osubucks1044

bought the truck not running. owner said he drove it home (when he bought it) 30 min to his house and it died a few times. got it home bombed around a bit and it would spit and sputter a bit then come out of it. then do it again and finally start, then eventually it did it and wouldnt start. hes not very mechanically inclined so wanted to sell it. i got it home and had it running in an hour, but only if you pour gas in the carb. " so maybe the mech. fuel pump was just ˟˟˟˟ting the bed and its not pumping anymore" i said. so i went and bought a new electric inline fuel pump- 4-7psi. got home hooked it up and took the line off the carb to make sure the pump was working and sure enough it poured out. so i hooked it up to the carb expecting it to start and run great. hit the starter and it fired up and ran for 3 seconds then died. long story short once in a while when i try to start it it will start and run for 3 seconds then die. only runs when u pour gas in carb.

so....

1 it runs, just not the correct way
2 theres fuel getting to carb and i can see butterfly getting wet when trying to start it.
3 WHY ISNT IT GETTING ENOUGH FUEL TO START AND RUN!?!?!

fuel cut solenoid?? anything else i should check? im at a loss! thanks in advance guys! love this site, its my bible for my three yotas!

osubucks1044

just confirmed the fuel cut sol. is getting power and it is clicking with keyed power! help!

slow-mo

Check the fuel level in the float bowl via the sight glass. The fuel needs to be in the middle.

Can I assume when you try to start it that you are pumping the gas pedal? If so, that could be why you are seeing fuel on the "butterfly" yet the engine not running. The main manual Accelerator Pump is working, when you pump the gas pedal, yet the idle circuit is not working correctly.

Check to see if the Idle Mixture screw has been tampered with. There is supposed to be a metal plug from the factory covering over the screw.






If there is no plug, then check how many turns it is by turning in the screw and counting the turns. That screw is supposed to be somewhere around, if I remember correctly, 2-1/2 turns out.

osubucks1044

What do you mean when you say "main accelerator pump" and "idle circuit"? I am not new to carburetors by an means but am new however to a vehicle carb, 22r to be specific, there is a lot more to one of these carbs then a dirt bike or snowmobile for instance! Haha thanks for the help and am looking forward to your and others response!

slow-mo

edit to add: just for general info, all of the names I'm using with capital letters is the same as what you'll see in the Toyota service manual.

The Toyota carburetor, made by Aisan, uses two Accelerator Pumps to inject fuel durning acceleration. The main pump is a full-time, manually controlled via a lever connected to the throttle valve. The secondary pump, the Auxiliary Acceleration Pump (AAP), is intake vacuum controled via a Bi-metal Vacuum Switch Valve (BVSV) which senses engine coolant. The AAP only functions on a cold engine. There have been some related rich running engines caused by a faulty AAP & BVSV, but that's a different story. Once the engine coolant reaches a certain temperature, the BVSV will turn off the AAP.

On a cold engine start-up, the driver would pump the gas pedal a few times. That causes the main Accelerator Pump (a full-time manual pump) to squirt fuel into the carburetor. The AAP does not function with the engine off.


The idle circuit is one of 5 fuel circiuts in the Aisan carburetor. I believe there's 5, I don't have the book in front of me right now.

1) idle speed circuit - controls the engine at idle
2) slow-speed circuit - controls engine at partial throttle
3) main circuit - controls engine above partial throttle
4) float circuit - controls fuel level in float bowl
5) power circuit - adds extra fuel during very high engine loads via the Power Valve/Power Piston

Actually, there's probably 6 circuits as the secondary barrel has a metering jet too. Anyways...





Since you can hear the Fuel Cut Solenoid clicking, indicating an opening & closing valve, I suspect there is something amiss within your idle circuit.

slow-mo

Oh, I forgot to mention, vacuum leaks.

If you have enough of a vacuum leak on the intake side (haha, that's redundant), it can prevent the engine from holding idle as well.

osubucks1044

Ok a vacuum leak seems easy enough to check for (look over the lines making sure there all connected and not cracked, I don't think any of the vacuum lines are hooked up wrong as the PO drove it home and around his house before it completely died so I don't think it's that, could be a cracked line though) but how would I check those circuits to make sure there functioning properly? Also I see you have diagrams, would you have any for the vacuum lines for future reference? Really appreciate the info!

slow-mo

There's really no way to check the individual fuel circuits. Basically, it's just a matter of fuel symptoms. If the engine has a symptom of _______, then check for _________. That's how the factory service manual is. However, some can be check like the two accelerator pumps as the rubber diaphragms are mounted externally to the carb.

Since there is no way to repair just one internal fuel circuit, you basically have to service the whole carburetor by doing a rebuild. It is then that one would tear it down and dip it in carburetor cleaner and that is supposed to clean all of the fuel passageways.



I don't have any vacuum lines schematics. Those pics I posted are from the Toyota carburetor manual.

junkyardog05

My truck did the same thing I put a new pump on it didn't help. There is a tube that runs from the fuel bowl to the top of the carb and when you hit the peddle it puts a small amount of fuel into the engine. The tube was stopped up on mine after unclogging it, the truck would start and run great.