I have a 1977 F150 with a 400 and factory air. In the picture, the bracket seems to be bent at #1, which is keeping the solenoid piston from contacting the throttle at #2. The solenoid is working, the plunger moves out about 3/16th of an inch when 12V connection is applied to #3. From what I can gather, this is to boost the engine rpm at idle when the air conditioner is turned on. Assuming I can get the bracket back into the correct position, where does the solenoid (#3) attach? I cant find a loose or open connection anywhere. Should there be a harness or wire somewhere that I am missing. Maybe one more thing the mice got.... Thanks.

Where does #3 connect?

 

The bracket looks fine, its way out of adjustment however. The screw on the side is the adjustment for it. The wire goes to the hot wire on the compressor.

 

if I recall correctly, only specific configurations were connected to the AC clutch...some were tied to switched 12v so the throttle would fully close when the ignition was turned off...

 

That was my understanding as well, it was an anti-dieseling solenoid. As stated, allowed the throttle blades to close to prevent the truck dieseling after the ignition was off. I do not have AC on my 77 and have the solenoid setup as pictured. I don't have mine operational, and as such, my motor will diesel for 2-3 seconds when its really warm out and I shut it off.

 

Thanks guys. dlburch - I hadn't heard the reason, but have seen somewhere, where it had been wired to a switched 12v along with the electric choke. ford3909gashog, I will keep looking for a good way to tie it to the compressor. I will give both of these ideas a try to see what happens. If anyone has a picture or diagram that they could share, that would be great. thanks all

 

My '71 only used it as an anti-dieseling solenoid and my '79 had a slightly different version, which also did not kick in with the A/C. Even though I had A/C on the '79, there was no connection to it.
On trucks using it as an anti-diesel solenoid there would be a Blue w/black wire floating around the engine compartment somewhere.
In one book for '77 it was listed as a "carburetor emissions control solenoid" so may have had a different purpose still yet. Or too, depending on where it was originally sold, may not even have had one? Dunno, but there were still variations on the smog theme in '77.

But at least part of the reason there is such a big gap between your solenoid's rod and the throttle lever plate is that your choke is closed and so the throttle is held up on the high-idle cam. Pull the throttle open slightly, manually open the choke all the way and then let the throttle lever fall back all the way to it's lowest available point. If at that time it still does not touch either the idle speed adjusting screw or the solenoid, you can adjust them accordingly.

Since you don't currently have anything to connect it to, you can ignore the solenoid for the moment and just use the idle speed screw.

Does your '77 have the charcoal canister and EVAP system? They all had them here in CA from earlier years, but apparently many of the full size trucks, especially the heavier duty ones, did not have the evaporative emissions systems until around your year, or perhaps '78. I've seen it mentioned here, so thought I'd ask.
Reason is that your carb has one of the bowl vents that connects to that system. Lots of people that buy remanufactured carbs seem to get haphazard results. Some that need the vent don't get one, and those that don't need one get a carb with the vent. Apparently not all rebuilders are as knowledgeable about their products and just grab any old core to rebuild.

If you don't have the system (he says, finally getting around to the point!), then you'll want to cap that vent tube coming out of the flow bowl.

Paul

 

Thanks Paul.... a lot of information there. My 77 is not a CA truck and does not have the canister and evap system. I put on a new distributor and plug wires today, and capped all the unused vents. I had one on the carb that you mentioned, one on the vacuum amplifier, one on the PCV valve, one on the vacuum reservoir canister, and one on the ported vacuum switch. Not sure that capping them all is the correct thing to do, but guess I will find out. A few more minor things to do, and I hope to fire it up this weekend. Once running, I will do my best to adjust the idle, the choke, and set the timing. I will be ignoring the solenoid for now, and try to get back to it when all else is running. Still baffled where the solenoid gets power. But then, the choke I have is electric, and is not connected either. It is apparently run by a hot choke tube from the intake manifold. Maybe I need a power line from the alternator? Anyway, thanks to everyone for the help. I am sure I will be adding lots of questions as this project continues.

 

Yes, the electric chokes get their power from the White w/black stripe Stator wire off of the back of the alternator.
If your truck has an amp gauge (ammeter) rather than a BAT (or is it ALT?) warning lamp on the dash, then this is the only function that the stator wire has.
If you have one of the more rare trucks with the warning lamp, then the stator wire does double duty and runs to the "S" terminal on the voltage regulator, but has a branch that is spliced in and runs up to the choke.

Paul

 

One more item to add to the list. I will have to look to be sure, but I think I have the gauge. Probably a dumb question, but if I have the choke tube from the intake manifold, why the electric choke? Is it a back-up to the system or an assist?

 

Yes. They're all there to assist each other and to perhaps cover different aspects. And certainly to "cover" for the other one in the event of a failure.
There was also the hot air inlet right into the air cleaner to help the engine run better on cold days even before the choke was opened. Allowing for a quicker opening setting on the choke.

A choke that habitually stays on too long is not just an emissions issue, but can also be an engine life issue. Too much fuel being dumped into the intake for too long a period can accelerate wear on the piston rings and cylinder walls. So it behooved them to try to guarantee a reliably opening choke, while still maintaining a good running cold engine.
That's my very unscientific take on it anyway.

Paul

 

I know this is an old post but I came to it because I couldn't find where to plug in the solenoid either.

For what it's worth, I did find it... it was on completely the other side of the carb and split off from another bunch of wires just after it came through the firewall. Maybe that'll help someone!

 

You've probably found the wire long ago but just in case. On my 78 Bronco (built late 77) the wire comes from a connection in the harness at the firewall above the heater box. It runs down the top of the intake manifold and takes a left in front of the carburetor to connect to the solenoid.

 

I thought it was primarily a anti dieseling deal, but I've read of guys repurposing it to kick up with AC.

 

It depends on the application. Even the factory used them in both capacities at different times, and on different vehicles.

 

On engines with air conditioning, the solenoid in question is used to slightly push up the throttle at idle, in gear, when the a/c is turned on. On many engines, as has been previously mentioned, the solenoid is also used as an anti-dieseling device.