Help - Glow Plug Circuit Is DEAD - PeachParts Mercedes-Benz Forum

bmeares · #1 02-21-2009, 05:54 PM

I had the air intake manifold off of my '86 190d 2.5 today to fix the rotten vacuum line going into the stop diaphragm that was preventing my engine from shutting off. After fixing the vacuum line and before putting the air intake back on, I started the engine and turned it off--sure enough, the fix had worked and the engine shut down properly, without me having to push the stop lever, like I've been doing everywhere I've driven for the past week. I was feeling fairly good--I'll I'd have to do was put the intake back on and I'd be done-right?.....

I got the intake back on with only a few stubborn bolts, and everything else back together, put the tools away and thought I was done.

I decided to test it one more time. Strangely, when I turned the key in the ignition, the light for the glow plugs in the instrument cluster didn't light up. The engine didn't start.

Somehow I've killed the circuit to my glow plugs. My only guess is it has something to do with the wiring harness that goes from the relay out to the plugs, because this is the only piece of the glow plug system near where I was working.

How do you test this thing--any ideas?

coachgeo · #2 02-21-2009, 06:08 PM

listen for relay clicking off

check for 12v at each plug durring the time period that relay should be on

Same but check for 12v at the pins ontop of relay

#3 02-21-2009, 06:10 PM

Check everything around the manifold, the wires going to the relay and the relay fuse (Should be on the drivers side fender). You may have pulled the plug out or pinched a wire (short circuited) when installing the manifold.

bmeares · #4 02-22-2009, 10:15 AM

Quote:

Originally Posted by ForcedInduction

Check everything around the manifold, the wires going to the relay and the relay fuse (Should be on the drivers side fender). You may have pulled the plug out or pinched a wire (short circuited) when installing the manifold.

After removing the cap to the relay, I noticed a break in the fuse. It's Sunday, no mercedes shops or dealership parts departments are open, and I have to get 25 miles down the interstate tomorrow morning to get my butt to work. In the true spirit of this forum, I'm going to redneck engineer something to bridge the gap until I can get the right part. Anybody got any idea what this fuse is rated - it's pretty big - i'm guessing 50 amps or more?

bmeares · #5 02-22-2009, 10:18 AM

Quote:

Originally Posted by bmeares

In the true spirit of this forum, I'm going to redneck engineer something to bridge the gap until I can get the right part. Anybody got any idea what this fuse is rated - it's pretty big - i'm guessing 50 amps or more?

80 amps -

#6 02-22-2009, 10:52 AM

Don't just jump it. The fuse blew for a reason, you probably pinched a wire. Trace the wires or remove the intake again if you have to.

Brian Carlton · #7 02-22-2009, 11:37 AM

Quote:

Originally Posted by bmeares

After removing the cap to the relay, I noticed a break in the fuse.

Did the fuse burn through from a short circuit.........or did it crack though from age?

Diesel911 · #8 02-22-2009, 10:56 PM

If you had to you could use a regular palstic 2 pronged fuse and holder wired to the fuse terminals. You would have to buy the fuse holder that can take the 80 amps and an 80 fuse for it and some eye type connectors for the wire ends would be nice.
My understanding is that the people who mount high power amps for there sound system use the 80 amp fuses and Fuse Holders.
It may be Radio Shack and the local Auto Part store has them.

Ebay had them named: 80 amp Maxi Fuses

bmeares · #9 02-23-2009, 11:26 AM

Quote:

Originally Posted by Diesel911

If you had to you could use a regular lalstic 2 pronged fuse and holder wired to the fuse terminals. You would have to buy the fuse holder that can take the 80 amps and an 80 fuse for it and some eye type connectors for the wire ends would be nice.

I did just that and used an 80 amp maxi fuse to bridge the gap. It blew as soon as I gave the glow plugs power. All of the wires going to the plugs look fine, but one of them must be shorting out somewhere, or a short somewhere in that wiring harness.

funola · #10 02-23-2009, 11:33 AM

In a pinch, you can use solder for a fuse. If it blows, add more strands to up the amps.

Quote:

Originally Posted by bmeares

I did just that and used an 80 amp maxi fuse to bridge the gap. It blew as soon as I gave the glow plugs power. All of the wires going to the plugs look fine, but one of them must be shorting out somewhere, or a short somewhere in that wiring harness.

vstech · #11 02-23-2009, 11:47 AM

that is a cool upgrade to the MB fuse link. I use a maxi fuse on my suburban for the electric fans... I wonder what the maxi fuses cost?

Diesel911 · #12 02-23-2009, 03:26 PM

Quote:

Originally Posted by bmeares

I did just that and used an 80 amp maxi fuse to bridge the gap. It blew as soon as I gave the glow plugs power. All of the wires going to the plugs look fine, but one of them must be shorting out somewhere, or a short somewhere in that wiring harness.

I am thinking that if you pulled the Glow Plug wire connector and checked them just as you would do (with the Ohm Meter) if you were checking for a bad plug the one with the shorted wire would show very little resistance.

Diesel911 · #13 02-23-2009, 03:42 PM

Quote:

Originally Posted by vstech

that is a cool upgrade to the MB fuse link. I use a maxi fuse on my suburban for the electric fans... I wonder what the maxi fuses cost?

I think the Strip Fuse is cheaper but requires you to keep a spare on hand.
The 80 amp Maxi Fuse may also take some looking around for but is available in more places than the Strip Fuse.

This internet site shows a pair of Maxies selling for about $3.50-$6.
http://review.zdnet.com/product/car-audio/kicker-maxi80-80-amp-maxi-fuse-2-pack-05maxi80/31346309

If you bought the fuse holder and some fuses it is easily 4 times as much as the OEM Strip Fuse.
I have 1 extra Strip Fuse somewhere in one of my parts boxes. If I re-discover it I need to make sure I put it in my Car where I can find it when I need it.

vstech · #14 02-23-2009, 03:48 PM

methinks you need to pull the intake back off, and find the shorted wire... sorry.
true you could test for a short to ground, but even if you locate it, you're going to have to pull the intake back off to find what you dinged and shorted.

vstech · #15 02-23-2009, 03:49 PM

wow, the strip fuses are only like .50 each... I keep 10 or so on hand, I agree, gotta put one in each car... never know when you're going to need it.