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stalling '87 lesabre


fielder
07-21-2004, 06:14 PM
in reference to the problem i sent in on july 4 i ran a fuel pressure test and came up with the following: when i turn the key on it reads18 lbs. whan it's running it reads 27 lbs. sometimes fluctuating between 25-28 lbs.does this still sound like the fuel pump? :eek7:

rustbucket
07-22-2004, 11:30 AM
Sounds a little low, but it could be the regulator. It is the little can-like thing mounted on one end of the fuel rail. Follow the line down to where it turns to a rubber hose and pinch the rubber enough to stop the fuel flow back to the tank, while the engine is running. The pressure reading should rise. A good pump should rise to 40-50 or better. If it rises above 30, the pump may be ok, but the regulator bad. My fuel pressure runs around 30 and it runs OK (the spec on the '87 says 34 psi). (My pressure meter is graduated is 5 psi, so it's not that accurate) 25-28 doesnt sound like it should be a problem as long as it doesnt get worse when hot. Make sure you also read it when it is having a problem.

(you should have continued messages in the original post instead of starting a new one, so all the info stays together)

fielder
07-25-2004, 02:02 PM
oops! sorry about the new post.i,m pretty new here.i hope answering in this post is o.k. since my most recent reply was in this one. I followed the metal line coming out of the bootom of the fuel regulator to where it turned into a rubber hose and pinched it. It made no difference to the reading, staying at app. 27 pds. pinched or unpinched

rustbucket
07-26-2004, 08:10 AM
The original symptom posted by fielder:
"i have an '87 lesabre with the 3.8 litre. the past couple weeks the engine will start stumbling real bad only after it is fully warmed up,never when its cold. it gets to the point where it will die and be very hard to restart.it acts like a stuck choke on a carb.car.it does this app. half the time its driven and is gradually getting worse and more often..once it restarts and smooths out,it runs fine.i ran a scanner and it doesn't bring up any codes. it also has to be pumped to start cold after it has sat for a couple days"


The fuel pump is definitely not the best, but I wouldnt replace it till you eliminate things easier to do. I replaced the fuel pump on my 87 because the pressure was reading low (like yours), but it didnt help my symptom.

You say once it restarts and smooths out it runs fine, which makes it look like something else.
Before you go for the fuel pump, do some other diagnostics.

1) Try to make sure the EGR valve is moving correctly. If it gets stuck open, it will cause rough running and bad restarts. When it is running good, then disconnect and plug the vacuum hose, so it wont try to open again. Then run it that way a few days and see if it screws up again.

2) Clean up the throttle area and the Idle Air Control (IAC) of carbon and gunk. If the IAC is stuck, it could cause bad running.

3) There is a fuel pump relay, and possibly and oil switch that may keep the fuel pump from running.
There is a green test connector up near the battery that goes to the fuel pump. You can hook up a small 12v lamp between the connector and ground. The lamp will light when the fuel pump is receiving voltage. I would hook up the lamp and bring it out so you can see it when you are driving. It should light for a second or two when you first turn on the key, and is should be always lit when the engine is running.

More details about the fuel pump wiring: The ECM controls the fuel pump relay,which goes to the fuel pump, but the oil pressure switch is in parallel with the relay, that is one side of the oil switch goes to +12 v and the other side goes to the fuel pump. The oil pressure switch (if closed due to sufficient oil pressure) will supply voltage to the pump regardless of the relay. If the relay fails, it results in long crank times because of the time to build up oil pressure enough to energize the pump.

buickmastermind
10-08-2004, 08:31 PM
Better safe that sorry. It most likely is a fuel pump issue.

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