I have been musing about what I "think" may be a problem with my neighbor's '86 SWB. Here's some background:

Stock '86 2.6, but with a new casting Clearwater head (mechanical lifters and all). Rebuilt carb from Guaranteed Carburetors. Truck runs perfectly when first started but absolutely dies as soon as it warms up and is near impossible to restart. I suspect that the choke is not opening. This has come to me at 4 a.m., so I'm not in a position to go outside and check this out. I tend to type to think sometimes.

For the uninitiated, the 86-earlier carbs on the 2.6 is non-electric and uses coolant flowing through two small hoses, one of which connects to the cooling system on the engine side and one that goes to the manifold base, just like the 87+ models. I seem to remember that Clearwater MAY have eliminated the coolant passage that would allow coolant to complete that loop (in their infinite wisdom). If so, this choke would never open. I'm not too worried about the carburetor base not getting coolant flow, but how could we restore the coolant flow through the choke portion of this system? I am not interested in retrofitting an electric choke.

I "think" the coolant feed comes off the engine, not the coolant pipe that returns back to the water pump (a return line, if memory serves). It's supposed to feed through the choke fitting, flow through the carb base and return via the head, but maybe I have that flow direction messed up. In any case, I need for that fitting on the choke to have flow. How can I do it? Put a tee in the heater hose that leads out of the heater core and connects to the metal pipe and re-route the carb base fitting like the '87+ models have it?

I'd like to stay as close to stock as possible. It HAS to pass emissions. And again, I'm not interested in retrofitting an electric choke. And I'm not even sure this is the problem - yet.

Any ideas?

John B.

So, I did get something a bit backward in the above post. Typically, Coolant feed comes off the engine after flowing from the water pump, through the head, then into the carb base, then on to the choke, returning to the system via the metal water pipe. So, what I'm NOT getting here is feed to the carb base, therefore no feed to the choke fitting. Something's coming to me here: There's a plug in the thermostat housing. I could possibly remove that plug and affix a fitting there and run a hose to the choke to provide feed BUT there wouldn't be any flow through that hose until the thermostat opened, therefore it still probably wouldn't flow in time to open the choke before the truck died.

I could use the heater feed hose and attach a tee there, maybe a tee from a Prestone flush and fill kit with the threaded fitting so I could attach a screw-on fitting with an appropriate-sized barb (like you might use in a drip-style irrigation system) to attach to one side of the choke fitting, providing coolant flow even before the thermostat opens. Anybody see where I'm headed here? Don't say "disaster," please!

John B.

I still had the flow wrong. The choke is fed off the same place as the heater. There's a tee there, with the heater feed hose and a smaller hose that goes to the choke. After the choke, a hose feeds the carb base. From there it exits the intake manifold and enters the metal tube around the back of the engine and returns to the water pump. So, it wouldn't really matter if the small passage between cylinders three and four was eliminated by Clearwater, since most of the coolant makes its circuit independently of that anyway. Dang.

It's almost light enough to see outside so I'll go take a look at the choke with the air cleaner lid off. Having the choke remain closed after warm-up would almost be too easy now, it seems.

Any other ideas?

John B.

Nope. The hoses get warm as the engine idles on the fast cam setting on the carb and the choke gradually opens with movement of the throttle. Then the truck abruptly dies. Blip the throttle at that point and you can hear fuel squirting into the engine. It's getting fuel. If I take the coil wire off and crank the engine, I get crazy spark jumping around.

This mystifies me, but it's starting to look electrical again. What would just cut the darn thing off? I mean, it runs so well at first...

John B.

Sent you a text but I'll post it here for group knowledge.

If the carb isnt from that truck the choke may need to be adjusted. this is done so by breaking loose the three screws on the retaining flange for the coolant section, you wont lose any coolant and you will see a series of 5 dash marks on the top, carb side and one detent cirlce on the coolant choke side, it's designed to be adjusted within the small range but I've had to go an entire rotation before (at which case you'll need to pop the coolant lines off for a minute and will lose coolant)

The second thing is the make sure that choke butterfly is moving FREELY and by freely I mean it should move if you touch it, no pressure needed to push the butterfly open if there's any resistance at all, you've got some gummed up varnish to clean. So if there's resistance, expect to spend the day cleaning your shaft.

But hey, isnt that what sundays are for? <img src="/forums/images/graemlins/smile.gif" alt="" />

Thanks A.M. It moves freely. This is a fresh rebuild for this year/series (85-86) from Guaranteed Carburetors. It's clean, clean. The choke is opening as the engine warms. It should continue to run but it cuts right off, and I mean RIGHT off.

Could it be that I have a bad ECU, as in when the engine exits closed loop/warm-up and hands off to the ECU, it isn't doing its job and cuts the electrical? I have a spare from my other '86, but it is an auto, not sure if that makes any difference, but I'm not using it and it used to work back when I had a 2.6 in it. Should I try that?

John B.

Now we're getting into the electrics of that carb and that's where my knowledge ends, you saw my solution, pitch it for a mechanical carb <img src="/forums/images/graemlins/lol.gif" alt="" /> I dont even have an ecu.

But, that said, if it's cutting power, once it's warmed check the fuel cut solenoid to see if it has voltage, it should remain hot to allow fuel to keep flowing. If it's a dead wire with the key on, problem found, kinda... then you'll need to diagnose why its doing that.

How long does it have to sit before it will start back up?

I have that spare carb with all it's electrics and a spare gadget box, you're welcome to all of it.

I too have a spare 87+ carb and a device box. I don't want to use it either.

I "could" check that solenoid. I "could" swap in the other ECU. I'll think on which would be quicker and easier. It's cold out there (for this AZ-acclimated) guy!

Grrr, I want this thing to RUN! I need to move on to my '95.

John B.

checking the solenoid will only require a test light and about 2 minutes, do it around noon when it's warmest out. <img src="/forums/images/graemlins/nana.gif" alt="" />

If it's still getting fuel at this point when it dies, wouldn't that indicate the solenoid is working properly?

Like I said when I got my carb, I had to adjust it just so I could the truck started. So maybe when it idles down it's not getting enough air/fuel?

Did you forget any connections, either vacuum or electrical, to the carb or any where else while you've worked on this thing?

Just throwing out a couple ideas for you. Hope this helps.