F250 not running right.....calling all mechanic types

[muncybob]

I put this in the DIY area since it's probably somthing that I did causing my current situation. Recently had to remove the front gas tank due to a leak and have not yet replaced it. I don't travel very far with the truck so it's not really needing 2 tanks. Ever since this she runs fine for awhile but then seems like not getting any gas...spurts/jerks and sometimes even stalls. I plugged the 2 lines that use to be attached to the front tank but still does the same. Just replaced the fuel pump but not resolved....any ideas?

 

[Ashful]

Does it have a manual transmission?

 

[heat seeker]

Just a WAG, but is one of the lines you plugged a return line? If it's blocked off, it may build up back pressure that's hindering the fuel pump. Just a guess!

 

[Adios Pantalones]

If the front tank had some sort of vent to equilibrate pressure, then removing it probably causes a vapor lock type dealio

 

[semipro]

Along the lines of the previous two posts.
Remove the gas cap after driving a while to see if a vacuum has built up in the tank. If so, you plugged the vent.
Vent lines from the fuel tanks run up to a charcoal canister in the engine compartment where the fuel vapors are absorbed into the charcoal. When the engine runs air is pulled through the charcoal and the fumes are pulled into the engine and burned.

 

[Hogwildz]

Might seem stupid, but check any/all fuel filters. Disturbing a tank can even clog a fuel filter when stirring up any sediment that is/was on the bottom.

 

[pyroholic]

All great suggestions here, check it out and report back.

 

[muncybob]

Does it have a manual transmission?

No, but that is funny. I don't recall when I last changed the fuel filter so I was planning on that too. Probably be trying to run it tonight to pull some hay wagons to the barn so I'll remember to check the cap.

 

[TMonter]

No, but that is funny. I don't recall when I last changed the fuel filter so I was planning on that too. Probably be trying to run it tonight to pull some hay wagons to the barn so I'll remember to check the cap.

Also check the fuel return line. What year F250 is it? On some models a single return line comes from the fuel pump on the engine and can feed back into one tank and not both.

Another potential issue is the tank switch, these are notorious for having problems on some models of the F250.

 

[higginscl]

What year is it? Depending on the year they had 2 pumps. One in the tank and one on the frame rail. The one in the tank is like a lift pump and the one on the frame is the high pressure. I could be wrong but I think the wiring for the two pumps in the tank piggy back off one another so by disconnecting the one it is not feeding power to the other one causing the expensive pump on the frame to be trying to pull fuel and push which will cause it to overheat and burn up.

 

[muncybob]

It's an 86. Only ran it briefly last night. Taking it to haul dirt tonight if it don't rain so I'll check the gas cap then. If my old tank has not been scrapped yet I may just reinstall it to see if that's the culprit.

 

[TMonter]

What year is it? Depending on the year they had 2 pumps. One in the tank and one on the frame rail. The one in the tank is like a lift pump and the one on the frame is the high pressure.

This is only true if it's a fuel injected model. If it's carbureted it's likely low pressure in-tank pumps or it *might* be a mechanical pump on the engine.

The pumps are not piggybacked off of each other but they are both routed through the electromechanical switch on the frame by the main tank.

What engine is in it?

Just FYI a new tank isn't that expensive, I paid a little over $120 for the rear tank on my 86' F250 2 years ago. In fact the new pump and sending unit I bought was more expensive.

 

[muncybob]

It has a 351 w/carb. Pump is mechanical(already replaced). Have not had time to run it yet but plan to work it hard this week end. No longer have the old tank but did keep the sending unit. May just hook up the sending unit and strap it up somehow to see if it runs any better. JC Whitney has tanks at reasonable cost but the vent assembly is another $60.

 

[semipro]

You shouldn't have to re-install the 2nd tank to fix this problem.

 

[TMonter]

It has a 351 w/carb. Pump is mechanical(already replaced). Have not had time to run it yet but plan to work it hard this week end. No longer have the old tank but did keep the sending unit. May just hook up the sending unit and strap it up somehow to see if it runs any better. JC Whitney has tanks at reasonable cost but the vent assembly is another $60.

Check the fuel filters, there may be an inline filter and there is likely one right on the carb. Also check the electromechanical switch on the frame.

I ended up getting my rear tank at Napa

http://www.napaonline.com/Catalog/CatalogItemDetail.aspx?R=STPF14B_0261757371

Here is the front tank For $129

 

[muncybob]

h eonly fiuel filter is located at the inlet to the carb, replaced that althoug the old filtre looked n god condition and after i dropped the new one it wa probably cleaner than the one I put in

So, new filer, new pump, connectd the old sending unit...still same problem. I did forget to check the gas cap and probably will do that tonight. So, if there is a vacuum build up then check the vent on the old tank?

 

[Hogwildz]

The the lines along the frame for an inline filter.

 

[Ashful]

The the lines along the frame for an inline filter.

I thought the same. My old pickups always had an inline filter on the line running inside the frame rail, usually right under the driver's side door.

 

[muncybob]

Traced the lines but could not find another filter. It now sits at a garage and will be looked at in the next few days. I never seem to get of of there without at least a $200 bill. Wife's off work and no pay until end of August...may have to sell a cord or so of wood

It will be my luck that the score of the century will now show up on CL now that I don't have my truck.

 

[Hogwildz]

Good luck with the mechanic, just some food for thoughtt. I had an early 80's Ford pickup, and I thought the mechanical pump went bad, and the problem turned out that the lobe on the cam was worn down to the point that it would not push move the arm on the mechanical pump worth a damn anymore. I ended up installing an electric pump.

 

[muncybob]

The kicker is that the truck runs fine for about 6 miles or so, then it starts acting up and seems to get worse if running up an incline.

 

[TMonter]

The kicker is that the truck runs fine for about 6 miles or so, then it starts acting up and seems to get worse if running up an incline.

Before you spend a lot of dollars on a mechanic you might try getting a new front tank installed. If there is a sealing issue on the frame tank switch you culd be sucking in air at that location which could lead to the issues you are having.

The issue with it running worse on an incline tends to indicate that something with the fuel pump isn't working correctly.

What pumps have you replaced so far?

I'm thinking if it was working with the front tank before, adding a new front tank is a potentially easy inexpensive fix and certainly cheaper than a trip to the mechanic.

 

[muncybob]

I was leaning toward replacing the front tank until it ran the same even with the front tank sending unit reattached to the lines??

 

[TMonter]

I was leaning toward replacing the front tank until it ran the same even with the front tank sending unit reattached to the lines??

That wouldn't quite be the same thing if you have some infiltration somewhere in the lines between the old front tank and the frame switch. I have a 1986 F250 with the same setup but mine has in-tank pumps front and rear instead of a mechanical pump. Some models had both a mechanical pump and in-tank pump as well. Something else to consider is if the in-tank filter is clogged (if it has one)it could cause the issues you are having

 

[semipro]

I'd suggest you remove/bypass the tank switching valve altogether.

I came across a somewhat similar situation once where the tank was not venting properly and a vacuum would form. The tank (a plastic one) would actually collapse during use and then re-expand when the engine was turned off. The collapsing tank bent the fuel pickup up so that the vehicle would seem to run out of fuel prematurely. The vent line between the fuel tank and charcoal canister was restricted causing the vacuum to build in the tank as fuel was sucked out.

You could just try running the thing with the gas cap off completely to see if it acts up.