I have an '87 pickup, 22R motor. I had a problem for a while with my fuel system, took down the tank and cleaned out the sludge, (9 years sitting) no tank rust, blew out lines, changed fuel strainer and fuel filter, new fuel pump, all is well there. I changed the carburetor because old one was gummed up and I had to get it outta where it was fast, so I threw on one I had (also from an '87) and drove it ten miles to my house. Since then I'd driven it another ~20 ish miles, that plus how much it's idled it burned through about 35 gallons of gas. And then one day it quit and didn't start. The float glass was empty, low pressure on the fuel pump, so I figured "f- it, I'll redo everything." So cleaned the tank and all that other stuff, another new fuel pump, (I have 3 new ones and one 22R, why not?) And I adjusted the float. After float adjustment it was a little lean, less than 1/8" from the center of the float glass, and it started up as if it were flooded, low speed, smoke until it got it all burned out, then ran fine. I turned the idle screw all the way out and it didn't die, but the idle went from around 3k to about 900. I drove it for about a half hour, took it up to 40+ MPH, drove it through mud and all that fun stuff, and after that it just kinda jerked and quit. Truck wouldn't start, float glass was empty. This has happened a few times. To get the truck running again I have to take the whole carb apart and retune everything, and again it quits after about a half hour. I'm stumped.

 

Sounds like vapor lock right up to the " I have to take it all apart and retune ". Does the carb have a cmh that is malfunctioning? Is it too hot to touch? Have you found any possible cause during all the dis and re assembly?

 

It does get a bit hot, yes. What's the CMH? It often sounds like it backfires into the carb at times. Started doing that after I'd driven it for awhile. I've had that happen before though on my '83 and it still worked. No cause found in disassembly.

 

CMH is the cold mixture heater.
"To reduce cold engine emmisions and improve drivability, the intake riser is heated during cold engine operation to accelerate vaporization of the liquid fuel."

I don't have a reference picture. It's a single wire hook up to the carb/manifold lower area. At operating temps, above 135, it should have no voltage reading.

The other heater coil is for the choke opener and it should be warm.

 

If it has a voltage reading, what do I do?

 

If you have voltage at operating temp, check the components.
Diagnostics start on EC-73.
Temp switch EC-31.

 

I got it all good. 'twas the solenoid on the side of the bowl.

 

Great to hear what the problem was. Thanks, It might help someone else out in the future.

 

I seem to have spoken too soon

 

Sort of but not really. You fixed the CMH running 24/7 problem that is progress

I don't think the carb heater has enough "umpf" to heat up the carb a lot but it's worth checking it's not malfunctioning. This one differs a bit from the CMH, as it IS always on but shouldn't get super hot.


Just a shot in the dark, pop the fuel cap off next time it dies and see if it restarts or reprimes the float bowl at least. If it sucks in air then your tank vents aren't working and the fuel pump is trying to suck the whole tank thru the line =)

 

What would my tank vents be

 

They pull in the fresh air thru the gas cap vent.

 

Inspected the cap, it all checks out as working. (Glad, it's original Toyota, has factory logo and all) Tried it without cap anyway, problem didn't change.

On a side note, the image above says "absorbed into the canister" several times. Is this the charcoal canister? I've never understood what it's there for.

 

Correct. The charcoal canister(s) capture the fuel that evaporates. They are prone to clogging, which makes them leak, you'll tend to smell fuel constantly when they fail with them being located right next to the cabin fresh air intakes..

 

Ok so the tank is not at vacuum. still assuming the lines and filter are clean. The next stop is the fuel pump, which is a replacement already. So now we're back to the carburetor... With it's empty float bowl. There is a vent for the bowl, so it can push out air and fill. If this is not functioning correctly you'll get a pressure build up, air is infinitely compressible, which the pump cant handle if it's return is restricted and it will lockup when done by hand such as in the FSM tests. Now with the pump mounted to the engine it's subjected to much greater forces on that arm and I would expect some damage to occur, Like a blown seal or bend arm, which reduces the pumping capability and makes the symptoms appear faster than they did the first time..

You could use a hand pump and get a pressure reading of what it takes to flow thru the system upstream/downstream of the pump. You can use a fuel pressure gauge after the pump and monitor for a pressure change while its running, if there is a restriction the pressure will climb.

Someone maybe knows what kind of flow rate you should have, but it's not me, and it's not as easy to check on a mechanical pump.

 

It's that solenoid on the side, no? Looks like a cylinder. I feel as though that'd be the vent. I replaced that. The new one I put on opens and closes, if I hook it up to power it can't close itself but closes with a bit of help. I thought it's supposed to behave as such, is it not?

 

Ovco is part of the evap system, I was under the impression there was a vent passage for the float chamber but I can't find the reference again.

We did kind of skip over some basics because you said it had all been replaced cleaned ect. Primarily where along the route does the fuel stop when it's not filling the float bowl and is it a complete blockage or just a low volume problem. If the tank isn't a virgin it's worth checking the pickup tube filter, even if it is brand new it's worth checking you didn't misplace a rag. Stragglers breaking loose in a refurbished fuel line plugged up the new filter. All those sorts of things, even debris from cinching up compression fitting can clog the opening in a banjo bolt for example.

 

After it dies, I can take off the line between the carb and fuel pump, and it sprays gas everywhere.

 

Nevermind

 

Okay so there's gas everywhere. I have confirmed the fuel line is clean. Fuel pump not bent. What do?