[250 Al head] Ongoing ignition trouble (long)

62Ranchero200

62Ranchero200

Famous Member
Greetings Ford Six Fans!

Relevant background:

250, aluminum head
DS II, custom curved by WSA111, set to 20 degree initial advance, vacuum advanced hooked to "timed spark vacuum port" on Holley 4412S (ported vacuum)
MSD-6AL, using magnetic pickup
Holley 4412S, "500 CFM" 2 BBL

In late April, as I was preparing to drive the Ranchero from Houston to an FCA (Falcon Club of America) regional in Baton Rouge, LA, I went on a fast food lunch run in the Ranchero, and it died in the drive-through. With a 300 mile drive set for the next day, I performed a traditional tune-up on the Ranchero - new plugs, cap and rotor, and checked the timing. After the tune-up, the Ranchero ran great all the way to Baton Rouge and back (600 miles)! Great acceleration, low RPM at 70 MPH (I'm running a T-5), and 17 MPG.

Life got in the way for the next two months, then one day in June I went to start the Ranchero because I needed the garage space to work on another car - it wouldn't start. I had no time to troubleshoot it that day, so I just pushed it back.

Fast forward to last weekend - four months later. I checked the cap and rotor - they looked OK; the coil - 1.5 ohms on the primary side; but the magnetic pickup seemed open (infinite resistance). I pulled the distributor and replaced the magnetic pickup. After reinstalling the distributor and timing the engine, the engine started easily and idled very smoothly, but wouldn't rev unless revved very slowly. If revved quickly, it backfired. The next day I came out to troubleshoot this and the Ranchero wouldn't start at all.

It was at this point that I decided that the ignition switch was probably original (1962) and might not be making good contact, so I would replace it. Found that the wires on the ignition switch connector were in very bad shape - with large spots where the insulation was either burned or scraped away - so am now replacing the ignition switch connector as well. Considering the condition of the wiring, it's a miracle that the Ranchero has run for six years with that wiring; the wires could have easily shorted out to each other or grounded.

Am hoping that after the ignition switch and connector replacement, the Ranchero will once again start easily and idle smoothly, then I can work on why it won't rev without backfiring. Have three thoughts so far:

* Accelerator pump
* Vacuum advance
* I assembled the distributor incorrectly after changing out the magnetic pickup, and the mechanical vacuum advance isn't free to move

Any suggestions appreciated.

Thanks
Bob
 
Bob, see my PM.
The mechanical advance should be free to move. Did you check initial timing with a timing light??
When you had to remove the reluctor did you reinstall it correctly??
The pickup should be between 400-800 ohms, most come in at 580-600 area.
You need to install a MSD coil with .5 ohms on the primary. 1.5 is too high for your combo. Check resistance in coil wire.
I have seen where the mechanical advance tabs hit the pickup coil & prevent movement??
Also with the 108 L/C cam you might be better to use manifold vacuum to the vacuum advance, use witch one gives you the best idle. Reversed polarity to the pickup & or coil will cause the timing mark to go spastic. Let me know. Bill
 
Ignition module? I would think you should be able to rev it in neutral with or w/o the advance working. Polarity to the pickup? Maybe it's just the wiring and once you fix that it'll be fine.
 
If you think it is spark-ignition related, it is probably fuel-carb related !
If you think it is fuel-carb related it is probably spark-ignition related!
Do not use color code for the hookup of the pickup to check polarity, actually check it ,some are wrong and not what it seems.
 
Pretty easy to check out your timing advance concerns/questions- put a timing light on it and rev it with/without the vacuum advance connected. On mechanical only watch for advance that totally relates to engine speed, if that checks out OK then reconnect vacuum and rev again. Look for advance that goes up with engine speed but goes higher and backs off slower on engine deceleration.
 
62Ranchero200":37g2jzmh said:
Greetings Ford Six Fans!

Relevant background:

250, aluminum head
DS II, custom curved by WSA111, set to 20 degree initial advance, vacuum advanced hooked to "timed spark vacuum port" on Holley 4412S (ported vacuum)
MSD-6AL, using magnetic pickup
Holley 4412S, "500 CFM" 2 BBL

In late April, as I was preparing to drive the Ranchero from Houston to an FCA (Falcon Club of America) regional in Baton Rouge, LA, I went on a fast food lunch run in the Ranchero, and it died in the drive-through. With a 300 mile drive set for the next day, I performed a traditional tune-up on the Ranchero - new plugs, cap and rotor, and checked the timing. After the tune-up, the Ranchero ran great all the way to Baton Rouge and back (600 miles)! Great acceleration, low RPM at 70 MPH (I'm running a T-5), and 17 MPG.

Life got in the way for the next two months, then one day in June I went to start the Ranchero because I needed the garage space to work on another car - it wouldn't start. I had no time to troubleshoot it that day, so I just pushed it back.

Fast forward to last weekend - four months later. I checked the cap and rotor - they looked OK; the coil - 1.5 ohms on the primary side; but the magnetic pickup seemed open (infinite resistance). I pulled the distributor and replaced the magnetic pickup. After reinstalling the distributor and timing the engine, the engine started easily and idled very smoothly, but wouldn't rev unless revved very slowly. If revved quickly, it backfired. The next day I came out to troubleshoot this and the Ranchero wouldn't start at all.

It was at this point that I decided that the ignition switch was probably original (1962) and might not be making good contact, so I would replace it. Found that the wires on the ignition switch connector were in very bad shape - with large spots where the insulation was either burned or scraped away - so am now replacing the ignition switch connector as well. Considering the condition of the wiring, it's a miracle that the Ranchero has run for six years with that wiring; the wires could have easily shorted out to each other or grounded.

Am hoping that after the ignition switch and connector replacement, the Ranchero will once again start easily and idle smoothly, then I can work on why it won't rev without backfiring. Have three thoughts so far:

* Accelerator pump
* Vacuum advance
* I assembled the distributor incorrectly after changing out the magnetic pickup, and the mechanical vacuum advance isn't free to move

Any suggestions appreciated.

Thanks
Bob
Click to expand...

Hi Bob, :unsure: it sounds like there could be severial possable causes to your Ranchero's running problems. Without seeing it though and going by your description, I would first concentrate and work on all that old dilapidated wiring. Replacing or repairing all the damaged wires and ignition switch before you start changing out too many other parts that you might not need. At least then you will have the proper electrical circuits with the correct voltage going to your engines Ignistion and the charging systems, this in my OPIN is job number one. Good luck (y) :nod:
 
The ignition switch wiring has been replaced and the ignition switch now seems to work in all positions (ACC, ON, and START).

Distributor:

There is no metal-to-metal contact between the reluctor and the magnet on the magnetic pickup; although I haven't measured this clearance yet (because I wasn't in a position to bump the engine over at that time, to line up the reluctor tooth exactly), I believe the clearance is somewhere between 1/16" and 1/32".
The reluctor is installed with the teeth protruding up above its base - I believe this is correct (not upside-down).
How would I tell if the reluctor was installed 180 degrees rotated from where is was previously ("backwards")? As far as I can see, both of the channels for the pin are halfway between two teeth. I don't see how installing it "backwards" would make any difference.
The magnetic pickup now shows a resistance of 660 Ohms on a multimeter, which I believe is ideal.
The coil now shows resistance of about 150 Ohms! I plan to make some jumper wires for the coil terminals to carefully verify this - if this is true, then the coil is bad and needs to be replaced. I did check this with two different multimeters, but it's not easy to lean over into the engine compartment and be sure you're getting a great connection to the coil terminals.

With the engine off, the rotor and distributor shaft can be rotated perhaps 15-20 degrees (about a third of the distance between two cap terminals).
The vacuum advance cannister arm moves when vacuum is applied (with a mighty vac).

To-do:

Check the clearance between the reluctor and magnetic pickup
Double-check the coil resistance and replace if necessary
Try to rev the engine while the engine is on a timing light; if the magnetic pickup polarity is reversed (manufacturing defect), timing may be erratic on revving the engine (I know that I didn't simply reverse the wires on the magnetic pickup because it came with the three-prong connector attached, which can only be plugged in one way; so if the polarity is reversed it's a manufacturing defect)

Carburetor:

Check that accelerator pump is still working
Check the a mist of air/fuel is coming out of the boosters once RPM is sufficiently high that the carb is out of the idle circuit

If I check all of the above and the car still isn't running right, then probably either:

The mechanical advance mechanism isn't working for some reason, or
There's an issue with the MSD 6-AL

Thanks,
Bob
 
I made some jumper wires to fasten to the terminals of the coil and measured the resistance carefully - it fluctuates, but is lower than 0.7 ohms, so it seems like it has an internal short.

Ordered this coil from O'Reilly:

https://www.oreillyauto.com/detail/...5c/2473956/1978/ford/fairmont?q=ignition+coil

Paid a little more for the chrome, but Accel yellow wouldn't go with anything else in my engine compartment, which is Ford blue (of course) and red (from the Optima battery and MSD ignition controller).

Had an MSD coil before and would prefer an MSD, but MSD is not available in any local auto parts store (not even special order), and I don't want to wait another week for shipping, nor pay double the price for priority shipping. Therefore, I settled for an Accel that should be similar (advertised 0.7 ohms primary resistance), although it's not a high vibration coil, which my previous MSD was. I noticed that, as WSA111 mentioned, the 0.7 ohm coils seem to be associated with breakerless ignitions; maybe the 1.5 ohm coils are associated with points ignitions.

Will also bump the engine over until a reluctor tooth is lined up with the magnetic pickup, and check clearance.

Thanks
Bob
 
.7 on the primary of the coil may be fine if it's a really hot coil. Resistance in DC is tough b/c we're working with only 12v. By ohm's law 20 amps ac @ 115v is 2300w, but it's 191 amps @ 12v in our cars. So the resistance in any 12v DC system is going to read low. That's why it's extra important when dealing with 12v to test the resistance in your leads and deduct it from the total to find the sum. It's also why it's preferable to use a test light in a 12v system. Low #'s. You can get a false reading on a VOM and the light proves there's real potential. The coil I was running was a Taylor 718205 performance stock replacement and it measured .7 ohms. I don't know what coil your running but a TFI is around .4-.6 ohms. But you run those w/o a resistor. With a conventional coil @ .7 ohm you'd need to have sat leat a .7-1 ohm resistor on a DSII ignition, at least the stock type resistor wire to the coil. And good wiring.

The stock coil is 1.5 ohms for points and around 1.2 for DSII and the so called 12v conventional coils are around 3 ohms

https://www.physics.uoguelph.ca/tutoria ... intro.html
 
Bob, the coil you got with .7 ohms on the primary is fine for your application. Do not install a resistor.
With the MSD-6al you already have full voltage so just install the Accel.
The MSD just uses the wire from the ignition switch to activate, voltage is not an issue unless under 9 volts.
The only upgrade because of the heat in Houston would be a TFI coil. Its not oil cooled, but is an epoxy contained unit. Hope that gets you back on the road. Bill
 
If you replace the coil get a TFI coil and run it off the battery through a relay off the ign switch.

btw, I was running an .8 ohm resistor and the coil leaked fluid. The coil still works and tests out fine but the DSII module is toast. Near catastrophic failure, carefully and barely limping loudly and stinkily home was the outcome. I swapped to an HEI module and a TFI coil. I baked my old module in the grill for the heatsink. The only downside so far is harder starting. And with quality components it only cost me somewhere around $60-80. It's just 2 oem replacement parts, pigtail for the coil and some kind of heatsink.
 
Seth, that is right if you are using a HEI module.
The MSD-6al already has full battery voltage to it. Being a capacitive discharge box it is slamming 400V into the primary to create the multiple spark discharge.
Using a coil over .7 ohms on the primary will not let it produce its potential, same with just a HEI module using as a trigger.
 
But can a conventional coil or a chinese made module survive long? Maybe the conventional coil kills the module? Analog power soak and spit, it'll take it but can the module give it? There's got to be some juice going through the negative trigger. We know what happens to points, I don't understand quite how they manage that in a microchip but somehow they do.
 
The MSD Blaster 2 & 3 Blaster coils are Chinese made. I also sell them in blue as well as red, same with the TFI's red or blue.
All this stuff is mostly Chinese made. Quality Chinese electronics are well made.
For example i own several Nikon high end cameras & the CF-SD cards made in China are superior to one USA maker. Very sad, but the results are real.
 
Update -

Ignition switch connector and wiring were replaced and seem to work (replacement from Mac's Auto Parts)
Magnetic pickup has been replaced with a new BWD pickup (O'Reilly) and resistance is 625-675 Ohms
Coil has been replaced with an Accel Super Stock (O'Reilly) and resistance is 0.7 Ohms

I believe that the MSD 6-AL is receiving sufficient trigger voltage, because it's doing things I expect it to do:

* The LED on the unit lights up briefly (for maybe half a second) when the ignition is switched on
* The tach receives a 5,500 RPM signal briefly when the ignition is switched on (5,500 RPM is the rev limit on the MSD)
* The LED on the unit flashes on and off quickly as the engine is cranked with the ignition on

Checked the clearance between the reluctor and magnet on the magnetic pickup - seems like about 0.015" (15 thousandths). It's not easy to measure precisely because there doesn't seem to be a well-defined point where the spark plug gauge fits at one size, then doesn't fit at the next size. Rather, larger spark plug gauge sizes just get progressively harder to fit into the space between the magnet on the magnetic pickup and the reluctor. (the distributor is on the engine, making this measurement a bit more difficult)

Since I cannot start the engine at this time, have not checked anything on the carburetor.

Currently running a set of Live Wires that were ordered with a DUI; and a coil wire that came from an Accel spark plug wire set.

Pulled the coil wire off and the metal connector on the distributor cap end was rusted; I couldn't get any resistance reading until I pulled the metal connector off and stripped the coil wire to expose a bit more fresh conductor. The Ranchero has never been in water, or even driven in the rain much, but I've washed the engine many times, so I suppose water got into the distributor terminal of the coil wire as I was washing the engine. I don't have any extra metal connectors for spark plug or coil wires, so I'll have to buy a new spark plug wire set (unfortunately, no one sells coil wires separately; this in spite of the fact that many people convert from a DuraSpark or DuraSpark II to an HEI type distributor, and no longer need their coil wire).

Have ordered this spark plug wire set from O'Reilly:

https://www.oreillyauto.com/detail/.../2473921/1978/ford/fairmont?q=spark+plug+wire

Would prefer a spark plug wire set that was already terminated because I don't quite trust my terminations of the spark plug wires; have terminated many other wires and even heavy duty cables like alternator, battery and starter cables, but not many spark plug wires.

On a side note, if any of you have converted from Duraspark I/II to HEI and no longer need your coil wires, I would be interested in purchasing them. :D

Thanks
Bob
 
Bob sounds like you had 2 problems, coil & coil wire.
Get the MSD Blaster 2 Super Cond. # 84039.
It converts your coil output to a male connector & contains a coil wire with female connectors.
Make sure you put silicone dielectric grease at all connections for easy installation and moisture control.
Advance Auto parts has them as well as Summit.
Take a look and no terminating necessary. Questions just give me a shout. Bill
 
62Ranchero200":s21c581h said:
Update -

Ignition switch connector and wiring were replaced and seem to work (replacement from Mac's Auto Parts)
Magnetic pickup has been replaced with a new BWD pickup (O'Reilly) and resistance is 625-675 Ohms
Coil has been replaced with an Accel Super Stock (O'Reilly) and resistance is 0.7 Ohms

I believe that the MSD 6-AL is receiving sufficient trigger voltage, because it's doing things I expect it to do:

* The LED on the unit lights up briefly (for maybe half a second) when the ignition is switched on
* The tach receives a 5,500 RPM signal briefly when the ignition is switched on (5,500 RPM is the rev limit on the MSD)
* The LED on the unit flashes on and off quickly as the engine is cranked with the ignition on

Checked the clearance between the reluctor and magnet on the magnetic pickup - seems like about 0.015" (15 thousandths). It's not easy to measure precisely because there doesn't seem to be a well-defined point where the spark plug gauge fits at one size, then doesn't fit at the next size. Rather, larger spark plug gauge sizes just get progressively harder to fit into the space between the magnet on the magnetic pickup and the reluctor. (the distributor is on the engine, making this measurement a bit more difficult)

Since I cannot start the engine at this time, have not checked anything on the carburetor.

Currently running a set of Live Wires that were ordered with a DUI; and a coil wire that came from an Accel spark plug wire set.

Pulled the coil wire off and the metal connector on the distributor cap end was rusted; I couldn't get any resistance reading until I pulled the metal connector off and stripped the coil wire to expose a bit more fresh conductor. The Ranchero has never been in water, or even driven in the rain much, but I've washed the engine many times, so I suppose water got into the distributor terminal of the coil wire as I was washing the engine. I don't have any extra metal connectors for spark plug or coil wires, so I'll have to buy a new spark plug wire set (unfortunately, no one sells coil wires separately; this in spite of the fact that many people convert from a DuraSpark or DuraSpark II to an HEI type distributor, and no longer need their coil wire).

Have ordered this spark plug wire set from O'Reilly:

https://www.oreillyauto.com/detail/.../2473921/1978/ford/fairmont?q=spark+plug+wire

Would prefer a spark plug wire set that was already terminated because I don't quite trust my terminations of the spark plug wires; have terminated many other wires and even heavy duty cables like alternator, battery and starter cables, but not many spark plug wires.

On a side note, if any of you have converted from Duraspark I/II to HEI and no longer need your coil wires, I would be interested in purchasing them. :D

Thanks
Bob
Click to expand...

A stock set of wires for a 1975 250 Maverick, Granada, etc. should work for a small cap DuraSpark I or use a 1976 up set for a large cap DuraSpark II. NAPA has very good wire sets with the terminated ends. I happen to have plug wire terminals and tool to install them if you wanted me to make you a coil wire. Good luck :nod:
 
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