Glow plug mystery. Car only starts without glow plugs
 

The car is a 1981 300SD. After the car has been highway driving for at least 15 minutes, and then parked, I'll turn the ignition key and get nothing, no crank or click. If I unplug the glow plug relay, the car fires right up on the first bump. When the car is cold with the glow plug relay plugged in, the car fires up on the first bump. This happened three times yesterday where the car would fire on the first bump after unplugging the glow plug relay.

I'd strongly suspect that the issue is in the ignition switch or starter solenoid and the glow plug relay functionality is a symptom, not a cause. It could also be the NSS giving issues. The tiny amount of movement from you getting in or out and opening the hood can be just enough to make it work.

Try jumping the terminals in the junction box next the alternator on the fender the next time it happens to see if the starter engages. If so, it points to poor connection problem somewhere in the ignition system.

My first thought was NSS because I replaced it about 6 weeks ago with a used one. The fact that I would slowly move the shifter between P and N several times without any luck, then disconnect the glow plug relay and immediately get a start made me think the issue was related to the relay. Also, my reverse lights work, so I think that the NSS is in the correct position.

I've jumped those terminals on the fender wall before, but forgot which ones. Is it far left wire to far right wire? Thanks

I can't remember

Here's a thought:

Starter solenoids that are on their way out can stick when they get hot. By unplugging the glow plug relay, the solenoid is getting the extra juice it needs to engage.

+1

Doesn't the purple wire stop the glow relay when you hit the starter?

Sixto
83 300SD for sale
98 E320 wagon

Started the car 6 times yesterday without any issue, and never drove for more than 20 minutes at a time. The day before when I took that 1 hour and 45 minute drive up to Auburn is when I was having problems. Only time it didn't give me problems is when we stopped for a long meal and the car had a chance to cool down. I don't know, it all seems temperature related to me. What else in the ignition system is going to fail because of heat besides the starter solenoid?

Older starter may be heat cooking. Not that rare. It gets hot and it refuses to function until it cools off.


I might do some connection checking first. Remove, clean and tighten down properly. Old connections and the terminations on these cars do qualify as old.

This morning I purchased an Ultima starter from O'reilly's and installed it. I know, I know. What was I thinking? This is my only car and I was in a pinch.

After installing the starter, I started the car 4 times within a minute, no problem. I go into the house for lunch, and an hour and a half later go to start it and get nothing from the turn of the key. I jump it at the fender terminal and get nothing, run a wire directly from the battery to the starter and get nothing. What's going on? Bad starter?

Did you check the ground wire to engine block? Make sure it is corrosion free and clean.

Other than that, possible bad starter.

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You have a bad starter (seems to be a common thing with the parts houses starters for some reason), or you have a poor ground somewhere between the starter and the battery negative.

When you mounted the new starter, did you clean the flange free of rust and debris and torque it snugly? Check the main ground strap from the engine/transmission to the body. It should be clean, tight, free of rust and corrosion. Inspect the ground strap from the body to the battery negative. It should be the same as the engine ground strap.

Didn't you just replace the starter recently (within the last 6 months)?

Found this http://www.peachparts.com/shopforum/diesel-discussion/381668-there-sign-your-starter-way-out.html

Is this the same car?

I replaced that starter with a spare that I had, but it would occasionally hang up on the flywheel after it turned the engine over. Then I replaced that one with a used one that Sixto had gathering dust in his garage, and that one was fine until the solenoid started sticking. I finally bought a freshly rebuilt, but that looks to be a bad choice. I'll check my ground connections.