How many glow plugs does an OM606 need to start? - PeachParts Mercedes-Benz Forum

shertex · #1 10-21-2014, 06:09 PM

Just curious what people have experienced. Assuming good 5w40 synthetic oil, good compression, and a low temp of 0F, how many glow plugs does an OM606 need to start?

Reason I ask is that, when glow plugs start to go, I'll probably wait till a few of them are dead before I get my indie to tackle replacement. At that point I might just do all of them.

On the 99, PO did all six plugs at 70k in 2007.....now 158k. On the 98, no idea if they've ever been replaced....86k.

vstech · #2 10-21-2014, 06:11 PM

All 6 need t be in the block... I'd think how many working would depend on ambient temp, and engine wear... And spray pattern

citationtech · #3 10-21-2014, 07:07 PM

My '98 had at least one dead plug (no CEL though) and it missed and coughed for the first 30 seconds below 45 degrees. Replace them. It's not a bad job, it just requires patience to work the buggers out.

engatwork · #4 10-21-2014, 07:11 PM

I'm thinking you should be able to get a healthy 606 engine to start with three or four glow plugs working.

shertex · #5 10-21-2014, 07:29 PM

Quote:

Originally Posted by engatwork

I'm thinking you should be able to get a healthy 606 engine to start with three or four glow plugs working.

That would be great if I could limp through a winter with three or four then replace them all prior to the following winter.

ah-kay · #6 10-21-2014, 07:30 PM

It needs 6 to plug the holes. I would expect engine with good compression would start without any GP. There is one way to find out. Remove the big connector inside the GP relay and try to start. Disclaimer - never try this before nor I wanted to.

What I do want to try is a circuit to cut out the GP if engine is above certain temperature and spin away to start engine. The idea is to extend GP longevity. Make sense??

engatwork · #7 10-21-2014, 07:32 PM

I had one come into shop one time that the previous mechanic had used a piece of baling wire to tie a glow plug to a bracket under intake manifold and left broken off plug in head. I was able to get the broken piece out

.

shertex · #8 10-21-2014, 07:35 PM

Quote:

Originally Posted by ah-kay

It needs 6 to plug the holes. I would expect engine with good compression would start without any GP. There is one way to find out. Remove the big connector inside the GP relay and try to start. Disclaimer - never try this before nor I wanted to.

What I do want to try is a circuit to cut out the GP if engine is above certain temperature and spin away to start engine. The idea is to extend GP longevity. Make sense??

Even if it was really cold you think it would start without any working? I know my 602 wouldn't do that....but it did have 240k miles when no GP were working.

Interesting idea about thermal cutoff....what ambient temp did you have in mind?

t walgamuth · #9 10-21-2014, 07:47 PM

Quote:

Originally Posted by engatwork

I'm thinking you should be able to get a healthy 606 engine to start with three or four glow plugs working.

but not if it gets really cold.... maybe down to freezing or so but why stress your engine so much?

ah-kay · #10 10-21-2014, 07:48 PM

Cold is relative. Some cars will not start with 6 GP or give it another 6 when it is really cold. So the subject is moot.

I have no idea of the threshold temperature yet. This is low down on my priority list. May be. 60C.

vstech · #11 10-21-2014, 08:44 PM

Block heater...

dieselbenz1 · #12 10-22-2014, 08:24 AM

From experience at minus 20 C a 617 3 glow plugs minimum maybe 15 seconds of cranking. A 602 3 glow plugs 25 seconds cranking. But the shake, rattle and smoke for a few minutes. Both were repaired promptly.

So why not replace the glow plugs soon rather than a battery maybe a starter and the glow plugs next summer?

Zulfiqar · #13 10-22-2014, 11:40 AM

It would be in your best interest to swap out all glow plugs at this mileage - its a risky task on a 606 if they are siezed in there.

dont try to nurse it along - it hurts other parts like the starter etc.

However you do have a block heater in your engine, just connect it to a power source and you are good to go, I tried it for giggles once, 22F, the GPs switched off in 2 or 3 seconds and the engine fired like it was just shut off hot.

BiodieselMB · #14 10-22-2014, 12:25 PM

Replacing the glow plugs is an easy job. it is a bad experiment to try to nurse it along.

Must have the engine hot before removing them, the last time I did it I took WHunters advise and removed the first one and then ran the engine and then the next and ran the engine etc. so that you know that they are all hot. And used a reamer (a drill bit also works) on the holes and used anti-seize on all of the plugs.

The last time that the 606 car was at an "indy mechanic" (and it was the best most expensive place in town) years ago, they had the car sitting cold overnight and first thing in the morning broke off the first glow plug and charged me thousands of dollars. After that I joined the forum and will never go "indy" again.

Also on a personal note the glow plugs that I used were hard to find and Phil Reinhardt worked on finding them for much to long that day. Hours later he called me ,triumphantly, in the afternoon after finding them in an obscure warehouse old stock. A few days later he was gone. So those glow plugs are close to my heart. Phil was the best.

KarTek · #15 10-22-2014, 12:41 PM

I can tell you that my engine will not start with no glow plugs at 50 degrees or less. I know this because something failed in the GP circuit a few years ago, can't remember what, and I had no glow.

I do remember going out to the GP relay and taking a piece of wire I found and shorting the power wire to each GP feed wire for about 10 seconds each and then jumping back in the car and cranking it while there was still residual heat in the plugs to get it started.