Fuel Pump??

[gyates]

I am having an odd issue with the fuel pump relay in my 2005 ST. I thought the relay was going bad so I recently replaced it, but still having the probelm. Basically what is happening is that on some attempts to start the truck the relay does not click on, so the fuel pump does not turn on until my cranking brings the oil pressure up enough for the oil pressure sending unit to trigger the fuel pump. This is an intermitent problem, but very annoying!! I will add that a few years back (before I owned it) the ignition switch was replaced in the truck, but this is a relatively new issue. Is there a specific wire in the steering column I should look for to see if it is not connected correctly? Ideas appreciated.

 

[Vic Sorlie]

I'm not a professional mechanic, but are you sure oil pressure is needed to activate the fuel pump? What's condition of your fuel filter? If it's been a couple of years (or more), I'm changing that first. Inexpensive ten minute job, but you want to ensure a clear path for fuel before diving into relay electrics, etc. After that, I'd check integrity of battery cables. If you've got a loose terminal or some corrosion, that could result in low/intermittent voltage to the fuel pump. After that, I'm into a Haynes service manual (or Ford's) to check wiring schematic for where to check voltages.

 

[EddieS'04]

Greg,

Im thumbing my '04 ford wiring manual.

Trying to come up with the shcmatic of the fuel start sequence.

Not having much luck.



Have you tried tilting your steering wheel up. we have the infamous wiring harness problem?

Also have you tried? Turn the key to the on position 3 or 4 times, dont start it. Then see if it starts. If it does your fuel pump is getting weak. Not holding a fuel charge in the rails.

until my cranking brings the oil pressure up enough for the oil pressure sending unit to trigger the fuel pump

Oil pressure is not tied to the start sequence. What you are seeing is your cranking is causing the pressure to come up. Starting at that time is coincidental.

 

[Bob McDonald]

What you are seeing is your cranking is causing the pressure to come up. Starting at that time is coincidental.

Seeing that statement reminded me of something. It sounds like the fuel may be draining back to the tank and it is taking a bit of cranking to get the fuel back up to the engine. Isn't there some kind of pressure valve that is supposed to keep fuel in the lines? Maybe part of the pump assembly? Maybe that is where the problem lies. Or is my thinking all messed up?

 

[gyates]

Thanks for ideas!!! Today is also frustrating related to this issue. This morning the relay and fuel pump definitely turned on with the key in the "on" posision. When I crank the truck it starts, but idles low (500 range, and rough). I gently press the accelerator and take the idle up to about 1200. When I let go of the accelerator the truck settled about 1100 for a few seconds, then dropped gently to 750 on its own, like it does when acting nromally. The entire drive to work idle was perfect @750 every time I had to stop. This is frustrating!!! This weekend I ahev a little free time to open up the throttle body and give it a thorough scrubbing. Maybe this will resolve this issue? I will aslo ck the IAC even though it is relatively new and see if maybe it needs a little cleaning.

 

[scott degroot]

It sounds like you are losing fuel pressure when the truck is turned off and the fuel line is draining back into the tank. Common fuel pump issue

 

[EddieS'04]

Greg,

I wouldnt spend my time on anything but a fuel pump.

 

[gyates]

Sadly I am now also thinking the fuel pump. This morning I turned the key to "on", then back off, than to "on" again briefly as I started the truck. It started perfectly using this "method" and ran fine all the way to work today. If it is the fuel pump that is disconcerting to me as the one it has now was done about 3 years ago by the previous owner, and it is a Motorcraft one. And as I mentioned earlier, I did take the time to clean the throttle body (it was not that bad actually) and I can't really say it has made any difference. Could a failing fuel pump have caused my Inertia switch to go bad? I had to replace it about a month ago. It kept tripping but would not reset, so it had to be replaced.

 

[EddieS'04]

Could a failing fuel pump have caused my Inertia switch to go bad? I had to replace it about a month ago. It kept tripping but would not reset, so it had to be replaced.

I wont say yes, but electrical components that are failing. May cause excesive amperage draw. The heat Can melt wires and damage other devices. The pump is an electric motor. With a 20 or 30 amp rated fuse and relay. So I will just say possible.

 

[Craig Long]

IT'S FIXED! Turns out the battery only had 12 volts most likely do to a bad cel and would crank the Trac sometimes but not always! New battery zero issues. Found out this out after I put a jump box on the battery.

 

[ZoNiE]

This is a strange problem. My 01 started having problems in the morning. I thought it was my son (operator error) as he seems to be a bit car challenged, and has had "other" issues with the truck, but today I decided to check things out and no start, but cranks fine. Couldn't hear the fuel pump running, checked the fuse, good, swapped the relay with another one, good, still no start. Batt voltage 12.6, jumped it with my 09 trac and fuel pump fired up and truck started fine. Starts fine after that without the jump, but batt still at 12.6, as is the 3 month old battery on the 09.



Scratching head. perhaps old fuel pump (11 years, 123K miles, 120 degree summers) and it is finally just tired? trac was reported idling roughly a few days ago too.



I did check the inertia switch, the wires have been hot in the past, they are a bit melted, but smacking it and wiggling the wires didn't cut the fuel, so not entirely sure it is this.



Batt is only 2 yrs old, voltage is apparently fine, but will check again in the AM after it has sat all night.

 

[ZoNiE]

This is a strange problem. My 01 started having problems in the morning. I thought it was my son (operator error) as he seems to be a bit car challenged, and has had "other" issues with the truck, but today I decided to check things out and no start, but cranks fine. Couldn't hear the fuel pump running, checked the fuse, good, swapped the relay with another one, good, still no start. Batt voltage 12.6, jumped it with my 09 trac and fuel pump fired up and truck started fine. Starts fine after that without the jump, but batt still at 12.6, as is the 3 month old battery on the 09.



Scratching head. perhaps old fuel pump (11 years, 123K miles, 120 degree summers) and it is finally just tired? trac was reported idling roughly a few days ago too.



I did check the inertia switch, the wires have been hot in the past, they are a bit melted, but smacking it and wiggling the wires didn't cut the fuel, so not entirely sure it is this.



Batt is only 2 yrs old, voltage is apparently fine, but will check again in the AM after it has sat all night.