F-150 fuel delivery problems
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F-150 fuel delivery problems
2 days ago my truck had a hard time waking up in the morning; she'd never, ever done that before. I drove her to to work (17 mi.) and everything appeared to be functioning normally. 10 hrs. later there was no waking her. The engine turns over beatifully on the nice new battery. I'm positive that there is spark. The fuel filter is only 1,000 miles old and I only pump 93 octane fuel. 1 day ago I replaced the high pressure fuel pump and the fuel filter (motorcraft). Once I got the new pump wired properly the engine ran as it never had before. No lagging under the pressure of the a/c pump. No shaking and sputtering at stoplights. Beautiful. Today she wouldn't wake up.
Could the new pressure in the fuel system have blown out the other pumps simultaniously? Is there a relay for the fuel system? I see a space for one on the relay block but theres no relay. I assumed that it was some sort of tester port. And if that is the case then how could the truck have been functioning all this time without the relay?
Could the new pressure in the fuel system have blown out the other pumps simultaniously? Is there a relay for the fuel system? I see a space for one on the relay block but theres no relay. I assumed that it was some sort of tester port. And if that is the case then how could the truck have been functioning all this time without the relay?
Tuned
Joined: Apr 2003
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From: 13th Colony
What year model is it? Also, can you hear the fuel pump run for a few seconds when you first turn the ignition on? You should be able to hear a buzzing/whirring sound of the pump running when you first turn the ign on. If not, the pump is not powering up. I had the plug on my front tank on my 90 f150 dual tanks come loose, thought the pump was bad and found the plug was loose. On a 90 model, the relay is in front of the fender between the master cylinder and the air filter housing. One relay is for the ECU the other the pump. You said high pressure pump, so I am thinking 88 or older when they had the intank low pressure pump and frame rail high pressure pump. If you replaced the high, I suspect it would still run if the low is bad (just not very well). You can siphon thru the low pressure intank pump. It is just to get the fuel to the top of the tank and to make it easier on the high pump. I once had a problem with the fuel cut off relay, the plug melted and was not making good contact making it not run sometime. I cleaned the plug and problem solved. The relay is mounted on the firewall and it gets fairly hot sometimes.
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Ended up being the relay. The previous owner had already changed the relay but he returned the plug the the slot marked "trailer lights" on the relay block. It didn't even occur to me that I should check to see if there was a trailer harness in the back. The funny part of the story is that there was a spare relay clipped into the spot for the "fuel pump". I couldn't find a harness for it I thought I was crazy. It took a little wisdom and 70 dollars to show me that I could've fixed my problem for free if I'd have looked at it more simply. Oh well at least I now have 3 spanking new fuel pumps. I'm sure that Kevin mobile mecanic didn't mind earning an hours wage in 5 minutes.
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