yes, putting power to the output of the interrupter switch is the same as putting it to the pump wires at the tank.
only difference is at the tank eliminates a chance of a corroded or broken wire between the tank and interrupter switch.

 

I'll try that when I get home. Is the interrupter switch the same as the inertia switch. We'll probably test both at the pump plug and the interrupter switch.

 

yes. same thing, different name.

 

So.... the situation gets a little stranger. If you remember I ran into a crank/no start situation at the beginning of January. Yesterday Dad decided to give it one more try just for grins and giggles. He said it fired up just fine......

Before, it acted like a carbureted vehicle with a broken choke - sputtering and kicking but wouldn't fire up. I confirmed that the PCM ground wires are still present and hooked up to the negative battery terminal. To my half-trained ear it really sounds like a fueling issue, even though I can smell raw gas when it won't start.

Just thought I'd give an update, even though the news is confusing.

 

Hello Evan, I’ve be tracking. I was actually going to mention to you to move your thread into this section for your engine issues, definitely more eyes on your multitude of issues.

Just a FYI from these posts;
The EECM has 6 Grounds; Pins; 6, 20, 40, 46, 49 & 60
Wires leading from pins 40 & 60 are spliced together in route from the EECM, then one wire leads to the Neg Battery via a connector.

Remove power, disconnect EECM connector, check resistance value of each pin to body ground.

 

I'd like to take an intermission from the no-start issue to pick y'all's brains on another very strange issue. The truck (Bronco) has another interesting quirk that, while I'm sure is a personality trait of an old truck, is sort of a safety hazard.

When you first hop in the truck and turn the key to "ON" (not yet cranked).... you have full electrical power. Turn signals blink, wipers work, radio plays, blower motor runs. AFTER CRANKING AND STARTING..... nothing! You have headlights and hazards and that's it for dash controls. Radio was silent for about a min then squawked to life. After maybe 5-10 min all other electrical components return to working function. This has been confirmed tonight, took it on about a 15 min drive.

Also worth noting..... headlights seem to pulse slightly - gauge indicates good charging. Multimeter on battery indicates 14.something volts. I did read something about the 2G voltage regulators going bad? This looks like a brand new alternator though.

Old trucks have quite the personality.... Someone help me get this old guy working 100%.

 

Clarification;

“AFTER CRANKING AND STARTING..... nothing!”

So, define “nothing? (Turn Sig, wipers, radio, blower motor), anything else?

Instrument panel lights, floor lights, dome lights, running lights, brake lights, back-up lights, Gauges, tailgate, windows, door locks, speed control, horn, cigar lighter, clock, clock light.

“After maybe 5-10 min all other electrical components return to working function”
Everything on your truck works at this point ?

"After maybe 5-10 min all other electrical components return to working function. "
Always after 5-10 min?

 

I think your problem is in your Ignition Switch.

You might want to beat it around....

Check the GY/Y & BK/LG wires at the Ignition Switch Connector.

Check that the connector is seated all the way on...

 

i agree. the ignition switch in the 91 and older trucks like to separate and cause all kinds of wierd electrical issues.
it is a two piece design. half plastic, and half aluminum body. over time the two halves start to loosen up, then separate.

 

Sorry Vinny. Normally EVERYTHING works perfectly before start up. After start up I still have instrument cluster lights, gauges, head lights, running lights, high beams, hazard lights, brake/reverse lights, speed control, dome/floor lights. DO NOT have turn signals, blower motor, power locks or windows, or tailgate switch on dash. 50/50 shot on wipers - sometimes they'll continue to work sometimes they wait to come on with the rest of the accessories. Radio will return to function much quicker, within 1-2 min. Radio clock light has never worked, but the clock works at all times.

On that diagram you gave me, besides headlights and hazards everything else does not work after startup.

Can't be entirely certain on the time till they come back on - I would say between 5-15 min. Sorry I can't give much more than that. Thank you for the diagram though, will be looking at that plug and ign switch.

That's what I've heard Tom. I talked to my old mechanic boss and he pretty much told me the same thing - he's on his 3rd 8th Gen F-150 so I'm glad he's saying the same thing as y'all are. Will give an update.

 

If I added a few more of these Items to the matrix, it leans even more to a defective Ignition Switch.

 

i bet i have replaced over 100 ignition switches over the past 30 years. ...it is the first thing i look at ( actually feel for) when electrical gremlins start.

 

Good to know guys. If it's all the same I'll stick to the '92-'96s without the troublesome ignition switch

I've discovered that by wiggling the ignition switch after cranking and turning it back towards "OFF" a few millimeters that I can make all electronic accessories work instantaneously.

Boss said to try WD-40 in the key hole and maybe it will free it up some and help it spring back easier, before I go tearing into the switch *****-nilly. Also going to install some quality Motorcraft replacement relays for Fuel Pump and EEC as per the original issues.

 

that is the key tumbler. the switch itself in down on the lower column roughly above the brake pedal.
there is a thin steel rod that goes from the switch up through the column to the ignition actuator that connects to the key cylinder.

 

Got the IGN problem fixed for now. Liberally applied WD-40 and contact cleaner to the tumbler, IGN rod, and IGN switch under the dash. Got it to spring back correctly and get everything to work.

Having trouble finding the fuel pump and EEC relays...



I figured this was the small relay box - right here by the air box. However, these relays (or whatever they are) are much smaller than the 1992+ relays that I have to replace them. The pinouts are different too. So I'm guessing that these aren't the right relays to replace.
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There was a larger looking relay mounted on the drivers side of the engine bay behind the hood hinge, but the harness label said it was for trailer lights.

Kind of stumped here, still looking to try to replace those relays with the updated kind.