My car (1997 E300D) will not start sometimes. The starter engages properly but the glow plug light does not come on. I lose the voltage that engages the glow plug relay anytime that the glow plug light does not come on.

I can turn the key a few times and then the glow plug light will come on, I get voltage to engage the glow plug relay, and the car starts fine.

What would cause this intermittant failure of the glow plug light and simulantaneous loss of voltage required to pull the glow plug relay in. Is the ignition switch the only possible culprit?

thank you for ANY thoughts you may have.

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Neil
1997 E300D - naturally aspirated
280,000 miles (as of November 2015)

Perhaps it is the GP relay itself...that is where I would begin.

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Marty D.

2013 C300 4Matic
1984 BMW 733i
2013 Lincoln MKz

Good suggestion.

I checked the glow plug relay. It operates as expected and the relay seems fine. The relay has a constant 12-V (big wire) supply and all six contacts that go to the six glow plugs get 12-volts anytime the relay is engaged. The relay must be engaged from voltage supplied by a smaller wire.

The problem is that I don't always get the voltage (small wire) required to engage the relay. I need to determine why I sometimes don't get this voltage when I turn the key.

Could this be only a problem at the ignition switch or could it be something else (the computer or something)?

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Neil
1997 E300D - naturally aspirated
280,000 miles (as of November 2015)

It's either the ignition switch directly, or a relay. A wiring diagram is needed.

Best Regards,
Jim

Another likely culprit is the glow-plug strip fuse. It is notorious for developing hairline cracks, and/or making intermittent contact with its mounting screws. Change fuse and try again.

Phil

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'95 E300 Diesel, 264,000 Miles. [Sold it]

Jim: I agree - I would love to have a wiring diagram but so far I can not locate one. I apologize if the post on the diesel discussion board was also mine that you responded to. I'm not sure if it was. I posted my question in the "Tech Help" AND the "Diesel Discussion". Please let me know if that's taboo and I will not do this again. I was obviously looking for maximum exposure. Thank you for your insight on my glow plug problem.

Phil: Where is this fuse that you speak of? What amperage rating is this fuse? I have seen no fuse. Thank you also for your input.

If I don't respond for the next few days it's because I just found out I live in a mandatory evacuation area for Hurricane Dennis. Tomorrow will be busy boarding up the house and who knows when I'll get back to the computer or have electricity.

Thanks again guys.

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Neil
1997 E300D - naturally aspirated
280,000 miles (as of November 2015)