318 won't stay running

-
harrytoes

harrytoes

Well-Known Member
Joined
Jun 7, 2005
Messages
123
Reaction score
36
Location
Santa Clara, CA
I pulled into my driveway last night and left the car running as I got out. Never made it to open up the hood before it stalled. Engine has been running great so this was a surprise.

I tried to start it and it wouldn't start. It fires right up with the starter engaged, but as soon I release the key it stops. If I keep the key turned and run the starter it will run. Release the key and it dies.

I just replaced the ballast resistor still no luck. The ballast resistor I got from O'Reilly's looks a little different but tried it anyway.

Any ideas as to what might be going on?

PXL_20250821_001348570.jpg
 
Do you have breaker points, electronic, or what?

Take a meter/ test lamp. Try to fire it and confirm it fires on the starter. If it dies when you release the key, see if there is power at the ballast. If not, move down to the IGN terminal there on the VR and see if it has power. If not, get out the service manual. You can download, them, free, at MyMopar.com. Find the ignition run wire, normally dark blue, coming out of the bulkhead connector. See if there is power there. If not, it is time to dig into the ignition switch and switch connector. If there is power there, then it is losing it between the interior and engine bay side of the bulkhead connector.
 
harrytoes said:
I pulled into my driveway last night and left the car running as I got out. Never made it to open up the hood before it stalled. Engine has been running great so this was a surprise.

I tried to start it and it wouldn't start. It fires right up with the starter engaged, but as soon I release the key it stops. If I keep the key turned and run the starter it will run. Release the key and it dies.

I just replaced the ballast resistor still no luck. The ballast resistor I got from O'Reilly's looks a little different but tried it anyway.

Any ideas as to what might be going on?

View attachment 1716444606
Click to expand...

harrytoes said:
Even tried bypassing the ballast resistor. No luck

View attachment 1716444651
Click to expand...

The symptom of the engine starting when the ignition key is turned to the start position, but dies when the key is released and returns to the run position is typical of a fault in the Ignition RUN circuit. Culprits can include one or more of the following:
  • bad ballast resistor
  • bad ignition switch in RUN position
  • bad wiring or connection somewhere in the Ignition RUN circuit, including:
    • bad connection in disconnect at the steering column for 1970 and later columns
    • bad connection at ignition switch
    • bad wiring from the ignition switch to the bulkhead disconnect
    • bad connection in bulkhead connector(s)
    • bad wiring to the ballast resistor from the bulkhead, typically blue for passenger cars
    • bad connection at the ballast resistor Ignition RUN side
    • loose or bad connection at the electronic control module (ECU) if equipped
Your installed ballast resistor appears to be the original type 0.5 ohm resistor for your 1968 Barracuda. The new ballast resistor is a later model style replacement, which is likely 1.25 ohms. It will function fine, with slight reduction in ignition coil delivered energy, which may not be noticeable.

Bypassing the resistor essentially rules it out as a problem, similarly for the connections at the resistor itself.

Because it died, then would not remain running when re-started, with the ballast resistor eliminated, look for a wiring or connection issue in the Ignition RUN circuit, or possibly the ignition switch. If you have electronic ignition, ensure the connector on the ECU is seated and secure.

If you don't already have one to trace the Ignition RUN circuit and components, the factory service manual is available as a compressed PDF zip file at MyMopar.com at the following link:

1968 Plymouth Service Manual
 
Vaanth said:
The symptom of the engine starting when the ignition key is turned to the start position, but dies when the key is released and returns to the run position is typical of a fault in the Ignition RUN circuit. Culprits can include one or more of the following:
  • bad ballast resistor
  • bad ignition switch in RUN position
  • bad wiring or connection somewhere in the Ignition RUN circuit, including:
    • bad connection in disconnect at the steering column for 1970 and later columns
    • bad connection at ignition switch
    • bad wiring from the ignition switch to the bulkhead disconnect
    • bad connection in bulkhead connector(s)
    • bad wiring to the ballast resistor from the bulkhead, typically blue for passenger cars
    • bad connection at the ballast resistor Ignition RUN side
    • loose or bad connection at the electronic control module (ECU) if equipped
Your installed ballast resistor appears to be the original type 0.5 ohm resistor for your 1968 Barracuda. The new ballast resistor is a later model style replacement, which is likely 1.25 ohms. It will function fine, with slight reduction in ignition coil delivered energy, which may not be noticeable.

Bypassing the resistor essentially rules it out as a problem, similarly for the connections at the resistor itself.

Because it died, then would not remain running when re-started, with the ballast resistor eliminated, look for a wiring or connection issue in the Ignition RUN circuit, or possibly the ignition switch. If you have electronic ignition, ensure the connector on the ECU is seated and secure.

If you don't already have one to trace the Ignition RUN circuit and components, the factory service manual is available as a compressed PDF zip file at MyMopar.com at the following link:

1968 Plymouth Service Manual
Click to expand...
It's a stock 318 in a 68 fastback Barracuda. All stock ignition. No ECU. Chaising the run circuit now.

PXL_20250821_014050181.MP.jpg


PXL_20250821_014007534.jpg
 
Ballast ruled out, I'd try either the ignition switch or bulkhead connections next. I had the same thing one time and all I did (after trying ballast) was pull the ignition wire from the bulkhead and spray contact cleaner in there real good and never an issue again
 
318willrun said:
Ballast ruled out, I'd try either the ignition switch or bulkhead connections next. I had the same thing one time and all I did (after trying ballast) was pull the ignition wire from the bulkhead and spray contact cleaner in there real good and never an issue again
Click to expand...
Spot on! Pulled the wire from the bulkhead. Cleaned it up and bam. Thank you
 

harrytoes said:
Spot on! Pulled the wire from the bulkhead. Cleaned it up and bam. Thank you
Click to expand...
The firewall connectors are always a point of contention for these old girls. I add maintaining them into the regular maintenance schedule and check and clean them about every other oil change. It's also a good idea to remove the cluster and periodically check, clean and tighten the ammeter connections.
 
Last edited:
Whew wee that red engine paint looks good...what did you clean the b8lkhead connector with? how did ya do it? I always look at that stuff and think "how do I get in there to clean it? especially the female ends...
 
318willrun said:
glad it worked and is running!
Click to expand...
Ok, another random issue. The car fires up instantly when cold, no problem at all. Will restart most, no problem at all. But a few times, after it has completely warmed up, I go to turn the key and nothing happens. If I jump the starter relay, it starts right up. Why would this only happen after it has completely heated up?
 
If you aren't trying to start an automatic with the shifter in the wrong spot, this is most likely the starter relay with the ignition switch a less likely option. Failing relays can start having problems hot before failing completely.
 
harrytoes said:
Ok, another random issue. The car fires up instantly when cold, no problem at all. Will restart most, no problem at all. But a few times, after it has completely warmed up, I go to turn the key and nothing happens. If I jump the starter relay, it starts right up. Why would this only happen after it has completely heated up?
Click to expand...
starter relay is very fast and cheap to replace. Buy a good one. I'm betting it's your problem. If not, you'll have a spare. Spares are good things :)
 
You must log in or register to reply here.
-
Back
Top Bottom