Trollhole carb with carb cooling fan (1 Viewer)

[michaelharrisco]

I've chatted a bit with Marshall (think thats his name) from Trollhole about this, but he mentioned he doesn't have a wiring diagram so wondering if someone here can help/has experienced this.

1978 FJ40 with 2F, new Trollhole carb and OEM has a carb cooling fan.

Carb has been installed by a shop here in NC, but the wiring is odd on the cooling fan because now the fan runs anytime the truck is running and the fan shuts off when the truck is shut off. Trollhole mentioned his carb doesn't have the same solenoid as OEM that has the temp control to only kick on the fan after a certain temp, but his carb can be wired up to have the fan kick on everytime the truck is turned off and run for 20 min. I'd like to have that set up and redo what the shop did where it is running when the truck is running (defies the purpose of the cooling fan).

Does anyone have a pic of theirs installed with a carb cooling fan or have a sketch of a diagram of how to do right? I know it there is a wire that has to be grounded to make it kick on, but more confused about why the fan is running all the time and not when the truck is turned off.

I'll try to post a pic of current carb and wiring as best I can later tonight.

 

[AdamKFarmer]

I'm pretty sure the carb cooling fan runs of the thermo sensor that hangs on the EGR arm near the manifold. Has nothing to do with the carb (unless it's different betwen my '82 and your '78) there is a computer/relay under the dash that operates the timing for that thing. If you ground the sensor then it should kick on upon shutting the truck off and run for 30 mins each time.

 

[spotcruiser]

Yeah, the carb cooling fan circuit on a '78 is independent of the carb. The circuit (other than the internals of the controller/timer) is shown on a standard '78 wiring diagram.

 

[John Smith]

They only wire on your Trollhole, or OEM carb is for the fuel cutoff solenoid, which should have no connection to your carb fan whatsoever. If the shop that installed your carb tied it into the carb fan circuit they hooked it up incorrectly.

 

[michaelharrisco]

okay, this is good info...

I'm familiar with the control box, fuse and the motor itself. 5 years ago I got it working (just a bad fuse behind the dash). I always assumed it was indy of carb and just kicked on from thermo sensor somewhere. The shop also took off some of the EGR stuff so I wonder if they removed the thermo sensor and that caused it to stop working.

I'll take a picture and see if anyone can help point me in the right direction. I've only had the truck back a few days and glanced at the wiring.

 

[spotcruiser]

See bracket #187 and sender #85 in this SOR diagram. That's what a '78 had bolted to the outboard side of the exhaust manifold, in the vicinity of cyls. 4 and 5, for the carb cooling fan circuit. If you look on the exhaust manifold, you'll see a flat spot with two threaded holes for the sender bracket. Earlier trucks ('76 to ?) had them on a bracket above the intake manifold.

Here's a view off my '78.

 

[Fast Eddy]

Try unplugging the thermistor (sensor) and see what happens. To test it, place it in a pan of oil with an ohm meter across the terminals. The resistance should go down as it heats up.

FSM details here: fj40 carb cooling fan...do you run yours?

 

[michaelharrisco]

Try unplugging the thermistor (sensor) and see what happens. To test it, place it in a pan of oil with an ohm meter across the terminals. The resistance should go down as it heats up.

FSM details here: fj40 carb cooling fan...do you run yours?

There is some irony you sent me that link (I remeber starting that tread years ago).

Here are some pics of the carb area (top view). I just dropped it back off at the shop that installed the carb for some fine tuning. I won't be able to get back to this fan fix until this weekend so stay tuned.

I'll read through these diagrams and see what I can figure out.

I did notice there is a wire going to no where now with the new carb. Is that the wire troll hole carb needs grounding to make it work?

 

[65swb45]

If you're running desmogged with a header, and the carb and cooling system are working properly, you shouldn't need a fan.

 

[x463]

I have a 12/78 built truck with a functional fan. No wires to the carb for the cooling fan - only to the sensor by the manifold.

 

[michaelharrisco]

If you're running desmogged with a header, and the carb and cooling system are working properly, you shouldn't need a fan.

Ha...I was certain I'd eventually get that response. I hear ya...but I like for as much stuff on my truck to work as it should. Plus even with all this new gear installed, it is struggling a bit on hot cranks here in humid and 90 degree North Carolina so ever bit helps.

With all this feedback on the thread, I've concluded that the shop removed these parts when they put on the new headers because even before the new carb when I got it back that is when the cooling fan quit working.

I'm going to try to get the parts back from them and put this all back together.

 

[65swb45]

I hear you too. My conclusion is still a little different.

If you find that a cooling fan is useful, I would still not expend the energy to hook up fourty year old switches to it just because they're stock.

 

[tls3601]

Yes my system also desmogged has no connection to the carb, and cooling fan runs for like 5-10 minutes after shutting truck off but only sometimes on longer runs.

 

[Fast Eddy]

If you find that a cooling fan is useful, I would still not expend the energy to hook up fourty year old switches to it just because they're stock.

I would, and have done so twice.

The '76 cooling fan is even less useful as it just blows air around under the hood, not even necessarily right onto the carb. My PS pump is right in the way.

 

[Helipilot]

I have a '77 (10-76 mfg) and it does not have a cooling fan. No evidence it ever had one. Any thoughts?

I am the third owner and am doing a total frame off resto.

 

[GA Architect]

I have a '77 (10-76 mfg) and it does not have a cooling fan. No evidence it ever had one. Any thoughts?

I am the third owner and am doing a total frame off resto.

FWIW - My '77 FJ40 (12/76 mfg) didn't have the carb cooling fan either, and is the High Altitude version that was sold in Colorado Springs. Being the rig resides in the South now, I researched the carb cooling fans and their usefulness. I studied their wiring and how they worked. However, in order to install one, I either needed to relocate the windshield washer bottle or omit it. Thus I completely removed the bottle and installed the carb cooling fan. My carb fan functions exactly like the OEM version, but without the OEM parts. Albeit, my FJ40's windshield washer bottle resides on the parts shelf in my basement now.

If anyone cares to see the thread of my carb fan installation/wiring, > click here <.

 

[emac]

Albeit, my FJ40's windshield washer bottle resides on the parts shelf in my basement now.
.

If you want to sell the washer bottle, I am looking for one! Mine is cracked.

 

[michaelharrisco]

Picking this back up and hoping someone can address a related question.

I got the sensor back from the shop that put the new intake on. I think I'm going to be able to fix this now and get it back stock like it should be.

Looked last night and found where the mounting holes are on the intake for the bracket, but it doesn't look threaded.

Do the new intakes come with those holes "plugged" and you have to tap them to tread them on if you want that carb cooling fan mounted? I assume OEM these intakes don't have them since most FJ don't have the carb cooling fan.

Any feedback?

 

[Fast Eddy]

It seems to me that they'd all be tapped, but who knows. Tap 'em.

 

[Mace]

I wouldn't worry about it personally considering that you are no longer attached to the exhaust manifold (cast Iron exhaust manifold transfers heat to the carb after shut down).

But if you really want the carb fan to function, if the holes aren't tapped already, there's not a single issue with tapping them as long as you do it correctly.