Slightly OT - CAV DPA injection pump problem?

I know this isn't exactly stationary engine territory, but I'm hoping somebody here may have experience or tips to try.
My neighbour bought a JCB 3CX last month (perkins 4.236 engine with CAV DPA 3241F350 pump), and it had been running fine until he ran out of fuel at the start of the week. He put 4 gallon of diesel in it, and I bled it up for him. He fuelled it up, and it ran fine for about an hour before spluttering to a halt again, and I've been unable to get it running again since.
Fitted a new fuel filter as the old one was full of dirt. Kept getting seemingly random pockets of air from the top bleed screw on the pump - we'd bleed up to the pump, then after several attempts at getting fuel to the injectors, check the pump again and get more air. After checking to see where fuel was going/not going, discovered the small hole in the bleed pipe banjo bolt on the filter head was choked. Cleared that out and it stopped the random air in the pump. Still wouldn't bleed to the injectors, so after more pipe disconnecting, discovered that no fuel was coming out the pump bleed screws with only the inlet pipe connected (the fuel that came out previsouly was obviously coming in via the pump return pipe as the entire fuel system is slightly pressurised due to the only return to the tank being via the bleed banjo/injector leak of pipes). Dismantled the regulator on the back of the pump and found the pump inlet filter was choked. Cleaned it which meant fuel could get into the pump the right way, and plenty fuel now comes out the bleed screws when opened (I still have the pump return pipe of).
But it still refuses to pump anything upto the injectors. When you first start cranking the engine, a couple small bubbles come out the injector pipes, but that's it. One thing I have noticed, is there is minimal fuel coming out the pump return port. Does anybody know if fuel should be able to flow freely through the pump?
I've now come to the conclusion the pump is most likely needing removed and overhauled, but is there anything obvious I've missed? Or any other tricks I can try to nurse it back into life?
thanks Moray
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All I can suggest is back to basics. Sometimes with these problems it helps if you put a length of clear pipe in the supply _just_ before the pump - that way you can monitor air bubbles and confirm the suction side of the system is tight.
I've a DPA pump on my Massey 575 - probably the same Perkins engine as the JCB and that's prone to clogging the ''last chance'' filter gauze situated just below the fuel inlet union. The lift pump strainer clogs too ('kin 'effin Diesel bug :-( )
One thing is certain, these pumps are really robust and the trivial cock-up of allowing it to run dry of fuel will in no way necessitate an overhaul!
Julian.
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You probably need to loosen the delivery valves on the pump.This is the 9/16" AF headed bolts that hold the injector pipe banjos to the pump body.Leave the pipes on the injectors and spin the engine over on the starter.If it`s the pump where the pipes come of the end plate forget I said that and just give it a squirt of ether. On things like that it`s better to start at the tank outlet and check the flow there,check the banjo bolts if it has them on the lift pump and filter housing as some come with gauze filters in them,take the lid of the lift pump and clean the gauze and also the one on the injection pump inlet that you have done.Unless it`s been well looked after you will find muck everywhere due to being filled from containers of dubious cleanliness over the years.I`ve done dozens of them over the years. Went to a Manitou forklift the other week that the owner had just put a recon engine in and wondered why the revs died after a few seconds.Everything including the injection pump was full of muck.He`d just refitted all the bits he`d taken of the old engine.
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Mean`t to add,don`t leave these pumps with the strangler pulled out.The bar inside the pump sticks after a while and doesn`t go back when you push the strangler in. .
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That's worth knowing - I've three DAP pumps, two on Massey Tractors and one on a Series Landrover
Julian.
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I've come across this problem twice. In each case the tank was full of s*** and the pickup strainer completely clogged.
hth
--
Roland Craven
Nr. Exeter, Devon, UK
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replying to mark, Crazy Welshman wrote: Hi I see this is an old post. Is there anyway of checking if the strangler has stuck ?... I'm not getting any fuel from pump after using the machine a day then parking up and now wont start.
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wrote:

I think slackening the banjo bolts is the only thing I've not tired, so I'll give that a try later.
I'm happy that enough fuel is getting to the pump, as there's a steady stream from the filter bleed pipe when cranking, and a continuous stream from the lowest of the pump bleed screws (I've never seen a steady a stream from the top bleed screw during cranking on any engine with a DPA pump)
The only thing that I'm not sure about, was when I removed the pump inlet filter (on top of the regulating valve), the regulating sleeve lifted out aswell as the filter was seized onto it, which meant I had to take the valve body of the pump (4 bolts) to get everything back together, as the piston and spring stayed in the body. I put everything back as it came out, but one thing I did notice was the small spring at the bottom was sitting on it's side. So I turned it so the smaller end of the spring (spring is tapered at one end) was pointing upwards so the piston would hit it and not fall into the spring. I also noticed the casing was pretty badly scored where the transfer pump runs against it, which is why I'm now swaying towards taking it of and at least getting it tested (I've told the neighbour of the prospective cost, and he's happy enough provided that'll solve the problem)
I've also tried the ether approach, but it made no difference.
thanks moray
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There are two springs in there.The larger one which has only a couple of coils is at the bottom and ends with the tail bent across at 90 deg.I think the plunger goes next and then the small spring on top but can`t remember as it`s three weeks since I`ve done it.:-) I will see if I can find a picture. The scoring on the end cap will affect fuel delivery pressure but will deliver fuel through an open injector pipe so I would not worry about it. Did it not fire on ether or did it fire but would not run? Mark.
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Have found a picture,quite a good one.It`s in the DPA instruction book I have,printed 1968 at a cost of 6d. If you email me your email address (mine works) I will scan the whole lot and send it to you.I can also scan you the matching injector manual which shows you how to test and adjust an injector. If anyone else is interested I also have a Lister instruction book for HR2 and HR3 engines.Published 1974. Also have a Hatz instruction book for models E95,Z95,D95 and V95.
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Thanks for the offer, but my brother-in-law handed in a CAV DPA workshop manual today which has all the relevant diagrams. Not sure of it's age though, but it has details on the back for sending a telegram!
thanks moray
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Thanks for the offer, but my brother-in-law handed in a CAV DPA workshop manual today which has all the relevant diagrams. Not sure of it's age though, but it has details on the back for sending a telegram!
thanks moray
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Is this any help?
http://www.fujiyachts.net/manuals/CAV%20DPA%20Pump%20Rebuild%20Manual.pdf
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That's very helpful thanks, I downloaded it to my hard drive thanks
Julian.
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wrote:

There's actually 3 springs. Small one at the bottom, which the piston pushes down against during priming. Middle sized one that sits on top of the piston which regulates transfer pump pressure. And a large one that goes between the piston sleeve and fuel inlet adapter.
I tried cranking the engine with the pump inlet pipe of again, and the pump is drawing in next to no fuel, which makes me think the transfer pump has died. The neighbour did say he thought it seemed a bit sluggish after he refuelled it, which I had put down the filter getting choked, but it turns out the previous owner also ran out of fuel a couple of times, and had had no problems bleeding it. He also said he'd never serviced it, so the filters have probably been full of dirt for a while.
With ether, it fired but wouldn't run.
I'll give it one last chance tomorrow to bleed up, and if it doesn't, I'll just take the pump of and drop it into the local specialist for testing, as I think every trick has now been tried, except ATF...
thanks moray
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Just an update on this.
The JCB was finally resurrected yesterday, after having the injection pump overhauled. Report back from the pump people was it was full of dirt (no surprise there!), and the cam ring was breaking up.
thanks moray
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And you damaged the engine with ether for no reason... Wtf did you hope to achieve, with no fuel reaching the cylinders?
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