TUD5 VZJ problem with CAV pump ?? - Toro mower with TUD5 ( saxo \ 106 ) low torque

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Mon 10 May 2021 07:44
TUD5 VZJ problem with CAV pump ?? - Toro mower with TUD5 ( saxo \ 106 ) low torque - simons mower

I have a diesel mower with a simple, old diesel motor, TUD5.

I bought the machine not running.

I have changed out the motor as old one had no compression. ( 4000hrs )

The new motor has 66000km and is as should be.

Compression.400+ on all cylinders.

The timing belt,water pump ,shims fluids etc all new.

The timing is 100% as should be.

The motor starts super easy and revs with no load.

It is super smooth ( for an old diesel )

The pump ( lucas CAV DPC from the new motor ) was sent off to a specialist to set up but i have a feeling it came back set up for a car and not the mower as the tick over was low ( mower spec states 1500.) and high end was set at 4000+ ( mower should be at 2650 )

I have changed out the new pump top section ( linkages, governor plate, metering springs etc.) from the original pump and it now revs perfectally between the limits (1500 and 2650 )

When I rev the motor to 2650 and load the motor with the hydraulic pump for the mower the revs drop to idle ( 1500 ) and wont build back to 2650.

If i move the throttle lever forward the revs stay the same ( 1500 ish ) although the noise changes slightly ( i think less clatter the more i advance the throttle ) but no change in revs.

If i cut the load it runs again as should. Revs freely etc.

I am sure that the pump is not set correctly.

Is there an easy way to increase the output pressure ( more fuel ) with these old CAV DPC type pumps or is it back to the specialist. ?

I found that if limited a little the return flow from the pump to the fuel tank it will rev up to 2650 and run perfectly under load but i am scared the this will push out a seal as there is defiantly too much pressure in the casing.

This tells me that the load is not too high ( faulty ) and i know max torque should be at 2200rmp on these motors not the 1500 it sits at.

Any thoughts from you guys with CAV roto pump knowledge

Thanks

Simon.

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Mon 10 May 2021 21:59
TUD5 VZJ problem with CAV pump ?? - Toro mower with TUD5 ( saxo \ 106 ) low torque - Railroad.

You need case pressure in the injection pump. There should be a restrictor in the fuel return on the pump body. Has this been removed or modified in any way?

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Mon 10 May 2021 23:41
TUD5 VZJ problem with CAV pump ?? - Toro mower with TUD5 ( saxo \ 106 ) low torque - focussed

The pump you sent off to the pump shop was from a car, the ref number on the data plate tells the pump shop what to set it to, so naturally it came back set for a car - injected fuel quantity, governor settings etc.

If the old engine had a CAV pump, (some had Bosch) you need to send the data plate from the old pump back with the new pump to get them to set it for what I suspect is the industrial constant speed spec for that engine as it's in a mower.

A better idea, if both pumps are CAV is to send both pumps back so the pump shop may be able to build the correct spec from both but don't count on it as parts get changed to alter the specs, it's not always about adjustments - and parts are getting rare for those pumps.

If the old pump is Bosch ask about getting that rebuilt, parts may be more readily available from Bosch.

The best shop to make sense of it would be Diesel Bob.

www.dieselbob.co.uk

Edited by focussed on 10/05/2021 at 23:52

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Tue 11 May 2021 06:46
TUD5 VZJ problem with CAV pump ?? - Toro mower with TUD5 ( saxo \ 106 ) low torque - Railroad.

With respect to the above poster I don't think that's right. Fuel injection pumps are not complicated. They just appear so to the untrained eye. Pumps do not create pressure. They facilitate flow. Pressure is created by opposing the flow. You need a restriction in the fuel return to create pump case pressure. Without it the engine isn't going to run as it should. This restriction will most likely be in the fitting which the return hose fits to.

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Tue 11 May 2021 10:40
TUD5 VZJ problem with CAV pump ?? - Toro mower with TUD5 ( saxo \ 106 ) low torque - focussed

You might be right as the DPC is a hydraulically governed pump- but how to select the right restrictor? Any ideas?

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Sat 29 May 2021 16:49
TUD5 VZJ problem with CAV pump ?? - Toro mower with TUD5 ( saxo \ 106 ) low torque - MikeU
What have you done? I have a same problem on my Toro.

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