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ANOTHER NO SPARK 74 charger

cuda Hunter

cuda Hunter

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1974 charger 318

No spark

I have changed the following

ECU
Coil
electronic voltage regulator
ballast resistor

Car has a bypass installed for the starter due to the interlock system.

pretty right?

I've set the reluctor to .08
Tested the resistence on the pickup coil and it's 325
Coil is not collapsing the field noted by a test light no strobing from the negative of the coil
I hooked up a jumper wire from the positive of the battery to the positive of the coil and still got no spark


ECU wire test.
Dark blue with yellow stripe to number 1 on the ecu.
Key on position- 10.5
Key on run position 8
Key on run and starter button pushed - 6.5

I reset the interlock system and still no change
I disconnected the interlock system and still no spark

I'm assuming that I am going to have a grounding problem that is not allowing enough volts to make it to the ECU.


Ideas welcome
 
I would first go through every ground wire, clean and tighten. make sure you have negative to the body and the block, and a ground strap from the block to the firewall. next take the ecu off and sand , scrape , whatever to get bare metal on metal from the box to the fire wall. the reluctor gap should be .008. I would also try another ecu , they tend to go bad after sitting or getting super hot. I would also look at the ballast resistor. the interlock only interrupts power to the starter relay and doesnt impede spark. make sure you have power at the ballast when the key is in the run position. mine also has a push button from someone screwing with it before I got it. I would bypass that interlock all together. just cut and splice or jump the two yellow/black tracer wires together at the relay.
 

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This may be a stupid thought but if I recall correctly there his some kind of (almost like a breaker) switch on the fire wall for 74 chargers if this go's bad no spark .if I remember correctly you can simply unplug it and hard wire the wires together.
I may be 100% wrong if you can take a picture of your fire wall and I'll look it over worse case I'll run out to my storage and look at the 74 i have out there .
P.m.if you need me to dig a little deeper

- - - Updated - - -

Also your neutral safety switch is wired into the equation. You may want to try bypassing it too .
 
I had a no spark when I first tried to start my 71 rr after I converted to electronic ignition. As it turned out, I had a tach wire attached to the negative side of the coil but don't have a tach. Once I removed that "extra" wire, it starting sparking just fine. You should probably go over your wiring again to make sure that every is routed correctly and that nothing extra is attached. Don't know if this will specifically help you but just thought I would throw it out there.
 
It does have the little button on the interlock. I hit the reset button and it appeared to work.

wp29 I will probably splice the wires in the future. but since it does not pertain to the problem I am having it will wait.


But BB70 you might have hit on something there. the kick down linkage is disconnected so I should probably look for the neutral safety switch.
What would the car do if the NSS is not hooked up?

- - - Updated - - -

JimT, there is a blue wire that goes from my positive coil to my intake. I will have to take a look at my wiring diagram better.
 
The car will not spark if the nss isn't hooked up. After my last build I was pulling my hair out because of a no spark . The trans shop failed to put in a new switch and it was bad . I pulled the plug and started to jump the wires till it got spark (then ordered the switch) I'll give you a hint the wires that need to be jumped are next to each other I don't remember witch side .
Hopefully this Is your problem .

The grounding thing doesn't affect theses cars I found I always run a ground strap but it's not necessary.
Good luck
 
A bad nss or interlock relay will only interrupt power to the starter relay. They have nothing to do with spark. That is why you can jump the relay and start a car. The no spark issue is somewhere in the ignition system . Look through the diagrams I posted . Grounds have everything to do with spark, that is why there are grounds from the battery to the body and the engine block and back to the firewall. you can see from the diagrams the ground from the coil goes to the ECU which in turn is grounded through the case to the firewall.
 
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"JimT, there is a blue wire that goes from my positive coil to my intake. I will have to take a look at my wiring diagram better."

If the O/P actually means what this says, you found your problem... ei, you can't ground the POS side of the coil and get spark.
 
Is that a ground line that goes to the choke on the intake?

I have not looked at that and will do so. That would cause a whole lot of problems. If it is a ground to the choke the previous owner must have mixed up his wires.

so, so simple. I'm hoping it is not that simple, but it would be awesome if it was.

- - - Updated - - -

I've been looking at this website and I am blown away by how much information there is concerning this system.

http://www.classicwinnebagos.com/forum/index.php?topic=3424.0
 
No I do not have those. thank you very much. I will save them and print them as well.
 
Have you tried jumping hot directly from the battery to the coil?
 
Bb70charger500 said:
This may be a stupid thought but if I recall correctly there his some kind of (almost like a breaker) switch on the fire wall for 74 chargers if this go's bad no spark .if I remember correctly you can simply unplug it and hard wire the wires together.
I may be 100% wrong if you can take a picture of your fire wall and I'll look it over worse case I'll run out to my storage and look at the 74 i have out there .
P.m.if you need me to dig a little deeper

- - - Updated - - -

Also your neutral safety switch is wired into the equation. You may want to try bypassing it too .
Click to expand...
ancient thread, I know- but is this the thing you meant?

IMG_3236.JPG IMG_3237.JPG IMG_3238.JPG
 
Interlock system ( similar to the NSS on transmission but with ground ) won't allow to crank the engine. Just affects the cranking circuit from the ign switch. If you don't have spark is for any other reason way ahead from the interlock system. It can be bypassed on any wished form... jump out the yellow wires at the reset/override button, turn around yellow wires at bulkhead, crank it out straight at starter relay with a jumper wire or even a wrench, but if doesn't get spark if engine is turning, the interlock has nothing to do.

At coil you should have between 4.5-9 volts ( depending on engine bay temp and RMPs once fired up ) with key in RUN and 11-12 volts while cranking

ECU should get around same voltage on blue wire with yellow trace but stages reversed.

This both readings are due the ballast. If your are not, it can be either ballast, ign switch or bad/broken contacts somewhere ( bulkhead, plug down the column, wires broken )

One way to know ballast is in working order is the brake warning signal on cluster ( oil too if standard cluster ). Key in RUN will obviously light on these lights. While cranking these lights will dimm out. If lights off, something of the ign1/2 switching system previously explained is not working propperly

ECU must be good grounded. You can check the ground with continuity between one of its pins and body ground... is one of the dist pick up coil wires, can't recall right now which one. Will post later. ( if pickup wire has been replaced for a newer unit with black and orange wires, is the one what feeds the red wire )

Pick up coil continuity can be checked too. It should be between 150 and 900 ohms ( tipically 250-290 rate ) and isolated from body ground. You can check it at dist pickup coil plug &/or ECU plug. That will assure the plugs to pickup coil are good too. It happened to me that quite often I had to shake the dist plug wire to be able to fire up the engine... bad contact into the dist plug OR broken wires inside still with pickup coil good. Sometimes we replace the pickup coil when is just the plug what got damaged, and you can replace/fix just that keeping the pickup coil inside the dist in place.

Black wire with yellow trace at ECU must read continuity from end to end of course ( - lead of coil ). Green wire with red traces too between ECU plug and ballast. Important if is a 5 pins ECU, not so important if 4 pins since this wire gets to nowhere with 4 pins ECU.

If everything of this tested good the next reasons could be, damaged distributor rotor or cap... or ECU itself
 
Last edited:
Nacho-RT74 said:
ECU must be good grounded. You can check the ground with continuity between one of its pins and body ground... is one of the dist pick up coil wires, can't recall right now which one. Will post later. ( if pickup wire has been replaced for a newer unit with black and orange wires, is the one what feeds the red wire )
Click to expand...

image-jpg.jpg
 
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