Delayed stalling

Hi!

Quick update on installing the Holley Sniper. Once I got it all wired up correctly (thanks to you guys), I hit turned the ignition on and after 9 long months, it ran! And really well. I was super surprised at how well and smooth. Since then though, I’m battling worsening issues…

Initially I could run it for upwards of 15 minutes at idle while I was burping the coolant system. After about that long it would just suddenly stall. No roughness or anything. It would just go. I suspected exhaust leaks and definitely found some, but those are now seemingly fixed. Didn’t change much though - it went right back to suddenly stalling for seemingly little reason. And soon it began to not start again once it stalled. It would take a couple hours before it would go again.

The Sniper comes with tons of data readings so looking at them all look strong according to EFI System Pro techs. All they are seeing is a slow AIC close as it warms up and then a sudden wide open spike when it decides to stall. I even tried to run it open loop to test if it’s a faulty O2 sensor to no avail. Same issue.

So now the question is… Is it Sniper? I was having stalling issue when I first bought it. Most thought it might be the old fuel tank and a roughed up carb. Now all that and the fuel lines have been replaced. That leaves me with the last few things that haven’t been messed with since attained to understand.

1. Distributor and plugs (it’s all new and motorcraft, but the PO had it installed when they were trying to get it to run again after the long 10 years in storage. It runs beautifully when idling before stall so I’m thinking it’s not this).
2. Vacuum advance - It’s seemingly original. Do the symptoms match up? Excuse my ignorance here… I tested vacuum on it with a Mightyvac and I can hear a click with some light pressure, but if I pull harder vacuum it just builds and doesn’t release. Is that correct?
3. ??? Something else I’m not thinking of?

I should also add that I added a new 3G alternator that is seemingly running well. I’m not getting any voltage droppage according to the Sniper data logs. Any suggestions would be helpful!

Thanks for getting me this far, by the way. Could never have gotten here with out this forum.

It sounds like the coil or module is flaking out. (at least those symptoms fit)
I'm not sure what your ignition looks like....

You might remove the distributor cap while you are testing the vacuum advance with the Mity-Vac, to see if it is advancing smoothly as you increase vacuum.
I don't think this has anything to do with your stalling, but you mentioned a click, so it may be that the pickup plate is getting caught on something or the orange and purple wires are jammed up in there somehow.

Ah the Coil! Maybe! That’s one thing I’m not sure how old it is. It looks newer, but I don’t know for sure. Is there any way to test it?

Thanks for replying Jim! I was starting to get dismayed…

With vacuum advance I have to assume this is a DSII ignition?

Is the coil scorching hot when the truck stalls?

Do you know if any of it has been rewired?
The horseshoe DuraSpark coil connector should have full battery voltage in 'start' but reduced power in 'run' (while running)

There should be some good wiring diagrams and troubleshooting in the DuraSpark conversion section under Bullnose Upgrades.

It could well be the module too.
Especially if the coil is getting full power all the time, or if it has been swapped out for another coil of lower impedance.
The transistor and heatsink of the module case can only dissipate so much.

That's why an Inline* resistor is incorporated into the DuraSpark harness.

You know, I haven’t checked the warmth of the coil. I’ll do that tonight for sure. But, yes, it’s DSII.

I do know that the Duraspark has been replaced with a new one right before I bought it in hopes it would solve their stalling issue (it didn’t). I don’t think it’s been rewired though. I’m pretty sure this coil is new too, but I’m not sure it’s the right impedance - or even the right model. All is says is “12V use with electronic ignition”. Here’s some pics of the set up - I’m not sure if it’ll give you much to work from though… note the yellow wire coming from the coil is going to (-)coil to the Sniper.

I agree with Jim - coil, module, or maybe even the pickup in the distributor.  But one of those things is quitting when it gets hot, and that's not unusual with the module or the pickup.

That's what the coil should say, and it does fit the horseshoe connector.
Also, a genuine Motorcraft module..
So I don't think component quality is the issue.

I'm not certain what that wire is, spliced into the coil ground.
Do you know where that yellow wire is going?

Because if the coil ground is messed up it could be an issue.

The yellow wire is one I added - the Sniper requires a connection to the (-) side of the coil so that’s going directly to the sniper. I don’t think it’s causing the issue only because the issue existed before.

I’m thinking with what Gary added it’s the distributor. It looks like the cap has been replaced, but I’ve never investigated inside. The base is definitely older… Not that it means anything, but at least I have something to look at that could be worn.

Any recommendations on if I have to replace that are welcome.

I've had to replace the coil pickup before. (the magnets had cracked)
It requires a bit of disassembly.
You can see how the reluctor wheel comes off in the distributor recurve links to Scottie's old webpages.

If the distributor is badly corroded you might be better off simply replacing the whole thing.
At least you would be sure to have a tight shaft bushing and new cam gear then.

I'd have to check price and availability for a new pickup v/s a complete rebuilt distributor.
I have a hard time finding a decent cap and rotor these days.  All of these ignitions are so antiquated nobody stocks parts anymore.

Yeah, I think I might just replace it. I’m going to need to dig into it a bit though. I keep reading stuff about HEI distributors, but haven’t paid much attention to what those actually are good for.

Thanks for your help as always, Jim!

They are an economical alternative when you need to completely replace your ignition system.

A few people here are vehemently opposed to anything that's not 'pure' Ford.
But these people don't look at the bigger picture, in my mind.

Your coil and module are new.  I don't know if they are good, but they seem recent.
There are things to be said for sticking with what you've got.
Which would include a huge knowledge base of how to fix it, and ready availability of replacement parts.

I'm not going to have any opinion beyond that.

If I were you, I would do some diagnosis the next time the truck overheats and won't restart.
Does your truck have a tach?
Do you have a multimeter?

Oh I agree to sticking with the system (beyond the obvious upgrade to the Sniper). I’m certainly willing to spend the money to make it right.

I do have a multimeter, but no tach. I think I know what you mean by overheat (if we assume the ignition system is doing so), but just to be clear, this happens with the temp as low as 120F (according the thermostat on the Sniper).

I’m about to grab this, honestly… https://www.ebay.com/itm/184541655769

I don't know how that compares to the cost of a re-man at the local auto parts, but I have bought from Sparks Surplus before, and everything has always been on point.  

Procured! Hopefully it’s easy to drop in if I keep everything in the right spot! Thanks for the insight, Jim!

I put a HEI style disti in the Bronco. It got me running. Now I am having the engine rebuilt I am going back to MSD/motorcaft. The HEI got me through a couple of year and was worth the $150 or so it cost. But it always looked odd in place.

Good luck trouble shooting, it will be worth it.

You say "sniper" can tell you things what does it have to say just before it stops running?
When hard to start is it getting fuel to the injector(s)?
Dose it have spark as that would tell you where you need to look?
It would be nice to know the cause before throwing parts at it.
Dave ----

Hi Dave,

Yeah, even EFI System Pros aren’t sure what the issue is. Everything seems to be working correctly to them.

Here’s an example of an effort to keep it running.

Interesting!
I asked if you had a tach, to see if the ignition just cut off.

But if I'm reading the red line correctly it shows rpm falling off over a few seconds, and not just ending?

Then the IAC goes high in an effort to keep it alive?

Helpful diagnostic at any rate.  

Ah, yes, I thought you meant stock (as in wiring was involved).

But yeah, what basically happened is it slowly closes out iac until it slams open and cuts out. I think it’s basically flooding the engine.

The reason is the sniper trying to slowly get down to what my idle setting is (700). It’s part of the set up process.  

What is the little purple band at the bottom of the scale for about the last five seconds representing?