M818 Engine Run-on

[Andrew Rowe]

Hi Guys, just a quick technical question. I have noticed recently that when I shut down my truck there is a little bit of run-on from the engine. It used to stop on the button
when I turned it off. Is this a common condition that is leading to something failing?, I would be interested in any ideas, cheers Andrew.

 

[WillWagner]

Check to see that there is no voltage at the shut off with the power off. If no power, could be a cracked plate in the shut off assembly, a failing coil, they will swell and keep the disc from completely sealing, or a plugged return. Symptoms of a plugged return are running on after shut down, idle creeping as it warms, black smoke and more power. Resistance can be checked on the coil to see if it is failed. IIRC, 24-50 ohms.

Disconnect the wire from the coil when checking resistance.

NZ, You know a guy named Danny French?

 

[162tcat]

Mine did that when it developed a small air leak in the fuel line going to the engine. It was slow to return to idle and it would run on for a couple of seconds when turned off. If you haven’t replace fuel lines that’s probably a good spot to start as well and check the fuel filter for leaks. You won’t see them visually because the line going to the engine is suction not pressure.


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[Scrounger]

Mine did that when it developed a small air leak in the fuel line going to the engine. It was slow to return to idle and it would run on for a couple of seconds when turned off. If you haven’t replace fuel lines that’s probably a good spot to start as well and check the fuel filter for leaks. You won’t see them visually because the line going to the engine is suction not pressure.


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One of my M818s was doing the same thing. There are six fuel lines at the fuel selector valve. They are known to cause problems over time due to age. If your M818 still has the original lines it would be a good idea to replace them. Contrary to the TM, the only thing that needs to be removed for access is the toolbox. After the fuel lines were replaced the engine returned to idle faster and shut down faster.

It is quick fix and an opportunity to check the other fuel lines.

As WillWagner has already posted the electric solenoid may also be a problem and it is easy to test for serviceability.

 

[Andrew Rowe]

Thanks for the ideas. I am running all original fuel lines on this 1972 truck with about 80,000 miles on the clock......so just run in !
One other little problem also is the starter is starting to stay engaged for few seconds from startup, but I suspect this is just dry armature?
And Will W. , I think I do know a guy you are talking about, Cheers Andrew.

 

[WillWagner]

Tell him hey!