Thread: 2.25; Diesel 30 second run....

What check valves are you talking about? The two in the lift pump?

Aaron.

theres 2 fuel lines on the injector pump...

on a series CAV pump the fuel goes In the top and out the bottom which is counter intuitive youd expect that it goes in the bottom and out the top. there is ment to be a check valve/restriction fitting/filter sieve on the return line from the bottom of the injector pump.

Added to this that the output side of the fuel pump hooks to the filter and the bottom of the pump...


I dont know how or whats been done to dobbos diesel but since I didnt have a fuel system on kermit (just the injector pump that I was just running out of a jerry) I copied dobbos piece by piece....

near as i remember the filter from dobbos diesel was only filtering the stuff that came out of the CAV pump then dumping the clean fuel onto the top of the injector line and from there dumping back to tank.

Now I have to work out how the hell his was running but I think it does explain why his was soo bloody hard to start and why it drained back all the time.

whats going to be Uber fun for me is when I plumb fozzy over to wvo and diesel.... can anyone else say complete fuel system remake.

Every CAV pump that I have seen, the fuel goes into the pump at the end where the injector lines come out. I have seen a fair few english trucks and tractors. Usually the CAV pump is horizontal, but it is a variation of the same beast.

I do not have a "check valve/restriction fitting/filter sieve" on the return line. I plumbed mine as shown in the manual.

1. Tank to lift pump.
2. Lift pump to filter.
3. Filter to injector pump.
4. Injector pump return to filter (other input).
5. Fitting on top of filter housing fitted with check valve to allow fuel/air to only come out. This fitting then takes a banjo bolt with a ~0.5mm hole to allow only minimal flow as to maintain pressure in the line. This is then the return to the tank.
6. Spillway splices into return to the tank.

By having the return to the tank originating at the top of the filter housing, any small amounts of air that find their way past the lift pump accumulate at the top, and are sent back to the tank. From what I have observed on various engines, this is standard CAV practice.

If you would like a picture of the diagram showing this, I could scan it.

Aaron.

Before I rebuilt my engine, it was hard to start. 30 seconds on the plugs, and still it needed 20 seconds on the starter. I knew that it wasn't a fuel drain back issue, as it would always roll start instantly even from cold. Roll starting would turn the engine over quicker, so start it easier.

Aaron.

I have the original workshop manuals, thats how I figured out that there was something amiss with the plumbing....

There is supposed to be a small adaptor that screws into the bottom of the cav pump where the line from the fuel pump outlet threads in.. Depending on which manual you read and which diagram in that manual you look at its listed as a filter, a restriction and a one way valve.


I'll get a look see and scan in the pic I used on saturday for ya...

If it helps, I can take a pic of how mine is plumbed up Dave. I have all the original pipework that came of a 1979 model 2.25D.