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Discussion Starter · #1 ·
I've got a 250 I6 that I run in 24 Hours of Lemons.

I just built a new motor (old one went kablooey) and can't get spark on my HEI distributor. That same distributor was running right up until it threw #1 through the block. I swapped in my old "backup" HEI unit and it also had no spark.

I said screw it and bought a new one, as they're cheap and time's getting short for the race, still no spark.

I've tested all 3 units (backup, old, brand new) on the bench and the coils ohm out as they should and they bring a ground pulse through as they should. I know these cheap HEIs are kinda notorious, but I'm skeptical all 3 are faulty with all 3 testing ok on the bench.

So, is it the car/electrical system?
  • I have a decent ~6ga ground from the bock to the body
  • I measure <1ohm between the ground on the HEI coil and chassis, so I think I've got a decent ground path out of distributor.
  • Battery is at 12.6 ignition on, but like 10V cranking...low...but still zero spark?
  • Starter cranks a little slow, but still...zero spark?
I'm like...super stumped here. Over the last couple years of running these things they were just plug-and-play, now I've got nothing. I know I've gotta be missing something dumb...
 

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I've got a 250 I6 that I run in 24 Hours of Lemons.

I just built a new motor (old one went kablooey) and can't get spark on my HEI distributor. That same distributor was running right up until it threw #1 through the block. I swapped in my old "backup" HEI unit and it also had no spark.

I said screw it and bought a new one, as they're cheap and time's getting short for the race, still no spark.

I've tested all 3 units (backup, old, brand new) on the bench and the coils ohm out as they should and they bring a ground pulse through as they should. I know these cheap HEIs are kinda notorious, but I'm skeptical all 3 are faulty with all 3 testing ok on the bench.

So, is it the car/electrical system?
  • I have a decent ~6ga ground from the bock to the body
  • I measure <1ohm between the ground on the HEI coil and chassis, so I think I've got a decent ground path out of distributor.
  • Battery is at 12.6 ignition on, but like 10V cranking...low...but still zero spark?
  • Starter cranks a little slow, but still...zero spark?
I'm like...super stumped here. Over the last couple years of running these things they were just plug-and-play, now I've got nothing. I know I've gotta be missing something dumb...
I have a Speedmaster PCE385.1005 but it came new with no book or details beyond “plug and go”. So I wonder if there is a minimum input voltage to fire the electronics? If the starter is pulling you below the minimum maybe that is a factor. I have heard that if your starter drops your battery volts more that 2 volts while cranking it may need to be replaced.
 

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Discussion Starter · #3 ·
So I wonder if there is a minimum input voltage to fire the electronics? If the starter is pulling you below the minimum maybe that is a factor. I have heard that if your starter drops your battery volts more that 2 volts while cranking it may need to be replaced.
Right, and the tricky part is it's borderline. Like, I'd be sure 9V is too low and it should still spark at 11-11.5, but right around 10V...like...I'm sure I've seen voltage that low cranking before and it worked...I think?

Anyway, I'm throwing a new starter and borrowing a newer/better battery from another car in the fleet. We'll see what happens.
 

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Is this a big-cap coil-in-cap type? Or a module conversion to a different distributor? Different checks, if so.

Verify you do not have the Ford "fat pink" resistor wire in the circuit, if you're using a factory switch or wiring setup. A quick check first would be to jump a wire directly from the battery (+) to the distributor power wire terminal and try it.

If that doesn't work, I'd look at the grounds again. Dist ground wire should go to the block. You should have a max of ±0.3 ohms from the distributor body to the battery (-) terminal.
 

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Discussion Starter · #5 ·
Is this a big-cap coil-in-cap type? Or a module conversion to a different distributor? Different checks, if so.

Verify you do not have the Ford "fat pink" resistor wire in the circuit, if you're using a factory switch or wiring setup. A quick check first would be to jump a wire directly from the battery (+) to the distributor power wire terminal and try it.

If that doesn't work, I'd look at the grounds again. Dist ground wire should go to the block. You should have a max of ±0.3 ohms from the distributor body to the battery (-) terminal.
It's a big cap, coil-in-cap one.

No resistor wire. Actually no factory wiring at all b/c it's a stripped track car:
(BAT)-->(kill switch)-->(30A fuse)-->(IGN sw)-->(HEI B+ term)

There's no provision for a distributor ground wire outside the unit. The coil and module ground to the body of the dist, which grounds through its base into the block. BUT, on my list is to run a dedicated ground wire out of there to the ground lug on the block.

Battery is in the under-bed storage thing (Ranchero), so it's a little hard to measure resistance, but it's got a beefy ground cable right into a welded-in battery mount back there. Still, will re-check it. Whenever people talk about mystifying electrical stuff I'm the first to suggest "check your grounds".
 

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While rare, also do a quick check of pulling the distributor cap and verify the shaft is spinning during cranking. As always, it's something simple, and you just have to find it. What is different from the bench to the car?
 

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Discussion Starter · #7 ·
OMFG IT WAS MY TIMING LIGHT...it's dead.

(ノಠ益ಠ)ノ彡┻━┻


I tested it with one of those inline spark bulb things, then dug out an old crappy timing light (that I thought I'd thrown away) and sure enough it's blinking. That's what I get for trying "just set the timing before I fire it with fuel".

I still have a suspicion that early in this process I did have an issue, but whatever.
 
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