The most annoying mechanical problems are the intermittent problems, right?

So I bought this 1997 F-250. It has ~125K miles.

5.8 liter automatic, two-wheel drive.

Very clean truck.

Sometimes, it will start up and run pretty well. I took it to the lumberyard the other day, no problem.

Sometimes, it will stumble and pop just like it is starving for gas. I think that's probably because it's starving for gas!

It will not accelerate, it will not go over about 45 MPH, and then only when it gets a running start downhill.

I know this is the 1987-1996 forum, but I am told the 1997 F-250/350s were a chance for Ford to use up the last of the '96 bodies.

Weird fact #1: There is no OBD socket on this vehicle.

I really don't have a Weird Fact #2, just yet, but the way things have been going, I'll be up to #72 in no time.

The Previous Owner fancied himself a mechanic, but I don't carry that burden.

I am a self-acknowledged hack, but I usually manage to keep my vehicles and yard equipment running nicely.

Remember that this doesn't happen every time I drive the truck, just 50% of the time. It is WAY more than enough for me to avoid using it whenever possible.

The PO insisted that the fuel filter was the culprit. When I got the truck home, I inspected the fuel filter, and it became clear that Ol' Gooberhead was WAAAYYYY more of a hack than I ever was, because he had done unspeakable violence to the filter. I had to cut the fuel line to get it off. When I had it all back together, I gave the filter a shake, and there was something rattling around in there. When I cut it open, the little filter element fell out on the bench.

Nice.

Because this is an intermittent problem, I suspect the injectors are still functional, the ECM is not bad, the air flow sensor is OK.

My suspicion is centered on the fuel pump(s).

The fuel gauge reads empty (I am told this means the sending unit is OK, because when it goes bad, the gauge will read past full), and when I switch to the rear tank, the engine starves to death almost immediately.

My suspicion, as I say, is that the fuel pump is failing. sometimes it will, and sometimes it won't.

Any other ideas from this august company, or should I simply take it to a mechanic and leave him with a stack of money?

Thanks!

John

 

There is typically no OBD-II port inside the cab on the 1996/97 F250/350 trucks. Only California emission trucks were OBD-II, the rest remained OBD-I which means the diagnostic port is still located under the hood near the driver side hood hinge. Some areas adopted the Cali. emissions so you may find a few in places like Massachusetts.

Best suggestion is do a complete tune up with fresh copper core plugs, new plug wires, distributor cap & rotor. Replace the air and fuel filters.

I would also check the fuel pressure at idle, at idle with the vacuum hose removed from the Fuel Pressure Regulator and also under load. The pressure should never go below 30 PSI. Removing the vacuum hose from the FPR should result in ~40 PSI. Same for under load.

As usual run the Key On Engine Off (KOEO) tests and Stored Code (Continuous Memory) display.

I see nothing in your post that suggests you need a wallet biopsy to fix.

 

THANKS!

After scouring the area under the dash for the OBD port, I did look around under the hood, but thanks for narrowing the search area.

My impression of this issue was the same as yours, in that it should not be some horribly expensive fix.

I should have mentioned that the tune-up was my first effort. The truck initially ran in one of its 'good spells', then relapsed to stumbling for a while. Then ran reasonably well, the next time I tried it.


On again, off again . . .


I will look into the tests you recommend.

Another thread on this forum suggests that a fuel pump relay could be going bad.

Where would I locate that critter?

Also the FPR? Where will I find it?

I hope y'all will bear with me. My life is a battle against my own ignorance, but the more I learn, the less I seem to know.

Thanks again!

John

 

Another thought that comes to mind is that Ol' Gooberhead used this machine to tow a big fifth-wheel camper. He said that he would disconnect the positive battery terminal when he got to the campground and unhitched the camper, because "that resets the computer".

Did the guy actually "RUIN" the computer?

Very frustrating.

 

The Diagnostic Port is here:



Near the driver side hood hinge.

You can run the Key On Engine Off (KOEO) tests and Stored Code (Continuous Memory) display as well as the Key On Engine Running (KOER) tests. Highly suggest you start with KOEO tests and CM code display.

You can do the above with a paper clip. Warm up the engine then do this: How to run a self test

Count the flashes. It's sort of a PITA. I recommend investing in a code reader such as the Equus/Innova 3145.

Test, diagnose before throwing parts at this....

Could be a number of things. Start with the code check. If you want to put your wallet on a diet:

Engine compartment Fuse and Relay box




Fuel Pressure Regulator



Located on the fuel rail return side. Behind the TAB/TAD relays near the firewall.

We are here to help. Photos courtesy of Subford and the old RJM Injection site.

 

It's possible the computer may have been damaged with multiple battery cable detachments. Checking for codes will be a good start to see if there are issues.

 

AWRIGHT!

I drew Code 33 (EGR Valve Opening Not Detected), and Code 542, (Fuel Pump Circuit Failure).

I'm guessing if the EGR valve is bad/sticking intermittently it could cause this?

I do not know what to make of the fuel pump circuit failure, as this could easily point to the fuel gauge malfunction/rear tank not operational.

 

OK, I cleaned up the terminals in the EGR connector, and ran the test again.

Now it throws Code 327, DPFE or EVP circuit below minimum voltage of 0.2 volts.

Now what?

 

Not so fast there pard'ner.....You cannot have a mix of two and three digit codes. It's one or the other. Since you have a 1997 model year truck that 33 is most likely 111 displayed twice (111 pause 111). That is the System Pass code for KOEO. That's a good thing.

Code 542 is from Continuous Memory (Stored Code) so something happened in the fuel pump circuit in the past. How many times it occurred or when is the question and limitation of OBD-I.

You can clear the codes from CM by pulling the jumper when the code flashes start. Drive the truck again, see if the stumbling occurs then pull the codes again. Code 542 may be triggered by the bad rear fuel pump. It may be an open circuit. On the other hand it could be the front pump circuit. So it's a matter of process of elimination.

 

When was this code displayed? KOEO or CM?

 

That was in KOEO.

 

Well then. Perhaps you did not get the connector back on completely.

Otherwise turn the key to Run position, grab a meter then back probe the EGR Valve Position (EVP) sensor to verify it output.

Use this as a reference: EGR Valve Position Sensor (EVP)

Spoiler alert: The EVP should read between 0.24 and 0.67volts at idle with a closed EGR valve.

 

OK.

Please remember that I'm a hack.

'Back probe'?

Also, am I to understand that I am to test between the terminal labeled 'EVP' and ground?

Thanks again for your patience and your willingness to share knowledge.

 

OK, while I was waiting for further enlightenment, I took the sensor off the top of the EGR valve, inspected it, gave it a squirt of WD-40 and reassembled it.

The plunger was operating smoothly and without hesitation.

Then I connected the ground on the test terminal, turned the key, waited for it to flash the initial rapid series of signals, and disconnected the wire to clear the reader.

Next, I turned the key to the 'on' position, and waited with pen in hand for the codes.

I got 111, repeated 111 then a long pause followed by 111 then a repeated 111.

nothing else.

?

 

OK! So, I omitted the 'Drive the truck again' step in the above tutorial.

Having realized that, I went and drove the truck again.



(I'm not real familiar with emoticons, and my eyes aren't what they once were, but I hope that little green, grinning smiley is wearing a dunce cap)

I think I may have fixed the problem that started this whole mess, with y'all's help.

The truck now runs. It is really rough, but I am attributing that to the broken fuel filter that Ol' Gooberhead left me to figure out. It is my understanding the the injectors on this engine have little screens, and I'm sure they got flooded with grit and goo when he knocked the element loose inside the filter housing.