Duster distributer short? wont start

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73 Plymouth Duster

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So 73 duster with a 318, starting problem has re-emerged. I have replaced
-ECU
-ballast
-alt reg
-coil
-mag. pickup in distributer
-ign switch

Car starts periodically. I swore it must be a loose wire in the harness but after looking for 2 hours and ohm checking everything it doesn't appear so. HOWEVER when you unplug and plug in the ecu box there is a clicking noise (like an electrical short) coming from the distributor.
We tested there IS voltage at the ballast in start and run, like 10volts but only 5volts and 8volts at the coil (so it is loosing half somewhere) (like a short in the dist?) anyways when we unplug and re-jump the plug to the ecu except the top plug the coil WILL get full volts.

I think there is something wrong in the distributor, the magnetic pickup is kinda loose in the distributer and is only tied down with 1 screw. and when the vacuum is (sucked on) the plate tightens down then slides. am I missing a screw? is something obviously wrong before I tear it apart?

Thanks guys
 
There might be something wrong with the pickup/ advance plate but they DO move. The only thing that keeps the advance plate in place is a pivot in with a 3 fingered spring keeper on the bottom of the mating plate.

Any evidence that the pickup/ reluctor suffered strike damage, or rust/ debri on either?

Work the dist. connector in/ out to scrub it clean and "feel" for tightness. Do the same for the ECU, ballast. Take your meter, hook into the disconnected dist. connector and crank. It should generate about 1V AC

Try a jumper wire from battery (starter relay) to coil +, check spark. Don't leave that connected any longer than needed to test

Make ABSOLUTELY sure the ECU is grounded.

Since you have all those spare parts, I'd be getting a "basic" harness together, and build an emergency/ bench test harness. That way you can "sub" about anything quickly. I two or three old ragged junker harnesses around here, and in about 5 minutes I can "make sparks"
 
Ya thanks, I think Im going to clean the crap out of my distributer. i tried the hot jump to the coil + already and it still didn't start, which even further fuels my thought that the problem is in fact the signal not getting to the coil via the mag. pickup. The distributer is tight and pretty clean, but the pick up doesn't seem to sit FLAT, it seems a little raised on the opposite side of the one screw (kinda driver side) I can push it down a little bit, and of course like I said when u suck on the vacuum advance it flattens down by itself then advances.
 
If someone lost and replaced the pickup hold down screw, with one too long, it could raise the plate, lock it, and not hold down the pickup. My question is, has the pickup to reluctor gap been adjusted using a 0.008" brass feeler gauge?

The click you hear in the distributor when plugging in the connector, may be a spark. It is not a good idea to hot plug the ECU. The connection with power applied, may generate an uncontrolled spark that may find the ground path via the sensitve pickup circuit. The ECU may be damaged.
 
I would pull the distributor out and spin it by hand while testing for spark from the coil output wire, with an in-line spark indicator ($4 at HF). It is real easy to put a SB or BB distributor back, if you don't turn over the engine (pull yellow connector off starter relay to insure), just note where the rotor is pointing first. While testing, don't leave the ignition on continuously or you might damage the ECU box. I would run a jumper wire from BATT+ straight to coil+ and disconnect the factory wire. If you apply 12 V for just a short time it shouldn't hurt the coil or ECU. That way you can leave the key in "run" all the time to power the ECU. A bad ground to the ECU is a common problem, so run a dedicated ground wire. Getting a spark when you connect the distributor pickup is not abnormal I think.

If it still drives you nuts, I bought a new "ready to run" HEI distributor on ebay for $45. Simple 2 wire hookup (child-proof), better spark, many posts here.
 
Here's an article on "getting into" a Mopar dist.

http://www.moparmusclemagazine.com/...opar_electronic_ignition_system/photo_03.html

Dave has a good point---something like the hold down screw being too long, or maybe the vacuum advance is not properly in place. The thing is sort of like a Chinese puzzle

Removing the advance: If you don't get the advance pin back into the hole it came out of, it could "****" the plate

http://www.forabodiesonly.com/mopar/showthread.php?t=232398

In this photo below, which is from the magazine article, the indicated pin is what the upper plate pivots on, and the only thing retaining it is a 3 fingered spring underneath
 

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Hey thanks guys, I pulled my distributer this morning and bought a like new one on cl for 20 bucks, the mag. pick up plate is secure and tight. mine was kinda sloppy. put it all in hooked it up and I still don't get anything. checked voltage and wires and all of them make connection. the wire going to the coil (brown +) gets like 10.5 volts in run. when that wire is hooked up to the coil it only reads 5ish volts IS THAT NORMAL?

This leads me to believe it is the trigger yellow wire to the - terminal not telling the coil to spark. that wire does hook up to the ecu too so wire is good. The two dist. wires have good connection to the ecu as well. Im wondering if in all of this the ecu could be cooked? I THOUGHT FOR SURE the dist. was it. it was very loose in my old one. I hooked up my old ecu box and the newer one I carry with you and neither work.

Also I hooked my timing light to the coil out wire and during spark I occasionally get a spark through it. Like in a 5 sec turnover run I may get like 5 sparks or so. So is there a way to test that ecu box? or the dist to make sure it works with it hooked up? I heard if you disconnect the wires and turn my volt tester to DCA volts I should get like 1v? I dont... Ideas?
 
my 73 duster had problem with the bulkhead wire...the harness that supplies voltage to the ignition system would move and then engine would die and would not start....i had to go out and physically shove the harness in harder...finally repaired the power feed wire...no problems now
 
I think you said you tried running a jumper wire to coil +? That should alleviate power troubles "for testing."

Measuring coil+ voltage is not relevent, other than to determine that 'something is there.' That's because the ballast and the current through that causes that voltage to change.

I would not be surprised with key on, engine off, to see nor more than 6-7V or so at coil+ because current is going through the ballast, through the coil and to ground through the box. The box basically replaces the points and switches the coil on/ off to ground.

What voltage do you have on the "key" sided of the ballast? That should be very close to "same as battery."

Also, cranking voltage AT COIL PLUS should be close to battery during crank.

Since you now have two distributors, I'd be rigging up your spare parts with a bench test circuit and determine what's good and bad. All you really need is the pigtail for the ECU and some clip leads. IN FACT if you are careful, you can rig the whole thing with clip leads.

Simplified diagram for a 4 pin box:

Ignition_System_4pin.jpg
 
The ECU box wasnt totally grounded, I have checked before and there was bare metal, and I hooked a small ground lead to my brake booster which was providing ample ground for all the other tests but when I grounded it to the neg battery terminal it fired right up. I Think I solved my year long problem. thanks guys!
 
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