Starting problem M998

[swabbie]

There is a starting problem with my m998 6.2 engine.
The starter starts the engine, but as soon as I let
off the key's start position, the engine dies.

This cycle repeats until the batteries get weak,
and the starter slows down.

Anyone here know what could cause this?
Thanks.

 

[Action]

Are you starting it with a key or a factory lever?

 

[Mogman]

Does sound like a possible key switch failure, but I have to ask why in the world would you "repeat" until the batteries get week? I hate to be harsh but you obviously have no idea how difficult and expensive replacing the starter is.

 

[swabbie]

Starting with a key which has worked very well for 2 years.

The battery was weak to begin with, and I thought I may have flooded it.
Maybe about 5-6 tries, the last 2-3 tries engine started, but only while
the starter was engaged, for a second or two each time.

 

[Mogman]

Can't flood a diesel, well you could hydro it but that is probably not the issue, as has been said on here many times the "replacement" key switches are prone to failure, how many years is just by chance, would be the best thing to start with.

 

[swabbie]

Can't flood a diesel, well you could hydro it but that is probably not the issue, as has been said on here many times the "replacement" key switches are prone to failure, how many years is just by chance, would be the best thing to start with.

Is there any way, that you know of to 'hot wire' or other method to ascertain that
it is a faulty ignition switch or not? I'm reluctant to order a new ignition switch
not knowing if this is the cause or not.

 

[Action]

Is there any way, that you know of to 'hot wire' or other method to ascertain that
it is a faulty ignition switch or not? I'm reluctant to order a new ignition switch
not knowing if this is the cause or not.

Yeah stick a multimeter on the START stud and see if it has power with key in RUN. Or just check for continuity between those two , if the switch is out of truck.

 

[Mogman]

Yeah stick a multimeter on the START stud and see if it has power with key in RUN. Or just check for continuity between those two , if the switch is out of truck.

His problem was not a run away starter, the problem seems to be the ign. switch only connects to the run wire when in start, as soon as he lets go of start it dies.
There are ONLY three wires, one is hot, one is run and one is start, just make sure you have "run" hot when in the run position not just in the start position.
You can use a volt meter to find the hot one, then a jumper to the other two and it will be obvious which is the start and which is the run, jumper hot to run then momentarily jumper hot to start to start, it should start and run.
The only likely suspect is the ign. switch if in fact what I understand to be happening is really what is happening.

 

[papakb]

This is a great opportunity to test the STE-ICE connector in your truck. Pins S and T are +24V and start connections to the starter. If you short these pins together with a short length of wire the starter should engage and as long as you have +24 volts on the Injector Pump #54 the truck should start. This test bypasses the START-RUN switch entirely. That voltage on #54 comes thru the control box on engine connector pin A. The voltage comes directly into the control box from the start switch on body connector pin B.

Turn the key or switch whatever you've got on and either listen for the solenoid in the injector pump to click or check for 24 volts on it with a multimeter. If it isn't there the starter will run but the engine won't start. Sound familiar?

 

[Action]

Turn the key to RUN. Will the wipers work?

 

[swabbie]

Thank you one and all. After the ignition switch was eliminated as the
problem, & after an 8 hour battery charge, I cleaned the posts & cables.
Only then it finally started.

Perhaps the batteries are getting tired, and couldn't keep it running for
the few critical seconds after the "pop". I dunno for sure, but thanks
for aiming me in the right direction!

 

[osteo16]

Immediately upon arrival of any ones new rig !!!! Please clean all your grounds/wires/contacts.. and fuel tank/lines/system... . .This will save you and everyone a lot of headaches... This is simple maintenance and very important to weed out electrical gremlins and fuel issues.
Just my ..

 

[revhrd]

Immediately upon arrival of any ones new rig !!!! Please clean all your grounds/wires/contacts.. and fuel tank/lines/system... . .This will save you and everyone a lot of headaches... This is simple maintenance and very important to weed out electrical gremlins and fuel issues.
Just my ..

This helped, but I also added that grounding harness that is on one of the stickies. Pretty simple to make and install. Just in case, not that I had issues after taking ownership.