Thread: 4BD1 injector pump question

no it doesnt.

if you think of that lever as the one that tells the governor what RPMS you want the engie to hit and hold you're on the right track.

Ok so that has confused my understanding of how it works.

I thought that the two ajustment screws on the accelerator were for max and min rpm, which would make the accelerator pedal more of an rpm pedal.

So does the lever on side move according to how far from the rpm you want the engine actually is? So that stop is not really a max fuel adjustment? If it isn't what is it actually controlling.

Sorry about all the questions.

Dan.

dont apologise for asking questions, asking questions shows interest, interested people tend to learn.

that lever doesnt directly control the amount of fuel.

the injector pump has a govenor in it,which via springs and linkages controls the fuel rack which controlls the spill ports on the plungers which controls the amount of fuel.

The lever that the accelerator linkage controls changes the pressure on the springs on one side of the governor This pressure makes the fuel rack open increasing the amount of fuel going into the engine if the engine makes more power than is required by the current load it speeds up. the governor has wieghts that spin the faster the governor goes the more it wants to pull the fuel rack towards less fuel. At some point these forces balance out and the fuel rack stops moving and constant engine speed is achieved.

the fuel cut off lever bypasses all of this and manually pulls the rack to the no fuel position.


does that help?

The full load set bolt on the side of the governor controls how far the U shaped lever can pivot - see 1st pic.

The sensor lever pivots from the U shaped lever and the fork at the top of the sensor lever engages on a pin from the control rack - see 2nd and 7th pic.

As the control rack moves, to change fuel delivery, it causes the sensor lever to pivot on the U shaped lever. The amount that the sensor lever can pivot is controlled by tip at the bottom contacting the torque cam - see 3rd pic.

But the pivot for the sensor lever is on the U shaped lever so the position of the U shaped lever controls how far the control rack can move in the fuel increase direction. So that is what the full load set bolt limits.

As the pump rotates faster (1/2 engine rpm) the flyweights (see 7th pic) move out and cause the tension lever to pivot against the governor spring - see 7th pic.

As the tension lever pivots it moves the control rack, via the guide lever and floating lever - see 4th pic. This increases fuel delivery as engine speed increases.

The tension lever also rotates the torque cam via a spring - see 3rd pic.

Thus the shape of the torque cam controls the maximum fuel delivery rate at different engine speeds (via the sensor lever, U shape lever and full load set bolt).

There is more to the governor than the above, but you were only asking about the full load set lever (1st pic).

Originally Posted by Blknight.aus

...

The lever that the accelerator linkage controls changes the pressure on the springs on one side of the governor ...

Not strictly correct.

The accelerator linkage controls the position of the floating lever - see 4th and 5th pic above.

BTW those diagrams were taken from the Isuzu service manual for the injection pump.

Edit: to correct pic numbers for floating lever.

bush65, you are very knowledegable there is no denying that, you seem to have a working knowledge of just about every thing to do with vehicles and trucks. But I think Blacknights description was great and was being delivered to people that have limited knowledge on this subject.

Your description is great for those of us that have mechanical trades, but I think Blacknight was just keeping it simple.

actually I pooched it, I read the original post and having just done the same set of adjustments on a FFR that wasnt making full revs thought he was talking about the control arm stops.

MY description vaguely describes how the throttle input controls the fuel injection quantity.

IF he was talking about the setscew further down the side of the casing that's the one that influences the agression and overall controlled travel of the movement of the rack

Dave you aren't making defence machanics look good mate