I need help diagnosing what's wrong with my engine

[icejawa]

I agree with the above posts, it sounds like a distributor/ignition problem. I had a bad MSD distributor and the moron mechanic I used to go to couldn't find the issue. The engine was missing and idling rough, and the car bucked when I gave it gas. Eventually it took 8 cranks to fire it up then it wouldn't start at all. I took it upon myself to learn the design of these engines and have never used a mechanic since (this car doesn't deserve to be experimented on by novice mechanics). I replaced my MSD with a cheap Summit Racing HEI distributor for diagnostic purposes and the engine ran normally. If you want you can have my old MSD Pro Billet distributor, but you would need to send it in to have a new control module put in it which costs around $100.

Edit: Oops, I don't think my old distributor would work for your 302 though, its for 351C/351W

 

[aasukisuki]

I'll finally have some time this weekend to look at this.  I've borrowed a timing light, so I should be able to at least make sure the timing is right (gonna need to watch some videos!)

I don't have the original distributor any longer, so if I were to go the pertronix II route, I'd need to buy one of those.  I'm leaning towards another HEI style from Scott Drake (only $100) or maybe an MSD setup?  I really have no clue.

 

[Don C]

Scott Drake products have a poor reputation on our site. A stock distributor with a Pertronix 2 module should be reliable. Another reliable option is a DuraSpark 2 distributor and box, parts are available at most auto parts store if it should ever fail.

 

[aasukisuki]

Scott Drake products have a poor reputation on our site. A stock distributor with a Pertronix 2 module should be reliable. Another reliable option is a DuraSpark 2 distributor and box, parts are available at most auto parts store if it should ever fail.

Ok, great to know.  I was only going off of reviews from the CJ Pony Parts site.  I'll do some research on the duraspark upgrade.  that sounds pretty interesting

 

[Don C]

There have been a lot of discussions about DuraSpark on the forum, here's a couple of examples, you can search the forum for more

https://www.7173mustangs.com/thread-electronic-ignition

https://www.7173mustangs.com/thread-another-duraspark-question--33764

 

[aasukisuki]

There have been a lot of discussions about DuraSpark on the forum, here's a couple of examples, you can search the forum for more

https://www.7173mustangs.com/thread-electronic-ignition

https://www.7173mustangs.com/thread-another-duraspark-question--33764

So I'm fairly confident that this distributor is dying.  I decided to again test spark to each cylinder, and 2 and 4 are not getting spark consistently (I didn't test the other side).  2 would spark 5-6 times when first starting up, and then would no longer spark.  4 would spark for a few seconds, completely stop for a few seconds, and repeat that cycle.

Thanks for the help so far.

 

[aasukisuki]

After reading the threads you linked, and doing some more research, i'm guessing I'll need to either source a duraspark distributor / control module from a junkyard, or order those directly through ford.  Seems like there are several coils that are compatible.  I'll probably want to replace my wires and plugs too, i'm guessing.  Does that all sound right?

I'm going to shoot to get one from a pre-EFI foxbody mustang.

 

[Don C]

You can get a new distributor from RockAuto for $56, rebuilt for less

https://www.rockauto.com/en/catalog/ford,1976,mustang+ii,5.0l+302cid+v8,1134571,ignition,distributor,7108

And a blue grommet box for $34

https://www.rockauto.com/en/catalog/ford,1978,mustang+ii,5.0l+302cid+v8,1134818,ignition,ignition+control+module+(icm),7172

Most local parts stores should also be able to get them.

 

[SteveO_71]

When you pulled and set gap on the plugs what did the #8 plug look like? Were any of them black and oily?

These are the plugs from 1 & 2, but I don't remember any of the additional plugs looking much different than these. I can pull 8 again tonight to be sure:







Not being an expert and as Fabrice has mentioned, these plugs look like its running too rich. Here is a little guide that talks about looking at a plug:

View attachment 41936

 

[Carolina_Mountain_Mustangs]

If you are getting miss fires the plugs would look a little black due to excess un burnt fuel.

When you get all your new stuff also include a tube of the the electrical grease. You can get at your local parts store usually on the same rack as the RTV. Permatex is one mfg. Ford also carries it. Put the grease on all connections, put around the boot for the plugs also prevents arch outs and keeps the water out also. I also use anti seize on my spark plug threads so they do not lock in place. You can get that at parts house also. Does not take much just makes it easier to remove them next time. Use on any bolts that tend to lock up like on exhaust headers or header to exhaust pipe clamps. Good for the thermostat housing bolts also. Do not use inside the engine ever.

 

[aasukisuki]

You can get a new distributor from RockAuto for $56, rebuilt for less

https://www.rockauto.com/en/catalog/ford,1976,mustang+ii,5.0l+302cid+v8,1134571,ignition,distributor,7108

And a blue grommet box for $34

https://www.rockauto.com/en/catalog/ford,1978,mustang+ii,5.0l+302cid+v8,1134818,ignition,ignition+control+module+(icm),7172

Most local parts stores should also be able to get them.

Man, thanks so much for your help.  So I need to order the

Cardone 842899 Distributor

Standard Motor Products LX203 Control Module

and I'll need a coil, since mine is long gone.  Something like this?

STANDARD MOTOR PRODUCTS FD476

finally, is it really worth spending the $125 on the conversion wire harness from NPD?

https://www.npdlink.com/product/conversion-harness-dura-spark-ignition-makes-converting-to-the/144692

 

[Don C]

I wouldn't buy the NPD harness, but it will depend on each individual's ability to read and follow wiring diagrams and making proper splices and connections. You will need the connectors that connect to the distributor and box, best to get them from a self-serve salvage yard.

Post #3 of this thread has more instructions:

https://www.7173mustangs.com/thread-installing-duraspark-questions?pid=274660#pid274660

And this link will give you more information about Duraspark systems:

http://351c.net/board/index.php?/topic/1446-duraspark-101-nov-2009-george-pence/

 

[aasukisuki]

My dudes,

I got the parts in from Rock Auto, and have the distributor in and the duraspark control module mounted near the battery, but I have no idea where to mount the coil.  I was able to find my original coil bracket, and tried mounting it in the original location on top of the intake on the passenger side, but it will not fit.  I have an Edelbrock intake, and when I had the new motor installed, a fuel filter / fuel line was run in that location.

I thought I would mount it on the driver side, using holes on the heads, but 1) I don't know if this is a good idea and 2) I have no idea what the thread size is of those holes on GT40 heads.  Any recommendations on the best place to mount the coil?

 

[Don C]

I mounted my coil on the front side of the passenger-side shock tower, to reduce heat and vibrations. That sounds like a good location for yours, near your control box.

 

[aasukisuki]

I mounted my coil on the front side of the passenger-side shock tower, to reduce heat and vibrations. That sounds like a good location for yours, near your control box.

Don, you've been invaluable during this process, and I really appreciate it.

Here's an update:  Distributor is in, and using your advice, I've figured out where I will mount the coil, and i'm going to order a new mounting bracket for that.  However, in my excitement, I failed to realize that I don't have a distributor wire since the previous distributor didn't need one.  So I've spent the morning tearing up my garage, hoping I had one from when it was previously points, but no luck.  None of the auto part stores near me sell single wires anymore, so I'm probably going to have to bite the bullet and buy all new wires, even though the 8.5mm MSDs on there now are practically brand new.  I also need to source the plugs that slide on to the terminals of the coil.  I think that's going to be fairly easy to do.

 

[Don C]

Times do change, all of the parts stores used to sell bulk spark plug cable off a roll, as well as the end connectors.

NAPA still shows it available by the foot, several different types, as well as single cables. I'm sure availability will vary by store, though.

 

[aasukisuki]

Times do change, all of the parts stores used to sell bulk spark plug cable off a roll, as well as the end connectors.

NAPA still shows it available by the foot, several different types, as well as single cables. I'm sure availability will vary by store, though.

Ok, I'm in the final stretch.  I bit the bullet and bought a pre-made wiring harness.  I've worked out that I don't need the yellow wire from the coil since I don't have an aftermarket tach.  I also understand that the white wire goes to the s side of the solenoid.  What I don't know is where the pink wire is (the one that should have an on-line resistor).  I'm also not clear if I should disconnect the wires that are already on the s and I terminals of the solenoid 

On the pink wire, is the resistor in line in the dash, or in the engine bay?  I assume I need to splice into this line before the resistor to run to the red wire of the ignition module?

 

[Don C]

The pink resistor wire is under the dash. There are two ways, you can bypass it at the ignition switch, or use the wire that connects to the positive side of the coil (red with light green stripe) to trigger a relay that provides full voltage directly from the battery.

Pertronix makes a relay kit that is designed to work off the reduced coil voltage and provides full voltage from the battery. A little pricey, but a clean way to go.

https://pertronix.com/pertronix-2001-ignition-power-relay-kit.html#.XUoU3DNlDkA

 

[aasukisuki]

The pink resistor wire is under the dash. There are two ways, you can bypass it at the ignition switch, or use the wire that connects to the positive side of the coil (red with light green stripe) to trigger a relay that provides full voltage directly from the battery.

Pertronix makes a relay kit that is designed to work off the reduced coil voltage and provides full voltage from the battery. A little pricey, but a clean way to go.

https://pertronix.com/pertronix-2001-ignition-power-relay-kit.html#.XUoU3DNlDkA

Do you think it's possible that the resistor has already been bypassed when the HEI was installed?  Is there a way I can test with a mutimeter?  Should the existing wire running to the s terminal of the solenoid drop to 6v when cranking but be at 12v when the key is only in the run position?

 

[Don C]

No, the resistor wire connects to the coil, only. The wire that connects to the "S" terminal on the solenoid should receive around 12 volts when cranking the engine.

Yes, the HEI distributors require 12 volts, so if it were wired correctly someone figured out how to power it with 12 volts.