Glow plug harness gone bad?

For discussing the modifications needed for diesel vehicles to run with 2 tank veggie oil conversions.

Moderators: SunWizard, coachgeo

Glow plug harness gone bad?

Postby MikeGoodman59 » Tue Mar 23, 2010 6:29 am

I have a 1983 300SD (300K+ miles) and had just run up to DC and back from central NC. Great trip.

I'd been noticing a delay in the coming on of the glow plug light. It took 1 second for about a week, then 2 secs. I don't think I was getting quite the start I should have been. Attributed it to the cold, but too warm for that now.

Then, suddenly, the light failed to come on. The car started right up, in the tail end of a warm day. The thing has great compression! [Good thing! I was in VA!]

Well, I go under the hood and start checking glow plugs. I'd changed 3 of 5, keeping 1 & 2 as is since they were good and easy to get to later. This was about 2 years ago, maybe 15K miles ... maybe.

I checked last night and all had continuity from tip to frame nut. That means they're good, right? I know because I tested some old ones and the two unused.

Then I check voltage to each tip, one at a time, each one lit a Harbor Freight test light BRIGHT, but it was hard to get a meter on before the relay kicked off. If I checked at all, the one I checked had 11.0 but that can be attibuted to voltage drop?

Then I check under the relay and each was 12.9+ volts to the exposed pin. I had a charger on the battery at this point.

Then I checked continuity, each female receptacle of the plug to the tip. Here's the problem. I get continuity from #2 to each of the tips. And others are the same way.

This means what? I fried my harness? How rare would that be?!

Find a new (junk) one?
Can one be made up from the existing relay end?

Mike Goodman
High Point, NC

83 MB 300SD (2 tank)
82 Rabbit "Caddy" Truck (2 tank)
Diesel Craft CF process in enclosed shed
Mike Goodman
High Point, NC
1983 MB 2-tank (Modified Greasel, 2005)
1982 VW Rabbit Truck (Custom Conversion, 12/09)
1998 Dodge 12V 5.9L (Golden Fuels, 07/12)
DieselCraft processor
Tinkering w/BD
2.8 KW grid-tie/batt back-up
6-4x10 solar heat/HW wood stove
MikeGoodman59
 
Posts: 31
Joined: Tue Dec 23, 2008 10:49 pm
Location: High Point, NC

Postby SunWizard » Tue Mar 23, 2010 7:45 am

Its probably not your harness. You can only check that by unhooking every plug from the harness or you will get what you see, since every tip is effectively ground.

Continuity isn't a good way to test them, since it only tells you if a glow plug is totally bad (open). Resistance with a digital meter is the best test, they should measure around 2 ohms cold.
YVORMV - Your veg. oil results may vary.
95 Dodge Cummins 4x4 SVO WVO conversion.
81 Mercedes 300D- stock and happy on V80/D20 blend.
Low fossil net zero house- 100% solar power and heat.
SunWizard
Site Admin
 
Posts: 1719
Joined: Mon Dec 11, 2006 2:53 pm
Location: N. Colorado

Glow plug harness gone bad?

Postby MikeGoodman59 » Tue Mar 23, 2010 8:16 am

SunWizard wrote:Its probably not your harness. You can only check that by unhooking every plug from the harness or you will get what you see, since every tip is effectively ground.

Continuity isn't a good way to test them, since it only tells you if a glow plug is totally bad (open). Resistance with a digital meter is the best test, they should measure around 2 ohms cold.


Really ... okay, then. It's becuase they're in parallel with the jumper. And if each is a good plug then the tip of each is grounded. Of course ...

But just to see where I'm at ... if I'm getting 12.9V to each of the pins, then the problem resides downstream of the relay (which is kicking off after the normal time). Is that right?

And thanks!
Mike Goodman
High Point, NC
1983 MB 2-tank (Modified Greasel, 2005)
1982 VW Rabbit Truck (Custom Conversion, 12/09)
1998 Dodge 12V 5.9L (Golden Fuels, 07/12)
DieselCraft processor
Tinkering w/BD
2.8 KW grid-tie/batt back-up
6-4x10 solar heat/HW wood stove
MikeGoodman59
 
Posts: 31
Joined: Tue Dec 23, 2008 10:49 pm
Location: High Point, NC

Re: Glow plug harness gone bad?

Postby SunWizard » Wed Mar 24, 2010 7:50 am

MikeGoodman59 wrote: if I'm getting 12.9V to each of the pins, then the problem resides downstream of the relay (which is kicking off after the normal time). Is that right?

Yes. Probably a bad plug.
YVORMV - Your veg. oil results may vary.
95 Dodge Cummins 4x4 SVO WVO conversion.
81 Mercedes 300D- stock and happy on V80/D20 blend.
Low fossil net zero house- 100% solar power and heat.
SunWizard
Site Admin
 
Posts: 1719
Joined: Mon Dec 11, 2006 2:53 pm
Location: N. Colorado

Re: Glow plug harness gone bad?

Postby MikeGoodman59 » Wed Mar 24, 2010 8:50 am

many thanks ...

Any reason why, when I reply, the subject must be entered manually by cut/paste?
Mike Goodman
High Point, NC
1983 MB 2-tank (Modified Greasel, 2005)
1982 VW Rabbit Truck (Custom Conversion, 12/09)
1998 Dodge 12V 5.9L (Golden Fuels, 07/12)
DieselCraft processor
Tinkering w/BD
2.8 KW grid-tie/batt back-up
6-4x10 solar heat/HW wood stove
MikeGoodman59
 
Posts: 31
Joined: Tue Dec 23, 2008 10:49 pm
Location: High Point, NC


Return to 2 Tank veggie oil conversion and General discussion

Who is online

Users browsing this forum: No registered users and 0 guests

cron