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Ignition issue

Tayder88

New Member
Joined
Apr 23, 2017
Messages
17
Loc.
Decatur
Hey guys need some advice on where to go from here. 1975 ranger all stock engine. Was starting just fine but now seems as though I have no spark. I’ve cranked it with the center distributor plug off to see if I can get an arch but nothing. Replaced the ignition control module and tried a new coil but still nothing. Maybe distributor? Or ignition switch?
 

Viperwolf1

Contributor
electron whisperer
Joined
Aug 23, 2007
Messages
24,316
Hey guys need some advice on where to go from here. 1975 ranger all stock engine. Was starting just fine but now seems as though I have no spark. I’ve cranked it with the center distributor plug off to see if I can get an arch but nothing. Replaced the ignition control module and tried a new coil but still nothing. Maybe distributor? Or ignition switch?
Exactly which ignition module did you put in it? 1975 had a unique wiring harness and a one year only module.
 
OP
OP
Tayder88

Tayder88

New Member
Joined
Apr 23, 2017
Messages
17
Loc.
Decatur
What have you tested before replacing?

Have you cranked it over with the cap off to see if the rotor is turning?

Do you have a voltmeter?
I’ve made sure we have fuel going into the carb, and just checked to see if I have spark at the distributor cap.

I have checked to make sure the rotor is turning and it is.

I do have a bolt meter.
 

DirtDonk

Contributor
Bronco Guru
Joined
Nov 3, 2003
Messages
47,355
Standard brand? And aside from the same wiring, did it use the same color wire strain relief (grommet) where the wires exit the module?

The question about what did you test was meant to inform you that by replacing parts before you found out they were actually at fault you have now added more potential failure points. Instead of getting rid of question marks like was your intention. And like we used to, by throwing new parts at some thing.
That’s because modern parts are often crap and a crapshoot. They often fail within a short time, if they even work right out of the box!
And no I’m not exaggerating. Yes it’s that bad…

So there are still some tests you will have to do with your voltmeter before replacing anything.
We don’t know if it’s an ignition switch, or a bad connection, or a bad wire, or a bad component in the distributor.

You can test the magnetic pick up/stator in the distributor with an ohm meter. You’re looking for between 400 and 700 ohms on the orange and purple wires.
You can test for a voltage reading at the positive side of the coil when the key is in the on position.
Same for the wiring to the ignition module.

How long have you had the bronco? When was the last time it was turned up? Has it given you any other trouble in the past?
Does it have gas? Had to ask!

Good luck
 

Viperwolf1

Contributor
electron whisperer
Joined
Aug 23, 2007
Messages
24,316
I replaced the module with a Standard module. It had the same wiring as what was in there.
I'm not asking about the brand. Broncos used a black (1974), green (1975) or a blue (1976-77) grommet module. The engine wiring harness is different for all three but all the modules will physically connect to it. They will not work though. The one year only parts are very difficult to find and a lot of parts people assume the next year's part is just as good. 74 BI.JPG 75 SSI.JPG 76-77 DSII.JPG
 

Broncobowsher

Total hack
Joined
Jun 4, 2002
Messages
34,835
Cap off, spin engine over. Does the rotor spin?
No. Not an electrical problem, mechanical problem. You may have added new electrical problems with all the parts you put on.
Yes. Start electrical diagnosis (not throwing random parts and hoping one sticks)

Unplug the distributor and put a meter on pins 9 and 10 (the 2 colored wires, not the black ground. Put the meter on AC volts, auto scale if you have it, 2V scale if you don't. Do NOT use DC scale. You are looking for an AC signal. Spin the engine and see if there is a voltage. It will be small, maybe 0.2xx Volts.
No. Start doing checks on the pickup coil. There are continuity and resistance checks. It may NOT be a bad pickup coil, it may be a wire worn through or something like that. These are why you test parts before putting new ones on.
Yes. OK, the distributor is making signals. Lest see if you are getting the 12V from the ignition switch...

That is the start of figuring the problem. This far there are still all the original parts installed.
As bad of a reputation as some of this stuff had when it was new, not all of it was bad. If it has lasted 45+ years, it was probably one of the good ones.
 

RBuck

New Member
Joined
Oct 23, 2022
Messages
11
Following because I’m having similar issues. Don’t wanna steal the thread but maybe we have the same problem.

New project Bronco just purchased and just trying to get it to start before I do a complete tear down. Unfortunately the end was cut of my distributor so I think I’ve got the wires sorted out per the diagram above for the 75.

Tested pickup coil and it’s putting out .5 which says it’s ok. Here’s where the help is needed. I can not locate a wire in the harness that’s supposed to go to the + of the coil, per the diagram it should run from the ignition post of the starter solenoid to the + post on the coil. Is that correct and can a run a wire straight to it for testing purposes?


Sent from my iPhone using Tapatalk
 

DirtDonk

Contributor
Bronco Guru
Joined
Nov 3, 2003
Messages
47,355
That normally brown wire is strictly an auxiliary source. And it’s not 100% critically required.
Just good to have…
Do you still have your red with green stripe wire to the positive side of the coil? If so that is sufficient for the coil at least. There should also be a branch of that going to the ignition module.
 

RBuck

New Member
Joined
Oct 23, 2022
Messages
11
I got nothing to go to the + of the coil. The wires are very hard to tell any colors unless you get right at the harness plugs and them track them down. The plan is to do a complete resto on it but I’ve got three broncos right now and just sorting out if the motor will start and worth rebuilding or plan to hunt another one down.

I’ve tracked down the green wire coming from the icm and have it to the - side of the coil but can’t find the wire for the + side.

Got lucky with the first one. Cleaned the points up threw a coil on it and it fired right off after sitting 20+ years.


Sent from my iPhone using Tapatalk
 

DirtDonk

Contributor
Bronco Guru
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Nov 3, 2003
Messages
47,355
Normally not an issue to join in with a similar issue, but I think yours is far enough off of the OP's problem that you should start another thread.
Theirs is no spark all of a sudden, and some replacement parts. Yours is cut and/or missing wires and no spark. Good enough for your own thread because we're going to do the inevitable and request lots of pictures!

Not too much hassle to start a discussion. Pretty straightforward on this forum and even first time posters can start their own. I say go for it.
And when you do, post up some pics!

Now that I've said that, it's not as easy here to post pics as it is to start a new thread. Several different ways though, so when you start yours we'll jump in and make suggestions.

Good luck! Seeya on the other side...

paul
 

RBuck

New Member
Joined
Oct 23, 2022
Messages
11
Will do.

Sorry OP some forums get fussy if ya start a new “ignition” thread and there are 3-4 others already active.


Sent from my iPhone using Tapatalk
 

DirtDonk

Contributor
Bronco Guru
Joined
Nov 3, 2003
Messages
47,355
It's ok here either way usually. Hijacking is a common thing and in most cases is kind of welcome. Sometimes it's just a bit far sideways and things get muddy within the same thread.
Better to get muddy in the forum than in the thread.

Thanks!

Paul
 
OP
OP
Tayder88

Tayder88

New Member
Joined
Apr 23, 2017
Messages
17
Loc.
Decatur
Thanks for the guidance gentleman! I have had no time to do any diagnosing yet as I’m in the process of moving. As soon as I have the troubleshooting complete I’ll let you guys know the results! Thanks again for the help everyone.
 
OP
OP
Tayder88

Tayder88

New Member
Joined
Apr 23, 2017
Messages
17
Loc.
Decatur
Standard brand? And aside from the same wiring, did it use the same color wire strain relief (grommet) where the wires exit the module?

The question about what did you test was meant to inform you that by replacing parts before you found out they were actually at fault you have now added more potential failure points. Instead of getting rid of question marks like was your intention. And like we used to, by throwing new parts at some thing.
That’s because modern parts are often crap and a crapshoot. They often fail within a short time, if they even work right out of the box!
And no I’m not exaggerating. Yes it’s that bad…

So there are still some tests you will have to do with your voltmeter before replacing anything.
We don’t know if it’s an ignition switch, or a bad connection, or a bad wire, or a bad component in the distributor.

You can test the magnetic pick up/stator in the distributor with an ohm meter. You’re looking for between 400 and 700 ohms on the orange and purple wires.
You can test for a voltage reading at the positive side of the coil when the key is in the on position.
Same for the wiring to the ignition module.

How long have you had the bronco? When was the last time it was turned up? Has it given you any other trouble in the past?
Does it have gas? Had to ask!

Good luck
Finally got some time to do some testing today between moving stuff. Ive put back the original parts so I can test things to see where the issue may be.

I tested the magnetic pick up/stator in the distributor. The ohms reading between the orange and purple wires was around 530.
Tested the voltage at the positive side of the coil it was reading 11.88VDC.
I did not test the wiring at the ignition module, what would be the best way for me to test that?

Ive had the bronco about 8 years. Not sure when the last time it was tuned by anyone that knew what they were doing. Its never given me any issues in the past other than the normal carburetor problems and that was taken care of by rebuilding it.
 
OP
OP
Tayder88

Tayder88

New Member
Joined
Apr 23, 2017
Messages
17
Loc.
Decatur
Cap off, spin engine over. Does the rotor spin?
No. Not an electrical problem, mechanical problem. You may have added new electrical problems with all the parts you put on.
Yes. Start electrical diagnosis (not throwing random parts and hoping one sticks)

Unplug the distributor and put a meter on pins 9 and 10 (the 2 colored wires, not the black ground. Put the meter on AC volts, auto scale if you have it, 2V scale if you don't. Do NOT use DC scale. You are looking for an AC signal. Spin the engine and see if there is a voltage. It will be small, maybe 0.2xx Volts.
No. Start doing checks on the pickup coil. There are continuity and resistance checks. It may NOT be a bad pickup coil, it may be a wire worn through or something like that. These are why you test parts before putting new ones on.
Yes. OK, the distributor is making signals. Lest see if you are getting the 12V from the ignition switch...

That is the start of figuring the problem. This far there are still all the original parts installed.
As bad of a reputation as some of this stuff had when it was new, not all of it was bad. If it has lasted 45+ years, it was probably one of the good ones.
Yes sir, rotor spins.

Tested between pins 9 and 10, reading was around 0.258
 

Viperwolf1

Contributor
electron whisperer
Joined
Aug 23, 2007
Messages
24,316
Turn that original ignition module over and see what color the plastic is that the wires go into. The new one looks blue. I bet the old one is green. If it is they are not interchangeable.
 
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