sibo191

I have a 1996 f150 5.0 has been sitting 4.5 -5 years. in the last few weeks I have been in the process of getting it running again, reviving it, before I pull the engine and rebuild or replace among many other things that need done.

so far I have changed the oil/filter, changed the fuel filter drained and replaced coolant and a new battery.

did the initial check out routine of pulling the plugs, adding some MMO to the cylinders and turning crank by hand and added new gas with MMO added.

It will start and run for about 10-15 minutes then stall. Basically long enough to get the engine up to temp (gauges seem to work). however it stalls at that point and wont start again until the engine is cold.another issue I noticed today was a fair amount of white smoke coming from the oil fill tube.

I haven't done a compression test yet, because I wanted to be able to get it up to temp and burn off the gunk in the head and cylinders. Im looking to test it just to see how bad it really is.

Any ideas? I will be pulling the engine regardless to either change out the oil pan gasket and what ever other seal is leaking and maybe do a rebuild on the engine if its not trashed, or replace if engine is too far gone.

As for right now Im stumped on whats going on. I know I can do the compression test cold but would rather it be warmed up.

I'm also having trouble draining the old gas out. the rear tank was empty so that is where I put in the new gas, but the front tank was/is full of old stale gas. any pictures on exactly where/how to jumper the relay so the pump will continuously run. Not sure exactly which prongs to jump for that.

Steve83

If it runs, why rebuild/replace the engine? The engine in my truck now sat in a JY so long that the injectors were stuck shut by congealed gas. I had to short them ON to get them hot enough to melt the goo to get the engine to fire up & run. Then I ran fuel system cleaners (Berryman's B12 & Techron) in the first several tanks to really wash them out.

That was ~22 years & 800,000 miles ago. It still runs like-new, never having been rebuilt. I did essentially the same thing to this truck (but with its original engine) nearly a decade ago, and it still runs fine, too:


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The dipstick smoke could be water cooking out of the old oil residue inside the crankcase, or the MMO burning off the rings, or several other possibilities. The hot compression test is the correct plan - click this & read the caption:


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These pics & the NEXT several after each one show a few engines that I've pulled out to re-seal, but only the last one has been reinstalled & is on-the-road right now:


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(phone app link) (there are several dozen pics after that one to get to the re-sealed engine)


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This caption explains how to lock the fuel pump relay ON for '87-95 trucks:


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But since yours is '96, it doesn't have that connector, which means the only way for you to do it is by pulling the relay out of its socket in the PDB and jumpering it directly. There are 2 concerns:
1) it will run continuously until you remove the jumper or the battery dies; the key will have no effect; &
2) it will pull a LOT of current through your jumper wire, so it needs to be well-built with the correct terminals (same type shown in the pic above) and wire size (at least 14ga, but maybe 10ga).
This shows how to crimp the terminals properly:



Solder is better, if you know how to do it. But even with good terminals installed correctly on the right-size wire, it may still get warm enough to melt the insulation near the ends, so be careful grabbing it to pull it loose. This shows the relay location:



In the socket & on the relay, there's 1 unused terminal in the middle, and a terminal at each of the 4 sides. 3 are parallel to their sides; pin #30 is perpendicular to its side, and it's either the hot (B+12VDC) or the output to the pump. The opposite terminal (#87) is the other function of those 2, so just jumper between them with the key OFF. If the pump doesn't instantly power up & buzz in the tank (you may have to lie under the truck to hear it), you may have the wrong terminals jumpered (but with the key OFF, you haven't done any damage). Once the pump is running, see if the engine will run long enough to warm up.

This photo album explains what's happening in the tanks:

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Connect the pressure gauge as shown in one of those pics to find out if that's why it's stalling. If the pressure stays good when it stalls, follow the diagnostic procedure in this caption (it's VERY long, but will positively ID the fault if you follow it):


(phone app link)

sibo191

Thanks Steve. That's a lot of helpful info. I won't have time until the weekend to do more tests but I'll let you know how it turns out.