Still have idle probleml

[JohnnyReb]

Hey Y'all;
Still have the idle problem with the deuce.
My son (Ga_Deuce) had originally posted the problem but we still can't figure it out!

Truck did not want to idle so I had to run it up over 1100rpm's to drive it. Kept the throttle open. To shut it down, all I had to do was close the throttle and it would die without the engine stop engaged.

My son and his friend found some fuel leaks and fixed em. They then set the idle for 800rpm. It will idle at that speed for various times then race up to 1500rpm and stay there. Sometimes it will idle for 15 sec's at the original setting and then race up; other times it will stay there for up to 2 mins then race to 1500.
I am totally baffled.
Thanks

 

[Boatcarpenter]

I'm not sure what all you guys have done, but if you have a flame heater on the truck, could that be dumping some extra fuel into the manifold? Maybe disconnect the fuel line to it and see if anything changes. Just a thought.
BC

 

[JohnnyReb]

No heater. Thanks for the thought!....any ideas are welcome. I am at a complete loss.
Even had the diesel mechanic instructor at the local Tech school to try and figure it out; the best he could do is suggest that the new low sulfur fuel is somehow affecting it.

Problem is that I didn't work on it (not that I could have done any different), but I don't really know what they did to it other than what they told me.

 

[WillWagner]

BC, good call. I'd look for an uncontrolled fuel source too. The flame heater is a good start. If that's no help, try cracking a fuel line to the nozzles, one at a time, and see if it shuts off. If not, most likely a fuel pump. BC any luck on your issue?

 

[mangus580]

JR, your truck should have a flame heater unless someone removed it.

Its attached to the intake manifold elbow...

 

[JohnnyReb]

Gotcha. I now know what you are referring to
I am not in any way a diesel mechanic....What does the flame heater do and how would I check it for the problem?

 

[Boatcarpenter]

Nothing since I got the oil analysis back. No time to do anything, too much work for other people and on my own house. Time and weather permitting, I'll pull the pan and see what I find.

 

[cranetruck]

The flame heater is used for cold weather starting (say below 20°F).

It consists of a fuel pump feeding a nozzle on the intake manifold adapter and an igniter firing a spark plug installed close to the nozzle.
A switch below the dash to the left of the steering wheel is your control.
The flame heats the air (what's left after combustion) to aid in starting in sub zero weather. Use only while cranking engine.

The nozzle on the intake manifold adapter has a built-in valve, which controls the fuel overflow and returns it to the common fuel return lines.

If this valve leaks fuel will dribble into the intake manifold and fuel the engine.
Original models with the flame heater system had solenoid valves in the supply and return lines to prevent an engine runaway situation.

In your part of the country, the flame heater would never be needed and you could simply pull the lines and plug them.