FUNrunner87

My buddy has a 1st gen. It is a 79, and has a FACTORY Electric fuel pump in the tank. The pump stopped working randomly one afternoon after he pulled the truck up to his shed. After a few mins i found that There was a wire running from the fuse box under the dash all the way to the pump. The wire hadf been wrapped around one of the fuses. It was hacked together with 2 or 4 different wires. It had a buch a bare spots and had crud all over it. I replaced the whole wire. I ran it back to the saem fuse as before. The pump is now working great. However, when the pump is running it will flood the card to the point it looks like a little hot tub. The fuel will FILL the carb till in runs over. Its even coming out of the vents.

NOW, I know for a fact that the truck ran perfect 4weeks ago. The power wire has been run from the same fuse for a few years now. I bought the truck in 2006 and it was like that. We tryed swapping another 20r carb on, same problem. Can anyone shed some light on what maybe the cause??

swampfox

The float might be stuck. Try unhooking the power to the fuel pump,then if it is not soaked in gas start the engine and run the fuel bowl dry. After it is empty tap the bowl housing with a hammer handle or something that won't damage the carb . This should dislodge the float. The oil is probley contaminated with gas if it was flooded that bad, the oil should be changed before starting. If it works put some sea foam ,or other brand of fuel system cleaner in the tank to clean the carb out.

FUNrunner87

I had another 20r carb, we swapped it on and same thing. I will have him try to run it with out the pump hooked up though.

xxxtreme22r

entertain me for a second here, is there a pump on the head on the passenger side of the front of the head?

it would look like this:



Also what is the build date of the truck? You sure it's the original engine?

1978.08-1979.08 trucks had an electric pump whereas 1979.08-1980.08 trucks had a mechanical fuel pump.

It is possible that the P.O. either changed engines with one that has the mechanical fuel pump which was drawing it's fuel through the original electric fuel pump in the tank. Apon rehooking the electric pump up it is now sending too much fuel to the carb causing it to flood out.

It's possible the float is sticking, but since it was working properly before the rewire on the electric pump, I doubt that.

None of these models I believe actually had a fuel pressure regulator and it's all done within the fuel pump itself.

FUNrunner87

It is not the OE motor. That motor let go back last summer. I was running the OE carb though. The motor we bought is a 20r also. It does NOT have a place for the mechanical fuel pump. The old motor did have a place for one but was blocked off and distributer gear did not have a lobe for a mechanical fuel pump. BOTH motors ran great with the pump wiresd to the fuse box, but now it is dumping fuel.

How does the fuel return work on that style truck? I cant find a diagram for the 79 fuel pump anywhere.. does anyone know where I can find one? I have Both haynes and a chilton, and I have looked at NCTTORA.

xxxtreme22r

I'm not sure on the trucks with the electrical pump. It's all internal to the mechanical pump, I didn't see a fuel regulator looking through the drawings for the 79's, but I could be wrong. Is it possible that you had the fuel lines off and got 1 or 2 mixed up?

FUNrunner87

There is a Banjo bolt that gets fuel from a small plastic cup looking thing that is mounted on the passenger fender well. The cup thing gets fuel from a line coming from the tank.

The is another hose that runs off of the front (of truck) left side of the carb. That goes to what I beleive is the charcol canister. No other lines that i know of go to the tank.

xxxtreme22r

sounds like there is no return line on the truck then. That cup thing sounds like the fuel filter.

here's the diagrams for the 1978.08-1979.08 trucks:

FUNrunner87

holy H*&^!! where did you find that? can you email it to me?

I guess what you are saying it that there should be a return line correct??

FUNrunner87

So its kind of hard to see, but does the return line run from the middle of the tank up to the canister? The hose that runs from the front left side of the carb to the canister is the return line correct?

If so with that line removed from the carb it still over flows.

xxxtreme22r

that's not the return line, that's just a vent. The canister is just to eliminate emissions vapors from the fuel tank. Does not appear there is supposed to be a return line on these. The mechanical pump trucks have 3 lines not just two like the electric pump trucks do.

lol. yYu can have the photos, right click save as on the photos. But I get them from www.toyotapartszone.com and then just put em in my photobucket account so I am not linking them directly from there.

FUNrunner87

Ok so make sure i have this right. Once line is from the pump bringing the fuel up the cup (filter) thing. the 2nd line is a vent running from the middle of the gas tank to the canister.

1. So how does the pump know how much fuel to pump?

2. What happends to the fuel that the Carb doesnt us?


seams like it would need psi switch to limit the amount of fuel that is pumped up to the carb..


Im still lost.

xxxtreme22r

not sure, I can't really accurately answer that, but since it shows a resister, I wonder if the voltage and thus the speed of the fuel pump is somehow controlled by the ECU. But that's just speculation on my part. Unless you or someone else sees it, there is no pressure regulator anywhere in that system.

FUNrunner87

hmm why would a Carb truck have a computer? I didnt think they did?

I wonder where that resistor is located?

Anyone else have anything to add?

xxxtreme22r

89550 COMPUTER ASSY, EMISSION CONTROL (NOT AVAILABLE) 89550-35090 1978.08-1979.08 RN32, 42

89550 COMPUTER ASSY, EMISSION CONTROL (NOT AVAILABLE) 89550-35100 1978.08-1979.08 RN3#, 42.. USA CALIFORNIA SPEC

FUNrunner87

ok.... ill do some more looking. I feel like im on a wild goose chace.


That manual is for an 85 truck and 4runner... Is that going to apply for a 79??

xxxtreme22r

scratch that FSM download link I added, it's just gonna confuse you. It's mainly for the 85, but ttora said 79-85 which it's quite a bit different.

FUNrunner87

I have looked threw the manual before. I just dont see anything 20r related. There is a TON of stuff for the 22r and 22re.. but How much 22r stuff works for the 20r?

FUNrunner87

bump, anyone got anything that might help?