UPDATE::::::
Well, I took my truck to a local shop (third different shop) & I think they are on to the problem. The owner is a real sharp electronic & computer guy. He didn't wait for it to stop or quit running he jumped in with a diagnostic computer & started tracking the problem.
What he has found so far is that the LOW & HIGH Computer fuel trim readings are reading in the negative. He found & fixed the LOW TRIM reading by seperating the 02 Sensor wire out of the loom. The 02 feed wire & the rest of the wires in that loom including the positive battery cable have acid in the the wiring between the copper & insulation but look perfectly OK. He believes when things get hot the acid is causing false reading to the computer. The High Trim he thinks is a faulty 02 sensor but hasn't really got into that yet. He just got the LOW Trim fixed. A negative fuel trim reading causes the computer to lean out the fuel. As bad as the readings were it would lean to a no run condition.
So I'm hoping he has found the GREMLIN I have in this truck once & for all.
Anyone ever had or seen this??? Any opinions or thoughts???
Craig

 

I've never seen it, or heard of "acid" in the wires. I've seen corrosion in wires before, but the acid issue is a new one to me.

At this point, I think he's on to the right way to diagnose by doing real-time monitoring though.

 

I think what he means is that corrosion, which he believed to be from leaky battery electrolyte, made it's way down the wires.

Usually it's just plain ol oxidation though. I'd have a hard time believing it's actual battery electrolyte unless it was overcharged at one point and boiled over or vented onto the wire harness.

And I agree the shop owner is off to a good start monitoring live data. That's why the capability is there, and he knows to take advantage of it.

 

Yea corrosion (acid) either way it provided a bleed over of electrical currant enough to throw the low trim fuel reading into a negative when hot. Remember I live where it get & stays in the 110-118 all summer. (So under hood temps exceed 300 degrees) You can't touch anything under the hood including the rubber & plastic dipstick handles when you have run a vehicle to temp without burning your fingers or hands. This issue never appeared until I brought this truck here in the summer heat. I drove this truck on two 1000 mile round trips down here in the spring before temps got warm with no issues.
I know enough about low voltage currant to know it can be disrupted by some pretty strange things. So anyway I'm hoping he is on to something. An 02 sensor replacement is sure cheaper than a fuel pump or the 3 tanks of fuel these other shops have ran out waiting for it to quit & never did.
So I'll keep you guys posted on the progress or results. Please wish with me that he has found the GREMLIN.
It is amazing to me how few of shops know or use live data. He is the first shop I have been to that has done anything like this. He has a nice Snap-On diagnostic computer, I'm sure that wasn't cheap. I own all Snap-On tools from my days in the business. I just found out if I needed to replace my 1" combination Snap-On wrench I was looking at close to a $100 unreal. In my 15 year career (1969-84) I spent like $3000 on Snap-On tools. Today's value is triple or more.

Craig

 

I think the problem lies with the older OBD 1 vehicles, in which a guy needed separate diagnostic tools for each manufacturer. In this case, a Ford, with a breakout box, and other specialized equipment. These days, OBD2 has made things much easier to record real time data.

Either way, it's great that you've found someone that has the diag tools to work on it!

 

Yea, I most likely would of never figured this out if this turns out to be the issue. I just want my Ford back & reliable again. I love this truck. These years are my favorite Ford truck. I need it to go back & forth to our summer retreat in the mountains we bought a few weeks ago.
So lets hope for the best.

Craig

 

Well talked to the shop owner this afternoon & he changed the 02 sensor & the high trim fuel reading is now in the positive range. He told me he was going to drive it 20 or 30 miles & see how it runs out. He drove it a short distance this afternoon & said it ran very well. So I should get it back tomorrow pm. I'll keep you updated.
Craig

 

Got my truck today. The shop owner told me to drive it for two or three weeks then come pay him. He wants me to be sure he got it. It runs great starts great. So far today no problem issues.

Craig

 

Sounds like an awesome mechanic!

Hope you got it fixed.

 

Well, this afternoon after driving it several miles I stopped to take my dog swimming when I got ready to leave it acted up again. But this time I was able to the shop. When he crawled under the truck the front pump would run a few seconds then start making noises then lock up, then start working a few seconds & lock again. He could hear it. If you let it set over night, it would work fine for well it is getting shorter in time, but a few days. So Monday he will pull the front tank & see what he finds. I think the pickup screen is deteriorated & pieces could be getting up into the pump. I have seen this when I changed my pumps in my 86 F250 years ago. After looking at the front pump & tank we will decide if we should do the rear pump also.
So I'm relieved to finally pin it down.
I will say the replacement of the 02 sensor & getting the fuel trim into the positive sure helped the starting & it runs better much smoother when it ran.

Craig

 

It honestly sounds like the pump is failing... My POS Airtex pump that the PO put in my truck did that..

Would run perfectly fine for days, then BOOM. Barely would run.

Then it got to the point you'd have to let it sit 1-2 hrs to cool off.

A new Bosche unit fixed the issue.

Here's a pick of the rear tank strainer I removed...


It fell apart when I barely touched it to the tank..



And the strained after being in gas since 1996.. (Swapped tank off another truck)



A new Delphi strainer is on both pumps now. $6/each.

 

That is exactly what the shop owner & I think will be found. In that case most likely will change both pumps. The truck has 140,000 miles has sat a bunch & has been run out of fuel a few times that I know of from PO.
The Shop Owner is going back with Delphi Pumps. I have had the best luck with Delphi. They made a lot of the OEM Pumps for many of the manufactures including some of the Foreign manufactures. When the front pump comes out I will post a picture if I remember. But it won't be until Monday.

Craig

 

A bad fuel pump being exposed by a hot ambient temps? Who ever heard of such a thing! Glad you got it all sorted out, hopefully this fixes it for sure.

 

The odd thing is every time I have had an in tank pump fail it QUIT. This one works for awhile then quits, then works again. When it quits it only stops working for a short period of time.

I'm thinking of adding the frame rail hi pressure pump as a back up so I never have an issues like this again. I would hook it up to a toggle switch that I could control manually only. ANY THOUGHTS???
My 86 F250 4x4 460/C-6 had a crappy fuel system. I put two new pumps on it when I got it. Back in the 90s only pumps I could find were dealer only. So Ford OEM PUMPS. I had trouble with even the new pumps. So I added a frame rail 14psi pump with a regulator (carb engine) that assured I wasn't stopped in the middle of nowhere.
Now my 95 & fuel issues.
The funny thing is we have owned about 7 total of Ford Rangers, Explorer, Mustang, & T-Bird & never knew that in-tank fuel pumps were ever a problem. Our T-Bird had a 190,000 miles & a few of our Rangers had over 160,000 miles.
But the F-Series sure haven't been that trouble free.

Craig

 

Intermittent problems are the hardest to find. Suggest checking your fuel pump relay. I had one fail intermittently causing the fuel pump to appear to be bad...... New pump and few days later back to the same thing!!! The pump was due for relacement anyway with the fuel sock rotted like Sidewinder's photos show.

It took OVER a year to finaly track down the problem. As soon as that relay opened contacts and reclosed when restarting the engine it ran good till "X" amount of time later(which could be months!) Finaly one day it hard faulted, I found it with in two minutes while on the side of the road with no test equipment at all(meter or test light) A small jumper wire bypass got me home to where I have 10 of them on hand but none in the truck.... Now I do keep a few relays in my truck along with fuses too!