'87 3CX Perking 4.236 Injector Pump Problem

[Slooby]

Ok, so it's been a while since I've had an actual fault with the JCB, but now I seem to have one :/

Yesterday I ran out of fuel while moving a soil mound about, or at least I thought I did as the engine died suddenly and wouldn't restart. My fuel gauge is duff, and you can't dip the tank as there's an elbow and a gauze in the filler neck.

So I grabbed a jerry can and transferred over 15 litres or so of *cough* heavy fuel oil, went round bleeding the fuel system, and on the third circuit of injector line cracking it fired into life. Rather than carry on digging, I decided to bring the JCB back to the yard and put more fuel in. It was getting late by the time I'd completed the palaver of fuel transfer so didn't fire the engine up, leaving the JCB blocking the exit from the yard to the field...

This morning I went out to fire up the JCB and while it cranks it won't fire, I've been going round trying to bleed the fuel system again and am getting nowhere, in a change to yesterday's bleeding session I don't seem to be getting any fuel worth mentioning coming out at the injectors, just the slightest dribble after about 30 seconds cranking on each injector, cracking on of the unions on the back of the pump distribution housing has the same effect. Pleanty of fuel comes gushing out of the two bleeds on the pump body and atomiser, just not after the distributor.

Cracking the fuel line from the mechanical pump to the engine mounted filter sees pleanty of fuel there, but it is less energetic on the other side of the filter on the feed to the injector pump, and actually seems more lively on the bleed back from the injector pump to the filter.

Before I go removing the injector pump and getting myself into a world of pain and trouble trying to 'fix' it, can anyone shed any light on what might be going on?

Could it be a clogged filter? In that there's enough fuel getting to the injector pump for it to pressurise internally, but not enough to make it out of the pump to the injectors themselves?

[Jeremy Rowland]

Tim if you have a sediment bowl try cleaning that, if it is free from muck you may have a different issue, does the lift pump squirt the fuel through the bleed nipples okay as that too could be an issue, finally if the injection pump is the rotary DPA type pump look at the transfer pump on the very back of this pump, there is a small piston that can get stuck and a gauze type filter in there. Also check that you are sucking fuel up and not air, just one dodgy fuel line connection can cause real issues. Let us know how you get on.

Jeremy

[Slooby]

Thanks Jeremy, I do have a drop out sediment trap on the chassis leg below the fuel tank which gravity feeds it. I admit I've not looked at it yet bar cracking a union to see that fuel came out cleanly from it.

One the main filter housing cracking union '3':



and giving the lever on the cam driven lift pump a few depressions see's lots of fuel come out, so I 'think' fuel is getting to the main filter ok.



Cracking Union '1' though (the feed to the injector pump) doesn't see as much come out of the filter housing as I would have expected considering the amount coming out at '3' when manually pressurising the lift pump system. More seems to be coming out when I crack the return line '3'

On the Injector pump fuel really gushes from the two bleeds on the side of body (above the ID tag) and the atomiser (the one above accessed through the slot in the throttle cable and stop cable bracket)



The pump appears to be a Lucas DPA, and I'm guessing the piston and gauze you describe are inside the aluminium housing on the end of the rotary distribution block. I've downloaded a copy of the Perkins 4.236 NT/TT manual (shock horror; not from here, unless it's hiding somewhere I failed to spot) and am having a flick through it now for ideas

[essexpete]

Be careful if you take out the gauze on the pump.

[Slooby]

Be careful if you take out the gauze on the pump.

Out of the Injector pump?

Am I correct in assuming where it is Pete?

My lifter pump doesn't have one, just the outer body of it the gauze is long gone

[Slooby]

Hum, the Perkins manual is somewhat lacking in detail on the pump beyond setting it up

[Slooby]

Lucas DPA Pump Rebuild manual of some type found on a yachting site...

So, I guess I'm looking to take off the inlet feed to the regulating body on the end of the pump marked '4' in this pic:



And the filter I need to be looking at, and being very careful with, is item '3' in this pic:



Right, to the JCB again!

[Slooby]

Yuk:







Even if it's not the problem, this needed doing!

Gently teasing at the edges of the nylon filter with a cocktail stick didn't seem to make it any more likely to come out with the endplate in situ, so rather than damage it I took the end plate off and engaged the service of a recent addition to the armoury:



The endplate and regulating valve parts are now having a warm bubble bath which sets my teeth on edge

[Slooby]

After the first 5 minutes in the bath I was able to strip the whole regulator valve down as the filter came out with the regulator sleeve

As plastic absorbs ultrasound there was no point leaving the filter itself in the tank soaking, so I left it out to clean it manually with brake cleaner. While the metal bits got another two 5 minute bouts of jiggle jiggle, resulting in:



Managed to get it all back together and assembled back onto the pump again, just in time for the heavens to open and it has only just stopped, so no chance to prime and bleed the fuel system this evening :/

[Jeremy Rowland]

You got that bit sorted correctly and spot on let's hope that was the issue.

Jeremy