all the connections by the pump. But, I will locate and check the ECM.  

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Vac line to the pressure regulator?  Or maybe the regulator itself?

 

It's the part the return line comes out of.

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I had a similar fuel pump problem, -turned out there was a short in the fp wiring right near the pump. Located it by having the key on, wiggling that wire around made the pump start/stop. I thought tapping the pump was doing something, but it was really moving the connection.

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Check for the kinks and sharp bends on the fuel lines to and from the regulator. I'd also hook-up a pressure gauge inline just before the injector.

 

you could also have a blocked regulator (attached to the TB, assuming its SPFI) or even a bad pulse dampener (those small canister things inline near the TB, there was one on the original FP and should be one inline to the injector and one after the regulator on the return line.

 

And when you open the cap to put gas in, do you hear any pressure or air escaping when you first loosen the cap? Could be causing a vacuum lock in the tank not allowing the pump to suck fuel out.. When you undo the feed line to the pump, does it flow well?

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I've been trying to get it to act up today, but no luck.  It seems like it only breaksdown when my wife is driving it.   No hissing from the tank when filling.  Just checked the trouble codes (I checked a while ago and had 34)  But today it says 32, for the O2 sensor.  Would this cause intermittent stumbling???

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I am really thinking maybe the regulator is to blame.  The problems for sure have something to do with something that is right there around the pump because the problems are always either fixed or caused when I am tapping, or messing with the pump and the pump seems to run as it is supposed to, and playing with the wiring doesn't seem to have effect, and there really isn't anything else down there except for the regulator.  Mine is mounted to the pump, but I'm wondered if the problem persists, if I can remove it and put in an inline regulator.

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That little capsule thing near the pump is NOT a regulator. It's a pulse dampener. The only regulator on either the SPFI or MPFI is no or near the throttle body, respectively. 

 

Could be a clogged/damaged dampener, but chances are it's the wiring...

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