Hi guys, I just bought a 1989 f-150 4x4 with the 4.9l inline6. The frame was cracked so I welded a plate to it...I managed not to disconnect the negative terminal on the battery when doing so and now my truck isn't getting enough fuel to run it. My pump makes a high pitched wine it never made before and it dies after idling for 30 seconds, and it will continue to whine until I start it. I cleaned all of the connections, EEC relay, and TPS connection. I can get pump the external pump for $30.00, that's not the problem I just want to make sure I'm not missing anything. I thought I could have fried the computer but I don't have any error codes and everything else's works fine.

Thanks.

 

Where on the frame did you weld it? It sounds to me like you could have caused a fuel line to partially melt and therefore restrict fuel flow.

 

Right above the driver side rear tire. I did melt the lines, ran it afterwords and it died, I didn't realize I melted them at this time. I repaired the lines yesterday with couplings from oriellys, no leaks from what I could tell.

 

That could have turned out a lot worse!

 

Yeah, I got lucky, they self cauterized so no fuel or fumes were leaked.

 

So do you all think its just the fuel pump that needs replaced?

 

The fuel pump shouldn't run continuously if the EEC sees that the engine ain't running. Might have damaged the EEC since it won't shut the pump off or run the engine... or it could just be a coincidence that something decided to fail right when you went to do some welding. Aside from the fuel lines of course, that damage was obviously caused by welding. I sure am glad you didn't set yourself and your truck on fire!

Not saying it's the right thing to do, but I've welded on a couple of my trucks with the battery connected, key on, and radio blasting. Didn't hurt anything... the trick is to put your ground clamp RIGHT NEXT TO where you're stinger/gun is. I suppose if you were welding AC you *might* induce a stray current somewhere that a DC arc wouldn't, but some Jeep guys mount a second alternator (w/o regulator or rectifier) as a welding power source for trail repairs.

Ford apparently recommends that you disconnect all the electronic modules and the battery before welding. F*** that... I'll stick to DC and take my chances.

 

You could try, disconnecting the battery and let it sit for about 30 minutes. Maybe the computer will reset itself.

 

Alright, so I checked the EEC relay, it's got power and works. Check the computer, took it apart and none of the capacitors are blown, it works. Took the inline fuel pump (high pressure pump) out, hooked it up to a battery and it works fine.

Could it be the dual function resivor!? I don't know what the problem is, please help.

Thanks.

 

I'm not exactly sure what you are trying to fix. I thought repairing the fuel lines solved your problem. What is it doing or not doing?

 

It starts it just dies after 30 seconds like its not getting fuel. If you try to hit the gas while its idling it just falls on its face.

 

Do you have a way to check the fuel pressure? Can you tell if the pump is running as it is dying?

 

I think you need to check fuel pressure at the injector rail supply line. I'd also pull codes. I realize this is what everyone tells you to do, but there is a reason for that.

For info:
Your '89 truck has a low pressure pump in the tank. It feeds a reservoir. The reservoir is located on the driver side frame rail. The reservoir acts like a float bowl in a carb. Low pressure fuel fills the reservoir and recirculates back to the tank.

A second high pressure pump is located on the driver side frame rail ahead of the reservoir. It pulls fuel from the reservoir (the float bowl) and sends it to the fuel rail. From there it recirculates back to the reservoir.

These model dual tank trucks have a different reservoir than single tank trucks. The dual tank trunks have a reservoir with valves that route the fuel. When you switch from one tank to another you are selecting which low pressure fuel pump (in the tank) is powered. The dual reservoir has valves (mechanical) that route the fuel.

Single tank trucks have a much simpler reservoir. You can use a single tank reservoir on a dual tank truck to convert it to only one tank, and you should pick the front 19-gallon tank.

 

Thanks xl I really appreciate your knowledge. I would like to keep this as original as possible as I am the third owner, second owner was a good friend of mine. It was originally a farm truck, I'm attempting to revive this bad boy.

Do I need to split the line before or after the external fuel pump? Also how would I be able to check codes? I'm new to the mechanic side, I'm use to new vehicles, this is my first "project".

I'm too cheap to take it to a shop, I'm determined to try and figure this out with y'all's knowledge.


Thanks guys.

 

oldfuelinjection.com will show you how to pull codes