JCB 3cx white cab hydraulics causing engine to cut out

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UnclejakeNZ
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Re: JCB 3cx white cab hydraulics causing engine to cut out

Post #11 by UnclejakeNZ » Sun Feb 02, 2025 10:24 am

We've done 22 hours on the machine since the vinegar incident mate, so its fine.

It's an old, rusty, largely worn out backhoe with a tired non turbo Perkins 4.236 engine that hasn't been looked after for decades Sandy. Calibrating the pump would be ideal, but I live on an remote island the size of Singapore but with only 700 people. It's a long, long way from anyone with the right gear to fettle injection pumps properly. I have a touch of black smoke I didn't have before, and now enough power to get up the driveway in second instead of first gear. I'm going to take that as a win! :-)

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Re: JCB 3cx white cab hydraulics causing engine to cut out

Post #12 by Billy26F5 » Sun Feb 02, 2025 7:56 pm

That sounds like you were reasonably careful, to set up a calibrating machine you can just get the pump driven off a motor you can change the speed of and run the pump as specified in the test page in the manual, with the injectors pouring into reinforced test tubes. You can then do many of the tests as specified. Not sure that's around for this but I'll have a look.
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Re: JCB 3cx white cab hydraulics causing engine to cut out

Post #13 by Billy26F5 » Tue Feb 04, 2025 2:11 pm

Can't find suitable stuff, these manuals are worth a look at anyway though:https://injectionpumps.co.uk/cav-dpa-manuals/
https://injectionpumps.co.uk/wp-content/uploads/2018/12/Lucas-CAV-Pump-Number-Reference-Chart.jpg
There's also this Ebro manual which does have the 4.236 in it: https://www.slideshare.net/slideshow/manual-de-taller-tractores-ebro-parte-1/13174938
https://www.slideshare.net/slideshow/manual-de-taller-tractores-ebro-parte-2/13175035?_gl=1*3k6ev5*_gcl_au*MTkwMTYyNDk2Ni4xNzMzOTEzNjgw
I think your max fuel should be 9.9 cc in 200 injections at 800 rpm but that's on the Ebro 470, not sure if JCB had the same setting. The Ebro 470 setting code is LS-49.5/800/4/2260. This is on the plate on the pump below the model number (3241F102 on the Ebro 470). Your pump will have similar information, but not necessarily the same.
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Re: JCB 3cx white cab hydraulics causing engine to cut out

Post #14 by gecko.cx » Wed Feb 05, 2025 4:05 am

UnclejakeNZ wrote:The Lucas CAV injection pump siezed and snapped in half


Where did your pump snap?
I bought a Linoln welder with a 4.236 that wouldn't start.
I lifted the top of the pump to discover it was 2/3 full of water (no rust though).
Haven't been able to bleed the pump, so assume it's not well inside.

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Re: JCB 3cx white cab hydraulics causing engine to cut out

Post #15 by Billy26F5 » Wed Feb 05, 2025 12:06 pm

Sounds to me like you'll need a new transfer pump and hydraulic head to start with, probably a meetering valve too. As that is likely needed you need to do the full test, which is different depending on the model number and setting code on the pump. Much easier in a diesel shop but worth knowing how to do these things anyway.
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Re: JCB 3cx white cab hydraulics causing engine to cut out

Post #16 by UnclejakeNZ » Thu Feb 06, 2025 4:11 am

gecko.cx wrote:
UnclejakeNZ wrote:The Lucas CAV injection pump siezed and snapped in half


Where did your pump snap?
I bought a Linoln welder with a 4.236 that wouldn't start.
I lifted the top of the pump to discover it was 2/3 full of water (no rust though).
Haven't been able to bleed the pump, so assume it's not well inside.


The shaft snapped just aft of the side cover plate Gecko. The metering assembly was still spinning but the actual pump wasn't... so it took a while and two people to diagnose so a little vinegar sat in the injection pump for more than 24 hours.

There would have been a few tablespoons of vinegar in a full JCB tank of fuel. The machine idled for around 4 mins after we topped up the fuel from the contaminated drum.. and then slowed and stopped due to a vinegar/fuel reaction emulsion in the sediment filter.

We drained the tank, cleaned out the sediment filter,.lift pump, fuel lines and replaced the disposable fuel filter but couldn't get fuel to the injectors. When cranking the engine on the electric starter sometimes there was a weird squeal and the starter slowed. I couldn't work out where the noise was coming from... but it went away after I wiggled the alternator belt (coincidence obviously) so we kept trying to get fuel to the injectors using the starter motor and even ether.

When I finally took the pump apart there was corrosion on its internal surface - which assume was from the vinegar. The squeal would have been the pump to housing interface seizing.

I was very lucky to find a similar pump on a nearby farm I could take parts from.

P.S. i did all this on the edge of a very windy paddock with the front bucket down. It was not a comfortable experience. I also wouldn't recommend lying on gravel with vinegar running down your arm creating a puddle to soak your shirt. The small stones were sharp enough to puncture skin. The vinegar isn't much fun

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Re: JCB 3cx white cab hydraulics causing engine to cut out

Post #17 by Billy26F5 » Thu Feb 06, 2025 9:30 am

Sounds like quite a hard day. Know all about working on gravel, definitely not recommended. I'm amazed it ran as long as 4 minutes, I would have expected issues the moment any vinegar got to the pump and poor running from lack of fuel too. Ether shouldn't be used for this, it might affect starting.
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Re: JCB 3cx white cab hydraulics causing engine to cut out

Post #18 by gecko.cx » Thu Feb 06, 2025 10:32 am

No vinigar - got it!
Thanks for the details - will be helpful when I get back to mine.
No idea when mine last ran, or even who owned it at the time.
I'll start by taking the rear cover off and see if the shaft is turning.


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Re: JCB 3cx white cab hydraulics causing engine to cut out

Post #19 by UnclejakeNZ » Thu Feb 06, 2025 11:01 am

It's probably easier to take off the CAV side cover first (two bolts. I used an 8mm socket but they’re probably imperial) to see if the shaft to the actual pump is spinning or not.... but i have read of others having trouble with stuck fuel shut off 'valves' (I forget the proper name) after engines sitting around for a while.

Remove the top cover to access the fuel shut-off arrangement. It's basically just a little vertical shaft with a slot cut out of the bottom of the shaft. If it's stuck in the off position your symptoms could be explained.

There's a pretty good Australian video showing lots of CAV detail. I found it on this forum... but I will re-post in a moment.

I have new respect for the Lucas CAV injection pump. It's incredibly well designed towards reliability and actually really easy to service.

https://youtu.be/h26p78YZIr4?si=jLnYKlwigJ5M0vww


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Re: JCB 3cx white cab hydraulics causing engine to cut out

Post #20 by UnclejakeNZ » Thu Feb 06, 2025 11:15 am

BTW.... this is what my old girl has been up to for the last month. The archaeologists are extracting an old ocean going canoe from the sand. I'm just helping from time to time.

I made the fuel metering adjustment on that exact beach. The difference in power was remarkable, but of course sand would have gotten into the disassembled injection pump. There was no choice.

I should have bought a 4CX. The little 3CX front wheels are terrible on sand.

Plenty of salt. No vinegar.

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