Isuzu 4LE2 engine will not stay running.

[slowgoesit]

Isuzu BB-4LE2 engine will not stay running.
I have the above auxiliary engine. The engine will start normally, but will not stay running.

Normal start procedure is:

• Turn ign sw to "preheat"
• when glow plug is hot, turn ign sw to "start" while depressing spring loaded single pull sw, which I believe engages or (disengages) the engine stop solenoid
• The engine starts immediately, and normally after about 5 seconds you release the spring loaded switch, however the engine immediately quits after you release the switch

Note:

• Oil pressure immediately shows on gauge.
• Engine has not been run enough for coolant temp to begin registering
• Oil level is normal.
• Coolant level is normal
• raw water coolant pump is working properly, with water coming out of the overboard exhaust.
• I've checked/cleaned all the connections I can't find any corrosion or loose connectors.
• The engine stop solenoid appears to be operating properly, with a "click" being felt with the spring loaded sw depressed prior to start.

I am leaning toward a faulty oil pressure sensor (not the one to the gauge), or a faulty over temp sensor that is actuating, or not actuating the engine stop solenoid, causing the engine to stop running due to lack of fuel.

I don't know if the engine stop solenoid is normally closed, or normally open

The manual, as a troubleshooting guide is pretty much useless. I need to check the oil pressure sensor and coolant temp sensor, but I don't know if they are normal open, or normal closed at this point.

Just for further info, this aux engine turns a hyd pump that supplies hyd pressure to either a get home hyd motor, or the on board generator. It would be really REALLY nice to have it running again! I'm fairly sure it is something simple, but need to nail it down.

Anyone have any thoughts?

 

[slowgoesit]

Pics are of:
Data plate
Engine
Start Panel
Engine stop solenoid

 

[rslifkin]

Does it stay running if you keep the shutdown bypass switch pulled? If so, that points to an issue in that circuit. I'd follow the wires from the fuel solenoid to see where the wires go.

I'm thinking that the solenoid is likely powered to run and has 2 parallel circuits to it. One through the momentary bypass switch and the other through an oil pressure and coolant temp switch. If that's the case, there should be 2 wires to each of the oil pressure, coolant temp, etc. switches in the circuit. Try a jumper wire to bypass each of the switches one at a time and see which one is causing the shutdown.

 

[O C Diver]

I would agree with the above diagnostics. What is the date of manufacturer? The other point would be to look for an electronics box that might have a relay. The sensors may be part of a loop that holds a relay engaged to maintain the shutdown solenoid in the run position.

Ted

 

[slowgoesit]

I figured it out. It was a spade connection that came loose . . . . inside black electrical tape . . . . which in itself was inside split corrugated abrasion resistant shielding . . . . inside some more black electrical tape . . . .
The wire was originally too short, and movement of anything risked pulling loose that particular connection . . . . which it did, after 18 years. I took out two splices, and wired in the correct length wire, of the correct color and put everything back together. What a pain in the ass.

Thanks for the suggestions. It was a simple fix, obvious cause, just the execution (finding the pulled loose connection under multiple layers of shielding/tape) that made it difficult.

 

[Portage_Bay]

Good troubleshooting and problem solving. Sometimes it is the simple failures.


Something I've done when hunting down similar problems in gen sets is to first determine if the system is energize to run or energize to shut down. If energize to run, and they often are try physically holding the solenoid in the run position. If the engine will run when you do that then try jumping the solenoid directly from a power source. If the engine will continue to run and the gen set makes power with the solenoid jumped then the problem is likely simple though can be challenging to find. A bad relay or sender.


Unless of course if the gen set has modern electronic controls. That's another animal all together.

 

[slowgoesit]

Ray, thanks for the input. The generator DID continue to run with the toggle switch held down. So I knew it wasn't the lack of fuel to the generator itself, and was focusing on sensors and wiring till I finally figured it out. I saw no need whatsoever for the splices and spade connectors. I put it on the list to do some clean-up at a later date.

I think what happened was that the installer, back in 2005, due too the location of the engine start panel, needed to lengthen the wiring loom, and just poorly executed the extension.

That poor execution with be corrected once I get my refrigerator back up and running.
I have a list of minor housekeeping items to do once everything else is fixed . . . . I may even get to some of them eventually!

 

[Portage_Bay]

Yes you found and solved the problem. My post was intended to help others who have faced similar problems. Mine was a failed relay. It was enough of a puzzle finding that. Then it cooked two more relay coils before I figured that part of the puzzle out.

For those running older gear I can't say enough about the gang at Smokstak.com. A very knowledgeable bunch over there willing to help sort out issues with the older stuff.

And, as you note, all the other To-Do items on the boat list. Never ending.

Ray, thanks for the input. The generator DID continue to run with the toggle switch held down. So I knew it wasn't the lack of fuel to the generator itself, and was focusing on sensors and wiring till I finally figured it out. I saw no need whatsoever for the splices and spade connectors. I put it on the list to do some clean-up at a later date.

I think what happened was that the installer, back in 2005, due too the location of the engine start panel, needed to lengthen the wiring loom, and just poorly executed the extension.

That poor execution with be corrected once I get my refrigerator back up and running.
I have a list of minor housekeeping items to do once everything else is fixed . . . . I may even get to some of them eventually!