'75 cranks but won't turn over. Help I'm going crazy!

[bmflinchum]

Situation: 1975 was running (fast but running) went to drive it and it just stopped. No spark.

Not a fuel problem - replaced tank, sending unit, has new pump, rebuilt carb, filter etc and its getting fuel in carb.

Replaced plugs and wires before it died.

After it won't start I started replacing more parts:
Ignition module
Rotor, cap, coil, coil pick up
new switch.

Checked grounds. Tried checking everything I can doing searches on here and found some threads but no solutions. Even checked wires based on some diagrams found here.

I'm at my wits end. Almost everything in the ignition system is new and it won't start.

Any help will be appreciated.

Ben

 

[garberz]

I would check the distributor shaft and make sure it spins while cranking the starter. Do you have 12v. at the coil?

Mark

 

[DirtDonk]

Hey Ben, welcome! Sorry to hear you have yet another Bronco mystery on your hands.

So the cranking seems normal, as in it's fast and no funny noises?
Does your '75 have the full complement of Dura Spark ignition stuff, or is it running something else?

And even though it's a traditional method of "finding" the problem by changing parts, that method can get you into more frustration than ever these days because many of the new parts are bad right out of the box.
You did say module though, so I'm assuming Dura Spark. You'll need to check some voltages.

You did verify you're not getting spark anywhere?
Check for voltage where it's supposed to be, such as at the Green w/red wire on the ignition coil and ignition module.
Could have been a coincidental failure as well. Happens a lot with these old rigs. Work on something and the next thing in line fails.

Disconnect the distributor trigger wires and check resistance between the Orange and Purple wires. Should fall between 400 and 800 ohms. If it's out of that range, or even nif it's right on the edge, it's out of spec and should be replaced.

Good luck. Hope some of those first steps bear some fruit.

Paul

 

[DirtDonk]

I see you replaced the coil pickup too. Is that the magnetic trigger in the distributor? If so, check it anyway. Remember the "new parts suck" rule.

Paul

 

[SteveL]

Like garberz said. Check out the dizzy. There's a pin on the dizzy gear that snaps if your oil pump has issues. If that pin snaps it does exactly what you describe.

 

[LilMixedUp]

auto or manual transmission? If auto check your netural safety switch and the wires going to it....

 

[jckkys]

The 1975 Solid State Ignition is unique. The module has a green strain relief. It is not interchangeable with Duraspark I modules that have blue strain reliefs. Many computer screen parts vendors don't know that. What module did you buy/install? Ie what manufacturer and part #? What color is the strain relief?

 

[DirtDonk]

auto or manual transmission? If auto check your netural safety switch and the wires going to it....

Never hurts to check it, but if his issue was the NSS then the starter would not crank either. In theory...

And something's I forgot to add bmflinchum, were the starter relay and the radio noise suppressor on the coil.
If you disconnect the Brown wire from the "I" post of the relay and it starts, you have a bad relay.
If you disconnect the radio noise suppressor from the ignition coil's positive side and it fires up, your suppressor is bad.

Paul

 

[bmflinchum]

Thanks for the replies.

Its a manual so no neutral safety switch.
The rotor spins when cranked.
Cranking sounds normal.

So how would I know if I have the wrong module? I picked up the one from Autozone that says its for the 1975. What is the strain relief - same as electronic module?

My father in law and I checked a bunch of wires (mostly him cause I hate electrical) based on a chart we found on here. We are thinking its gotta be something simple we are missing because there is not much to it....

Ben

 

[75MIKE]

Where the wires come out of your module, it should be a green plastic "grommet".

 

[JaxLax]

Its a manual so no neutral safety switch.

You do have a NSS.
For a manual, it's going to be under/on the clutch.

Can you jump from the + relay post to the I post and start?

But DirtDonk hit on all the main points to check.

 

[sandersnc]

Have you tried just pouring gas straight in the carb and cranking? Is the choke plate on the carb partially open?

 

[bmflinchum]

Never hurts to check it, but if his issue was the NSS then the starter would not crank either. In theory...

And something's I forgot to add bmflinchum, were the starter relay and the radio noise suppressor on the coil.
If you disconnect the Brown wire from the "I" post of the relay and it starts, you have a bad relay.
If you disconnect the radio noise suppressor from the ignition coil's positive side and it fires up, your suppressor is bad.

Paul

I will look into this - but if the starter relay was the problem would it not crank the starter? I will search for the radio noise suppressor and the brown wire....
I don't think I have a noise suppressor but will look for photos to see.

Thanks,
Ben

 

[bmflinchum]

UPDATE:
The ignition module has blue "grommet" but so did the old one and it ran with that one.

I tried disconnecting the brown "I" wire and still cranks but no turning over

I have looked all over for the radio noise suppressor and there is nothing else on the coil but the two wires plus the wire to the distributor. There is a small cylinder next to voltage regulator on pass side firewall - is this it? I have googled and searched and can find nothing so if anyone has photos then please post or link them for me.

Going crazy and getting frustrated......

Ben

 

[Nothing Special]

The title of this thread is a little confusing, and I think it's leading to some slightly misguided responses. To most engine people "turning over" means that the engine will turn, in other words, it's not frozen or rusted solid. "Cranking" means turning over with the starter motor. So any engine that cranks is turning over. I think what you mean is that it cranks / turns over, but won't fire (start to run on it's own).

Since it cranks / turns over you know the problem is not with the starter circuit, so the neutral safety switch, starter relay and so forth aren't the issue.

If it won't fire, then compression, fuel or spark must be the problem. Compression usually doesn't go away on enough cylinders at once to keep an engine from firing (assuming it was running OK before). Fuel is easiest to check (as sandersnc suggested, dump a little gas down the carb before cranking it, if it fires like that you have a fuel issue). But it sounds like you are pretty sure you have a spark issue. Most of the advice others are giving should help track that down.

 

[bmflinchum]

Nothing Special:
Sorry didn't mean to be misleading. It won't fire. I can't get spark out of the plugs or coil. New coil - new wires - pretty sure I have power to coil. Something between the coil and plugs is a problem and all has been replaced.

Could the timing be so out of whack it won't fire?

Just hoping for something that will help. Almost all the system seems new so what else could it be?!

Ben

 

[Slowleak]

First thing I would do is put the old pickup coil back in and try it. I have had several that were bad right out of the box...one worked fine until the vacuum advance kicked in. Then it would shutdown just like turning off the switch.

 

[DirtDonk]

So how would I know if I have the wrong module?

Usually it won't even connect because the connectors are keyed. And if you got, for example, a module that had 3 connectors and your truck only has 2, then you'd know right off something was up as well.
But you can always verify wire colors and where they go in each connector if there was any doubt.

I picked up the one from Autozone that says its for the 1975. What is the strain relief - same as electronic module?

As they said, it's the color of the plastic where the wire bundles exit the module. Usually called a "grommet" for ease of use, it's aka a "strain relief" because it protects the wires from flexing and damage.

My father in law and I checked a bunch of wires (mostly him cause I hate electrical) based on a chart we found on here. We are thinking its gotta be something simple we are missing because there is not much to it...

Could be still. Since you're getting so good at separating the connectors on the module(!) check for RUN and START voltages at the power wires.
Should be zero volts on either power lead (are yours Red and White at the module?) and 12v on one when the key is in RUN and 12v on the other when the key is turned to START.

Good place to start anyway.

Paul

 

[DirtDonk]

You do have a NSS.
For a manual, it's going to be under/on the clutch.

Never seen an EB with a neutral safety switch/clutch interlock switch for a manual trans.
Later EB's did have some oddball setups to do with smog and other things, but I've never worked on one that had a clutch interlock.

But again, his is cranking. It just won't fire.
Might have been something about the use of the phrase "turn over" in the title, or first post.
Cranking was correct, but the jury is still out on turning over Ben. Most of us use the phrase to indicate cranking, not the act of starting.
So to those of us like that, "cranking" and "turning over" are exactly the same things.

Some people still say "cranking" for firing too, and the British use "tick over" for the act of firing after cranking. Lots of people use turning over just like you do. But maybe that has caused some confusion anyway.

Paul

 

[bmflinchum]

OK to clarify - starter turns motor but it won't fire and run on its own. If I'm checking it correctly there is no spark from coil (old or new). I tried setting the wire from coil (to distributor) to engine block and cannot get spark with cranking. Not getting spark to plugs either.
Coil has power - I checked that.


Dirt -
So I checked the module and it is blue but so was the one on it I removed. The plugs all match up but one has 2 wires (red, white) the other side of plug has 3 (Red, blueish, brown). The other plug has 4 wires that all seem to match.

Last night we checked the power wires to module and it seems to register 12v with switch on but we didn't test cranking.

Right or wrong module?
Thoughts on why the coil has no spark?

Ben