3B Rotary Injector Pump Questions - Timer Cover Removal (1 Viewer)

[Hugh Heifer]

I have a 1988 BJ73 w a 3B. It is equipped with rotary injector pump and it has developed a bit of a diesel leak at the pump.
It appears to be coming from the Timer Cover.

1. Can I safely remove the outboard Timer Cover in situ and replace the o-ring inside?
2. If this is okay, is it even possible to get the inboard side cover off in situ to replace that o-ring as well?

Lastly, my pump does not have HAC or ACSD but it does have a vacuum unit on the back side. I am not seeing this in the FSM. Mine does not have a hose connected to the inlet on said vacuum unit. Should there be one and to where? And what is this for? Maybe someone can get me to the right page in the FSM on this.

 

[OGBeno]

The vacuum unit is for AC idle up, Chris.

 

[Hugh Heifer]

The vacuum unit is for AC idle up, Chris.

Cool. Thanks Onur. I guess the FSM is calling it an "Actuator" in the AC section. Looks like I should have a hose to it then. The "renter" of this truck disconnected the AC for some reason before we repossessed it. That is on the list to try to get going again.

 

[OGBeno]

Cool. Thanks Onur. I guess the FSM is calling it an "Actuator" in the AC section. Looks like I should have a hose to it then. The "renter" of this truck disconnected the AC for some reason before we repossessed it. That is on the list to try to get going again.

Technically, it does "actuate" the AC idle up function.

 

[Eurasiaoverland]

I have a 1988 BJ73 w a 3B. It is equipped with rotary injector pump and it has developed a bit of a diesel leak at the pump.
It appears to be coming from the Timer Cover.
View attachment 3827441
1. Can I safely remove the outboard Timer Cover in situ and replace the o-ring inside?
2. If this is okay, is it even possible to get the inboard side cover off in situ to replace that o-ring as well?

Lastly, my pump does not have HAC or ACSD but it does have a vacuum unit on the back side. I am not seeing this in the FSM. Mine does not have a hose connected to the inlet on said vacuum unit. Should there be one and to where? And what is this for? Maybe someone can get me to the right page in the FSM on this.
View attachment 3827442

There are three O-rings associated with the lower timer piston and its two covers.

-The inboard O-ring just seals a blanking plate and can be changed without recalibrating the pump. You will need to take the pump off but this is very easy on a B engine - just undo the 4 supply pipes, and it's a matter of 2 bolts and 2 nuts holding the pump in. Just be sure to align it the same way it came off.
-The outboard O-ring sealing the timer cover to the body - this can be changed in situ and should not need recalibration.
-The O ring on the timer adjuster nut (which is the black threaded piece coming out of the timer cover). This is the most likely O-ring to leak, but if you change this you should really get the pump recalibrated. If you are very careful and get the nut back in exactly the same position you should be OK, but it's an unorthodox procedure.

The vacuum actuator is both a diaphragm and an actuator arm which bumps the idle up by moving the governor adjuster (accelerator) arm. It should be connected to a VSV by a narrow vacuum tube.

 

[Hugh Heifer]

There are three O-rings associated with the lower timer piston and its two covers.

-The inboard O-ring just seals a blanking plate and can be changed without recalibrating the pump. You will need to take the pump off but this is very easy on a B engine - just undo the 4 supply pipes, and it's a matter of 2 bolts and 2 nuts holding the pump in. Just be sure to align it the same way it came off.
-The outboard O-ring sealing the timer cover to the body - this can be changed in situ and should not need recalibration.
-The O ring on the timer adjuster nut (which is the black threaded piece coming out of the timer cover). This is the most likely O-ring to leak, but if you change this you should really get the pump recalibrated. If you are very careful and get the nut back in exactly the same position you should be OK, but it's an unorthodox procedure.

The vacuum actuator is both a diaphragm and an actuator arm which bumps the idle up by moving the governor adjuster (accelerator) arm. It should be connected to a VSV by a narrow vacuum tube.

Excellent info. I appreciate the response.

 

[Eurasiaoverland]

Out of interest, is that an old-type 3B (with a rounded valve cover) or a 3BII with a flat-topped valve cover? There seems to be blue paint on the block but I don't see connections to the vacuum pump and the block looks more like the older casting to me.

 

[Eurasiaoverland]

Ah, looking again I see that it's an old 3B. I assume then that it's a JDM BJ73? I've never seen one with an old 3B and rotary pump, good to know they exist

 

[Hugh Heifer]

Ah, looking again I see that it's an old 3B. I assume then that it's a JDM BJ73? I've never seen one with an old 3B and rotary pump, good to know they exist

Yep. JDM RHD.

 

[Hugh Heifer]

Cleaned off the pump today and ran the truck. Could not duplicate the leak. I guess it is gonna be one of those things

I do see why it would be impossible to access the inboard plate with the pump in the truck. There is 0 room to get back there.

I also found where the vacuum line that was disconnected from the actuator had hidden itself which helped me find the AC VSV. It was nowhere near where I expected to find it.

 

[Eurasiaoverland]

Could I trouble you for a photo of how your vacuum line is routed from the VSV to the actuator on the injection pump?

With age the rubber O-rings inevitable dry out and slowly start to leak, so it's best to have the pump fully resealed. But this can be expensive as the recalibration needs to be done by a professional diesel lab. You can also try replacing certain O-rings, or just live with the odd drip of diesel.