2004 f225 LP fuel pump

[bravajo2]

Folks,

I could really use some help as I'm stuck.

Here's what I know. Took boat out for a 2 hr ride. Get back to dock, engine idling and it stumbles and stalls...strange. I pump the bulb, restart and seems OK. I watch the dash fuel flow gauge and it shows no flow. Clearly the LP pump is not running. I figured I was in for a costly new pump. Before blowing $500 i figured I'd test power to the pump.

Pump connector gets steady +12v on the red/yellow line. The blue/white line never gets continuity to ground (doesn't get commanded to run?).

Sounds like either the pump con*****er or ecu is having a problem ( or potentially wiring which I doubt but is possible).

Any tips on finding the offending part?

Thanks,
Joe.

[boscoe99]

If you start the motor and keep it running above 1200 will it continue to run? The low pressure pump only runs for 10 seconds out of every 30 seconds when the engine RPM is 1200 or below. It runs for 10 seconds, stops for 20 seconds, then runs for 10 seconds again...

Let us know what the situation is above 1200 RPM.

It should be fairly easy to see if the ECU is commanding the fuel pump driver or not. If it is, but the ground is not getting to the fuel pump then I would suspect the driver. On the other hand, if the ECU is not telling the driver to turn on and off that is another matter.

I would certainly do a continuity test on the wiring however as that is cheap and simple.

[bravajo2]

I am going to recheck itabove 1200 rpm. That didn't help last week.

I also have the YDS so I'll perform a static test and see where that gets me.

Agreed that a continuity test is simple. Consulted the wiring diagrams in the shop manual. I am not quite clear if I am checking continuity between the ecu to con*****er and then con*****er to pump? Kind of crazy tracing the wires given all of the tape around the harness.

Thx for your help!

[boscoe99]

Disconnect the connectors then probe the applicable pin/socket within the connector. Use the wire colors as your guide.

See below:

[bravajo2]

this diagram is beyond awesome. heading down to boat now.

thanks!

[fairdeal]

this diagram is beyond awesome!

that it is!

you are a cut & paste wizard, Boscoe


seems to be an unfortunate limitation of this site
your posts will be available for years
but the attachments disappear

[boscoe99]

I make them that way intentionally. They are made to be applicable to the person that is having the problem du jour with a specific model. Others may come along and try to use them for their problem, which may or may not be the same as the first guy had. Might not even be the same model motor.

[bravajo2]

Boscoe99,

I am not sure what did it but I checked connections and continuity everywhere and everything was fine. I put Humpty Dumpty back together and connected YDS to the diag plug. I ran the stationary tests for the HP and LP pumps and both hummed appropriately.

Things started looking up. I reassembled the air box and timing belt cover, put the cowling on and fired the engine up and bingo, the fuel flow gauge showed intermittent flow at idle and consistent flow above 1200 rpm.

There was no corrosion on any of the connectors and no loose wires that I came across so I don't think I did anything to fix the problem but it definitely is working properly now.

Thanks again for your help. Hopefully you won't be hearing back from me after a long time this weekend

Joe.

[boscoe99]

Glad the motor is running fine now.

In retrospect don't you wish you had run the stationary tests first and then messed with the wiring?

Some times the simple act of disconnecting and reconnecting connectors can solve some voodoo problems.

[bravajo2]

I definitely wish I had used the YDS first. Live and learn.

Let's hope it stays fixed.

Joe.

[TownsendsFJR1300]

Just a little bit of a bad connection can cause issues.

You apparently got that connection working again.

Congrates as well

[rodbolt17]

my vote is its not fixed.
my guess is the relief valve is failing .
above 1200 when the pump runs full time you wont ever notice it.
only below 1200 RPM will you get the stalling if the valve is failing.

[bravajo2]

Rodbolt,

Do you mean that inline metal check valve that runs on the return line from the top to the bottom of the LP pump and is zip tied to the bracket?

Joe

[rodbolt17]

that's the one.

you can either watch the fuel cup cycle less and less at idle or as its trying to slow down and die pinch off the line between the valve and the pump intake.

you can also watch it on the flow meter.

[bravajo2]

Right now I feel like things are back to normal.

Took the boat out for a 10 mile ride out and back with extended idling below 1200 on both sides of the trip (no wake zones) and watched the fuel flow gauge. Fuel flowed continuously above 1200rpm and intermittently at lower engine speeds. No stalling or fuel starvation.

I'll keep an eye on things and watch that inline check valve if issues surface again.

Thanks again,
Joe.