3.2 Intermittent Spark - suspect CA139EX comparator in DME

[nagromike911]

Hi y'all.

Getting intermittent spark pulse at the DME pin 1 output to coil. Traced to S800\B CA139EX voltage comparator. I get 4 volt pulses on pin 7 and pin 6 is steady 2 volts reference. I expected to see around 2 volt pulses out on pin 1 but see almost nothing coming out with a scope.

I've searched for this RCA part CA139EX but find very little in the way of availability on the web.

Just wondered if anyone knows of a source for this chip?

Thanks

Mike

[4flyboy]

Mike,

Ingo Schmidt is your guy for this.

ischmitz here on the boards helped me tremendously with time, advice and even a loaner when I had serious issues with my DME unit.

He'll be able to answer this question.

Good luck,

Scott

[nagromike911]

Many thanks for the reply, Scott. Actually, after further investigation the problem was not what I thought. I found I was not giving the cpu time to boot in the DME and was turning the engine over too quickly on the turn of the key. That's why the problem seemed intermittent; sometimes I was a bit slower than other times and then it fires. This has probably been discussed before on the forum but I'll put a message up about JIC. Regards

Mike

[4flyboy]

Even better! Glad it fired, I had reference sensor problems and Ingo went waaay beyond the call

[john walker's workshop]

Time to boot?

[brighton911]

Mike, I can say I do not wait any time at all between key on and cranking and have never had an intermittent start issue. I think there may be something more to your problem after all.