I changed the glow plugs on my car, did a pretty good test ahead of time, as described by Diesel Giant's site.

Changed all 5 plugs, turned the key to watch the wonder of my efforts .... and ... nothing. Apparently no power to the glowplugs, because prior to me changing the plugs, I could still start the car, which should mean a few of the plugs were working. Now that I changed the plugs, the car won't start at all, which would mean that no plugs are getting power.

Any idea of what I did wrong? I hear the relay coming on and shutting off after about 3o seconds as it's supposed to. Battery is fine, and putting out enough juice as prescribed. There is no glow plug fuse on my car, it's a resettable circuit breaker.

Thanks,

Jeff 1991 300d, 128k

 

Pull the dash and check the bulb.

 

I'll be more specific. The glow plug light is not coming on, because the glow plugs are not getting any power.

jeff

 

Have you tested voltage into and out of the relay?

Have you tested voltage to the bulb?

I don't know if Mercedes did this on the glow plug circuit or not (BMW did it on the charging circuit on their motorcycles) but the light could be part of the circuit. If the bulb is burned out or not well seated, it's possible the circuit isn't complete. Perhaps someone who knows this circuit better than I do can answer here.

Also, did it work before you changed the plugs? If so, go back and check all the connections you touched.

 

The bulbworks, before and after I changed the glow plugs. I've looked at all the connections, don't see anything we left undone.

The only weird thing when I was changing plugs, was that the #5 wire turned with the screw; they were nearly fused together. I kept playing around with it, and at once time turned the screw so much trying to loosen it from the wire, that the wireclipwas at a 90 degree angle to the wire, and I heard a tearing noise. After I had all the plugs in, I made sure to test the wires/plugs, as described on Diesel Giant's site, and all the plugs came up fine, which would then mean that the wire was fine, or I wouldn't have gotten a reading.

By testing the female end of the connector during the 30 second relay time when turning the key, all plugs came up with like 11.69 or something, which means they were getting power. But if they were getting power, they would glow andthe car would start. But it doesn't. Just cranks and cranks, which would mean the plugs are not glowing.

I don't know what else to do.

jeff

 

Okay, so now you know that it was something you did to the wiring harness. Perhaps it is only an intermittent fault or a burned section of wire. I think your answer at this point is clear - replace that section of wiring harness and start over.

Of course, you don't give the whole story at the beginning which means it could also still be something else. You say you could start the car, but not that it ran. Did it run? Did you drive it? Was it smooth? Did it get up to speed? With your description of cranking, cranking and cranking I think I would check fuel delivery and filters (although you seem pretty convinced it's the glow plugs).

 

Finally got the plugs working. Turns out one of the glow plug wires turned too much when I was tightening it, causing it to touch the manifold, shorting it out.

Thanks,

jeff