So I've owned this truck for about 3-4 weeks now. Its been running great and I had no problems with it until last week. I drove it to the store, it ran great; I came back out of the store and it the truck fired right up, after idling for about 20-30 seconds it starting sputtering and shaking like it was losing fuel. I thought that might be the case as my fuel level gauge doesn't work too well, so I switched it to the other tank that absolutely had fuel, it didnt seem to help. So I tried to turn the truck off, nothing. Decided to try to limp it home, I got one big surge of power in the parking lot in 2nd gear and then it cleared up and ran great all the way home. Pulled in the driveway and it shut off like normal.

Ever since then it seems to have been running just fine, no issues with it not shutting down until tonight, when I drove it to the same store(creepy!). Similar situation, I received a phone call so I was sitting in the truck with it idling for a 30-60 seconds and then it starting sputtering, then it started to climb in engine speed slowly and again it would not shut off. I don't know how high the engine speed got to as I don't have a tach, but it wasn't like it was WOT. I didn't think to pull the FSS as I was panicked. I again decided to drive the truck home; it started to act strange a couple of times at stop lights slowly revving itself or sputtering a bit. It also seemed to lose some power momentarily in 4th gear, but this is the only time that has ever happened. For the most part it seems to run okay in gear, it seems like it acts up at idle. When I got home it sounded like the truck was idling a bit high; and it still would not shut down. I cycled the key back and forth a few times and it seemed like it started to lose engine speed as I was cycling the key before it finally shut down.

Any ideas? I am suspecting the FSS to be acting funny as far as the not shutting down goes. Next time I'll try to remember to pull the wire on the FSS, I'm actually considering wiring in a manual toggle to it.
I have no idea about the sputtering and revving.

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Just went grocery shopping, it did it again. Pulled into the parking lot and it wouldn't turn off, and it was idling high again; or more like it was sitting there revving itself up, it was beyond high idle and it wasn't completely smooth. I tapped the pedal a few times and it came back down to normal idle but it still wouldn't shut off. I waited for a minute or so with the key in the off position and it finally shut down.
Also on the way home, while driving in gear it would increase throttle on its own.

Do I have two separate problems here? What would cause it to increase fuel on its own?

 

WOW.... the for truck version of christine...... never heard of these problems before.... maybe dieselcrawler might have seen or herd this before.... beyond me but it might seem like a FSS issue possibly.... the sputtering almost sounds like air in fuel.... check your filters and look close at the fuel lines and the tanks switch.... on frame by the front tank...

 

sounds like you FSS is sticking along with a major air intrusion issue. air in your fuel system will cause it to surge and "get one big surge of power in the parking lot in 2nd gear" as you put it.

 

Short version: I discovered my FSS has gone bonkers. Can air be introduced into the fuel system by switching tanks?


Long version:
So I replaced the cracked up rubber line that was running from the filter outlet to the IP with clear tubing and replaced the fuel filter at the same time yesterday.
Was a bit of a pain to get it bled and running again, but once running it ran good. Drove it to work and back last night with no issues. However this afternoon was the first time since last night I tried to start it, it would not fire. The clear tube had no fuel in it at all, so I tried bleeding the system again starting with the valve on the filter, then the injector lines on the back of the ip, then the injector caps. While cracking open the cap on one of the rear injectors I noticed the large tank return line was cracked wide open and spitting out fuel. Got it replaced and finally got everything bled and started after beating the crap out of top of the FSS.

I had been running off the rear tank which was a little low on fuel, so I drove to the gas station and put 10 gallons in the front tank and switched to it. Drove it to the hardware store and it started sputtering again. I left the truck running and checked my clear tube, almost all air; so I started bleeding as much as I could out of the schrader valve and drove home. Once home everything was cleared up and my clear tube was 100% liquid fuel again.

So I drove it around a bit tonight to run some errands and had no more problems; other than not shutting off. But I banged on top of the FSS and that solved it.

So I know for certain now the FSS is wonky. But can simply switching tanks introduce air into the system somehow? I'll keep an eye on it for now, but it seems like I only got one more air pocket after filling up and switching tanks.

 

One of your steel lines is probably cracked letting air in, switching tanks shouldn't let air in.

 

being an 83, do you still have the fuel water seperator on the firewall? if so bypass it for a few days as a test. they have been known to let air in.

 

thats what id do, We have a 1973 dozer and had to do that