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70 Challenger ignition problems #2467309
03/16/18 01:12 PM
03/16/18 01:12 PM
Joined: Sep 2013
Posts: 71
S.florida
J
Jupiter331 Offline OP
member
Jupiter331  Offline OP
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Joined: Sep 2013
Posts: 71
S.florida
Electronic ign. Car starts fine when cold but after driving a while it cranks but won't start in start position. You have to let the key return to run and catch it just right to start it. I know there's suppose to be a hot lead for start position. Maybe it's wired wrong but starts fine cold ??

Re: 70 Challenger ignition problems [Re: Jupiter331] #2467385
03/16/18 04:25 PM
03/16/18 04:25 PM
Joined: Jan 2008
Posts: 2,363
Cotati, CA
Dave Hall Offline
top fuel
Dave Hall  Offline
top fuel

Joined: Jan 2008
Posts: 2,363
Cotati, CA
I'm not positive but sounds like typical ignition switch or bulkhead connector problems. The car runs so I would look into the switch on the column and the connection at the firewall. It's not an ignition problem. Get a factory service manual. They are invaluable for making sense with this stuff.

Re: 70 Challenger ignition problems [Re: Jupiter331] #2467399
03/16/18 04:52 PM
03/16/18 04:52 PM
Joined: Jan 2003
Posts: 32,884
Grand Prairie,Texas
stumpy Offline
I Win
stumpy  Offline
I Win

Joined: Jan 2003
Posts: 32,884
Grand Prairie,Texas
You might want to check the ballast resistor connections. Could be loosening up with heat caused by current draw.

Re: 70 Challenger ignition problems [Re: Jupiter331] #2467403
03/16/18 04:54 PM
03/16/18 04:54 PM
Joined: Jan 2003
Posts: 6,363
Abilene, Texas
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fastmark Offline
master
fastmark  Offline
master
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Joined: Jan 2003
Posts: 6,363
Abilene, Texas
I just had this problem with a customers 70 Challenger. Could not pinpoint it because it never did the same thing twice. Drove me nuts. Installed a Petronix II and now it starts right up. Both the customer and I noticed right off the car even ran better. Ive been stranded by mopars ECU before. Good luck.

Re: 70 Challenger ignition problems [Re: Jupiter331] #2467416
03/16/18 05:18 PM
03/16/18 05:18 PM
Joined: Dec 2003
Posts: 4,951
northwest USA
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NANKET Offline
master
NANKET  Offline
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Joined: Dec 2003
Posts: 4,951
northwest USA
Had the same thing happen, it was the ECU

Re: 70 Challenger ignition problems [Re: Jupiter331] #2467558
03/16/18 11:31 PM
03/16/18 11:31 PM
Joined: Sep 2013
Posts: 71
S.florida
J
Jupiter331 Offline OP
member
Jupiter331  Offline OP
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Joined: Sep 2013
Posts: 71
S.florida
I actually just replaced ecu, distributor, coil, resistor and relay. Should have went with petronix

Re: 70 Challenger ignition problems [Re: Jupiter331] #2467566
03/16/18 11:54 PM
03/16/18 11:54 PM
Joined: Nov 2003
Posts: 36,040
Lincoln Nebraska
RapidRobert Offline
Circle Track
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Posts: 36,040
Lincoln Nebraska
4 pin ECU/2 terminal ballast conversion I am assuming. In your driveway get hot to where it wont (re)start & have a helper crank it & you under the hood see if you have voltage at the blue/yellow wire/terminal on the ECU pentastar connector and at the coil positive primary terminal. Work FAST while everything is hot for a valid test. This'll get us started.


live every 24 hour block of time like it's your last day on earth
Re: 70 Challenger ignition problems [Re: Jupiter331] #2467613
03/17/18 02:46 AM
03/17/18 02:46 AM
Joined: Feb 2003
Posts: 10,178
Someplace you aren't
S
SomeCarGuy Offline
I Live Here
SomeCarGuy  Offline
I Live Here
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Joined: Feb 2003
Posts: 10,178
Someplace you aren't
Check for bad connections as mentioned but don’t overlook the need for the ecu to have a good ground too. Guys all the time change out an ecu and don’t clean the mounting area or run dedicated ground to it. I’ve actially put “bad” ecus back on cars for people and they run fine for years when the corrosion builds up again on the new one.


I want my fair share
Re: 70 Challenger ignition problems [Re: SomeCarGuy] #2467635
03/17/18 06:00 AM
03/17/18 06:00 AM
Joined: Sep 2004
Posts: 491
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BLACKHEMIRR Offline
mopar
BLACKHEMIRR  Offline
mopar
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Joined: Sep 2004
Posts: 491
I agree with the previous reply about the ignition switch and bulk head connector. It might also be the connector under the steering column. The ignition switch has 2 different circuits for feeding the coil, one in the run position, and another in the start position. The start position circuit bypasses the ballast resistor (and feeds 12V directly to the coil) during starting. When it won't start, disconnect the battery and use an ohmmeter to measure circuit resistance from the + battery cable to the + coil terminal (with the switch in "start" position). You will probably measure high resistance. Wiggle the connectors and switch until you see a normal low resistance. That will indicate where the problem is. Good luck.

Re: 70 Challenger ignition problems [Re: Jupiter331] #2467915
03/17/18 11:40 PM
03/17/18 11:40 PM
Joined: Jul 2013
Posts: 1,272
Northern Calyfornua
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Sxrxrnr Offline
pro stock
Sxrxrnr  Offline
pro stock
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Joined: Jul 2013
Posts: 1,272
Northern Calyfornua
When it won’t start, hot wire it from battery to coil bypassing all the bulkhead and ignition switch connectors. This will give you a big clue. My money Is on either of those components.







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