[H.D.]

Since the TD-signal (voltage between terminal 1 & 2 at diagnostic socket) is so weak after the engine cooled down, I suggest to pull the CPS plug from the EZL and check the CPS’s resistance between both contacts at the coaxial plug (like shown in the video). It should always be between 680 and 1200 ohms (both cold and hot)!

Btw – I like the methodical approach of trouble shooting in this video.
Only one thing l didn’t like: the cable coming which connects the coil with the distributor should not be used for a spark test! As I mentioned in post 32, that can fry the EZL.
And: when he tested the voltage between both coil terminals 1 & 15 (up from 22:00 in the video), he cranked the engine. That's not really necessary – the key in “ignition on” would be enough. (The voltage should be zero then)

Liviu165’s suggestion to check for proper ground connection is absolutely eligible!
I did mention the coil’s connection to ground in post 29. But liviu165 is right – also the engine’s connection to ground via it’s ground strap should be checked. It is possible that the spark plugs depending on the engines heat don’t have connectivity to ground via that strap.
Also the EZL’s connection to ground should be checked (but I think that's probably okay).

Other things that should be checked, when the engine does not start (with the key switched to “ignition on”):

• voltage between terminal 4 of the diagnostic socket and ground (should be battery voltage)
• voltage between terminal 5 of the diagnostic socket and ground (should be battery voltage)
• voltage between terminal 4 & 5 of the diagnostic socket (should be zero)
  That’s actually the same test as done in the video between both coil terminals (terminal 1 & 15)
• pull the EZL plug (with terminals 15, 16, 31 and TD) and check voltage between terminal 15 & 31 (should be battery voltage at “ignition on”)

 

[anthonywclark]

Final Update

All,
I want to thank everyone for their input and help. It turned out to be the crank position sensor. It was intermittent and I was able to catch it a couple times. Don't know if it was the sensor itself or the wire. I replaced it with a new one I bought for $70! Everything is running fine, even during normal temp.
I also did the voltage test and everything seems to be OK.
I still feel replacing cap, rotor, wires and plugs was a necessity. Still the original parts.
Thanks once again.:grin

 

[liviu165]

It turned out to be the crank position sensor.

Thank you for coming back to this thread and letting us know how you fixed it. Is always great to see the thread starter coming back and posting the solution. Unfortunately not everybody does it. I am glad you fixed it, and we learned many interesting things from this thread.

 

[H.D.]

Congratulations, anthonywclark!

I enjoyed to participate in the troubleshooting and I would like to join liviu165 in thanking you for your feedback!

Happy motoring to your daughter!

 

[ianrandom]

All,
I want to thank everyone for their input and help. It turned out to be the crank position sensor. It was intermittent and I was able to catch it a couple times. Don't know if it was the sensor itself or the wire. I replaced it with a new one I bought for $70! Everything is running fine, even during normal temp.
I also did the voltage test and everything seems to be OK.
I still feel replacing cap, rotor, wires and plugs was a necessity. Still the original parts.
Thanks once again.:grin

Excellent, well done.

yes if the service parts are old, you might notice more smoothness if you replace them. I recently put a new set of genuine MB wires, cap and plugs on one of my 420's and the difference was worth it.

 

[hellah fresh]

All,
I want to thank everyone for their input and help. It turned out to be the crank position sensor. It was intermittent and I was able to catch it a couple times. Don't know if it was the sensor itself or the wire. I replaced it with a new one I bought for $70! Everything is running fine, even during normal temp.
I also did the voltage test and everything seems to be OK.
I still feel replacing cap, rotor, wires and plugs was a necessity. Still the original parts.
Thanks once again.:grin

Nice!!! My dad have been having almost the same issue with his car. The car will startup fine but it will idle rough for a little bit. Once we let the car sit for awhile the car will start ti idle normal. Im going to give this a try.

 

[GreenT]

I replaced it with a new one I bought for $70!

Can you give us the source?

Thanks.

 

[anthonywclark]

Can you give us the source?

Thanks.

The company was AIP Electronics. Purchased through Ebay.

 

[hellah fresh]

Yeah we replaced the CPS and its still the same. The car still has a minor miss and now he finally took it our for a test drive and after about 10mins the car would cut out. He can start it back up so we are kinda trying to see if it was maybe something else. He is leaning towards the Idle Control Valve sensor?

 

[Bruinou]

All,
I want to thank everyone for their input and help. It turned out to be the crank position sensor. It was intermittent and I was able to catch it a couple times. Don't know if it was the sensor itself or the wire. I replaced it with a new one I bought for $70! Everything is running fine, even during normal temp.
I also did the voltage test and everything seems to be OK.
I still feel replacing cap, rotor, wires and plugs was a necessity. Still the original parts.
Thanks once again.:grin

Howzt Bud
I was just wondering if your faulty cps ever caused your car to run rough,smoke and sputter as other symptoms?
Thanx