88 22r fuel pump return problem??

hope someone can help me here, 88 22r carbed,truck started losing power bucking and cuttin up like it was running outta fuel. checked site glass and it did seem kinda low so i put a new pump on, same thing, to keep this short i have so far found tht fuel pressure at the carb is 7-8 at an idle and fuel level is good. once you strt driving pressure slowly drops down to less than 2 lbs and if you get the hood up kwik enuff the level is way low. most of the fuel is being routed back to tank via the return line. have it running now by pinching off return line but tht eventually overfills carb of course. also tried another new pump just in case i got a bad one but nada. any suggestions guys??

Check the vent line to the carb.
Check the vent line to the tank.

Advance sells an aftermarket pressure regulator with five settings you could install in the return line. Are you sure they don't have a factory pressure regulator which is bad.

Sounds like a clogged fuel filter. Will flow enough gas at idle, but can't at the higher loads.

i have changed the fuel filter already,as far as the vents i have blown back thru carb and to cannister both seem to be open best i can figure the tank vents thru the cap and it seems fine too. i had already considered going with an aftermarket electric fuel pump and regulator but i would prefer to find the problem and fix it it cant be tht serious i wouldnt think is it possible tht the float is saturated? if so i wouldnt think the fuel level would be fine at an idle either. any more guesses?? thnx

The older 22R engines had a plastic spacer between the fuel pump and block. These have a habit of getting lost or broken. If you forgot the spacer the movement on the pump would change and the pump might not be putting out enough fuel. Its also possible the new pump is defective. Does the vent line come off the carb just above the fuel level if this is the case unless it is getting vacuum it would have to be the pump. Also check for a big dent in the fuel line.

Tank vents through the canister. Does the truck run differently with the cap off? Is the pick-up in the tank clogged by some floating debri?

...also tried another new pump just in case i got a bad one but nada. any suggestions guys??

I have found 22R's to be very finicky when it comes to the mechanical fuel pump. I once went thru a number of new aftermarket ones, and and old used stock pump was the cure.

The carb. on an 87 22R has a vent control valve on the side of the carb. where the return line attaches. I would check this for proper operation as the truck runs with the return line pinched. Apparently to much fuel is returned to the tank.

lets see here plastic spacer is definitly on the pump (bolts bottom out if you dont use it) the second new pump i installed ruptured the diaphragm after 2 days. ime guessin from the return being blocked. i have checked the vent/return system the way the haynes manual tells me to kinda vague though. i am ready to just install an adtermarket electric pump and be done with it. anyone know what the pressure rating should be for this setup? cant find it in the book anywhere.

Fuel pumps should always be tested on the vehicle. The larger line between the pump and tank is the suction side of the system and the smaller line, between the pump and carburetor or fuel injection pump is the pressure side. A leak in the pressure side would be apparent because of dripping fuel. A leak in the suction side is usually only apparent because of a reduced volume of fuel delivered to the pressure side.

Fuel System Pressure

For your 1988 Toyota Truck RN(4cyl)Truck 4WD:

Fuel System Pressure 2.8-4.3 PSI(Pounds per Square Inch)