hi guys,,,,...im done....
the car ....my brothers 72 satellite 318/904
the problem,,,....starts fine when cold ..runs 30/40 mins ..then dead stop...no spark at coil lead on upon cranking....

replaced all new parts.......ignition switch
....distributor
....ecu x 3
....eng bay wiring harness
....ballast resistors numerous (dual )
....coil
....volt reg
....pulled bulkhead connector cleaned , checked continuity everywhere , every wire....
....done everything known to man...!!!
....tested resistive ohms, voltage everywhere , had complete dash out of car back to firewall, every connection and crimp joint cleaned and tested...fusebox, etc etc etc..


now the strangest......after its been running and stops dead ( when warm) it has no spark upon cranking then when you turn it off it lets one spark go from the coil lead....
(thinking ballast resistor )
now if when hot , I unplug distributor ,just plug in another distributor...earth it and spin the shaft I have a beautiful intense spark rom the coil...so to break it down..
when its warm. it loses all spark, then hook aup another distributor , earth it. spin shaft by hand , it has a beautiful full spark!...
stranger....with ignition on, not cranking or running unplug ecu, plug another ecu in , then earth the ecu it throws a inch long spark out of the coil lead!...can any of you mopar igniton tech heads help out a frustrated aussie? I drove this car all over los angeles before I shipped it home never missed a beat...must be the clean aussie air!..

Pickup in the distributor failing hot.

Obviously you have a problem that crops up when the component is hot, bench testing cold does no good. Did you actually put a new distributor in the engine or did you "then hook aup another distributor , earth it. spin shaft by hand , it has a beautiful full spark!." That tells you nothing.

Ballast resistor is bypassed when starting.

Sounds like the pickup coil in the distributor is opening up when getting hot. After cooling down sometimes the pickup closes and appears to indicate normal. You need to check the pickup coil in the distruibutor for continuity with an ohm meter as soon as the engine dies. Unplug the 2 pin connector at the distributor and check between the two connections on the distributor side. Should read some resistance ( continuity) I just do not remember what ohms are Normal.
Ron

Measure it cold and working then measure it hot and not working, that'll give you your answer.

on the pickup coil.

I did have one years ago that one of the pick up coil wires had broken internally, that was fun to find

next time it acts up: (1) pull the yellow wire off of the starter relay to disable the starter (2) pull the dist secondary wire & hold it (dist end) 1/4" from a ground (intake) (3) seperate the dist pickup zigzag connector (4) have a helper hold the ign key to "start" (5) you under the hood & drag the metal tip of the body half of the zigzag connector across the metal intake to make/break ground with your right hand and hold the coil secondary wire 1/4" from ground with your left hand & see if you get profuse sparks. You gotta work FAST while the pickup is still hot to get a valid test as you are (A) isolating the pickup/reluctor gap and (B) testing it when it is HOT & electronics can cool off FAST once the current stops). Holler back

You said, "when you turn it off it lets one spark go from the coil lead...."

That tells me the coil is being charged.

In order for the coil to make a spark, first it has to be charged up (it's an inductor), then that circuit has to be opened, causing the magnetic field to collapse and driving the spark out of the coil.

Your system is for some reason not opening the circuit when it should.

I have had at least a couple of points type distributors that had the top bushing worn enough that the shaft could move sideways and the points wouldn't open. No Spark.

I have had a couple of electronic (non CD) systems where the pickup coil went open and so it didn't signal the box to open the circuit. No spark.

One of these things is happening to your car.

R.

thanks guys ..food for thought ...this is the second distributor , its a brand new mopar performance distributor, although that doesn't mean much..so I will test the pick up coil, change distributors and see what happens...

It could be a bad ground to the ignition box or coil.

R.

If simply swapping distributors when it faults out makes it work then odds are the problem lies in the distributor and the only part in the distributor that could cause the fault is the pickup.

Years ago we had a dist where the wires entering the dist were broken. Acted the same as a bad pickup. Sometimes when the vacuum advance moved the plate, it shifted the wires enough to open the wire break, sometimes it wouldn't.

Really sounds like a broken wire between the box and the dist pickup. The act of swapping parts closes to the wire break and things work, for a short time. Gene

How are your battery cables and ground connections?
This sounds like the typical Mopar ECU "Ground Loop" problem.
Basically the magnetic signal from the Dist is referencing the engine block ground, and the ECU is referencing the chassis ground (if the ECU case is even grounded good?
What happens is when the wiring gets hot, it creates higher resistance. Because voltage is Current * Resistance (V=I*R), the starter cranking current in the ground cable to the battery will have a voltage created. Because the Dist magnetic pickup is using a ground reference at the block, the signal at the ECU is at too high a voltage to sense the pickup signal.
Best fix is two parts, First good battery cables and ground connections, and second a ground strap from the engine block to the ECU box.

Hi gents, great forum you've got here.....this is my car. Thank you for all your posts. We've got some new things to look at.

^^^^451, I'm hoping you're onto something there. I get where you're coming from and a floating voltage wasn't something I'd considered. The battery cables were on my to do list down the track, they're pretty rooted. I'll clean up all the grounds, add a lead to the ECU and report back.

Lemme tell ya, the guy who finds the solution to this drama will be be in my good books forever! I don't think this a pick-up problem. As mentioned earlier, we've installed a brand new MP dizzy and a brand new engine harness since this problem developed, and the issue has remained.

One thing that I picked up on when I last had a chance to lay hands on the car, the brand new dual ballast resistor I'd installed for reliability insurance had been manufactured a55 about! The .5 ohm resistor was in the 5 ohm spot, and vice versa. "The drama" started sometime after this resistor was installed.

Lesson there....these things are cheap for a reason, and measure twice, install once.

Cheers,

Mr G.

^^^Brilliant.

I'm confused. If you have replaced the distributor with a new distributor one would think that would have changed the pickup coil. If the system seems to work with the other distributor, why not just put it in and see if the problem is solved?

even easier yet since you have a spare dist on hand you can plug in the zigzag pickup connector to the body harness & with the spare dist in your hand & spin the lower shaft tang with your free hand & have a helper hold the coil secondary wire 1/4" from the intake (ground) as another helper holds the key to start. have the yellow starter relay wire unplugged

Well, in the end that's what we did. The car is running gents, thanks for all your advice.

To tie this up and help the next poor bugga with this problem out, here's a summary of what went down:

The car was a daily driver when purchased, and was due for some love. I took it off the road and started the process of restoring it. Front bench off to the trimmers for repair, new carpets fitted. Heater box out, DMT foam kit rebuild completed. Whilst the cabin was stripped, I took the opportunity to remove the whole dash frame and check the wiring....usual black alternator wire damage at the bulkhead connector noted, had been bypassed with a feed direct to the starter relay stud. The ignition switch connector had been removed at some point and each wire was connected with bullet splices...not ideal.

Whilst waiting for the seat to come back, and with rest of the cabin under control, I did some brake work, fitted new Rallye's, and changed out the the old ballast resistor. They're cheap and they often fail.

Heater box back in, dash installed, seat back in....turn the key. Crank but no start. Check the bulkhead connectors, all in. Ignition switch wiring....still dodgy, but all connected correctly. Ballast, plugged in. New ECU fitted (NOS MP Orange Box). Whilst it worked when I parked the car for restoration, the original ECU had clearly overheated at some point in the past and the potting compound had melted and leaked down the firewall:






Hmmm, not an ECU issue. Had them on hand, so fitted new cap, wires and plugs...no joy. ECU earth checked, seems good. Try a known good coil, no joy. Got this NOS MP distributor on hand, fitted...still no start. This is getting weird. Bit more wire fiddling and head scratching, yay, car runs...for twenty minutes. That's when we discovered the "one spark" situation as described earlier. Car now seemed to start semi-regularly, but only when it was cold. It would then only run for a short period before dying.

It was like the key was being turned off, so maybe the ignition switch was dodgy. New switch installed, and an old Barracuda donated it's connector so the bullet splices were now history. Turned out not to be the ignition switch.

The engine harness had been patched a dozen times over the years and was going to be changed at some point, now seems a good time!! New harness purchased from Classic Ind and installed, problem remained. The old harness fell apart in my hands, so I was glad to be rid of it anyway.

Thinking cap on. What had changed since the car last ran?? Ballast resistor, and bulkhead connectors disconnected when the dash assembly came out. So....tightened the female spade terminals for a more positive contact, no joy. That's when I discovered the ballast resistor was manufactured incorrectly.

What this meant was this: I had .5 ohm in the auxiliary circuit to the the ECU. This circuit should have 5 ohms to protect the ECU, but since I now had a four pin Orange Box in the car now, no harm no foul as that circuit is now redundant....the .5 ohm was connected to nothing.

The other side of the ballast put 5 ohms into the coil primary circuit. This would have reduced the primary voltage and therefore reduced the coils output to the distributor and the plugs. May have contributed to the hard starting but clearly not the cause of the cutout whilst running.

This is when the good denizens of Moparts came in

Having read this thread and spending time this past week boning up on the intricacies of the "new for '72" Chrysler Electronic Ignition, I shaped up to the car yesterday ready to win this bout! The car started from cold again, and cut out eight minutes later. Multimeter out, and measured the new MP distributors pick-up coil.....1.2 Meg Ohm. One million, one hundred and ninety nine thousand, four hundred more ohms than specified in the factory manual!!

Original distributor back in, car ran like Carl Lewis in 1984.

The autopsy:

The dodgy new Standard Parts ballast resistor from Rock Auto likely caused hard starting, during which time a faulty new MP distributor was installed. After cooling down having been removed and put on the bench, the new MP distributor pick-up coil measured it's nominal 600 ohms. I had an intermittent pick-up coil fault in a brand new distributor.

Thanks once again to all who chimed in. I lost a few days changing bits, but they were mostly due for replacement anyway. Along the way I became a Mopar wiring expert and had the interesting experience of dreaming about running small block engines!

Cheers,

Mr G.

Oh yeah, I did clean up all the grounds this week....on the ECU, on the engine, on the firewall, and on the radiator support panel.

I also changed the dodgy ballast resistor!

Good show!