280SE 4.5 injectors 2&3 not firing - Mercedes-Benz Forum

 
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post #1 of 5 (permalink) Old 11-18-2011, 12:36 PM Thread Starter
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280SE 4.5 injectors 2&3 not firing

We have a problem on a M117,
No response to cylinders 2&3 while running.

At idle , I can disconnect the connectors to the injector body and no change (2,3) of idle quality
all others make a difference.

Also, during warm up, the exhaust manifold at 2,3 are cold to the touch during cold start operation. (yes I touch them)

Swapped out the 2 injectors and same result,

So I am wondering how to check the pulses at the connector to the injector body,
I have the digital volt/ohm meter, only, can I test static, or dynamic?

Compression good, good idle, no tailpipe crud blowing, valves adjusted, dirty intake manifold (old unknown seals and gaskets, an older motor,
While last run at freeway speed run mucho power at speed.

We've tried many things, plugs, points, wires, trigger points, tps, map sensor, brain box, ground connections, fuel pressure, all EFI subsystems have been cleaned, spiffed, touched and tested by substitution.

Any Ideas ?
Thanks in advance

Brian O
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post #2 of 5 (permalink) Old 11-20-2011, 11:54 AM
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Wow, thats frustrating after trying swaping so many pieces of the system. I dont know the answer to whether you can test static or dynamic but I would think that the problem at this point would lie in a broken wire or insulation cracked on a couple of them somewhere and they are shorting. Good luck Im looking forward to seeing what you find the problem is.

Last edited by galaxyjb; 11-22-2011 at 03:53 AM.
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post #3 of 5 (permalink) Old 11-21-2011, 04:42 AM
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Hiya Bostosh. The cylinders fire in pairs - 1&5, 2&6, 3&7, 4&8 - and are hard wired between injectors. If 2 and 3 are unresponsive but 6 and 7 aren't, you have bad wiring or bad connection plugs.
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post #4 of 5 (permalink) Old 11-21-2011, 08:46 AM
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If it's only 2&3, that are giving you problems, I concur on wiring problems. Check the wires that go to the ground points on the manifold.

Just to make absolutely sure: You are counting the cylinders 1 to 4 on the Left as you stand infront of the car, facing the engine) and 5 to 8 on the Right? It can be easy to get confused, if someone works on other makes of car a lot, too.

Scott

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post #5 of 5 (permalink) Old 11-21-2011, 10:03 AM Thread Starter
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I am thinking wiring also. Grube and Radio I like that logic.

Is there a way to check with a meter?
I will cut back some insulation and probe between plug and solid wire.

or just cut the plug off and splice another one on?

Trial and error or trial and trial

Brian O
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