Bad fuel pump? UPDATE 2/26/02

[Denny]

I pulled some codes tonight after driving back from Canada. I got 41, lean code and 83 "Low speed primary fuel pump circuit failure." Is that necessary a bad fuel pump? I'm still having ZERO CE lights. Can't still do the engine running test, but the stalling happens if I'm harsh with the throttle right at idle. Could there be something else that's making everything else "look" bad? Before I had two codes related to the ACT and MAF being out range, but those codes did not come up tonight. Oh yeah, these were codes were all in the cont memory. Nothing ever shows up in the KeyOnEngineOff, and runnint can't happen because it stalls out during the test

<small>[ February 26, 2002, 05:58 PM: Message edited by: Denny ]</small>

 

[sdpatt]

It sounds like your fuel pump is weak and not putting out enough pressure or flow to allow the engine to run at the correct air:fuel ratio. A weak pump would also cause the lean mixture. A plugged fuel filter could cause the loss of high load, high rpm power, but would not create the "low speed primary fuel pump circuit failure" situation. You could confirm this by measuring the fuel pressure, but the combination of the codes points accusingly at the fuel pump.

 

[Denny]

Thanks Scott! Nic sigpic btw! thumbs_u
What would be the correct pressure?

 

[sdpatt]

35-45 psig

Scott

 

[DeaconBlue]

The CD states 39 psi +/-2 psi at the Schader valve with the vacuum line removed (and plugged) from the FPR.

 

[Denny]

Uh oh
Here are my results
After cold startup, the idle pressure was 32psi
I got a range from 29-40
It hung around 31-33 at idle, then by opening up the TB it would go up at a reasonable speed I'd say. So some aggressive opening and I got it up to 40.
Pressure would drop and got down to 29 after opening up the throttle.

So Scott, looks like the pressure is lower than normal? Is the pump my culprit then?

 

[Birdoprey]

Denny,

Did you disconnect the vaccum hose from the fuel pressure regulator and plug it before you measured the fuel pressure?

 

[Denny]

No I did not. Would that fudge the readings then? The FPR is a grey looking metal thing?

 

[Birdoprey]

Yep, it'll give you incorrect readings. The fuel pressure reg is designed to lower the fuel pressure during low load/high vaccum situations such as idle or reving in neutral. Its round and located at the other end of the fuel rail near the front of the motor(left hand side looking at it from front of car). It has a small vaccum line comming out of the center and it connects to the intake plenum(towards front of car). Disconnect the line from the fpr and plug the hose. Now you can measure the fp. Should be around 37-40psi at idle. You should be able to open the throttle and the fp should remain close to the same. If it drops alot, your fuel pump may be the culprit. Hope this helps...

 

[Denny]

Thanks Birdoprey
I guess I'll have to correctly read the fuel pressure and then see what's up with the SHO
Here's to hoping burn_out

 

[Denny]

Alright! I took the measurement correctly this time! Here's what I got. . drumroll please:
40PSI at all RPMs! thumbs_u Looks good no?

 

[sdpatt]

Since the fuel pump tested okay, the loss of power at throttle tip-in may be due to a dead spot in the throttle position sensor. This sensor is located on the forward end of the throttle shaft and is relatively inexpensive and quite easy to replace. Good thing you checked the fuel pump output.

Scott

 

[Denny]

Thanks Scott! You're the third person to mention TPS, so that'll be the next step towards the stalling problem. Do you or anyone have recommendations for getting the TPS off? Ford threadlocks the screws I believe and I've never been able to actually get a screw off of any TB without striping it up or just completely ripping off the TPS
I hope my SHO makes it well past the 200K mark like yours Scott

 

[Mike Kopstain]

Thanks Scott! You're the third person to mention TPS

Who was the first? wink

 

[Denny]

I think it may have Ben Spada actually Really I don't know, in fact I think more people have mentioned TPS

 

[Mike Kopstain]

AAAWwwww common!!! You know the answer I was looking for!