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An M120 that was shutting off on right hand turns is now refusing to start. Where do I start?

817 Views 5 Replies 4 Participants Last post by  secondslc
Hi Guys,

I'm usually working on my w116 as my SL has been (mostly) fault free, but I'm stumped.I hope I can get some advice as I was hoping to get a few more weeks of driving before storing it for the winter!

A week ago my 96 was shutting off on sweeping right hand turns. As soon as the car straightened out, it would turn back on itself and be fine. Then it started shutting off after a hard acceleration run, and restarting just fine. I assumed a bad fuel pump (this has a later style pump), and put one in. Before I did that however, it stopped starting altogether. I was a bit annoyed but just figured the pump was done.

Put the pump in, lowered the car down, filled the tank back up..and nothing. I know I have fuel pressure as I cracked a line up front and got a nice spray.

Here is what I have so far
-It cranks strong, no issues with the battery .
-I can hear the throttle bodies when I turn the key to position two.
-All the cluster lights stay on, not sure if thats normal as I've never really had the car fail.
-The car always started fast, and I am not thinking its the crank position sensors as they shouldn't fail all at once. I would imagine the car would have started taking longer to start, or I would at least get one bank to fire. Right now I have nothing.
-Should I check anything else?
-I had no check engine lights when the car would shut off.

Guys, I have no idea where to start, but I'm willing to test anything.

My next idea is to test the crank position sensors, but I don't know where the wires lead to. I'd put an oscilloscope on the output and look for a signal...but where do I go?

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My money is on the cps. On mine it was only one of the two that went bad, yet it failed to start the car a couple times. Then started like nothing was wrong when cooled down. This was confirmed with STAR diagnostics. I replaced both, and the cars runs great again.
Word of advice: if I remember correctly, the instructions tell you do the service from above. Like that however you have to remove a bunch of things and it’s still a bitch to get to them. You can actually replace them from down below but it IS a very tight squeeze between the downpipes and the trans.
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