86' SDL No Glow plug light. Did all the checks on the relay and Battery voltage and time out and its ok. Then did the continuity test on the plugs through the connector, and 5 when to infinity and one was dead (G3). Seems to indicate that's the bugger. Only thing is, some say that ohms should read about 1.5. when checking resistance. My test promptly went out to infinity on all scales on the 5 plugs. What's the deal ??

New/good glow plugs measure at or slightly below 1 ohm on most digital multi-meters.

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I'm going to guess that you are using a analog multimeter - one that has a swinging needle to indicate the reading (not a digital meter, which usually reads out on a LCD).

And I will assume you have the meter set to read ohms on one of the scales (should probably be the lowest scale).

So, when the meter swings all the way over, that is zero ohms (or close to it). The meter swinging all the way across the scale should indicate continuity through the plug. Good.

If the meter does not move, that is infinity. No connection. Bad glow plug.

It looks like you have narrowed it down to GP3 properly. Unfortunately this one is not easy to get to. I think you'll have to remove the intake manifold to replace it.

Ken300D

Doh ! Yep, Swing needle type multimeter. I neglected to ZERO out the ohm setting so I was always getting "off the scale" readings.
Getting the 1.5 or so reading now. But G3 is in fact dead plus another one is bearly moving the needle.

Am I asking for big trouble taking the manifold off ?? Cause you're right, can't get to it. No way gonna get 12mm socket in there. If I have to take it off I may as well replace all six huh ??? Believe it or not, Pep Boys has Bosh Glow Plugs for $7.99 each. Just have to get them in.

I haven't had the intake manifold off yet. The bad glow plug on mine was for cylinder #1, and you can get to that one through the injection tube spider lines. In your case you have no choice.

It seems to me that someone here mentioned a new gasket that you'll need for the intake manifold. And people have said you should clean the insides out while you have it off. There's something about the action of the EGR system sending exhaust carbon through the intake and having it collect there. In the case of the vacuum connection to my EGR valve, I would like to plead the fifth amendment.

That's a good price on Bosch glow plugs - I didn't know Pep Boys had them. I just got new Bosch plugs, and they look slightly different from the glow plug I took out of the car. While the OEM glow plug is the same diameter along its entire heating element length, the new Bosch glow plug "necks down" about halfway along its length to a smaller diameter at the tip. I think this may improve the way it heats - it probably gets hotter now. So if I were buying them in person I'd take a look to make sure they are this newer design. I see that the box says "Duraterm" on it - don't know if that implies the new tip design or not.

In my case with the easy-to-access #1 GP being the only one bad, I chose to replace only that one. I'll bet you could get by for a long time with just replacing the bad ones (I think you have two bad ones) yourself. However, if I were in your situation, I'd go ahead and do them all - considering the effort to remove the intake manifold.

Actually, you might need to remove both the intake manifold and all the injection tubes that run from the pump to the fuel injectors.

Ken300D

You're right. The Bosch part # is 80006 on the GP box. I was mistaken. I got them from AutoZone not Pep Boys. It looks like it does have a secondary taper at the tip. Does not say "Duraterm" though. A set of six form the dealer was $87. $48 from AutoZone. They are identical, even the Bosch Box. Don't know why they had them but I noticed they carry alot of Bosche stuff. Nice to know for my MBZ and 911. Buying them was the easy part. Now for the torment of installing them. Well, here goes nothing.

One question. Do the GP #s run from front to back, ie, radiator to firewall or vise-versa ?? Turns out for #3 it doesn't matter.

I went ahead and broke the box seal on one of my new GP spares. The "neck down" taper is more like 3/4 of the way to the tip - not half way.

Got mine here on FastLane.

Part No is 0 250 201 039 as stamped on the GP itself and also on the box.

I would not be surprised at all if Bosch had more than one marketing level of GP product - kinda like spark plugs. The "Duraterm" may be some slightly different product line from yours. It also says "Made in France".

I never trust the people behind the counter to give me the right part. I always match up the new part with the old. I've seen people get new spark plugs on gas engines that were too long - if they had put them in it might have cracked the piston. So, I matched up the new GP with the old, not that I expected any difference - and they were the same length. (I don't think GPs can crack the piston, I believe they are in the "pre-chamber".)

On our cars the GP numbering is from 1 to 6, starting at the front of the car and going to the back. That is also the cylinder numbering.

I don't know how well your car starts, but with only one bad glow plug on mine, the engine spewed out a lot of unburned diesel smoke and ran rough until it warmed up for about five minutes. Now I get just a puff of smoke and it runs smoothly after about 5 - 10 seconds.

Good luck on the task.

Ken300D

'87 300D
'82 300D

Yea my GPs have the same as yours and made in france. Bought one from the dealer and the other 5 from AutoZone. sameo-sameo.

Well after 2 hrs- got the Intake man. and fuel lines off, the old GPs out,-installed the new ones and just finishing off putting all the ancillary nuts and bolts and brackets back on. Turns out the Int. Man swings back just far enough to get at all the GPs. dont need to take it out. Broke a few rubber overflow lines to the injectors but no big deal. Just snip and re-incert.

Not a bad job actually. It helps if one has the right tools. There are some very tight places in there.

Thanks for the info on the manifold and fuel lines. Gave me enough confidence to do the job. Couldn't figure out how the heck to get in there. I suspect it would be major bucks if done by dealer.

thanx again