All Small Six Diagnosing with air/fuel meter

[sixtseventwo4d]

Mine did something similar like yours, run decent until close to 2k- there about depending on how hard I was trying to accelerate. then act like I wasn't getting enough fuel, even buck or sputter; fall on its face as it got worse. The MSD self-diagnostic would pass so it presumed it was alright. After much tuning, checking and inspecting it was where I had the pos lead for the MSD connected at the solenoid. Pulled all of the connections, brushed and cleaned them and apply some dielectric grease. Now all is as it should be. My reason for not tying in at the battery as instructed is battery off-gassing fouls connection there as well.

Revisit the main power and ground connections. Check for stray a-c ripple in the charging system

 

[DON]

I will do that. Mine is connected to the relay as well. That thought crossed my mind when I was swapping boxes. In my case I will make sure the nut is tight first. If the problem is there my money would be on loose. . It interesting that solved your issue which is very similar to mine. Just curious on the other two points, what MSD do you have that has a self diagnostic mode? And how do you check for an a/c ripple? I am assuming that is from a rectifier going bad. I learned just to check rectifiers/ diodes on the bench. My reasoning is that it makes a cleaner looking battery area.

 

[DON]

Nope, positive connection was tight

 

[Frank]

It’s a full MSD ignition: dizzy, wires,al6 and coil. Not a compatiblity problem. I’m not sure of the type of trigger it has. I would call it a Hall effect. It has the tabs on the shaft that rotate past the sensor. I do know you can jump between the wire going to the al6 box and it will fire. A test eliminating the trigger. Is this what you describe as magnetic? Cap and rotor are new and have checked for signs of jumping, clean as a whistle

Ok, full MSD, I forgot, sorry. If it has the veins it is "Hall Effect", or digital. (On-off). All first gen electronic ignitions were magnetic pick up. The distributor blade reluctor passes a magnet, and signals the module. Thus it is a sine wave. Hall effect and ignition points are on-off, = digital. The GM and DS2 modules are designed for sine wave magnetic. You'd have to re-phase the rotor with Hall effect same as points, most likely. The TFI module does not know the difference between points and factor Hall Effect distributor, which is why I like it on the points distributors. It won't work on magnetic pickups.

Personally I'd figure what's wrong, and keep your matched MSD system. Cutting the center key out of a rotor and fabricating a new one to be screwed in 20* over- I'm not that good of a fabricator to trust that myself, and it seems a GM module (not matched to Hall distributors anyway) is a step down from the other MSD components. JUST my opinion.

 

[DON]

I am definitely going to keep the MSD system, I am just looking to easily eliminate parts with known good ones. For diagnostic purposes.
If I understand you, both pickups use a vein on the shaft. Can you tell which one it is by seeing if there is a magnet in it? I might have been wrong to call it a Hall effect, it’s just a term that stuck from school days

 

[Frank]

I am definitely going to keep the MSD system, I am just looking to easily eliminate parts with known good ones. For diagnostic purposes.
If I understand you, both pickups use a vein on the shaft. Can you tell which one it is by seeing if there is a magnet in it? I might have been wrong to call it a Hall effect, it’s just a term that stuck from school days

No, if it's Hall there's a shudder window on the distributor shaft, not an open vein.

TFI Distributor Shutter Wheel

The Truth About TFI Ignition, And Aftermarket TFI Distributors The Ford TFI ignition system may best be known for the troublesome TFI module that would fail when it got hot. The engine would run for about half an hour, the TFI module would fail, and you’d be stuck on the side of the road. After...

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[DON]

That makes sense, it’s just the opposite of veins, it triggers when there’s an opening.
So if I understand you right, I should be able to … borrow…. the module out of the DUI dizzy and wire it in place of the 6al. ( DUI says replacement modules are readily available, any GM application will work ) I didn’t think I would ever need that knowledge of wiring a module . I just might have to now!! I think that will be easier than swapping in the oem distributor, especially if no wires. Thank you for the info. Now I just need to roll up my sleeves……

 

[sixtseventwo4d]

In my case I will make sure the nut is tight first. If the problem is there my money would be on loos

My connection was tight as well. Being tight doesn't help a fouled connection, I brushed up both sides of each terminal that stacked together.

what MSD do you have that has a self diagnostic mode?

The 6AL digital- and it may actually be called a self-check or test mode. The check is meant to verify there are no internal problems within. See pg2 of the installation manual. The LED flashes help you look for problems if any

I have a alt-starter-battery tester that takes all the hit an miss out of it.

Are you running 50 ohm ignition wires?
How hot is the coil getting?
Ohm check the pick-up in the distributor while exercising the vacuum advance?
Have you verified a solid ground on the MSD?

 

[DON]

I have learned a couple things,
There wasn’t anything like what you talked about on pg2. Started poking around online, found a page with a Manuel on it, with the led flashing explanation( pg2). Figured my box is not digital. Must be old enough to be a previous part number. My manual says nothing about a led. The self check might not apply to my box. I do have the MSD wires. They are 50 ohms per ft. I run the MSD HVC II. I did buy a new blaster coil and no change in problem. The distributor has no vacuum advance, only mechanical. I don’t understand how moving the advance would change the ohm reading except for a damaged wire, is that the intention of that test?
I don’t have the tester you have for a ac spike, but I will note the volt meter when it is happening. That should show something as bad as its missing- if that is the issue.

 

[sixtseventwo4d]

I don’t understand how moving the advance would change the ohm reading except for a damaged wire, is that the intention of that test?

I should have went into more detail on this but yes, that was my suggestion to look for.

I am looking at the pic in post #15 it is pt#6415. Yours is the 6AL-2. Apologies for that, I need to pay closer attention.

In the instruction sheet, bottom of page pg5 for that box there is an status LED between the limit adjusters. See page 6 for the troubleshooting using that LED
Are you using the 2 step of the control, meaning you have the blue wire connected to a switched 12 volt source?

If you have DVOM you may use it to check for a-c ripple, although some meters may not have the sensitivity to pick it up.

If you want to just look for d-c voltage variations (drop), see what it is at the battery connection at the alt. since that is the highest voltage reading and then you can weigh out any lower drops in the other areas, like the solenoid where much of it ties together, the fuse panel, and at each end where the MSD pos and grounds terminate. I would do this with all of the accessory loads on. Always check the reading you get on the terminal (eyelet) against the voltage on the stud it is connected to. All of this is with the engine running.

I hope this helps

Where do you have the main ground for the MSD connected?

I also suggest ohm checking the coil and plug wires. When I was putting mine together I found a significant variation on one wire, so I cut and repeated the terminal. Same wide ohm variation from the others. The difference was actually on the end that was done by MSD

 

[DON]

Just an update, briefly, swapped in the second box, no change. I did notice the guages acting abnormally without engine running. Tac went to like 5k and held without engine running. Suspicious of ign switch. So ran a jumper wire for al6, switched ignition source directly to battery. Started and idled for 10 minutes or so then abruptly cut off, no spark. Wired up and bench tested both boxes, the back up, no spark, the primary one sparked. Eliminated the coil pick up wire from coil to box with a spare. I do have original manual for both boxes. Check ohms on power supply wires. All less than 1/2 ohm (.3 - .4) checked battery voltage supply to box , maybe 0.1 v lower, ign, switched source 0.3 maybe 0.4 v drop. Original box is back in and engine starts. Haven’t driven it yet. I did check led, all seems to be normal. When checking for a/c ripple, is the meter set to a/c volts?
Couple other points, the miss doesn’t happen in garage. Only driving. Guages are fine now. Not using the 2 step limiter- blue wire. MSD main ground is attached to frame at sway bar mount. Engine is grounded to frame with a 2/0 battery cable and 3/8, maybe 1/2 bolt, crimped connectors with heat shrink. I have two meters, digital with normal leads, volt ohm meter, the second it a clamp on style meter, it has leads as well, much more complicated. I might use that one if problem continues.
Looking forward, test drive, I think I might call MSD tec about thoughts on this, see what they say. Do more extensive volt ohm reading, with engine running. Will be sending back up box in for repair, maybe both

 

[DON]

Did the test drive, still the same.
I did check ohms on dizzy and moved the advance. A little puzzling, on the MSD dist, the advance moves the veins, not the pickup. The ohms were within 5 compared to a new one. Good. When I cycled the advance the ohm reading did move slightly. Even though nothing on the pickup was moving. The vein was moving in front of the pick up, so I attributed the readings to that. I moved the wiring only and no change. I am going to keep that in the back of my mind.
Called MSD tec, explained everything and he said it must be something in the box. So will pull it back off and send it in.
Still curious about testing the ac ripple

 

[Frank]

Most likely a dumb ?- is there a chance the box is hitting some sort of rev limiter incorrectly?

 

[sixtseventwo4d]

MSD main ground is attached to frame at sway bar mount.

Not a good place for reliability. Move your MSD ground to the engine block at the least. Humor me.
Your primary battery ground should always go the engine first. Is yours? You may have another ground from the block to the frame, in that order. Another smaller ground may go from the battery to the fender or core support (think 12 ga. here). Another 12 or 10 ga. from the block to firewall.
How are you performing your voltage drops? From point A to point B down the length of the same wire or just checking pos point differences?
You can't rely on body panels to make a complete and sufficient ground path.

It's hard to imagine both boxes being bad, I have seen them quit completely but never in a partial manner as you are experiencing. I am also more limited in experience with your al-2 than the more typical 6AL.

 

[DON]

Most likely a dumb ?- is there a chance the box is hitting some sort of rev limiter incorrectly?

A “dumb” ? Spell check error? dud?
I’m not sure what it feels like to hit the limiter, but yes, it’s that severe. The tec guy mentioned that and it had crossed my mind too

 

[DON]

I do know the battery ground goes to the block. That’s the 2/0 cable. Another 2/0 goes from the block to the frame. Can’t remember exactly where, but will check and let you know. But it is within a foot of the MSD ground, I will humor you and move it to the block. If you will be so kind to humor me ( in case you haven’t realized, my brain needs to know why on info) with a good ground from battery to block, good ground from block to solid frame, why is a ground to a clean solid frame 5/16 bolt, and the terminal is between the head of the bolt and the frame, not the nut side, any more unreliable than a bolt to the block? I can understand that it rust and corrosion was a factor, in this case it is not, garage kept, not driven in the rain. Also are you saying the other ground wires to cowel and core support could affect the MSD box? I do understand that is part of a properly grounded system.
I checked the voltage and ohms with one lead one the battery/ cable and the other at the end terminal, the entire circuit.
Thanks for your patience

 

[sixtseventwo4d]

If you will be so kind to humor me ( in case you haven’t realized, my brain needs to know why on info) with a good ground from battery to block, good ground from block to solid frame, why is a ground to a clean solid frame 5/16 bolt, and the terminal is between the head of the bolt and the frame, not the nut side, any more unreliable than a bolt to the block? I can understand that it rust and corrosion was a factor, in this case it is not, garage kept, not driven in the rain.

A parallel (there and back) circuit helps to prevent a problem from being introduced the way triangulated ground points do.

Too many times a problem has been traced back to where, and even how the ground is mounted.

Can you safely check these same pos and ground points with it running? This is how I was finally able to locate my bad connection when I had the MSD pos connected at the solenoid. The voltage read same as battery voltage with it off but when running and the alternator charging it was the same maybe even marginally lower. I had dismissed this connection simply because it cranked and started ok.
As a side note, the ring terminals MSD uses are too light; better ones are out there but it requires some searching.

 

[Frank]

Don, I will say this about electronic ignition hot/ground sources: I have not used an MSD box. But I've run "stock" electronic ignition on GM, Mopar, and Ford since they came out. I always run a dedicated ground to block or battery from the distributor and/or the module. Currently the GM module in one f150 and the TFI module/ignition points on two other vehicles have a dedicated hot and ground to battery, with it's own relay. The circuit carries no other components. The point?- easy to call it overkill, but I have never had a module failure ever, since 1976, nor any kind of mystery misfire. Several of those vehicles went to the scrapyard with 200-300K miles and the original module still in service.

If I had an MSD, 100% the power and ground for it would be it's own isolated system to battery directly.

 

[pmuller9]

the MSD uses more juice than these non- capacitive discharge systems.

Not necessarily. The MSD 6A box uses 0.7 amps per 1000 rpms.
An inductive discharge system without dwell control waste energy during the coil saturation period. The lower the rpm, the more waste.
The MSD system does not.

 

[Frank]

Not necessarily. The MSD 6A box uses 0.7 amps per 1000 rpms.
An inductive discharge system without dwell control waste energy during the coil saturation period. The lower the rpm, the more waste.
The MSD system does not.

Good to know! Thanks. I'll remove that line.