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Old 01-12-2003, 09:12 AM
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bhatt bhatt is offline
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Join Date: Apr 2000
Location: Oakville, Ontario, Canada
Posts: 421
Angry Uneven cold starting after glow plug replacement?

Hi guys..

My '86 300SDL (160k mi) is doing something weird since I replaced all 6 glow plugs. I replaced them strictly as a maintenance item (purchased the car 2 years ago and have no idea when they were last changed..)

When I turn the key to start, the glow plug light now takes about 1-2 seconds to light up, where it used to come on immediately. Once the light goes out, I start the car and it starts all bumpy, as if if one cylinder is "missing".

If I wait a little longer after the light goes off then start, it starts MUCH better. I know this is the best way to start a diesel in the cold, however I never had to do this before! Once the car is warm, it runs PERFECT.

My guess is one bad glow plug and/or I screwed something up while hooking everything back up.. Any thoughts on what I can check before I tear everything apart and look for the problem?

I'm thinking of testing glow plug resistance.. this should hopefully tell me if there is a bad new plug and/or if I screwed up in connecting one of the glow plug wires or something. Do I just pull the connector off the relay and test from each plug wire to ground? Is there a ground terminal in that connector or do I just find a good ground area in the engine compartment?

Thanks for all your help!

'83 300SD 335,000km (207k) mi SOLD
'87 560SL 163,000km (101k mi) SOLD
'86 300SDL 356,000km (220k mi) SOLD
'92 500SEL 250,000km (155k mi) SOLD
'90 300SL 140,000km (87k mi) SOLD
'01 S430 260,000km (161k mi) SOLD
'03 SL500 167,000km (104k mi)
'07 GL320 CDI 4MATIC 289,000km (162k mi)
'07 S550 4MATIC 170,000km (105k mi)
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