Jumping The Starter Relay to Start My Truck Fixed!

[Ranchman]

 
 Fifteen or more years ago Old Blue, the 86 F250 wouldn't start with the ignition. With the key in run I could jump across the starter relay and get the truck running. Not being my daily driver I ran it like that for a while. I replaced all the usual suspects, starter relay, ignition module, rack and gear on the ignition key, and I even polished the interior cab light bulb. That's what we did back in the day with no YouTube. Nothing solved the problem. So I bypassed the ignition with a push button and for years kept on driving. In 2017 the truck started running bad so I parked it.
 
 A few weeks ago I decided to get the truck back on the road. I have another post going about a back firing issue. So I wanted to fix the ignition just incase it had something to do with that. I started with the ignition switch. It's the only thing I didn't replace back in the day because I was lazy, and it was easier to put in a push button. I pulled it out and found that the start blade on the connector was broken. So I happily replaced it, problem solved, Happy dance, what an easy fix……. Nope, it didn't change anything.

Time for some testing.

 I started with the voltage on the wire that goes to the S post on the starter relay. With the ignition in start It was 7 volts. I checked at the ignition switch in start, it was 12 volts. So I traced the S post wire (R/B) back though the truck. I even removed the dash looking for a badly corroded wire. Everything looked good and clean. I traced the wire into the engine compartment to a main junction plug. It didn't look that corroded. It just had a little white powder build up on the pins, I did notice it was the only plug I took apart that didn't have grease in it. I sprayed it down with deoxit put it back together and measured the voltage. I got 12 volts on the R/B wire at the starter relay! It works, big happy dance!
It's late time for bed.

Now today, I'm wondering if that plug really was the problem. I'm no electric engineer, but It wasn't that corroded. Could it lose 5 volts though corrosion on the pins?
Maybe if the pins were made out of Aluminum and that white powder was Aluminum oxide. I checked and sure enough aluminum connectors.

Maybe this is old news to those that have done restorations before. But this one bit me for a long time.

 Live and learn,
Jeff
 
         

   

[85lebaront2]

This is why Ford started changing their underhood and chassis connectors to weatherproof styles. Chrysler used similar underhood, but packed them with grease.

[kramttocs]

Glad that took care if it!
I also would expect it to look a lot worse if corrosion was the issue but if cleaning it up worked...

Just for reference: C121

[Ranchman]

 Bill
 I'll be putting a little grease around this connector.
 Jeff

[Ranchman]

Scott

 Thanks I found that connector on the EVTM Start ignition page. But I couldn't find it on the Schematic for 86.

 I hope this really was the problem. Time will tell.

Jeff