The symptoms are at my house which is 7800 feet above sea level: my 87td is difficult to start. It acts as if only one cylinder is firing. Also this car is new to me from N.C. an eBay special. I have never seen a car with so many deferred maintance issues. To the point. Using a test light I checked at the glow plug relay the six plugs for continuity. Cylinder 1 and 3 = no light, #5 Dim light, #2,4,6 bright light. My guess is that #5 is the good glow plug, 1 and 3 are gone. 2,4,6 represent dead shorts and a harness problem.

Help!

I should replace the harness from the relay to the plugs and 12346 glow plugs?

Hey,
Assuming your testing from the socket on the glowplug fuse block to ground, I would change any plug that has no or little continuity.

Why do you think your harness is bad? Are you not getting continuity from the socket to the glowplugs?

You might get a better idea if you measured OHM's.
Danny

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1984 300SD Turbo Diesel 150,000 miles

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Number #5 Glows dull like there is resistance. 246 are bright white light like there is no resistance. 1 and 3 show no light. It starts like only one cylinder is firing. I have to crank for 2-3 minutes to get it to start, eventually more cylinder catch on and it picks up speed. I will buy another ohmmeter.

I removed the connector on the glow plug relay that goes to the glow plugs. I attached the clip of the light to the hot terminal of the glow plug relay and check continuity thru the glaow plug wire harness to the glow plugs.

I guess that I will have to check continuity thru each wire from the relay to the Glow plug terminal post.

better to check with - or black lead to grnd and + red to hot connection on each at glow plug at glow plug relay.be careful do not put voltage across your meter in the ohms mode!

I would do the same test but with the test clip attached to the fuse inside the relay top and the probe touched to the connection of the wire at each glow plug.

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1984 300SD 326,997 miles and counting . . . No wait, my odometer is still dead

glow plug resistance less than 1 ohm = probably OK. More than that, NG

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'82 300SD - 361K mi - "Blue"

"Good judgement comes from experience. Experience comes from bad judgement."

listen, look, .........and duck.

I'm headed to Radio shack for an Ohmmeter.

Thanks

Why does it seem as if it is only hitting on one cylinder?

The Haynes manual says to check from the plug socket (Should be numbered for each plug) to ground. Checking the harness and the plug at the same time. It has been recommended here to check from the battery ground.

Danny

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When I get the ohmmeter I will do that and also check across each other to see if there is a shortage in the wire harness. Ie 1-,1-3, 1-4 etc, 2-3,2-4,2-5 etc. That should verify the intregrity of the wiring harness.

Thanks again. for your help

Bought a digital Multimeter so I can stop guessing

Thanks

tsiero,

Proper way to test resistance GP is thru the female connections in the GP cable connector after it has been removed from the GP relay. You should read 0.6 +/- 0.2 ohms for each plug. Note, other lead from the ohmmeter must be connected to a good ground. A clip lead is best. Then see if the second lead to ohmeter, connected to ground, reads almost 0 ohms so you know you have a good ground connection.

I would suspect that 1,3 5 are bad and 2,4,6 are OK by the description of your lamp test.

P E H

Get a socket to remove the injectors.
Pull all of them and turn the key to 'run'.

Lean over the fender and take a shiffty down the injector holes.
6 bright glow plug tips....No ? Replace those that don't glow.

Go on...ya know you wanna do it !

That was easy, wont it ?

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tsiero,

Easier way than removing the injectors and replacing the heat shields is to remove the GP and connect them across the battery and see if they glow a bright orange. This way you have the GP that need replacement already out and you don't disturb the injection system.

To connect across the battery, hold the GP in a ViseGrip by the hex. Touch the screw end of the VG to one post of the battery and use a screwdriver to connect the terminal of the GP to the other battery post.

Be careful when you do this because the good GP get hot.

P E H