Cambelt powered diesel pumps

Honest John Back Room » Motoring discussion
View Threaded
Mon 18 Sep 2006 14:24
Cambelt powered diesel pumps - mss1tw
Is there any reason why manufacturers do this? Surely it would be best off driven by the aux drive belt, leaving the cam timing belt to do just what it says - keep everything in sync.

I can't see the aux drive belt being hard to keep correctly timed as long as everything was designed properly.

I can't see any money saving issues as the aux belt needs to be there for PAS, A/C, etc...
Reply | Report as offensive | Link
Mon 18 Sep 2006 15:29
Cambelt powered diesel pumps - DP
The old Ford Endura DE engine used in my Mondeo runs a separate belt for the fuel pump. This shares the crank pulley with the timing belt and runs inside the belt covers. I don't really see what engineering advantage this offers unless of course the fuel pump seizes, and it doesn't strip the teeth from the cambelt. Ford's thinking clearly ran out at this point because they chose to drive the water pump off the cambelt, which as a far more failure prone component, just leaves you thinking, why??

I guess the reason that injection pumps don't run on auxiliary belts is because the only way to achieve the required precise timing would be to use a toothed belt. Toothed belts exposed to the elements can pick up grit and debris which causes them to fail prematurely. Encasing the auxiliary belt and all its driven components in plastic would be difficult, not to mention a total pain from a maintenance point of view. Actually, on the latter point alone, I'm amazed no manufacturer has tried it yet judging by the "designed in" awkwardness present under the bonnets of a lot of modern cars.

Cheers
DP
Reply | Report as offensive | Link
Tue 19 Sep 2006 07:15
Cambelt powered diesel pumps - autumnboy
The old Ford Endura DE engine used in my Mondeo runs
a separate belt for the fuel pump. This shares the crank
pulley with the timing belt.
from the cambelt. Ford's thinking clearly ran out at this point
because they chose to drive the water pump off the cambelt,
which as a far more failure prone component, just leaves you
thinking, why??


These engines were renown for high failures on the cam-belts blamed on the idle pulley, but not the fuel pump belt.


Reply | Report as offensive | Link
Mon 18 Sep 2006 16:13
Cambelt powered diesel pumps - tr7v8
If you mean the high pressure pump then the power needed is much higher than a normal ribbed belt can offer, also some have critical timing which a normal belt can't offer. Some manufacturers use a seperate toothed belt to drive the pump & yes they do break! Not aware of it being an issue as others have said water pumps failing & taking the belt out is a far bigger issue.
Reply | Report as offensive | Link
Mon 18 Sep 2006 21:59
Cambelt powered diesel pumps - cheddar
A normal injector pump off the belt is not too bad though I have said before that PD is so illogical due to high pressure pumps being driven off the cams.
Reply | Report as offensive | Link
Tue 19 Sep 2006 08:47
Cambelt powered diesel pumps - cheddar
VAG is now starting to abandon cam-driven PD injectors in
favour of piezo injection.
HJ


They clearly are on the V engines due to packaging, also the LeMans R10 Audi uses CR so they can get PR out of CR however is there evidence that they are dropping PD on 4 cyls?
Reply | Report as offensive | Link
Tue 19 Sep 2006 08:48
Cambelt powered diesel pumps - cheddar
Afterall piezo is only a different type of injector within a CR system.
Reply | Report as offensive | Link

Looking for a garage you can trust? Honest John's Good Garage Guide has thousands of reader recommended garages, plus how-to guides and tips on servicing.

The Good Garage Guide