Isuzu 42 question.

[Kipper 2]

Yesterday I suffered my first ever breakdown when all power to my control pedestal was lost. All the gauges went to zero, the alternator warning lamp came on, but no buzzer and the engine stop button was dead. 
Luckily we was able to tie up, stop the engine manually and fix the fault, which was, to cut a long story short, a broken wire in wiring loom. 
On reflection and studying the wiring diagram, the diesel lift pump had no supply it it either - So why didn’t the engine stop? 
Can anyone shed some light on this please?

[MtB]

Was your diesel tank full or close to full? 

 

If yes the suction created by the injector pump may well have been able to pull fuel through the lift pump.

 

 

[Tony Brooks]

2 minutes ago, MtB said:

Was your diesel tank full or close to full? 

 

If yes the suction created by the injector pump may well have been able to pull fuel through the lift pump.

 

 

 

and the fuel level was high enough to give a gravity feed to the engine, so not just any suction from the injector pump(s)

[Kipper 2]

Full tank of diesel.

[Tony Brooks]

10 minutes ago, Kipper 2 said:

Full tank of diesel.

 

There you are, you have the answer. The valves in the lift pump will normally allow a gravity feed straight through the pump.

[LadyG]

How does one stop the engine manually if the stop button is dead.

I have an Isuzu LB33

[Russ T]

11 minutes ago, LadyG said:

How does one stop the engine manually if the stop button is dead.

I have an Isuzu LB33

Our Isuzu 42 used to have a manual stop lever (in addition to the stop solenoid). Consult your manual. Some engine I have seen have them in a pretty precarious position that makes reaching them on a running engine a health and safety nightmare. The Isuzu stop lever was located more sensibly iirc.

 

Some manuals here

 

https://www.enginesplus.co.uk/isuzu-canal-boat-engines/

Edited Monday at 08:31 by Russ T

[nicknorman]

If it’s anything like our Beta 43 install, there is an electric lift pump but also the mechanical lift pump on the engine. The former is “optional” depending on the installation, but anyway makes bleeding much easier. So there should be no problem with the engine continuing to run without the electric pump. Ours certainly does.

 

Our engine also has a manual shut off lever adjacent to the solenoid. In the absence of that I guess you could block off the air inlet to force a stop, probably better than turning the fuel tap off.

 

[b00ke23]

10 minutes ago, LadyG said:

How does one stop the engine manually if the stop button is dead.

I have an Isuzu LB33

 

There is normally a small lever on the injection pump that you can manually move to stop the engine. Sometimes not that obvious and does require a trip into the engine ‘ole!

[Tony Brooks]

14 minutes ago, b00ke23 said:

 

There is normally a small lever on the injection pump that you can manually move to stop the engine. Sometimes not that obvious and does require a trip into the engine ‘ole!

 

Or, in the case of some Vetus a rubber diaphragm assembly screwed into the injection pump to push in.

 

To others, get someone to operate the stop switch/button while you look around the engine to locate what is clicking.

Edited Monday at 08:48 by Tony Brooks

[Mike Adams]

If your fuel level is higher than the fuel injection pumps(1 for each cylinder) then the engine will run without the lift fuel pump and if the system is full of fuel it will also run if the injection pumps create enough of a vacuum to keep drawing fuel if it is not much higher than the tank, so if you have a tank in the counter the fuel level is likely to be higher than the injection pumps so it will run without the electric pump. I attached a manual cable to the mechanical stop lever on the engine in case the electric solenoid one fails.

[cuthound]

10 hours ago, nicknorman said:

If it’s anything like our Beta 43 install, there is an electric lift pump but also the mechanical lift pump on the engine. The former is “optional” depending on the installation, but anyway makes bleeding much easier. So there should be no problem with the engine continuing to run without the electric pump. Ours certainly does.

 

Our engine also has a manual shut off lever adjacent to the solenoid. In the absence of that I guess you could block off the air inlet to force a stop, probably better than turning the fuel tap off.

 

 

I used to specify automatic overspeed air shut off valves for the diesel engines on the standby generators I installed. You can also get manual versions.

 

https://www.chalwyn.com/products/air-intake-shut-down-valves

 

You need to be very careful to keep your appendages away from the air intake when stuffing something into it to stop the engine, particularly if it is running away!

Edited Monday at 19:01 by cuthound
Clarification

[ditchcrawler]

1 hour ago, cuthound said:

 

I used to specify automatic overspeed air shut off valves for the diesel engines on the standby generators I installed. You can also get manual versions.

 

https://www.chalwyn.com/products/air-intake-shut-down-valves

 

You need to be very careful to keep your appendages away from the air intake when stuffing something into it to stop the engine, particularly if it is running away!

We used them on all plant offshore in case they strated breathing gas and not air

[MtB]

2 hours ago, ditchcrawler said:

We used them on all plant offshore in case they strated breathing gas and not air

 

Air IS gas! 

 

 

[nicknorman]

10 hours ago, MtB said:

 

Air IS gas! 

 

 

Ah yes, so all this fuss about the Gas Safe register is just hot air!

[David Mack]

6 minutes ago, nicknorman said:

Ah yes, so all this fuss about the Gas Safe register is just hot air!

Don't give them ideas - there'll be an Air Safe Register next!

[Jen-in-Wellies]

2 hours ago, David Mack said:

Don't give them ideas - there'll be an Air Safe Register next!

And quite right too. Get the mixture wrong, or too much, or too little and you can die! Could argue that the BSS ventilation requirements, though advisory for private boats, are to make them air safe. 

[system 4-50]

A friend of my son was an 'air controller.  No, I've misspelt that.  He was a Hare Controller.  At Walthamstow's greyhound track.

[MtB]

3 hours ago, nicknorman said:

Ah yes, so all this fuss about the Gas Safe register is just hot air!

 

All true! But GSR forms an excellent moat to help keep the hoi-polloi away from messing with it. 

 

 

 

 

[Kipper 2]

On 01/06/2026 at 14:30, Mike Adams said:

If your fuel level is higher than the fuel injection pumps(1 for each cylinder) then the engine will run without the lift fuel pump and if the system is full of fuel it will also run if the injection pumps create enough of a vacuum to keep drawing fuel if it is not much higher than the tank, so if you have a tank in the counter the fuel level is likely to be higher than the injection pumps so it will run without the electric pump. I attached a manual cable to the mechanical stop lever on the engine in case the electric solenoid one fails.

That sound a good idea and one I’ll look at when I get back to home base 👍

[Tony Brooks]

5 minutes ago, Kipper 2 said:

That sound a good idea and one I’ll look at when I get back to home base 👍

 

Not to me, it does not. As long as they are not left energised long after the engine has been stopped the stop solenoids are remarkably reliable. Certainly locate the stop lever so you know how to stop it if the solenoid/wiring fails, but one of the most common "my engine won't start" causes on boats with a mechanical stop cable is the cable being left pulled out - human error.

 

 

[Mike Adams]

One of the main problems with the Isuzu marinisation is the wiring loom. They use a block connector in the wiring loom that tends to be unreliable and causes all sorts of electrical issues. I don't often disagree with Tony but if the mechanical shut off is not easily accessible then I would fit a mechanical stop outside the engine space. If you have any sort of fire in the engine space you probably wont be able to get to the stop control. Use a solid metal cable with metal outer sheath. You can buy them on Ebay with a Red Knob and just mark it Emergency Stop.

[cuthound]

15 hours ago, Tony Brooks said:

 

Not to me, it does not. As long as they are not left energised long after the engine has been stopped the stop solenoids are remarkably reliable. Certainly locate the stop lever so you know how to stop it if the solenoid/wiring fails, but one of the most common "my engine won't start" causes on boats with a mechanical stop cable is the cable being left pulled out - human error.

 

 

 

One of the first things I did in my Beta 43 was to paint the stop lever red (it was Beta green like everything on the engine, including the hoses) so that anyone unfamiliar with the engine could identify it and stop the engine should the stop solenoid fail.

[blackrose]

33 minutes ago, cuthound said:

 

One of the first things I did in my Beta 43 was to paint the stop lever red (it was Beta green like everything on the engine, including the hoses) so that anyone unfamiliar with the engine could identify it and stop the engine should the stop solenoid fail.

 

My stop solenoid became disconnected once and it's quite disconcerting when you push the stop button and nothing happens.

 

I drilled a hole in the control pedestal and attached one of these "Pull to stop" cables to the stop lever so I can manually stop the engine without lifting cruiser stern deck boards.

 

[David Mack]

I remember when all those "pull to stop" cables had the word "choke" printed on the knob.