Strange Starting Issue - 70 Roadrunner

[Hemibird]

Hey folks, this one has me stumped.

The patient - 1970 Hemi Roadrunner

The symptoms - Will only start if I jump the solenoid on the firewall with a screwdriver. Fuses look "OK". Is the solenoid bad?

As always, there are a host of strange things that happened just before. The car stalled at a light. Couldn't restart. Replaced the balast resistor and just as she wanted to start, the starter stopped turning. If I trun the key, I get nothing. When I jump the solenoid (On the forewall) with the ignition on, Starts just fine.

Is the solenoid bad ... or the ignition switch? ... OR ... there is a "Fuseable Link" on the wiring harness. Does that have anything to do with it?

Thanks in advance

 

[Mopars & Missiles]

Nothing strange about it. Very typical problem and the starting system is actually a VERY simple circuit, its just that most people don't understand electricity and how to test electrical things.

1. Yellow wire on the starter relay on the firewall is the +12 volt start signal from your ignition switch. When you turn the key to start, you should have +12 volts on this wire. Check for this voltage with your DMM.

2. Brown wire on the starter relay on the firewall is the relay ground signal from your neutral safety switch. It provides a ground to the relay ONLY when the transmission is in Park or Neutral. Check this for a ground with your DMM.

3. If both of those signals are getting to the relay, THEN you can check to see if the relay is energizing. You should hear or feel a "click" when both the "start" signal and the "ground" signals are present at the same time. When these two signals are there, the relay coil is energized which closes the contacts between the two BIG wires on the relay which connects the battery to the starter to crank the engine. Sometimes the internal relay contacts can burn and go bad, but rarely. Sometimes the relay coil can burn out also, but rarely. Most likely you are missing one of the signals to the relay, either the start, or the ground.

4. If no "start" signal on Yellow wire, check your Ignition switch and the wire from it all the way to the relay.

5. If no "ground" signal on Brown wire, check your NSS and the wire from it all the way to the relay.

6. You mentioned that before this happened the car stalled and wouldn't restart. Sounds like you meant that it wouldn't CRANK. This symptom is closely related to everything I mentioned above. The "start" signal and the "ignition" power to keep the car running both go through the "bulkhead connector" on the firewall. It is common to have loose, dirty, corroded, contacts in this bulkhead connector. Check these connections and clean them as necessary. I think you will find your problem here.

I have referenced wire colors from a '69 model, I believe the wire colors are the same for a '70 as well, but cannot guarantee that. Hope this helps you find the problem.

 

[383man]

Are you saying the car cranks over but wont start with the key ? Or are you saying it wont crank at all ? If it cranks but wont start but starts when you have the key on and crank it from under the hood then that would be a problem in the ign 2 circuit from the ign switch or the ign switch itself. Ron

 

[Hemibird]

Nothing strange about it. Very typical problem and the starting system is actually a VERY simple circuit, its just that most people don't understand electricity and how to test electrical things.

1. Yellow wire on the starter relay on the firewall is the +12 volt start signal from your ignition switch. When you turn the key to start, you should have +12 volts on this wire. Check for this voltage with your DMM.

2. Brown wire on the starter relay on the firewall is the relay ground signal from your neutral safety switch. It provides a ground to the relay ONLY when the transmission is in Park or Neutral. Check this for a ground with your DMM.

3. If both of those signals are getting to the relay, THEN you can check to see if the relay is energizing. You should hear or feel a "click" when both the "start" signal and the "ground" signals are present at the same time. When these two signals are there, the relay coil is energized which closes the contacts between the two BIG wires on the relay which connects the battery to the starter to crank the engine. Sometimes the internal relay contacts can burn and go bad, but rarely. Sometimes the relay coil can burn out also, but rarely. Most likely you are missing one of the signals to the relay, either the start, or the ground.

4. If no "start" signal on Yellow wire, check your Ignition switch and the wire from it all the way to the relay.

5. If no "ground" signal on Brown wire, check your NSS and the wire from it all the way to the relay.

6. You mentioned that before this happened the car stalled and wouldn't restart. Sounds like you meant that it wouldn't CRANK. This symptom is closely related to everything I mentioned above. The "start" signal and the "ignition" power to keep the car running both go through the "bulkhead connector" on the firewall. It is common to have loose, dirty, corroded, contacts in this bulkhead connector. Check these connections and clean them as necessary. I think you will find your problem here.

I have referenced wire colors from a '69 model, I believe the wire colors are the same for a '70 as well, but cannot guarantee that. Hope this helps you find the problem.

Thanks. It looks like all the wire colors match up. I'll deal with it tonight when I get home. Just to clarify the whole situation, I believe I had 2 problems hit at about the same time.

The car stalled at a light. Acted like the idle was set too low. Turned the key, and fired back up. Drove to the next light ... stalled again and wouldn't start. It cranked but wouldn't start. Had spark & fuel, but just wouldn't fire up. On a hunch I changed the white resistor on the firewall. As I started to crank the engine, it sounded like it was going to start(It was probably flooded by now), stumbled a bit, but then it just stopped cranking. Turn the key again ... no response. Had radio, lights, etc ... but no cranking. Fortunately I know the folks who run a local garage & towing company and they sent out a flatbed and got the car home.

Once I was home I started checking connections, and figured ... what the hell ... I stuck a screwdriver in between the two poles on the starter relay. The car cranked and fired right up ... ran fine. ALTHOUGH, there was a little smoke coming off the new resistor. I'm hoping that was due to it being new and burning off some paint or coating. Stopped smoking in a few minutes.

One last thing. The car has been completely restored, and all wiring harnesses are new.

I had this exact problem with my Charger when I was in High School(Almost 40 years ago). Spent weeks starting the car from under the hood before I managed to figure it out, and I can't remember what the fix was. I have a friend coming over with a meter tonight and we'll get it diagnosed. Thanks again for the info above.

 

[Mopars & Missiles]

Yep, the smoke from the new ballast resistor is normal. It should stop after a few minutes of run time. Yes it does sound like a couple of different problems going on at the same time, but those may still be caused by intermittent connections at the bulkhead connector on the firewall. Hopefully you have the FSM with the wiring schematics, this will help you to track the problem down. Good luck!

 

[nm9stheham]

Check all the test on the starter relay and neutral safety switch, but I suspect the ignition switch. It has 2 outputs for the ignition system: one sends 12v direct to the coil when the key is in START, and then when you release the key to RUN, it sends 12V to the ballast that in turn sends a lower voltage to the coil +. Also, the ignition sends 12v to the starter relay. You're reporting multiple symptoms all involving the ignition switch as the possible culprit.

 

[bigmanjbmopar]

Well said,

Nothing strange about it. Very typical problem and the starting system is actually a VERY simple circuit, its just that most people don't understand electricity and how to test electrical things.

1. Yellow wire on the starter relay on the firewall is the +12 volt start signal from your ignition switch. When you turn the key to start, you should have +12 volts on this wire. Check for this voltage with your DMM.

2. Brown wire on the starter relay on the firewall is the relay ground signal from your neutral safety switch. It provides a ground to the relay ONLY when the transmission is in Park or Neutral. Check this for a ground with your DMM.

3. If both of those signals are getting to the relay, THEN you can check to see if the relay is energizing. You should hear or feel a "click" when both the "start" signal and the "ground" signals are present at the same time. When these two signals are there, the relay coil is energized which closes the contacts between the two BIG wires on the relay which connects the battery to the starter to crank the engine. Sometimes the internal relay contacts can burn and go bad, but rarely. Sometimes the relay coil can burn out also, but rarely. Most likely you are missing one of the signals to the relay, either the start, or the ground.

4. If no "start" signal on Yellow wire, check your Ignition switch and the wire from it all the way to the relay.

5. If no "ground" signal on Brown wire, check your NSS and the wire from it all the way to the relay.

6. You mentioned that before this happened the car stalled and wouldn't restart. Sounds like you meant that it wouldn't CRANK. This symptom is closely related to everything I mentioned above. The "start" signal and the "ignition" power to keep the car running both go through the "bulkhead connector" on the firewall. It is common to have loose, dirty, corroded, contacts in this bulkhead connector. Check these connections and clean them as necessary. I think you will find your problem here.

I have referenced wire colors from a '69 model, I believe the wire colors are the same for a '70 as well, but cannot guarantee that. Hope this helps you find the problem.

- - - Updated - - -

I bought an after market starter relay off ebay just to have a "newer " looking one, when I got and compared it to the old one it was a lot lighter in weight figured wth install it and you know what it was intermittent at times got sick of it switched back and have never had an issue since. stupid cheap knock off parts can't trust them. Find a member here who has a oem one and get it.

Thanks. It looks like all the wire colors match up. I'll deal with it tonight when I get home. Just to clarify the whole situation, I believe I had 2 problems hit at about the same time.

The car stalled at a light. Acted like the idle was set too low. Turned the key, and fired back up. Drove to the next light ... stalled again and wouldn't start. It cranked but wouldn't start. Had spark & fuel, but just wouldn't fire up. On a hunch I changed the white resistor on the firewall. As I started to crank the engine, it sounded like it was going to start(It was probably flooded by now), stumbled a bit, but then it just stopped cranking. Turn the key again ... no response. Had radio, lights, etc ... but no cranking. Fortunately I know the folks who run a local garage & towing company and they sent out a flatbed and got the car home.

Once I was home I started checking connections, and figured ... what the hell ... I stuck a screwdriver in between the two poles on the starter relay. The car cranked and fired right up ... ran fine. ALTHOUGH, there was a little smoke coming off the new resistor. I'm hoping that was due to it being new and burning off some paint or coating. Stopped smoking in a few minutes.

One last thing. The car has been completely restored, and all wiring harnesses are new.

I had this exact problem with my Charger when I was in High School(Almost 40 years ago). Spent weeks starting the car from under the hood before I managed to figure it out, and I can't remember what the fix was. I have a friend coming over with a meter tonight and we'll get it diagnosed. Thanks again for the info above.

 

[Hemibird]

It's Alive!!!! The balast resistor was bad. The starter realy was shorted out, and I took every connection from the firewall and put a little dab "Dielectric Grease" on them with a toothpick, and seems to be "OK". Thanks for all the suggestions guys. The lingering question is "What Caused it"?

One interesting note - The first relay I ordered was listed for a "Manual Transmission", and had 3 poles. It didn't match the one off the car, so I ended up with the "Automatic" version (4 Poles) of the relay. I also looked at my 68 Roadrunner and it too, used a 4-pole starter relay. Anybody else encounter this? Both cars are born 4-speed cars. :thinker:

 

[sleepar]

Neutral lockout for auto... can start a std. In gear...

 

[Hemibird]

Neutral lockout for auto... can start a std. In gear...

OK ... that makes sense. The question is ... why would they have that starter relay on a manual trans car? Saw 4 others mopars today, same thing. 4 pole starter relays on Man Trans cars.

 

[nm9stheham]

At some point, they started putting these on manual cars with a clutch switch as a substitute for a neutral start switch, so that you have to depress the clutch when starting for safety. If you chekc out schematics for those later years, they will have both safety switches on the schematic.

 

[Dragon Slayer]

Neutral lockout for auto... can start a std. In gear...

You can only start a 70 RR manual transmission with the clutch in, regardless of shifter position (in gear or neutral). G

 

[chermik1999]

Similar Issue 68 RR

Nothing strange about it. Very typical problem and the starting system is actually a VERY simple circuit, its just that most people don't understand electricity and how to test electrical things.

1. Yellow wire on the starter relay on the firewall is the +12 volt start signal from your ignition switch. When you turn the key to start, you should have +12 volts on this wire. Check for this voltage with your DMM.

2. Brown wire on the starter relay on the firewall is the relay ground signal from your neutral safety switch. It provides a ground to the relay ONLY when the transmission is in Park or Neutral. Check this for a ground with your DMM.

3. If both of those signals are getting to the relay, THEN you can check to see if the relay is energizing. You should hear or feel a "click" when both the "start" signal and the "ground" signals are present at the same time. When these two signals are there, the relay coil is energized which closes the contacts between the two BIG wires on the relay which connects the battery to the starter to crank the engine. Sometimes the internal relay contacts can burn and go bad, but rarely. Sometimes the relay coil can burn out also, but rarely. Most likely you are missing one of the signals to the relay, either the start, or the ground.

4. If no "start" signal on Yellow wire, check your Ignition switch and the wire from it all the way to the relay.

5. If no "ground" signal on Brown wire, check your NSS and the wire from it all the way to the relay.

6. You mentioned that before this happened the car stalled and wouldn't restart. Sounds like you meant that it wouldn't CRANK. This symptom is closely related to everything I mentioned above. The "start" signal and the "ignition" power to keep the car running both go through the "bulkhead connector" on the firewall. It is common to have loose, dirty, corroded, contacts in this bulkhead connector. Check these connections and clean them as necessary. I think you will find your problem here.

I have referenced wire colors from a '69 model, I believe the wire colors are the same for a '70 as well, but cannot guarantee that. Hope this helps you find the problem.

Hi,

I know its a year ago, but I have a similar issue. I replaced my Stock ign with a MSD all in one dist. 3 wire. Now prior to this I was running a junky Procomp and feed power from the ballast wire from the ign I thought. It ran, but needed replacing.

So I just figured same wires and move on. Only this time I spent the better part of the night trying to get it started. Finally my helper went home and I was still determined to get it running. I finally used a starter button to find spark moving the dist back and forth with a plug on ground. So found spark!

Hooked it all up again and tried to start. No start.....but for giggles I tried the starter button....well away we go. So the switch in the car wont start it but a starter button will off the relay. So I believe Im tied into the wrong wire.........

Thoughts or insight help...

thanks