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Old 08-08-2006, 03:14 PM
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440 Dodge weak to no spark - won't start..

Hello,
This is my first post, and of course, a plea for help..

Besides trying to finish my wifes car, I'm trying to get our old (1978 w/440 V8 & 727 AT, Dual Ballast/Non-leanburn/5 pin ECU/Elec. Ign.) Class C dodge Motorhome running (about 4 months late for the season as well...) for a much needed getaway..

Here's where I'm at;

The Truck was running one day, and when turned off...never started again..
At this time Spark is little to None.
I've tested per the Haynes manual and found-

With Ign. to 'Run' & ECU connected:
1) 5.6v at the coil positive.
2) 1.5v at the coil negative.
3) 12v at the Ballast resistor(Pink wire - out)
4) Ballast resistor -primary circuit 1.2 ohm resistance & aux circuit 5.1 ohm resistance.

With Ign. to 'Run'& with ECU disconnected:
1) 12v at Coil positive and negative posts.
2) 12v at the ECU pins where applicable
3) 300 ohm resistance for the dist. pickup through the ECU connecter(pins 4&5 I think) with no ground outs..
4) At pin 5 it is showing the case is well grounded.

At one point I did get the Timing light to flash while cranking the engine, but it was very intermittent. As well, I was able to get the coil secondary wire to spark directly to the engine ground..but it was weak yellow/white spark..

When I began troubleshooting the issue, I found that the PO had bypassed the Ballast resistor, and was running the coil positive directly from a 12v supply.
I also noticed the connections to the primary(1.2 ohm circuit) ballast circuit we're paritally melted. >I'm assuming the PO replaced the ballast and connected with the circuits switched, causing the wire and connector to heat up because of the 5.1 ohm resistance from the Aux circuit side of the ballast resistor - any feedback on that assumption would be appreciated...

While changing it back the factory configuration, I found the 'Ballast' to 'Start Relay' Pink wire had a break in it (32k ohm resistance), so I replaced the wire with an equivelent size.


So, I'm wondering what other circuits may have been damaged by running the 12v directly to the coil, with out going through the ballast resistor.

As well, any input on what I should be considering for the overall 'weak spark' and 'no spark' conditions I'm encountering...

Thanks for looking, and best regards,
dB

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Last edited by dabongo; 08-08-2006 at 05:21 PM. Reason: Forgot year, etc.
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Old 08-08-2006, 05:08 PM
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Doc here,

OK, you didn't include the year of the Motor home, and if the Distributer is HEI / Electronic as opposed to points..I am assuming it is ...(HEI)

The first easy test is just run a 12 volt jumper to the + side of the coil..try and start it..If it cranks and fires..your ballast or secondary ignition is at fault..track that line..(Could also be the coil)..

If it won't , remove ALL the wires from the coil..and get your DVOM out, set it for OHMS scale, R X 1, calibrated 000, Measure the primary , It should read less than an ohm, but more than 000, out of that range, get another coil.

Next measure the Secondary, set the scale for R X 10K or higher..It should read between 10,000 and 11,000..outside of that range, toss the coil..

If that is good, pull the module, and have it tested at auto zombie, (Free Test) Have it tested several times to "Heat It Up" , If a new one is needed, have it tested as well BEFORE you leave the store..they have a high "Out of Box Failure Rate" ..and once you leave the store...It's YOUR problem!

In either case..(replace or Renew module) Clean the old Heat-sink Compound from the parts and apply new , generously (but not sloppy) , Else you WILL be doing this again very soon..

If that is not the problem, It may be the magnetic pickup has gone bad..look up the resistance specs for your motor home, and ohm it out..If out of spec, replace as needed..

Somewhere , I remember the ballast resistor on a Dodge is a duel element (for two circuits..) check that out and replace if needed..(I'm Not a Dodge guy at all..but I remember that has a duel function for some reason)

Check the starter relay, It may be bad , not providing ignition during Crank cycles (secondary Ignition)

That's about my experience with a Dodge..so a manual should help a bit..(more than I have provided)

Doc
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Old 08-08-2006, 05:22 PM
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Thanks Doc.

I've updated the post with the required details as well.

Thank you.
dB
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Old 08-08-2006, 09:52 PM
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The Coil tested ok. And the dist. pickup showed 300 ohms(acceptable is between 150 and 900 per the Haynes manual)..

I'm going to go back and pull some more hair out....

Thanks Doc.

dB
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Old 08-09-2006, 12:30 AM
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Doc here,

Hummm...Shorted Tech????

Are you sure it's a spark issue?

Have you tried some starter fluid down the carb yet?

Just tossing ideas...

Doc
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Old 08-09-2006, 11:48 AM
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Yes, I've used starting fluid, misted and dribbled fuel...but no 'boom'..

And the old truck has no tach.(I don't want to know how hard the beast is working to get over Mt. passes...)

The one thing in testing that concerns me, is the 5.6volts at the coil positive while the ign. is on 'run'. I expected 9v at the lowest(just off past experience - I really don't know about the spec. for these old mopar electronic ignitions). As well, I'm finding 1.2v at the negative coil terminal under the same conditions...

So I'm wondering if this is causing weak/no spark condition. Just to mention, I decided to install a MSD blaster coil to see if my coil was bad but was tested 'OK'.. but still no 'booms' when cranking....

This may be a dumb question, but do the dist. electronic pick-ups ever test 'good' but actually end up malfunctioning during start/run cycles?

Thanks again for the input/follow up - I do appreciate it.

dB

Last edited by dabongo; 08-09-2006 at 12:31 PM. Reason: no tach in the beast
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Old 08-09-2006, 12:22 PM
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My experience with these ol' rigs tells me it's very likely the E.C.U.I had a '76 Dodge camper van for some years and it consumed 2 or 3 of them in 10 odd years,and I have never replaced one in a car or pickup application (I've owned many Mopars with electronic ign) I think it has to do with the heat generated under the hood of a van.+ side of coil should be at least 8 volts with ign in the "run" position.Hope this helps
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Old 08-09-2006, 12:30 PM
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Thanks for the input. But I've actually tested and replaced the ECU anyway(and tested the new one as well because the failure rate is higher than the success rate......appearantly)

Thanks!
dB
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Old 08-09-2006, 04:24 PM
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Doc here,

The pickup's usually "are" or "Aren't"..They consist of a simple solid state switching device to replace points..HOWERVER, because it tests OK, Does not mean it will Carry current..If you suspect it replace it.

The coil..Normal ballast resistance is usually around 1.5 Ohms..6 to 9 Volts is not unusual on a loaded coil..(and assuming the battery may actually be around 11.5 Volts not running sitting for a few days) You could Try a jumper to the + side of the coil, from the battery and see if it will start and run..That will tell you a lot.

You could also be losing Ignition (secondary ) while cranking..That would be the solenoid or start relay..(not sure on Mopar's which they use..)

Doc
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Old 08-10-2006, 01:02 PM
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Thanks Doc. That was it..

The distr. pick up was testing out within range. So I was still suspecting something in the start/run circuits(only because i've replaced a dozen wires end to end that showed volitile ohm readings during the 'wiggle' tests..

Since I had a new coil in there I didn't want to run a jumper to the coil positive(always thought that would fry the coil...). I decided to go ahead and try the jumper from Bat+ to Coil+, and to my surprise, no 'booms'....but had a huge spark from coil secondary to eng. ground....

Since this points to the distributor as the issue I went ahead a swapped in a new dist. pick-up...it immediatley fired up, but ran inconsistantly. Not rough, just somewhat inconistent.
I pulled the cap and rotor and gave the dist. shaft a good push/pull and found the side to side movement to be more than the .006 air-gap. It appears the reluctor has been itermittently hitting the pick-up causing damage to both...

So, I'm ordering a mopar performance dist. from Summit and going Camping!!!

Thanks for the input. I was convinced to pickup was still good because of the correct resistance was measured... even all my manuals state 'leave the pick-ups alone' unless you're absolutely sure nothing else is causing the problem....

My overall problem was an internally broken 'pink' wire running from the Ballast resistor to the Starter relay and then to the Coil+. And, the fried reluctor/pick-up combo.... Boy has this been a fun last two weeks...

Now I need to re-wrap all the harnesses I've disassembled(eng. compartment looks like a spagetti feed....) and put in the new distributor... and I think I'm done....for now..

Best regards,
dB
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Old 08-10-2006, 04:16 PM
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Doc here,

Well, Sorry to hear the Dizzy is shot....BUT..

Glad to hear a new one is forthcoming..and you have the problem under control and Vacation is sure to follow!

BTW, on bypassing a Coil..You can get away with that for short durations with no problem at all..Good for testing or "Limping home" without damage..Just don't make it a practice to run without it..

Keep Us updated!

Doc
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