Of Glow Plugs, Ohms, and Rough Starts... - PeachParts Mercedes-Benz Forum

Joe Vitessa · #1 03-14-2007, 12:29 PM

So, I followed the excellent DIY info on Dieselgiant.com (http://www.dieselgiant.com/glowplugrepair.htm) about checking for faulty glow plugs and found that my No. 1 plug was bad. The other plugs checked out at .6 ohms. Replaced the plug. Everything was fine.

Two months later, when I start my 1985 300D-T (it always starts), I'm getting a lot of missing and rough running for about 30 seconds and then it smooths out. So I checked my plugs with a multimeter and each plug reads 0 ohms. Weird, huh? I can zero-out my meter, so I don't think it's the meter.
Any ideas about what's going on? I should say that the only other thing I have done is clean out my banjo bolt. (http://www.dieselgiant.com/mercedesaldaboostsystemservi.htm)

Joe

winmutt · #2 03-14-2007, 12:58 PM

Check your GP fuse?!

Joe Vitessa · #3 03-14-2007, 01:21 PM

Thanks for your reply. Yep, glow plug fuse is fine.

rrgrassi · #4 03-14-2007, 03:55 PM

Zero ohms usually means direct path to ground. My meter's numbers display randomly when the circuit is open.

I had to change all of my GP's, as the 80 amp strip fuse popped. All plugs read .6 ohms, except one that read 0.02.

Joe Vitessa · #5 03-14-2007, 04:51 PM

Quote:

Originally Posted by rrgrassi

Zero ohms usually means direct path to ground. My meter's numbers display randomly when the circuit is open.

I had to change all of my GP's, as the 80 amp strip fuse popped. All plugs read .6 ohms, except one that read 0.02.

So if 0 ohms means direct path to ground, does that mean my strip fuse really is bad? And GPs as well? Or could it be something else?

rrgrassi · #6 03-14-2007, 05:17 PM

Quote:

Originally Posted by Joe Vitessa

So if 0 ohms means direct path to ground, does that mean my strip fuse really is bad? And GPs as well? Or could it be something else?

All 0 ohms means is you have a good complete electrical circuit. Like you want zero ohms or as close to zero when testing cables, connections, etc. resistance causes heat, heat causes meltdown and possible fire. You only want resistance from items designed for it.

If you get continuity through the fuse, then it's fine. The fuse can get hairline cracks in it. It's best to remove it to test.

What brand GP's did you get? I found Bosch 80006 at Auto Zone for $9.99 each. I replaced all 5 like a maintenance item.

You can test all of yours by pulling them and giving them 12v to see if the tip glows. Just because a GP passes the ohm test does not mean it's good.