Diesel Injector Pumps

[Wendelspanswick]

My John Deere tractor refused to start yesterday, first time ever. It was turning over but no firing, no vapour from the exhaust so guessed it was a fuel issue.
Plenty of fuel in the tank, opened the bleeder on the CAV Roto Diesel pump and manually pumped the fuel and sure enough air came out. Once bled it was back to its reliable starting.
Can't understand how air got into the system apart from the seal has gone on the throttle spindle so it pee's out diesel when running. As the tractor sits with the pump in the full sun could the heat have expanded the fuel forcing it out of the throttle spindle and then as it cooled and the fuel contracted it drew air back into the pump?
It has promted me to sort out the throttle spindle seals, looks to be a pair of O rings and I suppose I will need a top cover gasket as well?
Anyone done one before as they seem to be a very common pump?

 

[ratherbewindsurfing]

Don't think this is the same pump but the video may help

 

[premmington]

Not much of welder! But I do know about diesel pumps.

No parts left for CAV Rotas

www.remmington.info

 

[CKJDJK]

Check the fuel inlet. Some CAV pumps have a small filter in the unions (difficult to find). If it is getting clogged then it can cause bad starting and low fuel in the injection pump. Priming becomes difficult. Eventually the engine just will not start.

 

[Wendelspanswick]

Doesn't have leak off / spill off pipes does it?
If so they go porous and let air into the fuel system (but not liquid out) causing fuel to drain back and airlocks etc, along with making it a mare to start...

I did them on my diesel car, along with the starter...sounds a lot healthier and a lot easier to start now...

The large pipe exiting vertically on the right of the pump is the return, its steel but just out of shot it slides into a length of braided plastic pipe which has gone hard.

 

[colnerov]

The large pipe exiting vertically on the right of the pump is the return, its steel but just out of shot it slides into a length of braided plastic pipe which has gone hard.

Hi, the large pipe on the end of the pump is the fuel supply, the return pipe is the one at the front of the pump by the drive gear. If the braided pipe you say has gone hard then that may be drawing air in but not show signs of leaking, then that could be where your problem lies. check if there are any non-return valves in or around the fuel filter as they may be allowing fuel to drain back.

Colin

 

[Bill Edwards]

Ah, the CAV DPA pump.

As said by colnerov, the pipe on the end of the pump is the supply. Under there is a small filter which can block up, but it probably isn't causing any problems and I suggest you leave it, they can be fiddly.

Chances are the pump itself isn't drawing in air, look at the rest of the fuel system first.
It's probably a worn, perished or cracked fuel pipe, leaking fuel filter seal or a bad lift pump.
To find this kind of air leak can be a nightmare. Is the fuel supply gravity fed to the lift pump, or sucked out of the top of the tank? If it's the latter, the pickup pipe in the tank can be suspect along with everything else.
If there is dirt in the system causing a blockage, this will sometimes allow air to be sucked in through joints that are not perfect but working OK the rest of the time.

The DPA pump is very sensitive to air in the fuel, it simply will not tolerate it and you end up stuck in the middle of a field or roadside bleeding the thing for the tiniest air leak.

As to the o-rings on the throttle spindle, you have to remove the top cover. But before you do anything to the pump, you must pressure wash the entire area first as you cannot allow any dirt into the pump.
Once you are inside, take very careful note of how everything is connected - springs must be put back in the same holes on the internal linkages. Photo's are helpful. Injector pump require a great deal of care, but it can be done by yourself.

 

[colnerov]

Hi, one other place to check which is not always obvious. if you have a banjo fitting on the fuel pump check the copper washer that goes between the fitting and the pump. It tends to twist into the lead for the threads and lets air in, replace it but don't forget to anneal it first.

Colin

 

[Wendelspanswick]

Just an update and the tractor has been back to its normal, reliable starting, self.
I have changed the seals on the throttle and stop shafts, really easy to do, even when your view is partly obscured by the loader bracket!
Should have replaced the gasket as there is a very slight weeping from the joint, minuscule in comparison to the amount of fuel I was losing from the throttle shaft though.
I haven't tinkered with anything else as she is behaving herself but I now have a list of things to check if she starts being difficult again!
Thanks for all the help and advice.
A virtual beer to you all.