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1980 - 1986 Bullnose F100, F150 & Larger F-Series Trucks Discuss the Early Eighties Bullnose Ford Truck

1981 F250 Sporadic Engine Stalls

 
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Old 02-10-2019, 12:55 PM
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1981 F250 Sporadic Engine Stalls

I bought a 1981 F250 with dual fuel tanks a couple of weeks ago and am slowly fixing it up. I have been driving it every day for about a week now and am getting sporadic engine stalls. I’ll be driving for 10 minutes and then my engine will cut out, as if it is not getting any gas. I then just roll to the side of the road and try starting it again. Sometimes it fires right up, other times I will have to wait a couple of minutes. This happens every 5-20 minutes.
I am rather new to the world of Fords in particular and would appreciate some input on possible causes.
 
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Old 02-10-2019, 02:38 PM
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First welcome to FTE.
You did not post what size motor as that may lead us to something else than what I listed below.

That is a sure sign the IGN box on the inside of the fender well is going bad.
It heats up and stops working and motor shuts off.
Motor off it cools down and will start working again.

This can do this for years if you can stand it that long or stop tomorrow and not work again.
If you find that it does the same thing you now have a spare for when it does goes bad.
Post back if it works or not and if not we can dig deeper.
Dave ----
 
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Old 02-10-2019, 03:00 PM
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Thank you for taking the time to reply.

It has a 351 engine in it. Funny thing is that it is actually sitting on the side of the road right now because it won’t start anymore. I have a little bit of a suspicion that something with the fuel system is not in order as well. The way it stops, is that the engine stutters and then only runs in extremely low revs before going out completly. After leaving the truck and coming back to it, it fiered up very briefly and stopped again. Once I I get it towed back, I’ll check if the fuel pump works. If it does I am guessing that you are right about that IGN module.
 
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Old 02-10-2019, 03:03 PM
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Simply take the air cleaner off, look down inside the carb and push the throttle wide open. If you see two streams of gas squirt into the engine, you have fuel, and you can surmise you have a spark problem. Harbor Freight also sells a cheap spark tester.
 
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Old 02-10-2019, 03:28 PM
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Originally Posted by Franklin2 View Post
Simply take the air cleaner off, look down inside the carb and push the throttle wide open. If you see two streams of gas squirt into the engine, you have fuel, and you can surmise you have a spark problem. Harbor Freight also sells a cheap spark tester.
Yep easy to do wile waiting for the tow.

How much fuel is the gauge showing?
I would also replace ALL the rubber fuel lines.
Should have a short piece at each tank to metal lines, more short pieces at the duel tank switching valve, short piece from the metal line to the pump and may have some between pump & carb.
Todays fuel eats the older rubber hose from the inside out even if it looks good.
Dave ----
 
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Old 02-10-2019, 04:00 PM
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Well, the gauge isn't working right now. (I am working on fixing that right now) Both fuel tanks are full though. As I was waiting I poured some gas into the carb and it started right up. I am guessing that means that it is either the fuel pump, or something related to it.
 
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Old 02-10-2019, 04:41 PM
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Originally Posted by BlueWhiteFord View Post
Well, the gauge isn't working right now. (I am working on fixing that right now) Both fuel tanks are full though. As I was waiting I poured some gas into the carb and it started right up. I am guessing that means that it is either the fuel pump, or something related to it.
Well to test the pump a long rubber hose into a gas can and see if it pumps.
I think the duel tank valve if it fails will only pull fuel from 1 tank not the other. Could always bypass the valve with rubber hose to check.
On the later years I think it can fail and not pump from either tank.

IIRC the gauge goes thru the tank switch on the dash. Have you tried to flip the switch back & forth a few times? The contacts could be dirty inside the switch.
To check the wiring & switch, ground the wire at the tank senders, turn the key on and the gauge should move to full if everything is good from tank to gauge.
If it does not let us know and we can dig deeper on it.
Dave ----
 
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Old 02-10-2019, 08:44 PM
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Thank you for the tips, I will do all of those tests. Getting a good diagnosis is a lot cheaper and probably more reliable in the long run than just throwing parts at it. Do you know by any chance ford used mechanical or electrical fuel pumps in 81? I can’t seem to find a decisive answer on that.
 
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Old 02-11-2019, 06:00 AM
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Originally Posted by BlueWhiteFord View Post
Thank you for the tips, I will do all of those tests. Getting a good diagnosis is a lot cheaper and probably more reliable in the long run than just throwing parts at it. Do you know by any chance ford used mechanical or electrical fuel pumps in 81? I canít seem to find a decisive answer on that.
I am pretty sure the factory pump is a mechanical bolted to the left front side of the timing cover.
It is easy to find, start at the carb and follow the fuel line back to the tanks.
Some one may have installed a fuel filter between carb & pump and think the carb may have a filter screwed into it but not seeing it I cant say for sure, my 300 six it is screwed in.
If you follow the lines back from the pump on the inside frame rail under the cab you should come to the duel tank switch valve.
Has 3 hoses - 2 in 1 from each tank and 1 out let, should also have a think 2 wire plug.
Going back from there should be the tanks.

Now a PO could have added a filter anywhere in the system or an electric fuel pump, why who knows?
Dave ----
 
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Old 02-11-2019, 06:58 AM
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you could also have an ignition coil breaking down when warmer, mimicking fuel delivery issues, my 390 Galaxie did that and had me chasing carb issues quite awhile.
 
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Old 02-21-2019, 09:08 PM
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81 f 250 351 ... sporadic stall

I have a 81 250 with dual and I had the same problem.there are two low pressure pumps one in each tank and 1 high pressure on frame rail under drivers door and 1 mechanical pump on the engine my problem was one on the block sporadic pressure replaced it and it fixed my problem
 
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Old 02-22-2019, 01:56 AM
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10-11 years ago I had the same problem......the truck would start & run fine but would cut out as if the key was turned off, when left idling.

Over a period of months it slowly became worse, to the point that if you pulled up at lights it was almost guaranteed to cut out............& for some reason, always at an idle (only once ever while at driving speed).

Eventually I found it was a bad connection at the distributor loom plug. I cut the plug out & soldered the wires - it never recurred.

But if you have a fuel problem, the cutting out would typically not be instant - as it is with ignition.
 

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