Setting a 12HT injection Pump (1 Viewer)

[Gengis]

Hi All
I have just rebuilt a 12HT, and have set it up for bench running in the garage. I have hooked up the fuel supply and cooling via a suspended bucket and it starts and runs quite well.

Now I don't want to run her for too long without being able to load it , but I can tell that it is running rich and it puffs a gob of smoke out when I open the throttle . I can see that the previous owners has messed with the IP settings and there are no paint marks or wire ties left. I also need to sell it off now and don't want to spend more by taking the pump in for setting. They will just want to rebuild it anyway, which i don't believe it needs.
What are the rules of thumb that I can use to set the fuel screws, I believe that there are more than one ( normal and slow running???).
I would appriciate a little help on this one if possible.

 

[relaxedcruiser]

Hi Gengis, difficult to tell you a rule of thumb for the settings of the fuel srews. There are two main screws which are easy accessible.
The off boost screw (at the rear of the boost compensator housing) causes a lot of smoke when screwed to far in. you can try to turn it out and see if the combustion is less rich / less smoking when you are accelarate from idle. You can´t adjust the max. or on boost screw ( at the front of the top IP housing next to no. 6 delivery valve ) without load. But if tinkered with - it causes more smoke on startup as the enginge starts with the fuel rack on it´s max. position.
What I can do is measure how far my screws are out of the housing - this would be roughly a point to start with on your IP. Not tonight though.
Anyway - it is way easier to adjust both settings on some empty stretch of road once you are good to go.
There is also the star wheel inside the boost compensator housing - this srew is setting the preload of a spring which is behind the diaphragm which again is moved by the increasing / decreasing boost pressure according to the engine load. A bit more unlikely that the PO has tinkered here as you need to get the pump or inlet manifold out to access it.
Would be very good though to check the timing of the pump, you can do that while the engine is out.
Will measure the screw settings this weekend for you.

 

[Gengis]

Thank you

This is my setup:
Which is the off boost compensator? Top or bottom screw? If it's the top screw, then what is the bottom one for. And where do i connect the little pipe on the top actuator to??

Is this the fuel screw?

Is this the correct place for the oil pressure pickup or should it be in the hole to the left and lower. My oil pressure is quite high, but within specks.

 

[relaxedcruiser]

Thank you
View attachment 2381775


This is my setup:
Which is the off boost compensator? Top or bottom screw? If it's the top screw, then what is the bottom one for. And where do i connect the little pipe on the top actuator to??

The top one - and it´s the boost compensator diaphragm behind it, this screw allows you to adjust the fuel delivered before the boost comes up - with the cap nut and copper washer off I measured here 8.8 mm from the end towards the locknut. The port on the boost compensator is connected with an little hose to a port just before the butterfly shut off valve actually in the cross pipe coming from the turbo. The boost pressure is then working on that diaphragm to alter the fuel delivery according to the boost. Your cross pipe looks different is the engine out of a coaster ?
I don´t know exactly what the bottom screw is for, but I believe it is setting a preload on a spring "dampening" the return to idle moment.
I have that on too but it is not mentioned in my workshop manual which is from 1986, it seems that this adjustment point was added afterwards. Maybe someone here has a newer Manual and can tell us exactly what it is for ?

View attachment 2381776

Is this the fuel screw?

You are dead right - this is the max. fuel screw - you can adjust the amount of fuel which is delivered with boost - it sits under the cap nut. With the cap nut and copper washer off I measured here 6.1 mm from the end of the adjusting screw to the locknut.
View attachment 2381777

Is this the correct place for the oil pressure pickup or should it be in the hole to the left and lower. My oil pressure is quite high, but within specks.

Yep that´s the right point for the oil pressure pick up - normally the sender unit for the stock inside gauge is located there. I put a tee in there to be able to run that and an aftermarket gauge. I´ts normal that you have a high oil pressure - because you oil is cold - it will drop once your engine has run for a wee while and the oil getting thinner.

View attachment 2381779
There is a good write up here :1987 Toyota Landcruiser HJ61 12H-T | landcruiser | Tim Law

Happy tinkering !

Tell us whats going on, cheers..

 

[Gengis]

Thank you so much.
Yes, it comes out of a Coaster.
I will have a go at the measurements tomorrow.

I had a quick peep at the diaphram on the boost compensator. It looked in tact, but I could not extract it ( and the rod). Is this normal? Is there a trick or should i just leave it well alone.
I have a good found a good diagram for the vac and boost tubing tubing so Ill get that sorted.

G

 

[Nz Nath]

It's probably hooked behind something, and would require further disassembly to remove and refit. To test if it leaks use a bicycle pump on the boost input. Use one with a gauge and see how long it holds pressure for.

If the boost comp bolts directly on to the full load stop housing then it probably hooks behind the sliding plate directly, or even runs through it. On the 13bt, the back of the rod is a bolt head that hooks behind a lever. That lever limits the travel of the sliding plate(full load stop). When the rod pushes forwards under boost, the lever can move further allowing more sliding plate travel, and more fuel.

 

[relaxedcruiser]

Good write up Nz Nath, It´s probably quite similar with the 12ht setup.
It´s easy to take out (and fit back) when the top inspection cover is off - as you can see what you are doing. But to get theat off the inlet manifold or entire pump has to come off.
As Nz Nath was saying it is a good idea to test whether it is holding the pressure. You do not need to kake it off for that.
I have made myself a simple test setup using a cheap normal syringe which is working perfectly as a pump and a simple gauge from a pneumatic shop and a one way valve which I found somewhere in the original vac pipe setup on my 12ht. With that I was able to test the boost compensator for leaks and also for the stroke it would do according to the pressure applied.
I think that the WSM is wrong here as I never could get the stroke which is mentioned in the WSM. Thought my old diaphragm was to hard - fitted a new one but still couldn´t get the stroke. It´s working perfectly though. Just had the WSM page at hand....

 

[Nz Nath]

I'm just able to get my full load housing cover off in situ on my 13bt. Needed to make up a custom spanner from a cut down 10mm socket. I think the governor and pump are almost identical between 13bt and 12ht, just the ancillaries that are different (hac etc).

You can see in the diagram that the back of the boost comp has a bolt screwed into the central rod, with a lock nut to secure it. I unscrewed my bolt till there were only about 3 turns holding it into the rod. This translated into about 5mm more movement of the sliding plate(full load stopper). However this didn't seem to result in any more fuel.

I've since pulled the sliding plate off and shoved a cheap endoscope camera in there to see what's going on. I also ran the truck with the sliding plate removed, just to verify there's no more fueling available. On the 13bt pump you're able to get full rack travel with just the normal adjustments. The shackle that attaches to the fuel rack pretty much fouls on the pump housing at full travel so there's definitely no more rack travel available. If there's any more fueling available in these pumps it can only be from adjusting where the pump elements are synched to the rack.

 

[EdenSeen]

Hi there!

Is there such a thing as a 12H-T rebuild/reconditioning kit?

Any link?

Thanks