I am trying to check out the wiring that is plugged to the injectors ---what reading should I be getting across the plug when I crank the engine

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syd 81.300SD
72.300SEL 4.5

There is a "voltage" frequency sent by the computer to the injectors. The injectors are triggered in pairs by 4 sets of points(mounted in the bottom of the distributor).

this engine runs--misfires and is rough--- like it is not running on all cylinders---plugs are black ---have replaced plugs --new air filter---checked points ---checked all plug leads nicks and the suchlike also for resistance--checking timing and compressions tomorrow ------trying to figure out if there are any problems with the wiring to the injectors---have dicovered tonight that when pulling plug off injectors corrosion is very visable---so will clean them as well---any advice would be apprecciated ---need this engine up and running to see if rest of car works it was delivered to me on a low loader

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syd 81.300SD
72.300SEL 4.5

Hi,
Pull the distributor and check for oil on the trigger-points in the distributor base. You can also trace the problem on a scope. The injectors are fired in the following pairs: #1&5, 2&7, 3&6, 4&8. Usually when you see a problem on any of these pairs of cylinders...it's trigger-points.
Regards,
Randy D.


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W.R.Durrance
ASE Master Tech
Mercedes Tech 19 Years

Now that you have described the running problem as running rich I'll bet that the cold start relay is stuck, un plug the cold start valve & see if the engine runs better. Also the vacuum hose for the M.A.P. sensor has been known to leak.

thank you for all answers I received on this topic syd

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syd 81.300SD
72.300SEL 4.5

whilst I'm running rich I was spitting and banging and could not rev it up--all injector boots disintergrated and all injector plugs were coroded--(think its been standing a long time)no5 was welded solid with corosion --I am waiting for new injector plugs to be delivered---tried to get workshop manual from 1-800-for-merc --no luck --got told the old cd story--QUESTION --so M.B.DOC help me out here---- where is the cold start valve and the M.A.P.sensor--I feel I will have to replace N05 injector --but as soon as plugs arrive I will try it before replacing it

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syd 81.300SD
72.300SEL 4.5