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I have an 89 suburban with the 6.2 and sometimes when I try to start it the engine will only turn over a few times, even though batteries are fully charged. How does the engine turn off by the ignition switch? It seems that may be malfuntioning and preventing the engine from turning over.

I know on Mercedes engines the vacuum activated STOP lever on the IP turns the engine off, but I don't see anything on this engine.

Other times, the engine just turns off suddenly, as if it has the PMD problems of a 6.5. Usually it turns over merily but only starts some of the time. Could it be the throtte position sensor? other ideas?

Thanks much!
Paul
 

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Sounds like it might have something to do with the ignition switch. I'm sure someone with more electrical know-how than me will chime in.
 

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I would check all your battery connections. pull the plugs off the batt and clean it all up with a wire brush. make sure that the power wire at the starter is clean and tight. and all the grounds going to the block and body are good.

the ip has a fuel shutoff solenoid that turns off the fuel. if you look at the top of your ip there is a red/pink wire that should have 12v when ign is on, and nothing when ign is off.
it could very well be the ign or something in the wiring harness, but i would start with the simple stuff first.

I believe the tps is only for the tranny, the motor does not have a computer of any sorts. the computer stuff is behind the glove box.
 

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pablocasa;1563940; said:
I have an 89 suburban with the 6.2 and sometimes when I try to start it the engine will only turn over a few times, even though batteries are fully charged. How does the engine turn off by the ignition switch? It seems that may be malfuntioning and preventing the engine from turning over.

I know on Mercedes engines the vacuum activated STOP lever on the IP turns the engine off, but I don't see anything on this engine.

Other times, the engine just turns off suddenly, as if it has the PMD problems of a 6.5. Usually it turns over merily but only starts some of the time. Could it be the throtte position sensor? other ideas?

Thanks much!
Paul
Sounds like you are describing two separate problems - that may, or may not have a common cause.

First - actual cranking of the engine. It requires at least 10 volts to reach the solenoid on the starter - and is routed through the key switch, neutral safety switch (or clutch switch), fuse, etc. It the problem is intermittent - seems you've got a bad connection or switch somewhere.

Second - the case of the engine actually running or not - or maybe starting and stalling. Again, you need at least 10 volts applied to the fuel-shut-off solenoid. It is a "dead-man" type switch and needs power for the engine to run - and with no power a spring turns the fuel off. Most Mercedes shut-offs work differently.
Also keep in mind that a cold diesel might quit shortly after starting for non-electrical reasons.

If you find both problelms are from a central electrical supply problem then just work your way up from the source - and start from where the entire electrical system gets its power. Try turning your headlights on - and then turn the key and try to crank. If no crank, but the headlights stay bright - that will help narrow down the problem. The main power-tap is usually from the big stud on the starter-motor solenoid.
 
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