beware the quick splice- 351C cutting out at idle

[SA69mach 39]

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This little thing has caused me a lot of grief in the last two weeks.

My Bronco with 351 Cleveland was developing an annoying habit of cutting out dead at idle, when warm.  Would start right up again, but then die while driving, intermittently, but mostly at idle in gear (C6 trans)  Often while driving it would come back to life within a second or two.

I checked and adjusted idle mixture, checked for vacuum leaks at intake and carb.  Checked the coil, replaced the ignition module, checked resistance on all the plug wires. Checked and cleaned the distributor.

 

While cleaning all the connections for the coil and distributor, I noticed the two wire tachometer plug in the wiring harness  had one crimp connector splicing into the negative wire of the coil (to distributor)    I opened it up and saw two things wrong.  First the wires had corroded slightly, since these splice clips are not waterproof.  That was most likely the cause of the problem, an intermittent loss of signal to the distributor.

However, IF the genius who spliced in the tacho feed had left the wire intact from the negative post direct to the distributor, this problem would not have occurred.

They had actually cut the main wire, and   made THAT WIRE the splice, and run a single wire directly from the negative post to the tacho feed.

 

This might seem like easy peasy common sense, but it can cause you problems if it is done "reversed" 

They should have spliced a short wire into the INTACT and UNCUT distributor feed wire.  If the join corrodes, you just lose your tacho feed, NOT your engine..... 

 

So, I soldered them all, threw away the splice, and have to be happy I found the fault before buying a whole new ignition system.  I hope this might help someone in the future.  The lesson for me was that if you see wiring that is not factory loom, then investigate with a suspicious attitude. It is a problem waiting to happen, and was possibly done by a fool

 

These splice crimps have no business in an engine bay. 

[69 red fastback 20]

Good info

[Rsmach1 71]

Yeah those things are junk, always best to solder connections. Just good you were able to find the problem before throwing big $ at it. Good job!

[RPM 1,190]

Thanks for sharing good info.

[Midlife 814]

"These splice crimps have no business in an engine bay."

 

Actually, those splice crimps have no business whatsoever in automotive wiring.  I hate them.  Whenever I see them, I remove them and then have to cut the original wire and splice it properly, as the insulation is broken.

[1969_Mach1 333]

Yeah those things are junk, always best to solder connections. Just good you were able to find the problem before throwing big $ at it. Good job!

+1.  Solder and shrink tube the connections.  You'll never have to fix them again.

[SA69mach 39]

Soldering three wires together at once is a PITA, not made easier by doing it in the engine bay.  I will give this repair some time to prove itself, but so far, so good.

 

Interesting and perhaps helpful information - I did notice when the car would 'die' while driving is slightly erratic tacho needle.  It would drop to dead bottom, then sort of spike.  That points me to coil.  In this case it was not completely right , it was the wire from coil to distributor, but, it was right in the fact it was electrical, not carburetor. 

The tacho did not just come back to life and climb to the correct revs, it would spike and then settle.

Perhaps that is an indicator of spiking signal along the wire as the connection is re-established.

 

Also, there was no indication of any heat or burning at the crimp.  Just that white-greenish powdery crap on the bare wires, and the aluminum blade of the crimp.  It was just a weak connection that was killing the mighty Bronco with its mighty Cleveland.  lol.  It did its best to live.  At least it did not leave me stranded.