190D Glow plugs not working - PeachParts Mercedes-Benz Forum

KBCB · #1 03-11-2012, 05:23 PM

Hi all, I was hoping to get a few questions answered. I have a '89 190D. recently the glow plugs have stopped turning on. I suspected they might not be coming on when the usual hum and relay click were absent when first turning over the key. Today I got the meter out and only got .5v at the connector. The plugs themselves are only 3-4 years old. So I don't think it should be them.

Does anyone have a wiring diagram and locations of the entire glow plug system?

Are there any relays that are known issues?

The battery that is in the car is just about at the end of its life. It will still start the car, but does need to be replaced. Would it make sense that even though there is enough charge to start the car that there isn't enough charge to fire the plugs?

Thanks in advance.

ROLLGUY · #2 03-11-2012, 05:33 PM

Check the strip fuse in the glow plug relay located on the driver side wheelhouse. If the fuse is good, check each plug with your meter. Remove the wiring connector that has the wires going to each GP. A better way is to use a jumper wire connected to +12v, and touch each terminal on the wiring connector. If you get a little spark, the GP is good. No spark, and the GP is bad.

MB-Owner-in-ind · #3 03-12-2012, 10:54 AM

.5 volt would be too much resistance upstream. Can you check voltage at the relay?

KBCB · #4 03-12-2012, 12:26 PM

Where is the relay located?

BrianCostello · #5 03-12-2012, 01:25 PM

driver's side fender.

large black box.

you can unplug the connector going to the motor. and test each glow plug from the connector. test the ohms (should be .1 ohm any/a lot higher = bad GP)

you can also test the controller, have a friend cycle the key as you test each output for 12volts. A bad controller will not put out 12volts at each GP.

I would not be surprised if the controller was bad. The do go bad over time (23 years) but they are not cheap, so you want to test it out to be sure.

KBCB · #6 03-12-2012, 06:30 PM

Inspected the fuse, all good.

Tested the controller, bad news. Looks like I'll have to get a replacement.

Thanks for the help!

Dave Donaldson · #7 03-12-2012, 07:18 PM

which are better Beru or Bosh ? ty

BrianCostello · #8 03-13-2012, 10:35 AM

I was wrong on my Ohm's . ..the VW glow plugs want .1-.3 ohms. .

I forget what the MB's want. I have new plugs in my car and they tested at 4.5 ohms. is that right??

Beru or Bosh . . .same difference. whats a better price?

chazola · #9 03-13-2012, 11:29 AM

Quote:

Originally Posted by BrianCostello

I was wrong on my Ohm's . ..the VW glow plugs want .1-.3 ohms. .

I forget what the MB's want. I have new plugs in my car and they tested at 4.5 ohms. is that right??

Beru or Bosh . . .same difference. whats a better price?

Beru seem to be the most long-lived, compared to Bosch. Beru is what you get at the dealer here in old Europe. Your plugs should be reading 1 ohm or under resistance if they/the wires are good.

Dave Donaldson · #10 03-13-2012, 08:24 PM

First thanks to all who posted here I tested the voltage at the glow plugs and no volts ,,, the fuse strip looks good , and so far the relay is suspect.
( yesterday the glow light on the dash went out.. ) so my question is until I get an used or new relay will it harm the engine if I keep driving it,, starting in 50 degree weather is normal,, 2 or 3 sec crank time and it's running. At night it goes to 32 F. ps what is a used relay worth,, Cheers Dave D. ps can the relay be rebuilt or fixed ? my 1962 MGA had coils and points, aka volt reg. easy to refurbish. :}

MB-Owner-in-ind · #11 03-14-2012, 01:05 PM

Just a thought, I didn't read where you tested the voltage to the relay. Check that before changing the relay. Grinding on the starter to start the car will work and only hurts the starter.

Bio300TDTdriver · #12 03-14-2012, 03:48 PM

Quote:

Originally Posted by Dave Donaldson

First thanks to all who posted here I tested the voltage at the glow plugs and no volts ,,, the fuse strip looks good , and so far the relay is suspect.
( yesterday the glow light on the dash went out.. ) so my question is until I get an used or new relay will it harm the engine if I keep driving it,, starting in 50 degree weather is normal,, 2 or 3 sec crank time and it's running. At night it goes to 32 F. ps what is a used relay worth,, Cheers Dave D. ps can the relay be rebuilt or fixed ? my 1962 MGA had coils and points, aka volt reg. easy to refurbish. :}

Did you actually remove the fuse? They can have a hairline crack that doesn't show itself until you take it out.

Dave Donaldson · #13 03-14-2012, 04:19 PM

I tested the relay by voltage check at the glow plugs positive, at plug and ground on eng, ,, I had my grand daughter turn the key to start the glow plug sequence ,, no volt reading,,
As for the fuse I will check to night if it has voltage reading up stream and down stream ,, good point you guys have there !!
The car started ok this AM,, at 32 F 2 sec crank and a wee bit rough idle of about 60 seconds.. hope this does not harm the engine,,,,ty

unbused67 · #14 01-26-2024, 10:29 AM

My wife ran out of fuel in my 1989 190d and now I am having the same issue. Glow plug relay light is longer coming on except for after starting the car at which point it comes on and "pre heats." I had a dead battery and had to jump start the car while cracking injectors to get the thing to start after fueling it in 10 degree temps. Not fun. I have had it running since but am wondering if it worth spending money on a new battery/relay or just giving up.

Quote:

Originally Posted by KBCB

Hi all, I was hoping to get a few questions answered. I have a '89 190D. recently the glow plugs have stopped turning on. I suspected they might not be coming on when the usual hum and relay click were absent when first turning over the key. Today I got the meter out and only got .5v at the connector. The plugs themselves are only 3-4 years old. So I don't think it should be them.

Does anyone have a wiring diagram and locations of the entire glow plug system?

Are there any relays that are known issues?

The battery that is in the car is just about at the end of its life. It will still start the car, but does need to be replaced. Would it make sense that even though there is enough charge to start the car that there isn't enough charge to fire the plugs?

Thanks in advance.

vstech · #15 01-26-2024, 05:42 PM

Giving up?
The horror.

At -10F, i imagine you need the block heater.
What happens when you turn the key on, when motor is cold?
Nothing?