Intermittent ignition problem.

[Mr Gorsky]

Hi gents, hoping someone has come across this before.

I have a '72 Satellite 318 auto with the factory electronic ignition and the car has developed an intermittent ignition problem. It will start from cold and run perfectly for a while (up to 30 minutes), and will then die and refuse to restart.

I've changed the ignition box twice (ensuring it has a good earth), put in a new MP distributor (incl rotor and cap), fitted eight new NGK plugs, fitted new ignition leads, replaced the dual ballast resistor twice, replaced the coil, replaced the ignition switch and manipulated the wiring while it's running to try and find a fault, but with no joy.

The car has had a chequered history with wiring work done prior to my ownership. It has had the black alternator output wire bulkhead pin burn out (as commonly occurs), and this has been bypassed with power running directly from the alternator to the starter relay stud. As a result, the ammeter reads incorrectly with just the one red wire feed going through the bulkhead, with the black wire from the ammeter continuing to power the welded splice and all the loads as per normal.

There is one odd thing that may be significant, but I'm not sure. Whilst fault finding, a second distributor was electrically connected and spun by hand with the ignition switch on and the coil lead output showed a good spark to earth. However, when the car is cranked with all connected normally and the coil lead held near an earth, there is just the one good spark immediately after cranking begins, then nothing. It's as if something is dragging down the ignition circuit.

I have ordered a new engine harness and hope to have that in the next week, the engine bay wiring is pretty ugly as can be expected on a forty year old car.

Cheers,

Mr G.

- - - Updated - - -

Oh, I should add that I've disconnected the bulkhead connectors and cleaned them of corrosion and sprayed them with contact cleaner...they seem ok.

Had them on and off a few times.

 

[mopar 3 B]

ECU is still not grounded well enough or a bad coil.

 

[coloradodave]

When the car stalls, you need to do a couple of basic checks. First, pull the air cleaner and work the throttle by hand. Verify that there is a strong squirt of fuel from the accelerator pump, indicating that there is fuel in the carburetor bowls. If so, then pull a spark plug and lay it on a good ground (engine, manifold, etc) with the plug wire attached. Crank the motor with the key on (either with the key if you have help, or by jumping the starter relay) and verify that you have a good, strong spark. You need to narrow down the possible problem area. Good luck.

 

[The 500 Foundation]

I had a broken terminal in the ecu wiring loom once on a brand new MP part

 

[Mr Gorsky]

Thanks for your responses, gents. I got a chance to work on the car again this week and here's the latest update:

The issue is 100% spark related. When the problem occurs, I get one single spark from the coil when the engine is cranked. However, when this occurs I can plug in a second distributor and get excellent spark from the coil wire to earth when the rotor is turned with the ignition switch on. This would tend to point to a problem in the ignition 2 (cranking) wiring circuit, however when the car cuts out it's using the ignition 1 (run) circuit.

I fitted a new engine wiring loom (that I'd purchased from Classic Ind). The old loom had been patched at least half a dozen times over the years and pretty much fell apart when I removed it. With everything else I'd done surely the new loom would fix my problem?? Nope.

Having spent some time studying the wiring diagram in the shop manual, I was hopeful that the issue might be in the bulkhead connector. I removed each wire one at a time and closed the female spade terminals a tad with pliers, before re-installing. Contact was much improved and I'm now certain there is no issue there. Car still ran intermittently.

This problem started just after I got the car. I'd picked it up and driven it 100 miles without drama, then parked it for a mini restoration. I'd removed the whole dash assembly (incl the bulkhead disconnect) when I restored the heater box. At around that time I also did some under hood tidying up incl replacing the ballast resistor with a new one (for reliability purposes).

With the bulkhead connector now seemingly not at fault, I focused once again on the ballast resistor. As many of you would be aware, they are pretty idiot proof....you can't connect them incorrectly, one connector has a locating dowel that prevents misfitting. Nothing, however, prevents poor manufacturing.

I discovered that the new ballast resistor I'd installed (to improve reliability!) was manufactured incorrectly. It was purchased from Rock Auto. It had the 5 ohm and the .5 ohm resistors swapped so that the 5 ohm aux resistor was wired into the (ign 2) cranking circuit and the .5 ohm was wired into the run (ign 1) circuit.

I'm unsure of what damage (if any) this may have caused to the ECU, as I ran out of time to fault find further. I hope to get time to continue work on the car next week.

Anyone come across this before?? I have had three ECU's fitted while this dodgy ballast resistor was installed......:icon_pale:

 

[Sixpactogo]

Thanks for your responses, gents. I got a chance to work on the car again this week and here's the latest update:

The issue is 100% spark related. When the problem occurs, I get one single spark from the coil when the engine is cranked. However, when this occurs I can plug in a second distributor and get excellent spark from the coil wire to earth when the rotor is turned with the ignition switch on. This would tend to point to a problem in the ignition 2 (cranking) wiring circuit, however when the car cuts out it's using the ignition 1 (run) circuit.

I fitted a new engine wiring loom (that I'd purchased from Classic Ind). The old loom had been patched at least half a dozen times over the years and pretty much fell apart when I removed it. With everything else I'd done surely the new loom would fix my problem?? Nope.

Having spent some time studying the wiring diagram in the shop manual, I was hopeful that the issue might be in the bulkhead connector. I removed each wire one at a time and closed the female spade terminals a tad with pliers, before re-installing. Contact was much improved and I'm now certain there is no issue there. Car still ran intermittently.

This problem started just after I got the car. I'd picked it up and driven it 100 miles without drama, then parked it for a mini restoration. I'd removed the whole dash assembly (incl the bulkhead disconnect) when I restored the heater box. At around that time I also did some under hood tidying up incl replacing the ballast resistor with a new one (for reliability purposes).

With the bulkhead connector now seemingly not at fault, I focused once again on the ballast resistor. As many of you would be aware, they are pretty idiot proof....you can't connect them incorrectly, one connector has a locating dowel that prevents misfitting. Nothing, however, prevents poor manufacturing.

I discovered that the new ballast resistor I'd installed (to improve reliability!) was manufactured incorrectly. It was purchased from Rock Auto. It had the 5 ohm and the .5 ohm resistors swapped so that the 5 ohm aux resistor was wired into the (ign 2) cranking circuit and the .5 ohm was wired into the run (ign 1) circuit.

I'm unsure of what damage (if any) this may have caused to the ECU, as I ran out of time to fault find further. I hope to get time to continue work on the car next week.

Anyone come across this before?? I have had three ECU's fitted while this dodgy ballast resistor was installed......:icon_pale:

It still sounds like your ECU is not getting a good enough ground. I am also wondering if the plate coil in your distributor is weak and opens up when it gets hot.