New Member

[Bux]

New to the forum.

1986 F250 XLT Supercab 4x4. 460 CID. Stock truck with all California emissions on it. Only aftermarket parts is smog legal Doug Thorley Headers installed back in the day. Low milage truck under 126,000 miles.

 Joined forum for information on Bullnose trucks. Currently running through fuel system and fuel gauge issues. This site has been very useful in diagnosing and ordering parts.

Diagnosed and repaired 2 failed fuel pumps. Replaced Selector valve. Rebuilt carb. Replaced midship tank fuel sender. Waiting for rear tank fuel sender to see if it the correct one. After cleaning out all fuel lines still having issues with brass fuel filter. Sits over night and clogs up. Waiting for parts to do fuel system rework (different style filter).

Problem now is I do not have voltage to the electric choke wire. Alternator charges fine but no voltage to choke wire. Anyone know if alt can charge and have no voltage to the choke wire?

[Gary Lewis]

Welcome!  Glad you joined.  

On the choke, I don't think the 460's had a choke relay.  If not then the W/Bk wire went from the stator connector to the choke directly, so if you don't have power at the choke then there may be a problem with the alternator.  But it is unusual for there not to be stator power and yet the alternator be charging.

If you have a relay then that may be the problem.  So follow the W/Bk wire from the alternator to see where it goes.

[grumpin]

Welcome!

[ArdWrknTrk]

Welcome Kurt!  

As Gary said, you should have stator power (approx 7V) on the blk/white bullet going to the choke, but only when the alternator is turning.
Ford wired the choke this way so it will only be opening the choke with the engine running.
Not with the key on (run)
This way the choke doesn't continue to open if the truck stalls while warming up.

As long as you got an 85-86 tank you should be fine.
These have the bigger bung but still have the vent support in the filler neck.
87 on don't have the ring in the inlet to support the vent tube because they went to fill through the center, helping eliminate "burping"

[Bux]

With the engine running I have over 14 volts at the battery and the choke wire has nothing. I have not tested the back of the alt yet, that is why i wondering if it is charging the choke wire should have power.

Also thank you for the responses

[ArdWrknTrk]

14.35V is the set point of the regulator.
The alternator is charging correctly.
12.6V is the 'resting' voltage w/any surface charge removed.
Are you measuring the choke wire on AC volts?
Stator should be about 7V

[Bux]

Just checked the stator wire while running and is at 15.5V at the back of the alternator. Still no voltage to the choke wire. Is there a resistor in line or is it all incorporated in the alternator itself.  

[Bux]

Just reread your post and I am using a power probe to test voltage. Is the stator voltage AC?

[ArdWrknTrk]

Let's go to the 1986 EVTM!    

This is the charge and power distribution for DSII vehicles.



You can see the 'S' terminal connects directly to the choke heater.
The choke should only see power if the engine is turning the alternator.
But it's unrectified current so you only get 1/2 of the approx 14V the alternator is producing...

Does that help?

[Bux]

I understand that the choke wire should only see approx. 7V with engine running. I connected my power prob to the stator wire (Blk/Wht, S terminal) at the alternator, and started the engine. It was reading 15.5V on the read out. I checked the other end of the wire that hooks up to the carb for the choke and have no output (0V). The wire harness has never been opened up and appears factory.

So if I understand correctly the wire I am reading 15.5V should only be reading approx. 7V. First problem.
Secondly I should be reading the same voltage at the wire that hooks up to the choke (Which reads 0V).

[ArdWrknTrk]

There are two connectors in that wire C231 & C233 I believe
Maybe one of those is completely corroded?
Otherwise I can't understand how you get voltage at one end of the wire and not the other.

15.5V seems high for any alternator output, but especially for the choke heater.
I suspect that it would come off really fast, if that kind of voltage actually made it to the bimetallic spring.

Maybe you want to start a new topic in the main forum?
Not many members even bother to look at the NMSH...

As you see it's not any kind of complex circuit, but perhaps someone else has encountered what's happening here?

[Bux]

ArdWrknTrk,

I just got it working. I cut into the factory wire loom going to the alternator. I traced the choke wire and appeared intact. I went to disconnect it and the wire pulled apart. The wire was broken inside the insulation. I repaired the wire and now the choke works correctly and has 6.7-7.1 volts. Thank you for your help.

[Gary Lewis]

Well done!  

[ArdWrknTrk]

I'm glad to hear you've got it working!  

Strange indeed that the choke wire failed internally.