LJ78 Prado fuel issues

[JMac1969]

We have a 91 RHD Prado that we cannot get to start, we are not getting fuel to the engine compartment. I am told that it should have a Lift pump in the Tank, however we cannot find any drawings or paperwork to substantiation that. We have scanned the Parts pages right from Japan, and none of them show a Lift pump anywhere, besides the injection pump. We have followed the fuel lines from the tank to the Injector pump and the Fuel filter and have not found the pump. Can here confirm as too where this pump might be? Whether we need to drop this tank out?

 

[CRSWA]

There's a priming pump on top of the fuel filter. That should be capable of pulling fuel from the tank to the injector pump. Push up and down on the black knob on top of the fuel filter until it gets hard to push. Then try starting.

 

[JMac1969]

Ok so that is great but that doesnt help us with the fuel pump question, where is the lift pump? is there one?

 

[AirheadNut]

There isn’t a lift pump, just the priming pump on the fuel filter and the injection pump. It sounds to me like either an injection pump issue, an air leak in one of the fuel lines, or a clogged pickup screen in the tank.

 

[coldtaco]

No lift pump

 

[JMac1969]

There isn’t a lift pump, just the priming pump on the fuel filter and the injection pump. It sounds to me like either an injection pump issue, an air leak in one of the fuel lines, or a clogged pickup screen in the tank.

Thank you Airheadnut, That is what we needed to know, we primed the filter with a turkey baster until we could not push the pump down, then released the injector collars and cranked the engine till fuel pissed out, by the time they all leaked out and got tightened, it took us about 10 revolutions of the motor and it was running out of a make shift fuel tank, that we held in our hand. Sat and idled for a good 15 mins. Thanks again for the help.

 

[roscoFJ73]

We have scanned the Parts pages right from Japan, and none of them show a Lift pump anywhere,

Its a rotary pump and they have a vane pump inside that draws the fuel to the pump. It actually can draw about 4 times more than the engine needs with the excess being used to cool the injection pump. When the pump is full , a bypass valve opens and the excess is sent back to the tank where it can cool.

 

[JMac1969]

Thank you to everyone for your help. RoscoFJ73 where is the rotary pump? is it inline or is it sistered to the Injection pump?

 

[roscoFJ73]

It is a rotary fuel injection pump you have. An American invented them in the 1930s? Instead of having 4,6 or 8 small cylinders and pistons, it uses a single plunger to charge all the injectors. It is lighter and uses less parts than an inline pump and is supposedly capable of higher rpm speeds. They tend to run hotter , so they really need excess fuel to cool them
At the other end from the injector lines , there is a rotor with 4 vanes connected to the main shaft and the plunger at the other end.
I call the vane pump the low pressure end, it keeps the pump full of fuel so the high pressure end (injector head) can compress it and send it to the injectors
The Denso rotary pump is basically a Bosch design. Its very common on other makes like VW.

The speaker is a bit hard to understand but his working diagram offers a good explanation.

 

[roscoFJ73]

This is the vane pump showing its rotor and vanes. As you can see , the vanes can slide back and forth as the rotor runs on its elongated cycle. This is a VW pump but it would identical to yours except in size, although it would be close in that as well for LJ78