Hello all, I am hoping someone can help me with some advice. I originally posted this on the general board, but thought it would be better here.

My Dad has a 99 E300 diesel, with about 70,000 miles on it. Recently it has become hard to start. It is very loud at start up, runs rough, and spits out a bit of smoke. After a minute or two, it runs fine.

My first thought was a bad glow plug. My experience is with VW diesels, which often won't start at all if a glow plug is bad, however, I figure on a 6, it might start, but work like I describe.

I also thought that on this more sophisticated system had a warning light system. If a glow plug goes bad should the dash glow plug indicator come on?

Well, here are my questions...

1. Does this sound like a bad glow plug?

2. How the hell do you get them out? Does the big intake manifold need to come out? If so, is it just the visible torx screws on top that need removing (I know, I know...I can't be that lucky!)

I thanks anyone in advance who might have some advice.
--
Tony Bad

02 Jetta Wagon
01 Eurovan MV
95 Golf 2.0
91 Jetta 1.6 Diesel
86 Jetta
83 Subaru GL10 (gone to rust heaven)
79 Rabbit 1.5 Diesel (semi-retired for now)
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Try doing an electrical test on the glow plugs (GP) first. You need a 25 amp DC ammeter for the best test but an ohmmeter with a scale that will measure below 1 ohm will usually indicate a bad GP. I would suspect any GP that has a higher resistance than the other plugs may be the culpret Nominal resistance should be in the order of 0.5 ohms. You can check the resistance thru the GP cable after pulling it's connector out of the GP relay.

I never worked on a E300D to remove the GP so I can't help you there. If one GP is bad it doesn't mean others havs to be replaced.

P E H

I had the same problem with my 98 E300DT. The preglow light didn't show the fault unil I did the following: Turn the key to the preglow position. After the light goes out, wait about thirty seconds. My preglow light came back on and now is on constantly, unless ignition turned off. Replacing plugs soon. I live in St. James if you want to do job in tandem.

Tony,

How many miles are on the vehicle? If less than 50k, it is still under the new car warranty. That said, it definitely sounds of symptoms relating to a glow plug problem.

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Chris

'04 ML500 - 53k, Inspiration Edition, Desert Silver
'11 Audi A4 Avant - Brilliant Black
'87 300SDL sold
'99 C280 Sport sold
'85 190E 2.3 sold

Yes the intake manifold must come off to do this job.
While you are there, replace the rubber o-rings on the plastic fuel lines & replace the rubber fuel bleed-off lines on the injectors!!

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Will replace parts listed above when changing glow plugs. Should I also replace the intake manifold gasket and the large o-ring (just upstream from the intake manifold)?

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The glow plugs (GP) were not working in my '79 300SD (200K miles) but it started OK down to about 40 degrees F. It started when it was even colder if the block heater was plugged in. The only difference was that the starter had to crank the enging 8 to 12 revolutions instead of the normal 1 or 2 when the GP are working.

The engine ran fine, not any different than when the GP worked. Since the GP are turned off as soon as the engine starts, they should have no effect on the running of the engine. It is extremely rare that more than 1 GP goes bad at once. And on bad GP will only cause a miss in one cylinder for a short time.

I fixed the problem by R&R the connectors on the glow plug relay.
This is called contact wipe which breaks thru any oxidation or corrosion on the surface of the contacts in the connectors.

Antnip: So by the above explanation I am trying to tell you that I don't think you problem is a bad GP. Before I would go to all the trouble of removing the manifold to R&R the GP, I would do an electrical test on the GP.

P E H

Replacing the glow plugs looks like a big job, so I'll be sure to do as you have suggested and R&R all connectors at the GP relay. As far as electrical testing of the GPs, use an ohm meter on the connector that goes from GP relay to GPs, right?

Colinc,

The GP cable has a connector with female contacts where it plugs onto the GP relay. If you have banana plug wires on your ohmeter, they plug easly into these female contacts. The other end goes to a good ground. If you have alligator clips on your ohmeter wires, you should clip them directly onto the end of the GP.


This is the way my '80 300SD is but it is possible yours is set up differently. You should have a digital ohmeter or an analog meter(pointer needle type) with a 0 to 1 ohm scale. Most analog meters do not have a scale this low.

You are looking for one GP that is different from the others, either higher or lower resistance. The nominal resistance is somewhere in the range of 0.5 ohms. It is also possible that there is a higher resistance in one of the wires to the relay or the connection to the GP. So I would also check for that before I blamed the GP for being bad. This would be done by measuring the resistance directly on the GP, not the wire.

P E H

Thanks P E.

The problem with testing the plugs directly is that they are so buried (98 E300DT), If I do have to remove the intake manifold, I'll replace all of them regardless of how they test. Car has 107k miles. I do have a digital multimeter and will get the correct connectors so I can test at the relay. If I find a resistance value that is out of line with the others, it will have to be off with the manifold. Even if the problem is a bad connection at a plug, or a bad wire, I'll still replace the GPs so I wont have to go back in.
CC