HHow do I make a glow plug test circuit? - Page 2 - PeachParts Mercedes-Benz Forum

#16 12-23-2005, 07:07 PM

BTW there are more ways than an inductive amp meter to test the glow plugs.

If you have tested them all, and they all output heat on the bench when connected, then in the car, assuming you can measure voltage (around 10.5-11.5V) at the plugs then you can make the assumption safely that they are getting hot.

Any ideas what is causing the problem?

#17 12-23-2005, 07:11 PM

Quote:

Originally Posted by Pete Burton

great idea. Simple, yet complete. This gives me another thought. Try doing this with engine off and headlights on. The headlights should bring the voltage down just a bit, slightly safer for the glowplugs (which are designed to operate on 11V)

That may be a good idea. I did this test with the car not running, so I assume I was getting close to 12V at the GPs. I only energized them long enough to verify that the fully heated (maybe 5 seconds). Hopefully the extra voltage didn't hurt them.

#18 12-23-2005, 07:15 PM

Quote:

Originally Posted by Craig

That may be a good idea. I did this test with the car not running, so I assume I was getting close to 12V at the GPs. I only energized them long enough to verify that the fully heated (maybe 5 seconds). Hopefully the extra voltage didn't hurt them.

Well assuming you were using your battery charger to test them (not a battery) your charger might have actually put out MORE than 12volts with the given load (usually they put out along the 13.9-14.6 range).

3 seconds is a long time but if you didn't see any catrostrophic failures on the bench you are probably okay.

So, in the car, you are getting 11V or so at the glow plugs for sure? (Using a volt meter.)

#19 12-23-2005, 07:25 PM

Quote:

Originally Posted by Brandon314159

Well assuming you were using your battery charger to test them (not a battery) your charger might have actually put out MORE than 12volts with the given load (usually they put out along the 13.9-14.6 range).

3 seconds is a long time but if you didn't see any catrostrophic failures on the bench you are probably okay.

So, in the car, you are getting 11V or so at the glow plugs for sure? (Using a volt meter.)

Sorry for the confusion, I was responding to an earlier post about using jumper cables from the car battery (with the car off) to test the GPs. I agree that using a charger at 13.9-14.6 V could damage the GPs.

#20 12-23-2005, 07:55 PM

Quote:

Originally Posted by Craig

Sorry for the confusion, I was responding to an earlier post about using jumper cables from the car battery (with the car off) to test the GPs. I agree that using a charger at 13.9-14.6 V could damage the GPs.

Ah okay.

No problem. Just worth mentioning for those who may not know battery chargers do "magical" things

biopete · #21 12-24-2005, 01:30 AM

Quote:

Originally Posted by P.E.Haiges

biopete,

High compression is very important to get a Diesel started. The temperature of the air in the prechamber is proportional to the compression, higher compression equals higher temperature. You need the temperature in the prechamber to be above the ignition point of the Diesel fuel or the engine won't start.

I had a 220D that I fried the rings by overheating it. It wouldn't start when cold, even in the summer, unless the block heater was on for along time. If I was at a location where electricity wasn't available for the block heater, I had to park it on a hill to roll start it. Luckily it had an manual transmission. When I was in Nawlins, I had to park in a high rise garage so I could roll it down the ramp.

After the engine started it ran as good as it ever did. So good running after the engine is hot is not a sign that the compression is good.

P E H

Thanks for the great info PEH. That was like water to a thirsty mouth. I really dont want to hear my compression is bad but that sure would make sense. Im hoping that fuel start of delivery or injection timing could make just as much sense

biopete · #22 12-24-2005, 01:36 AM

Quote:

Originally Posted by Brandon314159

Well assuming you were using your battery charger to test them (not a battery) your charger might have actually put out MORE than 12volts with the given load (usually they put out along the 13.9-14.6 range).

3 seconds is a long time but if you didn't see any catrostrophic failures on the bench you are probably okay.

So, in the car, you are getting 11V or so at the glow plugs for sure? (Using a volt meter.)

Yep, charger i have puts ut like13 at 50amp start which is what i had it on (DOHH) . But it put out less on the 10 amp setting. Glow plugs are getting hot in car. I put one in i tested on charger, pulled injector, turned on key and saw it glowing as soon as i got out of the car.