Just wanted to ask a few questions on glow plugs. Will replacing the old ones with new help the starting on 0 digit mornings or not? Also, do you need to replace the relay at the same time or not? I noticed some that were called fast glow plugs. Is there any difference there on them? Just wanted to get some feed back before purchasing and changing. I am starting ok in warmer weather, but it seems a little more difficult in very cold temperatures.

Helps to know year, make and model.

New glow plugs will help if there's something wrong with the old glow plugs. If your car uses loop type plugs, updating to pencil type plugs should reduce glow wait time though I don't know it helps starting. If your car uses pencil type plugs, the basic test is 0.7-0.8 ohms of resistance for each plug at the glow plug relay. If your car does not have the afterglow feature (standard in the US from 1990), defeating the engine start signal to the glow relay will allow glow to continue until the relay times out which should allow smoother running immediately after a cold start. Or you can upgrade to an afterglow relay.

Sixto
87 300D

Perhaps you could explain what a "0 digit morning" is.

How long is the glow cycle with your current relay?

Thanks for the replies. I meant to say single digit mornings instead of 0 digit.

I understood what you meant, but again, what car?

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83 SD

84 CD