fuel pump coupling

[billy]

Hiya all,

This might sound stupid but how much play should there be in the coupling, the flexible pad bit... I've go about one or two mm in either direction, is that too much??

Thanks

[oehrick]

Side to side between the disks or rotational ??

Never measured it but I think mine probably has this and runs OK, perhaps a little less between disks, if rotational make sure the slack is taken up in the drive direction before checking or retiming the pump.

[billy]

yeah its rotational, but the tractor is running with a fair amount of smoke, so I was just thinking the coupling might be upsetting the timing?

[oehrick]

The pump presents pure drag (as far as I know) so increasing coupling slack will retard the point of injection. have you checked the timing ? I would think it would have to drift further than described to make smoke.

As a rough idea, if you take the coupling as roughly 60mm diameter the circumference is going to be about 180mm so each mm at the outside edge equals about 2 degrees of movement, if timed at the mid point of the slack this reduces to 1 degree.

HTH

[Billy26F5]

End float should be 0.010", rotational play isn't particularly desirable, but up to 1 mm is quite alright as long as the timing is adjusted to compensate. If there's more the drive pad will likely shatter. The more play the louder the coupling will be. The pump presents drag most of the time, but when one plunger starts to descend it pushes the pump forward, causing the noise from the coupling as it drives itself forward only to then get picked up by the engine once the play has been taken up.
Sandy