Fw: 81-83 EFI system circuit analysis: Was (RE: IML: Question, of cours

It would sure be interesting to have a test light monitoring the output from the ASDM when this happens. If it dies with this line high, the problem is elsewhere, but it sure sounds like the ASDM is shutting it down.

The cause could be any one of the shutdown causes, or noise.

However, the fact that it won?t restart until it cools off sounds like the distributor pickup coil ?open? that was somewhat common with these ? that would of course be heat sensitive, and would cause a loss of ignition pulses, thus the ASDM would shut it down as it is supposed to. Have you replaced the reluctor and magnet? These are cheap, and relatively easy to change ? I?d say it?s worth a shot! The EFI cars have only one set, not the two that are used in normal Mopars. You will find it easier to pull the distributor to do this, and you do need to reset the initial timing afterwards.

Dick

From: Ken W Stephenson [mailto:kss37215@xxxxxxxx]
Sent: Monday, July 25, 2005 9:48 AM
To: dickb@xxxxxxxxx
Subject: Re: 81-83 EFI system circuit analysis: Was (RE: IML: Question, of course!)

Thanks for the clarification, Dick. Agree the ASDM design looks like an afterthought. Reminds me of some of the quick fixes they made us do to ship "prototypes" out to customers. But my quest here is not purely academic, I have this machine running near perfectly, however, out of the clear blue it will suddenly just die. Does not stumble, cough, or anything, just dies at random times. All modules are the late production, non-meltdown, all new filters, cleaned tank and pickup filter. Will not restart until it gets stone cold again. Has fuel, spark, and turns over, but no start. Same effect with bypassed ASDM. That's how I isolated the common lead to the CCC. I am about to bite the bullet and gamble on a "new" or "refurbished" CCC.

Even after 6 months on this project I refuse to trash the EFI.

Ken

On Mon, 25 Jul 2005 10:10:03 -0700 "Dick Benjamin" <dickb@xxxxxxxxx> writes:

I?m copying the IML with this discussion because I want to get all the thinking into the archives for the future use of folks who are going to be keeping these cars going; I hope you don?t object.

I hadn?t read your suggestion carefully enough ? I see now that you were proposing to disconnect the wire at the ASDM and CCC, but leave the pump drive alone. I can?t see a reason to do this, as the signal from pin 6 to the ASDM cannot cause a noise problem once the car has started; the NAND gate consisting of pins 12, 13 and 11 of the IC is in the ?don?t care? state. This is due to the fact that the starting signal (pin 13 of the IC) has gone (low) once the key is released. The connection is there only to initialize the first ?flip/flop? and start the in-tank pump for the purge cycle as soon as the circuit comes alive ? it is then ignored until the next cycle.

I can?t tell you what the pump drive signal is used for inside the CCC, as we have no information on that item. I assume it is used as a feedback signal for whatever analog circuit generates the fuel demand signal ? if that is the case, grounding it would probably cause the pump drive to go to max (80PSI!) and stay there. Fuel mileage would suffer, to put it mildly!

The bottom line is: try an experiment if you wish, but my advice is - leave well enough alone.

The noise problems in the ASDM are due to a very poor design, namely the use of ?tied back NAND? type (unclocked rather than J-K) flip/flops, and the absence of any solid grounding provision for the unit ? both mistakes invite severe noise problems, thus the service note about adding a ground wire to the case.

Dick Benjamin

From: Ken W Stephenson [mailto:kss37215@xxxxxxxx]
Sent: Sunday, July 24, 2005 9:23 PM
To: dickb@xxxxxxxxx
Subject: Re: 81-83 EFI system circuit analysis: Was (RE: IML: Question, of course!)

Agree, but we would not disturb drive to Control pump, which is internal to the hydraulic plate, just disconnect pin 6 and keep line to CCC, pin 2, and ASDM, pin 4, low. Seems redundant the way it is. Just a thought to eliminate another noise input to ASDM and CCC.

Ken

On Sun, 24 Jul 2005 21:37:36 -0700 "Dick Benjamin" <dickb@xxxxxxxxx> writes:

Pin 6 of the power module is the pump drive signal output to the Control Fuel pump from the push/pull pair of power driver transistors.

You must have been asking about some other pin or connector ? you won?t get far without pin 6!.

Dick

From: mailing-list-owner@xxxxxxxxxxxxxxxx [mailto:mailing-list-owner@xxxxxxxxxxxxxxxx] On Behalf Of Dick Benjamin
Sent: Sunday, July 24, 2005 1:36 PM
To: 'Ken W Stephenson'
Cc: mailing-list@xxxxxxxxxxxxxxxx
Subject: 81-83 EFI system circuit analysis: Was (RE: IML: Question, of course!)

-----Original Message-----

From: Ken W Stephenson [mailto:kss37215@xxxxxxxx]

Sent: Sunday, July 24, 2005 11:42 AM

To: dickb@xxxxxxxxx

Subject: Question, of course!

The lead from pin 6 of the Power Module to the CCC and ASDM. Obviously

controls shutdown. For what reason? The ignition pulse train does the

same thing. Can I disconnect it at the PM and ground the side to the CCC

and ASDM without losing anything? Just trying to simplify this design.

Did anyone ever do a theory of operation on the Power Module?

Fw: 81-83 EFI system circuit analysis: Was (RE: IML: Question, of course!)