1981 Shutting off randomly

[Crumback]

I have an 81 bronco 302 cid automatic. I have replaced the fuel tank and pickup, entire fuel line, fuel pump and filter. Electronics side I have replaced the column mounted ignition switch, the ICM, coil, distributor and all connectors. Truck runs great but at random times and sometimes months apart the truck will just die, not like a run out of gas die, like a all of the sudden dead type of die. I coast to the side of the road and it starts back up and runs fine, sometimes for months sometimes for only a few miles before it does it again. Nothing consistent in when it does it. It is wrong to think that I may have the ignition switch slightly off adjustment, I am out of ideas so I registered here to see if anyone had experience with this and could point me in the right direction.

 

[David D]

I had the same problem with a Bronco II, drove me nuts for a while. It turned out being the fuel pump shut off switch connections being corroded. Replaced the connectors and switch and cured the problem.

 

[Tiha]

So will it restart right away?
OR does it have to sit a while?

 

[miesk5]

Yo Crumback,
Welcome!
I assume the 5.0 has a carburetor. I'm not knowledgeable of other engine controls.

Let's begin with;

Source is 1981 Bronco/F Series Electrical & Vacuum Troubleshooting Manual (EVTM), partial via Gary cited below.
●
"Ignition Switch Adjustment Procedure
The following proceedure is from the 1983 Ford Service manual, with a few minor wording changes, but should work for any year.
1. Remove the electrical connector from the ignition switch.

2. Rotate the key back and forth to either side of LOCK, until a 5/64 in. drill bit can be inserted through the locking pin hole as far as possible (minimum 3/8 inch). The lock pin hole is located on the right of the switch next to the steering column tube.

3. Loosen the two ignition switch mounting nuts.

4. Turn the key to LOCK (feel for detent) and remove the key.

5. move the switch up and down along the column to locate the mid-positionof rod lash and tighten the mounting nuts.

6. Remove the drill bit from the ignition switch lock pin hole.

7. Plug in the electrical connector and operate the lock cylinder to insure the switch is positioned properly.

8. Confirm that all accessories are deactivated with key on the OFF position, and that all accessories are operable in RUN position.
Good luck"
by our late friend here in the Zone, Seabronc (Fred)
●

I included this for you to select your ignition system;


●
1981 Bronco Brochure - Gary's Garagemahal (the Bullnose bible) by Gary

1980-1986 Bronco/F Series Fasteners by Gary

1980-1986 Bronco/F Series Carburetors, Chokes & EFI by Gary

1980-1986 Bronco/F Series Specifications by Gary @ Axle Ratios - Gary's Garagemahal (the Bullnose bible)

Differences in 1980-1986 Bronco/F Series by Gary

➡ 1981 Bronco/F Series Electrical & Vacuum Troubleshooting Manual (EVTM), partial via Gary @ 1981 EVTM - Gary's Garagemahal (the Bullnose bible)

EEC III Testing, if not used or removed or disabled by a previous owner or shop via Wayback Machine by Tommy

Haynes Red Manual for 80-95 Bronco & F Series @ Hanes guide 80-96 bko f series.pdf via BroncMom

Partial Chilton Manual for 1978, 1979, 1980, 1981 Bronco. Scanned by broncocity.com @ Bronco City

1981 Bronco Advertisement @ Ads0002.jpg
●
Al

 

[Crumback]

So will it restart right away?
OR does it have to sit a while?

Restarts right away.

 

[Crumback]

I had the same problem with a Bronco II, drove me nuts for a while. It turned out being the fuel pump shut off switch connections being corroded. Replaced the connectors and switch and cured the problem.

Mines got a mechanical pump, and yes it is driving me nuts as well…

 

[Tiha]

Restarts right away.

Okay, a couple of approaches here.

First pay attention, does the radio shut off when it dies? Or keep working?

You can open the hood with it running and take a garden hose, break the engine compartment up into sections like a grid, 4-6 areas. Spray each area with a garden hose for a couple minutes, see if any of those areas **** the engine.
that would expose any lose connections, bare wires and such.

 

[Crumback]

Yo Crumback,
Welcome!
I assume the 5.0 has a carburetor. I'm not knowledgeable of other engine controls.

Let's begin with;
View attachment 27911
Source is 1981 Bronco/F Series Electrical & Vacuum Troubleshooting Manual (EVTM), partial via Gary cited below.
●
"Ignition Switch Adjustment Procedure
The following proceedure is from the 1983 Ford Service manual, with a few minor wording changes, but should work for any year.
1. Remove the electrical connector from the ignition switch.

2. Rotate the key back and forth to either side of LOCK, until a 5/64 in. drill bit can be inserted through the locking pin hole as far as possible (minimum 3/8 inch). The lock pin hole is located on the right of the switch next to the steering column tube.

3. Loosen the two ignition switch mounting nuts.

4. Turn the key to LOCK (feel for detent) and remove the key.

5. move the switch up and down along the column to locate the mid-positionof rod lash and tighten the mounting nuts.

6. Remove the drill bit from the ignition switch lock pin hole.

7. Plug in the electrical connector and operate the lock cylinder to insure the switch is positioned properly.

8. Confirm that all accessories are deactivated with key on the OFF position, and that all accessories are operable in RUN position.
Good luck"
by our late friend here in the Zone, Seabronc (Fred)
●

I included this for you to select your ignition system;


●
1981 Bronco Brochure - Gary's Garagemahal (the Bullnose bible) by Gary

1980-1986 Bronco/F Series Fasteners by Gary

1980-1986 Bronco/F Series Carburetors, Chokes & EFI by Gary

1980-1986 Bronco/F Series Specifications by Gary @ Axle Ratios - Gary's Garagemahal (the Bullnose bible)

Differences in 1980-1986 Bronco/F Series by Gary

➡ 1981 Bronco/F Series Electrical & Vacuum Troubleshooting Manual (EVTM), partial via Gary @ 1981 EVTM - Gary's Garagemahal (the Bullnose bible)

EEC III Testing, if not used or removed or disabled by a previous owner or shop via Wayback Machine by Tommy

Haynes Red Manual for 80-95 Bronco & F Series @ Hanes guide 80-96 bko f series.pdf via BroncMom

Partial Chilton Manual for 1978, 1979, 1980, 1981 Bronco. Scanned by broncocity.com @ Bronco City

1981 Bronco Advertisement @ Ads0002.jpg
●
Al

Thanks for all the info! It gives me a place to start and the proper way to execute it.

 

[Crumback]

Okay, a couple of approaches here.

First pay attention, does the radio shut off when it dies? Or keep working?

You can open the hood with it running and take a garden hose, break the engine compartment up into sections like a grid, 4-6 areas. Spray each area with a garden hose for a couple minutes, see if any of those areas **** the engine.
that would expose any lose connections, bare wires and such.

To be honest with you I rarely have the radio on as I’ve been trying to figure out if I can hear a change in the engine sound before it shuts off. I will turn it on and see if I dies along with the engine. I’ll try the hose truck this week. Thanks

 

[Crumback]

Hey everyone, I wanted to reach out and let everyone know what was causing my ‘81 to randomly shut off. While installing the new line on my tank that runs to the fuel pump I pinched it while reinstalling the tank creating a small tear in the line causing the pump to **** air. I’m assuming the randomness was how hard I was accelerating causing the truck to effectively run out of gas. Only reason I found it was I dropped the tank to check if the new pickup had an issue. Thanks for all the input. I’m sure I’ll be reaching out again.

 

[Tiha]

Made any progress on keeping the truck running? New information?