# Turning up the fuel on a rotary distributor pump



## Coondle (Aug 28, 2013)

My Case 1490 had an extreemly hard life before I rescued it. A bit like those rescue horse places.

I bought it really cheap. It had 4 brand new R1 tractor tyres. Why someone would fit 4 new tyres to such an abused tractor is beyond me. That and the front end loader plus 4wd sold me.

It had no steering (the PS pump reservoir was empty. $60 in PS ram seals (it is a double ended ram) fixed that.

No brakes except for a pipe extension on the hand brake. Adjusted the brakes and $300 for a new disc brake slave cylinder from the UK,

No clutch. Proper mineral oil (yes it has mineral oil in the clutch and brake master cylinders) and a master cylinder kit plus $800 clutch kit. The pto clutch plate was brand new with the manufacturer's label still on it.

Fill transmission with oil.

Weld up the cracks in the loader arms.

Ignore the rough/rusted tinwork and forget the bonnet and I had a backup 85hp 4wd tractor.

Put it to work, and was very disappointed......... no pull, would not even match a 50 hp tractor I have.

No smoke, no matter how hard I tried, the governor was working, and given that no black smoke I assumed the turbo was working too, so it seemed to me that there was insufficient fuel. So how to get more fuel to it?.

The tractor has a CAV rotary pump on the left side of the motor.

Now to turn up the fuel and if you do this, I am not responsible for your motor.

In any event do not turn fuel up more than 3 turns and only one at a time to make sure you are not overfuelling, evidenced by black smoke.

Tools needed:

2 x 8 mm combination ring/open end spanners, one to be modified one to use to start and finish.

Pocket knife with a 3 inch blade.

Piece of thin but strong wire.

Torch, a good led torch is useful.

My "old man's long arms" , that is glasses to help my tired old eyes.

Small engineer's hammer.

Small but sharp chisel to mark wheel and plate.

No special clean down was carried out but all tools, fingers etc that went into the pump were scrupulously clean.

1. Turn the fuel off at the tank.

2. Remove the plate on the side of the pump, it is sort of a rounded rhombus. 2 studs using a 5/16 or 8 mm ring spanner. Diesel fuel in the pump spills out. Be careful to not damage the gasket.

3. inside there can be seen a steel wheel with letters and lines stamped on the circumference, you may also be able to see a notch in the wheel. To the front of the wheel are 2 black coloured bolt heads (12 sided) that go through the wheel.

Loosen these bolts (8mm or 5/16 combination ring spanner) VERY TIGHT so use a good quality spanner.

The motor may have to be turned by hand to get access to both bolts.

4. Keep undoing these bolts but now a modified combination ring spanner is needed. Grind down at the ring end of a 8mm spanner until is about 3mm thick. Use this to undo the bolts all the way. This is necessary to clear the conical taper at the front of the shaft.

At the top position as the bolt comes out the bolt may foul on a spring above the central shaft. Again rotate the motor by hand to clear the bolt.

DO NOT pull these bolts out.

5 Carefully move the stamped steel wheel toward the front but DO NOT LET THE WHEEL COME OFF THE SPLINED PART OF THE SHAFT. It is apparently a pita to get back on in the right position. Making the wheel at this stage may be prudent.

The wheel sits on a splined shaft that is reduced diameter toward the front and smooth.

I used a piece of 12 1/2 gge wire to block excess forward movement of the wheel.

6. Moving the wheel forward exposes a dark coloured plate with a tag sticking back onto another serrated wheel behind.Mark with a the chisel the position of this plate.

Making sure the bolts loosened earlier are clear of the dark plate, I used a pocket knife blade to edge the bolts forward, rotate the dark plate and the serrated wheel behind top toward you (ie clockwise when viewed from the drive source).

If the pump is on the other side, of motor, i.e. right side as in a Ford 4300 it is still clockwise but the top of the wheel is turned away from you.

Turn one full turn i.e. 360 degrees until the mark so carefully applied earlier comes back again.

Looking carefully you will be able to see the bolt hole/s in the serrated wheel.

7. Ease the steel wheel back toward the dark plate but leave enough room to see the bolt hole in the serrated wheel.

Using the thinned-down spanner start the bolt into the bolt hole.

May take some time and patience to get started because the bolt can be turned only 1/12 th of a turn at a time.

Once started, do the bolt up only until it is "finger tight".

8. Rotate the motor by hand until the second bolt can be done up..

Tighten bolts up to very tight with an unmodified 8mm combination spanner. Finish off with a few sharp but not excessive strikes with SMALL hammer on the spanner.

9. Refit the cover plate.

10. turn fuel on at the tank.

11.Bleed all air out of the pump.

12. Crack 2 or more fuel lines at the pump outlet and crank motor until got spurt from the lines cracked, then retighten.

13. Crack those lines at the injector and crank motor until good spurt from those lines, then retighten.

14. Start motor and rejoice in the extra power.

My initial trials, pushing with the fel showed a significant power increase. I will put the tractor to sustained draught work and if still under what I expect power/performance to be another turn will be applied.

A no-cost adjustment that will get me the power expected and I am still well under $4,000 int it, when a 4wd loader tractor in rough condition should fetch circa $6 to $8,000 particularly with $3,000 of rubber on it.


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## carcajou (Jan 28, 2011)

Thanks for posting. If you do an additional turn post a few pics please.


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## Coondle (Aug 28, 2013)

My tech skills are not good enough to get pics on here, and the access is so limited that pictures are very very difficult to get so tried to give an explanation that someone with the pump in front of them could follow. Autofocus on the smart phone adds to the degree of difficulty to get pics at such close quarters.

The task took my brother and me about 2 hours to do but with the ground-down spanner now to hand, knowing I need a torch and the experience under my belt I expect I would be able to do the job on my own in about an hour. Undoing and doing up the two bolts is the most tedious and time consuming part. The most difficult on my own will be turning the motor by hand.

The good part is no-one would have to listen to my cussing if things went awry.


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## Gearclash (Nov 25, 2010)

My nasty and suspicious mind would be wondering why the pump was under fueling? Surely the previous owner would't have turned the fuel down?


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## Coondle (Aug 28, 2013)

Do not know how or why the tractor was underfuelling. The fact is the mechanical governor would pull in when the motor was placed under load but no appreciable power resulted. The exhaust had no additional smoke even to the point of stalling, so my diagnosis was underfuelling. Power was abysmal barely able to pull a 14 disc plough and would die down if a slight uphill slope was encountered.

In my experience a diesel motor, particularly one that is turbocharged, will produce increasing quantities of black smoke when gradually brought down in revs as load is applied and the motor transitions toward stalling.

In the case of a turbocharged motor the smoking is the more extreme because the exhaust gases that drive the turbo lose their velocity and the turbo loses efficiency thus drastically reducing the amount of air fed into the motor per revolution. However the fixed displacement injector pump keeps injecting a fixed quantity of fuel per revolution leading to incomplete combustion of the fuel resulting in visible black smoke, progressively increasing as the stall point is approached. Visible smoke was almost entirely absent from this tractor when brought toward the point of stall despite the govenor's action being audible.

This meant that the proportion of air to fuel despite the reduced efficiency of the turbo was still sufficient to support full combustion, hence my diagnosis that the fuel settings on the pump were too low. On a CAV pump there are two pistons that pressurise the fuel which a distributor feeds to the respective injector and the injector operated by the pressure in the line. The pistons' travel is activated by the steel wheel assembly referred to in my first post, but the length of travel is adjusted by the relationship between the steel wheel and the serrated wheel. Turning the relationship between these 2 wheels adjusts the stop point for the travel of the pistons to either put less o more fuel into the injector line connected to the pistons through the distributor.

The pump does not have the locking wire twists on the access points so in a previous life someone may well have played with the settings, but I have no way of knowing that. The pump is painted the same as the rest of the motor so it is assumed to be originally fitted to a Case /David Brown motor. It may not have been matched to this motor, it may be a transplant from a smaller displacement motor that had been equipped with a CAV pump.

I simply do not know the history of the pump but had the need for more fuel.


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## slowzuki (Mar 8, 2011)

On a turbo motor with a more modern turbo cav style pump with boost aneroid this is a common symptom of leaking boost diaphragm. The boost moves a blocking element to allow the metering valve to open further. If the diaphram leaks the extra fuelling is not available.


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## Coondle (Aug 28, 2013)

You are 100% correct Slowzuki but the tractor is of older vintage so no boost regulation on this tractor, the metering valve is adjusted by a screw at the outer end and on top of the pump.

CAV pumps also come with 2 types of governor, hydraulic, and mechanical via weights. My tractor has a mechanical governor. If the governor was not working then there would be no power rise as load was applied l, however in testing with application of additional load(standing on the brakes) the governor could be heard to work but power rise was minimal.

Internally the pump has two pumping mechanisms, a vane pump at the inlet which provides transfer pressure to the two pistons that provide the very high pressure to the injectors.

The two pistons are horizontally opposed are situated inside the hydraulic head and rotate inside an outer cam of the pump. They are fed fuel from the vane pump, which is located in the outer end of the pump at the point of entry of fuel from the lift pump (or gravity in some cases) when the port to these pistons is open. The pistons are forced out by the transfer pressure from the vane pump to a distance set by the adjustment outlined in my first post. Allowing the pistons to travel out further under transfer pressure increases the amount of fuel supplied on each discharge to the injector thus increasing the fuelling of the engine. The pump is also fitted with a metering valve because transfer pressure is not constant but rises with increasing rpm. The metering valve is a piston that is adjusted by a screw usually under a tin cap wired on over the screw adjuster. Changing the metering valve setting is far more problematic and not recommended by even this inveterate tinkerer. A test bench is necessary if changing the metering valve.


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