Hay everybody glad I found this website!! I have a 95 F150 with a 5.0 liter. Excellent shape for the and I'm planning to restore it this spring. Recently replaced the fuel pump, filter and tank. I know I'm getting power to the pump, I've checked the relays fuses and the inertia switch as well as a few other suggestions from a good mechanic. Still the truck will only start for a second and will not run. Over a week before the mechanic can get it in the shop. I'm wondering if I temporarily ran a jumper wire from battery to pump if I could damage anything?? I've done this in the past years ago on a much older vehicle in a pinch with no problems but I sure don't want to ruin the computer or my brand new pump!! Anybody out there ever done this on a 95 or perhaps know why I should be able to or should not do this?? Really don't want to borrow a car all week or have to tow it to the mechanic. Any feedback would sure be helpful. Thanks!!!

 

Did the pump you bought require cutting the stock harness and splice in one that matches the new pump harness?

 

It required that I splice the wires that were connected between the old pump and the cover that fits on to the tank that the fuel lines connect to but I did not have to splice the wire to the harness. This application you use the old wire harness

 

Reason I ask is I just had an issue where my pump was running backwards due to the hot and ground being reversed. You can rent a fuel pressure gauge that attaches to the Schrader valve on the fuel rail to check your fuel pressure to start eliminating things. You can also activate the pump by grounding the LB/O 926 pin at the data link connecter.

 

Oh I see. Yeah I'm sure it's all hooked up correct. I only spliced two wires, red and black that connect to new red and black wires on the replacement pump inside the tank. To connect my jumper I would disconnect the harness coupler and connect my wires to that. I know this would mean no gas gauge or safety shut off until properly fixed. I'm just not sure if I could damage anything if I did this. Any thoughts??

 

You can achieve the same result by running a piece of wire from any ground to the pin shown in the diagram above. Someone else will have to chime in on the consequences of running the pump like this for driving.

 

I gotcha now. I must have scrolled right down past the diagram in your reply. That would be a much easier way to go for sure!!! Still like you said I'm not going to do it unless somebody can tell me for sure I'm not going to hurt anything.

 

The pump runs all the time the engine is running or cranking so no you will not hurt the pump.
Are you saying that the selected pump will run for one second each time the key is turned on?
And are you also saying each time you try to start it without spraying anything into the intake that it will try to start each time?

If you said yes to the two above then it sounds more like you have an ignition switch problem than a fuel problem.

 

look at ya go!


very valuable tool, is it not?

 

to the op: I have a permanent jumper setup built into my truck. I had to replace my fuel pump relay plug a while back due to corrosion, and as much as I avoid using sta-kon connectors on auto stuff, I used two of them for the voltage input to the relay and the voltage output to the pump, and one for a ground. in the event the relay fails or something else funky happens, I can just bypass the relay and run the pump with a simple switch in plugs.


I do this wherever possible, both for diagnostic purposes and so I don't get stranded. just food for thought.

 

If the key is turned on and off a few times the truck will fire for a second but only once and awhile will it fire at the first attempt .If I put a little gas in the intake it runs until the fuel is burned up. I did have a mechanic bring over his diagnostic tester that indicated something electrical and he pointed out a few possibilities for me to check but I could not find the problem. So....to the shop it goes! Knowing I won't hurt anything jumping power to the pump is a great help as I should not have to tow the truck in to see him. Also an ignition problem does seem very reasonable. Thanks a bunch that was a great help!!!

 

Extremely!!!!!!!!!!!

 

You could try swapping the fuel pump and horn relays and see what happens.


/

 

Awesome suggestion I did not try yet but I sure will today. Tried grounding the diagnostic connection yesterday with no success but the previous day the truck was pulled out of the heated garage it was in to make room for a tractor that wouldn't start and also figured the truck was going down the road in tow to the shop. It was -30 wind chill and snowing sideways yesterday so I may not have taken enough time to see that I had a proper ground!! Thanks again for all the help everyone!!!!

 

Looks like you got you issues sorted out, so that's great.
I'm posting here because the issues I had a few months ago were similar, and I thought maybe this would be an appropriate spot to let people know what I found.
I was having intermittent issues where my truck ('96 F150 4.9L 6 cyl 5spd 4x4 short box) would turn over but not fire every now and then, for the better part of a year. Difficult to diagnose when the problem disappears as suddenly as it appears. After taking advantage of the wealth of helpful info submitted on this site, (thank you VERY much everyone) I was able to narrow it down to a crappy electrical connection right at the motor of the fuel pump. There are two regular old spade terminals right on the motor, with regular old spade connectors clipped onto them. One of the connectors was all loose and jiggly. Not corroded at all. Just loose. I don't know if it had been jammed on too hard, when originally installed at the factory, which can spread the clip more than necessary....but anyway. Unfortunately, I found this out too late in a post-mortem exploratory surgery, after having had the fuel pump replaced (I'm at the stage in my life where I'm less willing to take on more and more of the dirtier jobs...and more able to pay to contract some of them out) by a mechanic. I got the old pump from him, took the plastic housing off, and proceeded to kick myself for basically wasting over $600.
In retrospect, there's a number of things I'd have done differently, but the main thing is that I'd have taken the advice of a buddy at work and seriously considered cutting an access hole in the bed of the truck to get at the fuel pump. (BTW I'm not sure why it isn't a common thing for the manufacturer to install an access panel on the floor of the bed) I'm sure I could come up with a patch job for the hole that would work well enough under the mat I keep in there as a bed liner. I hadn't considered that beforehand and it was the dealing with the gas tank or removing the box entirely that put me off the project, after all the head-scratching I'd done (my bald spot grew a bit through all this).
The other thing worth mentioning is that mechanics are often NOT much more capable than you and me (at least in the small community where I live). Maybe they have better facilities and tools but with access to forums like this, we can probably out perform many of the so-called professionals. My pump could have been fixed for much cheaper if my mechanic had thought to look a little further before ordering a new pump. He could have listened a little closer to one of the symptoms I passed along to him...at one point before I delivered it to him, I had rigged things up so that when I turned on the ignition, the pump would continue to run (normally it shuts itself of after a few seconds once the fuel pressure has built up). I could hear the pump working all the time up to when I cranked the starter. The engine would fire briefly and die right away. With the ignition still on, I could hear that the pump was no longer running. I hit the bottom of the tank with a rubber mallet and it would start running again. Crank the starter, pump dies / bang the tank, pump starts working...over and over again. I guess the electrical surge of the starter was playing with crappy connection of the pump. I trusted my mechanic when he assumed that the pump couldn't be repaired but he obviously was wrong. Oh well. Live and learn. My truck has been running flawlessly for the last few months, so life is good again.
Don't know how likely it is that my story well help anyone else but after all the help I received here, I'm hoping there's a nugget of help for someone.
Cheers!