No start by turning the key, but will start at relay.

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C2ndLTpigeon

C2ndLTpigeon

Mopar or no Car!
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So I have a weird one here, and I'm not a fan of electrical problems. My 1975 Dart sport has started giving me issues when I try to start it. It will crank over but will not fire most of the time. Some days it does but most of the time it acts up. If I keep the key in the run position and use a screw drive at the starter relay it will fire right up.

I also noticed that while the car cranks by using the key, the gauges will start to return back to their off positions. The fuel gauge starts to return to empty while cranking, like something is not supplying them power. So something is going on when cranking the car.

Here is a video showing the issue. Any help would be greatly appreciated. Might be something simple and would love to learn why its doing this.
Thanks
 
1...You need a service manual. There are not free ones that I'm aware of
2....Go to MyMopar and downlad the aftermarket 2-page diagrams for your year / model
3....You need a multimeter, a 12v test lamp, and some alligator jumper leads

Acesss the connector coming out of the column for the ignition switch. It is long and slender. Determine if you are getting power there

NOTICE (I will have to look) there has been wiring changes all through the years, so I'm not sure, (but probably) that the ignition switch works as earlier models

That is, there is IGN1 "run" which feeds power out through the bulkhead, into the engine bay, to the ignition system, the alternator field (blue) the vr ign terminal (blue) and maybe some smog doo dads, and electric choke if you have one

THAT POWER GOES DEAD during cranking

The starting power to the ignition system is provided by IGN2, which is ONLY HOT during "start" just like the yellow start wire, except it is a separate dedicated switch contact.

WHAT you should see between coil + and ground

With key in "run" and engine stopped you should NOT see full battery voltage, but rather, somewhere between 6-10V, because of the drop through the ballast resistor. Again that source GOES DEAD during "start."

With key held to "start" and the engine cranking, you should see "same as battery" in other words if the battery loads down to say, 11.5 during starting, then you should see "about" that at coil+
 
There are a few pictures from my 1975 service manual and regards to the wiring diagrams. As well as some pictures of my connectors at the bottom of my steering column. I have recently gone through and put a new multifunction switch and ignition switch in the column as well as removing some of the wires in the connector that were not needed such as the gear selector indicator light Etc. The two ignition wires the red and black are isolated onto their own connector which it seems they started doing in the mid-70s due to the high current in the rectangular connector. Here is a video as well showing you the voltage of the battery as well as the voltage when it is in the Run position and then with the leads on the positive and negative side of the coil while cranking.
Click to expand...
20221019_131404.jpg


20221019_131421.jpg

 
Think I may have found a potential culprit at the brown wire that comes out of the bulkhead that is connected to the section of fusible link that goes to the Red wire to the starter relay. The wire looks beat and I think I will replace it with a new section of fuse link. After wiggling it around to a position where it cranks and starts, it will fire every time now.
 
IMHO

Clear case of no voltage on the IGN 2 lead that by passes the ballast resister.


When key is in run, battery voltage is applied to one side of the ballast resister, the other side goes to the coil. This gives reduced voltage to the coil

In start, a seperate cir supplies battery voltage to the coil side of the ballast resister giving full battery voltage to the coil.

When you have the key in run and jumper the starter relay you have some voltage to the coil.

When you use the key, in the start position, the IGN 2 cir is supposed to apply battery volts to the coil but it is not. In IGN 1 cir disengaged at that same time so you have no voltage to the coil.


Lots of tests you could do to prove this but a quick one would be to run a jumper from battery plus to the coil side of the ballast resister.

You proved what I'm saying when you showed 0 volts while cranking.
 
After further inspection of the wire harness it was a bad replacement of the fuse link to the starter relay. Soldered in a new one and the car is starting every time.
 
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