Everything was going so good

[gtgto]

My car (70 Duster 340) has been pretty dependable for a while now but now I'm having issues. Car fires right up after sitting for a week or two. Take the car out for a drive and everything is great. When I park is when the issues start. The other night I went to a local cruise and was there for a bit. When I went to leave my car would turn and turn and turn but wouldn't start. Spark was definitely the issue. Tried checking for loose connections and saw nothing obvious except my negative battery cable to the drivers head was loose. Anyways killed the battery and called AAA like I used to do so many times when I first got the car but not for a while now. Someone at the cruise offered a jump while waiting for AAA and the car fired up. I cancelled my flatbed ride home and drove home without issue. I took my car out again last night and drove all over without issues till I got home. After parking the car I went inside for about 20 minute and then went to try and start my car.....Same thing, turning over fine and no spark. Again checking connections found nothing out of the ordinary but turned the key and with the gas to the floor she fired up....ran fine but when I turned the key to the off position the car would not shut off. With the key in the off or aux position the car was running. I had to stall the car out to shut it off......Then I turned the key and she fired right up and turned off like normal. I started and turned off the car 5 times before heading back inside....I plan on taking a good look over the weekend but not even sure where to start at this point.

 

[CFD244]

Not shutting off leads me to think ignition switch.

 

[Mike69cuda]

Sounds like ignition switch. I have wired up a little indicator light to the positive side of the coil (or the coil side of the ballast resistor) and put it inside the car so I could watch power to the coil while driving. That could help you diagnose problem.

 

[famous bob]

Not shutting off leads me to think ignition switch.

hyymm : I had to tie 3 wires together to get my fast fuel inj. , E Z rewired barracuda to start and run =?????
"at the advise of Sean at E Z wiring ."
And it will continue to run in the acc. position ...

 

[Cranky]

My car (70 Duster 340) has been pretty dependable for a while now but now I'm having issues. Car fires right up after sitting for a week or two. Take the car out for a drive and everything is great. When I park is when the issues start. The other night I went to a local cruise and was there for a bit. When I went to leave my car would turn and turn and turn but wouldn't start. Spark was definitely the issue. Tried checking for loose connections and saw nothing obvious except my negative battery cable to the drivers head was loose. Anyways killed the battery and called AAA like I used to do so many times when I first got the car but not for a while now. Someone at the cruise offered a jump while waiting for AAA and the car fired up. I cancelled my flatbed ride home and drove home without issue. I took my car out again last night and drove all over without issues till I got home. After parking the car I went inside for about 20 minute and then went to try and start my car.....Same thing, turning over fine and no spark. Again checking connections found nothing out of the ordinary but turned the key and with the gas to the floor she fired up....ran fine but when I turned the key to the off position the car would not shut off. With the key in the off or aux position the car was running. I had to stall the car out to shut it off......Then I turned the key and she fired right up and turned off like normal. I started and turned off the car 5 times before heading back inside....I plan on taking a good look over the weekend but not even sure where to start at this point.

Not shutting off leads me to think ignition switch.

Had a car do something similar once....started it up and released the key when the engine fired up but the starter stayed engaged. The problem was the starter itself. Intermittent electrical problems suck for sure but I'd be looking at the ignition switch too especially if it's the original.

 

[Mattax]

I plan on taking a good look over the weekend but not even sure where to start at this point.

A multi-meter and some leads with aligator clips may be helpful for this and future diagnostics.
Spend some time looking at the wiring diagram - in fact drawing a copy of the circuits of interest is a good way to get familiar with how things work.

Spark was definitely the issue.

You are probably right, but I must ask, how do you know this?
Did you do a spark check with a screw driver or spark tester?

when I turned the key to the off position the car would not shut off. With the key in the off or aux position the car was running

Two possibilities that I can think of.
1. Switch is faulty.
2. Wires shorting allowing the alternator and ignition to get power - possibly direct from the alternator.

For visual checks I would look at
a. The ignition circuits wiring under the hood. This includes the alternator's 'field' wire and the ignition start circuit.
b. Steering column connector and wires.

 

[Dana67Dart]

Do you have electronic or point ignition?

What we know...

1. The car starts easily when cold
2. The car is hard to start or no start when it is hot.
3. Car did not shut off with key in off position.

1 and 2
Sometimes engine heat makes restarting difficult, fuel delivery issue.

3 not shutting off,

• either the wiring is not correct
• The wiring or a connector is melted together
• The ignition switch is bad

I would do as mentioned earlier,
Check the under dash wiring from the ignition switch thru the bulkhead connector to the ballast then to the coil.

check for battery plus voltage with key in run and start WHILE it is in a no start condition

 

[Oldmanmopar]

My 71 340 Duster . I went to a car show after sitting there all day car fired up and I drove to an Ice cream stand up the street close to home I sat there for about 20 minutes and the sub started going down. I went to start it and it would not start .

What I notice is the fuel pump was not changing sound like it always does when pressure was up. I shut the pump off and took the air cleaner off it was flooding. So I left the pump off and held it flat to the floor and it started but when I turned the pump on it died. So I kept turning the pump on and off and after a couple times it stayed running. I felt like a fool in front of all the other people there with cars.

This puzzled me it never did this before. But On the way home from the show I stopped and top the tank off with pump gas before going to the ice cream stand.

After some research and talking to others we determined the ethanol / oxygenated fuel was boiling in the line and carb. This caused the needle and seat not to close due to the floats not being lifted and the constant dead ending pressure on them

I installed a return line in the car using return regulator. This allowed the fuel to circulate. The car never did this again. I found out in the late 80's mopar install a return system on all there cars for this reason. Now every car I build gets a return filter if it has a mechanical pump. Electric pump cars get a return regulator.

The picture below of the orange car you can see I added the return line . on the other engine with the mechanical pump was for a car I just finished. It works perfect just went to the same show and stopped at the same ice cream stand.


I believe this is your problem if you don't find it to be spark related. My car never did it after it started and restarted unless I drove it and went to start it after it sat for only 15 minutes. Once it cooled down there was not a problem or if I restarted it soon after it was shut off..

Before the return on the Electric pump car

After the return regulator was installed

This is the return filter used on the mech. fuel pump cars by the factory in the 80's due to this problem with the fuel boiling

 

[Mattax]

spark tester?

the wiring diagram

Some things that can go wrong.
If wire R6 (althernator output) contacts any J2 or J3 wire, the engine will keep running. R6 is always hot because its connected to the battery.
If J1 (power to key switch) shorts to J2 or J3, same thing.

Shop manual has the full wiring diagram. The diagram above is just a schematic of the main circuits of interest

 

[slickchick]

what ignition sysytem do you have ??

 

[Cranky]

View attachment 1716094555

View attachment 1716094551

Some things that can go wrong.
If wire R6 (althernator output) contacts any J2 or J3 wire, the engine will keep running. R6 is always hot because its connected to the battery.
If J1 (power to key switch) shorts to J2 or J3, same thing.

Shop manual has the full wiring diagram. The diagram above is just a schematic of the main circuits of interest

I have what looks like a fat pen with a metal tip with a angled groove that fits on the plug wire. All ya have to do is lay it on the plug wire and it'll flash a small light if there's juice running through the wire. Super easy to use.

 

[gtgto]

what ignition sysytem do you have ??

Before I owned the car it was updated from factory points to factory style Mopar electronic ignition like what would be used in 72. Upgraded to a Blaster Coil, 4 pin module with 2 post ballast resistor.

 

[Mattax]

Doesn't really change the diagnostics needed. Just adds some wires. It is certainly possible the ECU fails when hot but that would not explain the failure to shut down.

 

[Darter6]

My 70 Duster had a problem with a burnt connection where the switch wires connect under the steering column.
No start with the key but started jumping the relay. May also have something to do with not shutting off.Maybe..
Now that we know it has Mopar electronic ignition you may have a faulty ECU for the hot no start.

 

[gtgto]

Doesn't really change the diagnostics needed. Just adds some wires. It is certainly possible the ECU fails when hot but that would not explain the failure to shut down.
View attachment 1716094562

Well since I was recently in my steering column multiple times I am going to start there. I have 2 ignition switches and I have had them both in the car and the not shutting off symptom was present on both intermittently so its not the switch unless I have 2 that act the same. Maybe all the routing and re routing of the wiring in the column caused a bare wire and it's shorting out. While in the column I also replaced the broken key in buzzer switch with a NOS piece. I'll be out early in the garage tomorrow morning with my wiring diagram, meter and seeing what I can find.

 

[Cranky]

Well since I was recently in my steering column multiple times I am going to start there. I have 2 ignition switches and I have had them both in the car and the not shutting off symptom was present on both intermittently so its not the switch unless I have 2 that act the same. Maybe all the routing and re routing of the wiring in the column caused a bare wire and it's shorting out. While in the column I also replaced the broken key in buzzer switch with a NOS piece. I'll be out early in the garage tomorrow morning with my wiring diagram, meter and seeing what I can find.

Oh man, you hooked up the key buzzer? That's THE problem lol. JK JK but the buzzers were the first thing that got disconnected on ALL of my cars. Don't need any buzzer to tell me my key is in the ignition ....and the newer cars with the gong gong gong gong is even worse. Actually hate the new cars with all the crap they come with.

 

[Frank Mopar]

Had same problem. Cold start easy, hot start acted like it was flooded.

Reluctor gap of the Summit brand dizzy was way too big.

Easy enough to check.

Good luck

 

[gtgto]

Oh man, you hooked up the key buzzer? That's THE problem lol. JK JK but the buzzers were the first thing that got disconnected on ALL of my cars. Don't need any buzzer to tell me my key is in the ignition ....and the newer cars with the gong gong gong gong is even worse. Actually hate the new cars with all the crap they come with.

Definitely a glutton for punishment. Fixed key in buzzer and clutch safety switch and still have Left an Right handed studs on my car. My color changed, not by me , nothing special 340, 4 speed 70 Duster....hahaha

 

[gtgto]

A multi-meter and some leads with aligator clips may be helpful for this and future diagnostics.
Spend some time looking at the wiring diagram - in fact drawing a copy of the circuits of interest is a good way to get familiar with how things work.

You are probably right, but I must ask, how do you know this?
Did you do a spark check with a screw driver or spark tester?


Two possibilities that I can think of.
1. Switch is faulty.
2. Wires shorting allowing the alternator and ignition to get power - possibly direct from the alternator.

For visual checks I would look at
a. The ignition circuits wiring under the hood. This includes the alternator's 'field' wire and the ignition start circuit.
b. Steering column connector and wires.

I checked for spark the old fashioned way.....Took a plug wire off and put it close to metal, turned the car over for a bit...Nothing. I hate electrical but I have the tools and wiring diagram to learn more about my current issue.

 

[Mattax]

What do you disagree about?
I've personally had ECUs fail to start when hot. By the time a ride or jump was available it worked.
Never had an ECU itself cause an engine to keep running. In fact there is no way it can do that.

 

[gtgto]

What do you disagree about?
I've personally had ECUs fail to start when hot. By the time a ride or jump was available it worked.
Never had an ECU itself cause an engine to keep running. In fact there is no way it can do that.

I meant to hit reply.....Didn't mean to disagree.....

 

[Darter6]

Don't need any buzzer

That reminds me of 1974 seat belt no start switch that Mopar had. Every new car we sold that was the first thing disconnected.
THEN the key in buzzer !!

I've personally had ECUs fail to start when hot.

The district Mopar rep told us to use Freon to get cars started. Take a can on the road call and freeze the ECU.
Car would start and bring it back to the dealership for a replacement ECU.Freon was about 50 cents a can back then.

 

[MOPAROFFICIAL]

My fave is when it won't start until you let off the key from the cranking position.
Check the ignition switch down to the starter switch, ballast to box.

 

[TF360]

If you have a ECU, check it.

 

[gtgto]

I have a couple extras in case of emergency along with extra ballist resistors. Didn’t want to start throwing parts at it without a clue as to what is causing it.