Basic CAV DPA pump question

Rod Reidnauer · Nov 10, 2019

Hi all, just have a relatively simple question about the CAV injection pump that runs my 201ci Ford diesel.
Besides the three high pressure injection lines and the back bleed line, the pump is fed by two separate inlets.
The one on the transfer pump (and currently where I think I'm having an issue with fuel starvation) makes perfect sense to me, but I don't know why there is a second line connecting to the main body of the pump. Is it there to simply flood the governor section with fuel? It seems the area is pressurized by the transfer pump when the motor is cranked, (indicated by shooting a stream of fuel from the bleed port when opened and motor cranked) so I don't understand the need for this second input. Just trying to get my head fully wrapped around this little beast.
Thanks!
Rod

Dieseltech · Nov 10, 2019

The side cover line is the return back to the filter, the rear small line is an air bleed line back to the tank across the injector leak off return line.

Al Baker(pumpman) · Nov 10, 2019

On all DPAs the line that goes to the head of the pump, between the high pressure lines is the line that feeds the unit. All other ports are returns. The pump housing is pressure filled by the vein pump bolted to the head. Al

Destroked 450 · Nov 10, 2019

As has been said the line connecting to the pumps body is a return line.
Some of the primary issues with fuel starvation on a Ford tractor with 3 cylinder engine is.
Plugged fuel filter
Fuel strainer in the tank valve stopped up.
Fuel filter gasket in the wrong position.
A gasket placed inside the filter housing like in the photo below will severely restrict fuel flow on some filters.

Rreidnauer · Nov 10, 2019

Thanks guys. Makes sense. I just noted both lines are shown as outputs on the filter, but I guess they figure keep clean fuel returning to the clean side of the filter.
That second line feeding into the pump and out the bleed screw had me befuddled for a bit. Pretty sure I'll find the little screen varnished up on the head connection.

Basic CAV DPA pump question

Rod Reidnauer

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Dieseltech

Well-known Member

Al Baker(pumpman)

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Destroked 450

Well-known Member

Rreidnauer

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