hey folks,
I'm working on a '95 E300 diesel that belongs to a family friend. its got 100,000 miles. it cranks but will not start. when i turn the key to position 2, the glow plug light doesn't come on, but the glow plug relay contacts close. the plugs glow for about 20 seconds and the relay switches off. as soon as the relay switches off, the glow light comes on in the dash. this seems to be the opposite function of every other m-b diesel i've encountered.
anyway, i pulled off the intake manifold and removed each of the glow plugs. i tested them all and 5 out of 6 are working fine.
i noticed large amounts of carbon buildup and sludge in the intake manifold and the intake ports. i am thinking maybe that the glow plug holes need to be reamed out, or there maybe carbon preventing valves from sealing properly and it won't start because of low compression.
any ideas?

thanks,
jim

From my experience having one bad plug will alter the way the dash light operates.

When was the last time the engine was running?

I'm not sure if the non-starting problem is related to the glow plugs. Are you sure you are getting fuel? Perhaps the fuel system lost its prime because of air leaking into the system? Are there air bubbles in the lines?

If the system lost prime it takes a while to "self prime." Check the owner's manual. I believe it says put the accelerator to the floor and crank for up to 30 seconds and then try again.

Just my thoughts. You need fuel, air and proper compression at the right time for a diesel to run. Verify you have fuel. You can crack the injector lines at the injectors to see if you have fuel there. If not check your filters and move on to fuel pump. Does this have a manual stop lever controled by a vacuum device. If so it could be as simple as the vacuum line has come loose. Good luck and report back on your findings.

If you've got a good glow and compression it sounds like a fuel leak.

All the plastic fuel lines to and from the filter and IP rely on oring seals which may cause an air leak resulting the IP losing its prime. There are more orings at the shutoff valve, beneath the prefilter and on the kill switch/bolt the main filter attaches to.

OM606 is primed my turning the engine over. No manual pump.

Most members here would recommend the GP be coated with anti-sieze before being reinstalled.

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Terry Allison
N. Calif. & Boca Chica, Panama

09' E320 Bluetec 77k (USA)
09' Hyundai Santa Fe Diesel 48k (S.A.)

the last time the car was running was a few days ago, but the owner reports that it was running poorly and would stall intermittently. i can see air bubbles in the plastic lines between the injection pump and the filter housing. perhaps i'll replace all of the o-rings and seals, and then start cranking.

May as well puit new glow plugs in since the old ones may have lots of use already, and when one goes out there's soon to be another fail.
If the engine is getting fuel (crack open one injector or two maybe) then you may have a plugged Oxidizer Cat, if there is one in the exhaust line. You can open the exhaust manifold to let it breathe out better then see if it will start.
Carbon in the GP area will not cause the car not to start, valves will close.

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'95 E320 Wagon my favorite road car. '99 E300D wolf in sheeps body, '87 300D Sportline suspension, '79 300TD w/ 617.952 engine at 367,750 and counting!

I think you found your problem.

Change the oring under the pre-filter first. Often overlooked as has its own part number.

Get ALL the air out first, then move on to second steps if needed.

__________________
Terry Allison
N. Calif. & Boca Chica, Panama

09' E320 Bluetec 77k (USA)
09' Hyundai Santa Fe Diesel 48k (S.A.)

Jim,

I agree w/ Chuck. You probably have more than one thing going on here.

When I purchased my 95 E300D (OM606), I had the reverse glow plug light symptoms you mentioned. However the car started fine. The pre-purchase inspection revealed that one of the glow plugs was bad. (...just like your analysis of your own GP's.) Once the faulty GP was replaced, the GP light extinguished properly upon heated GP's.

Regarding the starting issue, I'd check the fuel and air bubble related replies to your post first.

Being relatively new to diesels, I was surprised at how quickly their fuel filters can clog and restrict flow. I had to change the filters just last week after only 11k miles. The early symptom was fuel starvation (slight bucking) at higher rpms preventing a 3-4 shift under full throttle. The new filters restored proper fuel flow and completely fixed the problem.

KylePavao mentioned bad fuel/gelling due to cold weather in another post. If that applies, you might want to check out his solution.

Wittenberger

1995 E300D Blk/Blk 184Kmi

thanks for all of the replies. the reason i looked at the glow plugs first is because of previous experiences i've had with mb diesels i've come across. one was a 140 with 603 engine and the other a 115 with 617 engine. on both, i had a crank and no start condition. i replaced glow plugs on both to no avail. it was only after reaming the carbon out of the glow plug bores that they would start properly.

Your problem is most likely a fuel leak, and seeing as the 606s are prone to them, I wouldn't doubt it. Glowplugs will affect cold-starting ability, but if you even have five good ones (as I do), and the relay switches on, the car will start fine. I have heard of one person whose diesel wouldn't start because of a plugged catalyst, but I believe those occurrences are very rare. Your problem is probably a leak that allows air to enter on the suction side of the fuel pump (not IP)...read: PREFILTER O-RING. The pump would draw air and not fuel from the tank, causing the motor to fail to start. Replace this O-ring first and see if it makes a difference...once you replace you may have a bit of purging to do too; hook it up to a battery charger.

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99 E300 TD -- sold
01 540i 6 spd