electrical shut down 1986 F-250 6.9 IDI Real problem and quite scary happen to anyone

[GrizzW]

Hi all, after almost 3 years of flawless operation my 1986 F-250 XLT Lariat , 6.9 IDI has developed a sudden shutdown. We are talking every thing. Engine, electrical, I mean everything. It's happened twice, once after starting in a parking lot and once on the road. Is there some relay, or some electrical part that can cause this. Scared to drive. Starts fine and made a 40 mile round trip with no problem. My least favorite word "intermittent" has raised it's ugly head. Any suggestions as to where to start trying to hunt this problem down? Mostly scared of nighttime use. Just won't try it at this time.

Thanks
M. E. "Grizz" Wallace
Near Seattle

 

[IDIoit]

first of all, welcome to the forum.
dont be skurred.
break out a volt meter and chase the issue, start with battery connections, starter connections and work your way back.
corroded battery cables are common.

 

[fsmyth]

Your most likely suspect is the starter solenoid battery connection.
That is the only point where everything is common to battery (+).
The next most likely is the main feed to the fuse box and ignition
switch. Do your lights still work when that happens?

 

[GrizzW]

No, nothing. clock resets, radio presets go away. dome light, even my under hood light. That's how I know it came back on as I was looking under the hood. Start's right up as if nothing happened.
Grizz

 

[BDCarrillo]

Check your grounds as well

 

[madpogue]

All of the above, plus keep in mind that all the "wires" coming off the junction point on the starter relay, that feed the rest of the truck, are fusible links. One or more of those may be faulty.

 

[GrizzW]

Okay, thanks, and I will start tracking down cables, corrosion and things like that, but if it's a fusible link, wouldn't that just blow instead of working part time. i.e. broken link would be permanent? I will start with obvious connections and work my way around. Thanks for your comments please keep 'em coming. Sounds that there is no such thing as a some type of circuit breaker in the system. Will let you know if I find anything.

 

[IDIoit]

but if it's a fusible link, wouldn't that just blow instead of working part time.

ive seen weirder things happen

 

[CDX825]

There is a big yellow wire on the passenger side that goes through a connector to two fusible links. One feeds the lights and the other feeds the ignition switch power. Your problem is most like near the connector where it plugs in.

 

[bobs_idi]

^ ^ ^ definitely check in area of the starter solenoid. Especially the yellow wire. Look for butt connectors anywhere, gifts from from PO. Don't ask me how I know

 

[OLDBULL8]

It's most likely that connector that lays over the pass side valve cover, that disconnects/connects everything. probably corroded contacts.

 

[inked469]

I had the same problem with mine when I bought it. Replaced all my battery cables and cleaned all the plugs and pins I could find. I ended up using ring terminals and threaded post batteries as I kept having corrosion under my battery posts. Since then no issues. Also the factory ford battery cable has a pass thru connection on the passenger side batttery that was where my issue was.

 

[LCAM-01XA]

It's most likely that connector that lays over the pass side valve cover, that disconnects/connects everything. probably corroded contacts.

The connector you speak of is for the engine alone. That would be my #1 suspect if it was only his engine that was shutting down, but he's losing power inside the cab as well. The cab is handled via the harness that starts at the starter contactor near the passenger-side battery and runs across the rad support and all the way back to the cab where it enters under the cruise control servo. Most likely culprit in his case would be the fuse links mentioned by Madpogue and CDX825.

 

[madpogue]

The cab is handled via the harness that starts at the starter contactor near the passenger-side battery and runs across the rad support and all the way back to the cab where it enters under the cruise control servo.

On an '86? My '85 has no such harness, AFAIK. In-cab power comes from a fusible link off the starter relay, but it's all wired along the firewall.

 

[LCAM-01XA]

Yeah you're right, looked up the '85 shop manual and it showed the harness running along the firewall. It's the later ones that have it running across the rad support. Nevertheless, the connector on the valve comer is still for engine purposes only, thus not likely to be the cause if the OP's particular issue.