Fuel Pump Issue?

[jman1200]

Went to the local scrapyard and was able to get all 3 connectors with about a foot length of wire on each.


Cut and spliced the wires going to #3 and soldered the new one in place. Used heat shrink on each individual wire.



This morning car died again. Disconnected and reconnected #3 and nothing. Then disconnected #1 and #2 and car started (see post above on how I numbered these). As on previous occasions, CEL came on showing P00C6 which is fuel rail low pressure, so it doesn't really point me anywhere.

I'm tired of this issue and not sure what to do next. Been hesitant to replace the fuel pump or any other parts as everything points to a connection issue in the wiring. Because the issue is intermittent it makes it hard to diagnose when it is not present. I already took it to a local mechanic and could not find anything. A dealer most likely throw parts at it, fuel pump, fuel pressure sensor, harness... all that plus labor will be worth as much as the vehicle itself.

I feel my only option left is replacing #1 and #2 as well, I'd hate to keep chopping down the harness but as said, not sure what else to do here. I already replaced (twice) the fuel pump relay (or module) so I don't think that is the issue. I have to wait to fail again to test if there is voltage going to the fuel pump.

Arghhhh... !

 

[Shadow351]

Hmm, Intermittent fuel pump operation is a classic symptom of a fuel pump with a dead section in the commutator. If the pump stops in the dead section, it cant restart until it moves past the bad spot. A vibration could move it past the dead spot, which is why the 'classic' test for a dead fuel pump is to bang on the bottom of the tank when the pump is failing to start and see if it will run then. The only sure way to test an intermittent pump that I know of is with a lab scope and a current clamp (which most don't have at their disposal). Next time it decides to act up, instead of messing with the wiring, see if you can just tap/pound on the bottom of the tank in the vicinity of the pump. Its a free test and might be worth a try.

 

[jman1200]

@Shadow351 , appreciate your advice. If this is the case, can a pump with a dead section also stop while it is running?

 

[jman1200]

Update:

As the problem persists, last weekend I disconnected all 3 plugs while the engine was running, one at a time.


Plugs 2 and 3 did nothing, the engine kept running normally for 5+ minutes, no CEL's, no nothing. So those two are out of the equation, wish I've done this before replacing 3.
As expected, unplugging 1 did "kyll" the engine but only after 60 seconds or so. Fuel gauge went down to 0.

Yesterday I built the first FPMS (Fuel Pump Monitoring System) for the SHO. I added two LED's to be able to see if there is power going to the pump and coming out of the pump relay.
Added one right at the pump connector and the other one right after the relay (no wires cut).


Ran wires and placed the LED's at the front where I can easily monitor them. This is temporary so ignore the duct tape.



So, next time the car dies I just need to look at the LED's. Top LED is the one at the pump and the bottom one is from the relay.
- Top LED OFF, bottom LED ON: issue is the wiring between the relay and the pump.
- Both LED's OFF: issue is the relay or something else upstream of it.
- Both LED's ON: issue is the fuel pump.

If now I go into months without an issue, this could mean that the wires I slid into the pump connector (#1) are making it tighter and maybe the issue is the plug itself.

Ironically, now all I need is for it to fail again...


PS: Site replaces the word "k i l l" with **** so typo was intentional.

 

[FiveLeeter918]

Update:

As the problem persists, last weekend I disconnected all 3 plugs while the engine was running, one at a time.
View attachment 82635

Plugs 2 and 3 did nothing, the engine kept running normally for 5+ minutes, no CEL's, no nothing. So those two are out of the equation, wish I've done this before replacing 3.
As expected, unplugging 1 did "kyll" the engine but only after 60 seconds or so. Fuel gauge went down to 0.

Yesterday I built the first FPMS (Fuel Pump Monitoring System) for the SHO. I added two LED's to be able to see if there is power going to the pump and coming out of the pump relay.
Added one right at the pump connector and the other one right after the relay (no wires cut). View attachment 82636
View attachment 82637

Ran wires and placed the LED's at the front where I can easily monitor them. This is temporary so ignore the duct tape.

View attachment 82638

So, next time the car dies I just need to look at the LED's. Top LED is the one at the pump and the bottom one is from the relay.
- Top LED OFF, bottom LED ON: issue is the wiring between the relay and the pump.
- Top LED OFF, bottom LED OFF: issue is the relay or something else upstream of it.
- Both LED's ON: issue is the fuel pump.

If now I go into months without an issue, this could mean that the wires I slid into the pump connector (#1) are making it tighter and maybe the issue is the plug itself.

Ironically, now all I need is for it to fail again...


PS: Site replaces the word "k i l l" with **** so typo was intentional.

Great idea for diagnostics use, way to use the noggin to think outside the box.

 

[jasong_10]

Great idea for diagnostics use, way to use the noggin to think outside the box.

I agree, very clever