2001 Isuzu NPR

[Delmer]

Simplest way to test the solenoid, no voltage with key off I assume? turn the key on, does it have battery voltage? start the engine, does it have battery voltage? after the engine dies, does it have battery voltage?
more complicated way, run a test lead into the cab, and watch the voltage on a multimeter as you turn it on, start it, run it, and watch it die.

If there's only those two solenoids, then the fuel shut off is what you want to test. If the voltage is still present after the engine dies, then check the ohms of the solenoid before starting it, and again after it dies, in case it is an intermittent failure as it warms up, and works again when cold.

 

[R8f1k]

Ok, I can do that. I have a good meter. I have a couple broken and bad vacuum lines, could they be controlling this feature and shutting off fuel?

 

[Delmer]

5% of full fuel rate will not kill the engine, it would be hardly noticeable in most driving.

 

[R8f1k]

Got it.

 

[R8f1k]

Ok, tried it all over again.

1) Inspected the fuel lines, found a tiny leak, ran new line again. No change, runs for about 3-4 minutes, shuts off.
2) Removed the fuel lines from the water separator, connected that together to bypass the water filter, no change. No change, runs for about 3-4 minutes, shuts off.
3) Checked all the connections to make sure no air leaks, bled the system again. I mounted my camera on my toolbox to record the fuel shut off cable. Cable doesn't move, runs for about 3-4 minutes, shuts off.

I'm at the end of my knowledge on this kind of thing. Thinking about taking it in and having an experienced diesel mechanic look at it.

 

[heymccall]

Unbolt the muffler from the exhaust brake and retry.

 

[R8f1k]

I will try that, any thoughts on what that might be doing?

 

[cfherrman]

Let it idle and be ready with a can of ether, when it dies give it a snort and see if ether keeps it alive, do a few more puffs to make sure you are well past the period when it normally dies

 

[cfherrman]

I will try that, any thoughts on what that might be doing?

Fuel compression or heat, well it runs so it's not the last two, I'm wondering if it's running out of air, either by air in or air out.

 

[R8f1k]

I have to bleed it every time.

 

[R8f1k]

How do you find air leaks in a fuel system? Could it be the fuel pickup in the tank?

 

[Delmer]

There's so much going on here it's hard to tell what's what. How about a picture of the "fleet monitoring" device, and trace some of those wires in the wiring diagram to see if it ties into the ECM. I'm assuming this has an ECM that controls the pump in some way, since it's Japanese and 2003.

Have you ever walked away from it for an hour when it dies, and see if it starts up without bleeding it then? so that it's only time, and not bleeding that makes it start.

If it still needs to be bled the next day to start, then a vacuum/pressure gauge, and clear tubing will help you find air and blockages if that's the last resort.

 

[R8f1k]

There's so much going on here it's hard to tell what's what. How about a picture of the "fleet monitoring" device, and trace some of those wires in the wiring diagram to see if it ties into the ECM. I'm assuming this has an ECM that controls the pump in some way, since it's Japanese and 2003.

Have you ever walked away from it for an hour when it dies, and see if it starts up without bleeding it then? so that it's only time, and not bleeding that makes it start.

If it still needs to be bled the next day to start, then a vacuum/pressure gauge, and clear tubing will help you find air and blockages if that's the last resort.

There is a lot going on. Hard to determine sometimes what to do. I forgot to get some shots of the fleet monitor. I will get that ASAP.

I have walked away and tried, still needs to be bled. Every time it dies, there is no fuel at the injectors.

I am considering running all new fuel lines and not using any of the old solid lines. I replaced all of the hoses that were connected to the solid lines running to the tank. I have 3/8" hose, I am going to replace all of it soon and see if that changes anything.

Is there anyway to intentionally pressurize the system with air and search for leaks?

 

[Nige]

I've been an interested bystander in this since the start. FWIW I would be ruling out a problem in the tank before going any further, even if that meant taking it off and turning it upside down. If something is floating around in there it could easily be producing the symtoms you are experiencing.

 

[R8f1k]

I've been an interested bystander in this since the start. FWIW I would be ruling out a problem in the tank before going any further, even if that meant taking it off and turning it upside down. If something is floating around in there it could easily be producing the symtoms you are experiencing.

I am thinking about pulling the tank, cleaning it out and putting a new pick up assembly in to ensure I am not sucking air. Any experience with issues like this in the past?

 

[R8f1k]

I've been an interested bystander in this since the start. FWIW I would be ruling out a problem in the tank before going any further, even if that meant taking it off and turning it upside down. If something is floating around in there it could easily be producing the symtoms you are experiencing.

Might I be better off trying to plumb a remote tank with an electric pump and see if I get the same issue?

 

[Nige]

I am thinking about pulling the tank, cleaning it out and putting a new pick up assembly in to ensure I am not sucking air. Any experience with issues like this in the past?

Basic diagnostics for me is that when diagnosing a fuel system you start from the tank and work towards the engine. Until you can definitively rule out the tank as a possible source of the problem you shouldn't be moving forward. My 2c, YMMV.

 

[Delmer]

You don't need a remote tank and electric pump. A gallon jug half full of diesel with the supply and return lines stuck in the top will work.

The other thought I forgot, use a stop watch when you start it, if the shut off is near exactly an even minute mark, then I'd suspect the "monitor" and try it again to see if it runs the same time.

 

[R8f1k]

I have been using a stop watch, we are right around 3:30-4:30 minutes. I’m going to try the tank tomorrow. I will also add some photos of the monitor and see if you guys know what it is.

 

[heymccall]

It's a purely mechanical injection system. The only electrical interface, of consequence, is the fuel shut off cable.
Unless someone has installed an electric shutoff solenoid in the fuel line.

Earlier, I suggested disconnecting the muffler, as, technically, it's a catalytic converter of sorts. They can get plugged/ restricted.