bad fuel pump troubleshooting?

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railer

Golden Member
Apr 15, 2000
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Working through an intermittent no start (and no fuel pump activity) on my 2001 F150.

It's definitely true that the fuel pump is not activating when the truck doesn't start, the only kicker is that the last time it happened and I sprayed down the throttle body with starting fluid, the truck still didn't start. That makes me think that it could be something upstream of the fuel pump, but I don't know what that might be. It also could be true that I just didn't spray enough starter fluid into the truck. I'm tempted just to simply drop the tank and change the pump, but I'm kind of looking to exhaust all other options first.
 

lsd

Golden Member
Sep 26, 2000
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Stick a fuel pressure gauge on the fuel rail. If bad check the voltage coming out of the fuel pump relay. If good then it's most likely the pump.
 

iwajabitw

Senior member
Aug 19, 2014
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How about the fuel filter. I think the fuel pump throws a code if it drops pressure. My 07 F150 through a fuel code when I first bought it, but it was just the gas cap not seating properly. Is the CEL on?
 

iwajabitw

Senior member
Aug 19, 2014
828
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Yeah I just looked at a book for my programmer, fuel pressure is measured at the rail, so I would think it should throw a code. Any chance the EGR, O2's being messed up, causing it to flood and then not start?
 

railer

Golden Member
Apr 15, 2000
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I can definitely hear (or not hear) the fuel pump when it does or does not come on. For the past couple of days the truck starts and runs 100%. One thing I did think to do was to pull the fuel pump relay, and then try to start the truck with starting fluid down the throttle body. That did not start the truck, so that makes me feel better about it being a fuel pump issue, as it was that experiment from my OP that had me questioning whether it was the fuel pump. I think I'm going with fuel pump. So hard mentally to replace this when the truck is running great.
 

boomerang

Lifer
Jun 19, 2000
18,883
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I can definitely hear (or not hear) the fuel pump when it does or does not come on. For the past couple of days the truck starts and runs 100%. One thing I did think to do was to pull the fuel pump relay, and then try to start the truck with starting fluid down the throttle body. That did not start the truck, so that makes me feel better about it being a fuel pump issue, as it was that experiment from my OP that had me questioning whether it was the fuel pump. I think I'm going with fuel pump. So hard mentally to replace this when the truck is running great.
You've completely lost me there. You expected the truck to start with the fuel pump disabled while using starting fluid and because it didn't, you are suspecting the fuel pump? Does not compute and especially with a fuel injected engine.

I have no first hand knowledge of how Ford does things but so much is common between car manufacturers. The pump should come on at key on, run briefly and then quit. When cranking the pump should be running and then obviously stay running if minimum oil pressure is reached within x number of seconds. If not, the pump will stop and the engine will too. Ford uses an inertia switch in the FP circuitry that kills the FP if the vehicle is in an accident. As far as I know that's unique to Ford. Are they problem children? I don't know but it may pay to find out. From what I can see at the RockAuto site they are used on their trucks but I don't know what engine you have to know for certain. I am also seeing mention of fuel shutoff solenoids so there are a number of components that make up the fuel system.

Throw parts at it if you wish, it's commonly done. But dropping the tank to replace the FP on a whim is not something I would do but to each his own. One thing is for certain. If you throw enough parts at it, there is a huge chance that you will eventually fix it.

Is there an identical relay that you can swap for the FP relay? Quick way to tell if you have a flaky relay. I'd swap the relay first. If that doesn't take care of the problem I would be trying to determine if current is actually reaching the fuel pump at key on which I know is going to be a toughie because sometimes the pump runs and sometimes it doesn't. So first, get under that truck and start unplugging the connector or connectors that lead to that fuel pump looking carefully for signs of water entry or corrosion. Try to trace those wires back towards the front as far as you can get unplugging and checking connectors as you go. You have an intermittent problem which has electrical problem written all over it. I'd also be trying to get my hands on a wiring diagram. I'd be doing that because I have no firsthand knowledge of how Ford does these things. What would also be handy would be a troubleshooting tree for your exact problem which would be "intermittent no start condition".

And I get it, intermittent problems are very difficult to diagnose and even more exasperating when it's an intermittent no start condition. But personally, I never see throwing parts at a problem as a solution. My opinion is of no help to you, I understand that.

You should tell people here the mileage on the truck and what engine it has. I think that could help people to help you. Your local Ford mechanic might be willing to give you some guidance for a six pack of beer. It might be worth trying to get in contact with one. For all you know you may have a common problem that he can tell you with near certainty what the problem is just from your description.
 
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railer

Golden Member
Apr 15, 2000
1,552
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You've completely lost me there. <snip>

Back in the initial post, I mentioned that when the fuel pump was not working, that spraying it with starting fluid did not start the truck. This gave me pause that it was actually the fuel pump, and that I might be dealing with a different issue upstream of the fuel pump. So now that the fuel pump is working, then by intentionally disabling the fuel pump, and only the fuel pump, and determining that the truck still does not start with starting fluid, I'm less concerned that there is something else driving this. It's still possible, of course.

And yeah I've swapped the relays - The PCM and fuel pump relay are the same, so they're easy to swap. I think the most likely cause of intermittent failure is the fuel pump. I'll probably take this to a shop to have it done, as when I looked under the truck tonight I just LOL'd. It's a 2001 in NY....so everything is going to have to be cut off vs. simply unbolted.
It won't be cheap I'm sure.

Fuel pumps dying intermittently is a fairly common issue found on F150 forums: http://www.f150online.com/forums/1997-2003-f-150/461900-fuel-pump-problem-sometimes.html
Mine is a 5.4 with 130k on it.
I was just trying to to eliminate everything else before jumping on the fuel pump....but I don't see anything else to eliminate, other than a random open somewhere in the wiring harness...which would be even worse than changing the fuel pump.
 
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LTC8K6

Lifer
Mar 10, 2004
28,520
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Won't the PCM relay also cause a no-start?

I mean, is it a good idea to swap those two relays to diagnose a no-start?
 
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