1990 JCB 3cx no power/no high revs/stalls

[Jeremy Rowland]

I'm guessing here, but if it's DPA rotary fuel injection pump, there is a small filter in the fuel entry to the pump, think it's called the transfer pump, just be careful when you take it out.

Jeremy

[Billy26F5]

The transfer pump filter is a possible thing for cleaning but you have to be very careful as any dirt in there will wreck the pump. It is a DPA on the 4.236.
Sandy

[UnclejakeNZ]

I have a similar 1989 machine.

On mine there's a chassis mounted fuel sediment filter well below the cartridge filter. That sediment filter can be manually cleaned. Between the sediment filter and the tank there's usually no fuel tap which is a pain, but I have had three instances of fuel starvation like yours due to rust accumulating in the tank outlet (upstream of the sediment filter).

It's a messy job, but a simple job to clear the rust out.

There's a hatch part way up the tank you can unbolt to get your hand and a rag into the interior of the fuel tank to get some of the rust flakes out if the problem keeps repeating.

[SimosSoldatos]

qute a big update, i wasn't able to figure t out so i had a mechanic come out, it was refusing to start and there was no fuel coming out of the injector lines, he checked the cables going to the electronic shutoff valve and he said there's an electrical issue for sure, he bypassed it and it fired right up. Come to think of it lately whenever it was having the issue the rpm gauge would also not work properly. now it starts but after a while the same issue occurs, no power stalling etc. He said i should call an electrician, untill i find one should i change the electronic shutoff valve? Could that be the culprit causing electrical gremlins?

[essexpete]

Well at least you have partial resolve. I wonder if you have any large multi pin plugs on that era, they are often the culprit on some tractors?
I suppose you could also rig a jury wire and switch as temporary fix.

[kaos]

Congratulations on getting a big step nearer to a full solution. I confess that I, like other commenters, had been thinking in terms of fuel problems. Should have thought of this possibility.

untill i find one should i change the electronic shutoff valve? Could that be the culprit causing electrical gremlins?

Highly unlikely, I should say. An intermittent fault in the shutoff valve is conceivable, but if a bypass wire (taken, I presume, directly from the battery or the plus terminal of the alternator) provides a reliable, if temporary, solution then that isn't it. Also I can't imagine how such a fault could affect your tachometer. Much more likely is an "upstream" fault; a bad ignition switch or, as essexpete suggested, a bad contact in a connector, a bad contact in the fuse box, etc. One big clue is the tachometer problem. I would presume that the problem lies in a part of the electric circuit that is common to the tachometer and the shutoff valve.

--
Best regards, Kári.

[gecko.cx]

The wiring diagrams I've looked at don't show an electronic Tacho, but presumably your is?
(is your serial above 400000?)

The solenoid earths direct to the pump/ engine block, so that the that rules out an earth problem at that end.
Does your battery Neg lead go the the block or chassis?
If you never use the lights, you may not notice a poor earth - worth checking.