did diesel purge kill my glow plugs? - PeachParts Mercedes-Benz Forum

geoffraynak · #1 10-22-2012, 11:43 PM

okay.
i'm trying to recount my weekend of events
it is killing me that i can't find the cause of the glow-plug failure
coincidence is causality in my book.

i had a previous post on 'order of operations'
and that list was effectively to do a valve adjustment, purge, do a compression test

i never got to the compression test because i started chasing the lack of a gp light on my dash

question: can diesel purge kill my glow plugs?

here is a before/during/after set of videos
https://www.youtube.com/watch?v=DC9zZGPFyE4&feature=g-upl
https://www.youtube.com/watch?v=iDbcQ-O14wA&feature=g-upl
https://www.youtube.com/watch?v=7Z9vyrbtQI4&feature=g-upl

as you can see with the 'during' ... the fuel is pretty nasty and black
do you think that the carbon/soot/gunk deposited on the glow plugs and made them inoperable?

i cannot remember if the GP light worked before starting the 300SD after the purge or not ...
but the car was definitely warm after 45+ minutes of revving to burn through two cans of purge.

never stop learning.
geoff

scottmcphee · #2 10-23-2012, 12:08 AM

No, a purge won't kill your plugs.

A GP light on the dash, or not, is not a good indicator for "good" GP's, it can give a false impression about plug condition. Best way to test a GP is pull it, put it on a cement garage pad, attach booster cables to it and the battery. If it doesn't glow at least yellow hot in about 15 seconds (and your battery is good) get a new GP for that hole.

Maybe your GP relay is bad.. not making a good contact. Then no GP's get power. This is also the thing that feeds the indicator light on your dash. So get your volt meter out and hook it up to each individual output of the GP relay (with all GP's disconnected) and do a glow cycle from the key - but don't actually start the car.. each output should read battery voltage. When you actually connect the GP's to the relay you can test voltage again and will be somewhat lower because it's a lot of battery power sucked up to glow those babies. If all that's fine, and you don't have an indicator on dash, check that bulb.

torsionbar · #3 10-23-2012, 12:12 AM

Quote:

Originally Posted by geoffraynak

do you think that the carbon/soot/gunk deposited on the glow plugs and made them inoperable?

no. more likely you just bumped some of the wires while working under the hood. go over them all and test with multimeter.

but for how dark that fuel was, it ought to run a whole lot nicer now. i'm sure you'll feel more power and get better mpg's. diesel purge really works well to clean these fuel systems out. i do a can every 30k miles as routine maintenance.

scottmcphee · #4 10-23-2012, 12:15 AM

You can run straight ATF (dexIII) as fuel through the IP and it cleans it just as well as purge. I think some purge brands are just relabelled ATF anyway... just speculatin' on the red color similarity.

qwerty · #5 10-23-2012, 12:25 AM

Quote:

Originally Posted by geoffraynak

i never got to the compression test because i started chasing the lack of a gp light on my dash

Why not send 12 volts up the wire to the GP light and see if the lamp actually works?

Doktor Bert · #6 10-23-2012, 02:14 AM

Quote:

Originally Posted by scottmcphee

You can run straight ATF (dexIII) as fuel through the IP and it cleans it just as well as purge. I think some purge brands are just relabelled ATF anyway... just speculatin' on the red color similarity.

X2

cho · #7 10-23-2012, 04:59 AM

.

you also dont have a cigar hose..cccc..

.

cho · #8 10-23-2012, 05:22 AM

Quote:

Originally Posted by qwerty

Why not send 12 volts up the wire to the GP light and see if the lamp actually works?

which 2 ports are designated for bulb,I suppose those are on small connector
on the relay.
Also could it be tested by resistance...0 or 1...?

just curious....

.

toomany MBZ · #9 10-23-2012, 08:13 AM

Quote:

Originally Posted by scottmcphee

You can run straight ATF (dexIII) as fuel through the IP and it cleans it just as well as purge. I think some purge brands are just relabelled ATF anyway... just speculatin' on the red color similarity.

Unless atf contains naphtha, not sure. At least as far as Lubri Moly is concerned.

Using a multimeter set on ohms, test each plug.

jay_bob · #10 10-23-2012, 09:24 AM

Jump 1 and 3 on the small connector to test the dash light. Key in pos II (normal running position).

The flow is +12 from fuse -> pin 1 -> internal gp relay contact -> pin 3 -> bulb -> ground in cluster.

qwerty · #11 10-23-2012, 09:49 AM

Quote:

Originally Posted by cho

which 2 ports are designated for bulb,I suppose those are on small connector
on the relay.

12 volts to terminal three should illuminate the lamp.

geoffraynak · #12 10-23-2012, 09:53 AM

Quote:

Originally Posted by cho

which 2 ports are designated for bulb,I suppose those are on small connector on the relay. just curious....

i have a dual thread running here ... sorry.
i maybe had a few too many barley pops trying to solve the mystery last night...

anyway, pins 1 and 3 are the bulb light. red/black (?) and white/blue
on the relay-side that is connector 15 and 'LA' ...

Quote:

Originally Posted by qwerty

Why not send 12 volts up the wire to the GP light and see if the lamp actually works?

just did that in the dark this morning ...and was greeted with the warm dash light of a glowing glow plug light.
the lamp is fine ...
so i can cross that off my mystery list.

also, my purge was moonshine clear ... not red!?

FYI, the reason i thought the purge may cause the failure is because of all the soot and gunk it was dislodging from the injectors and injector pump. before that makes it back to the filter (where we can see it) some of it gets injected past the prechamber and into the cylinder. my brain was thinking that maybe there was so much gunk, that it could have build up on the plugs and caused a fault.

now ... back to your regularly schedule program.