2001 Isuzu NPR

[Wolfish-Greg]

If the shutdown actuator is working or disconnected to run position and air is bled out of the IP most likely one or more plungers are stuck causing the fuel rack to be locked up in shutdown position. I have had 6 or more injection pumps in the past year with the rack stuck because of varnish gumming up the plungers which sticks to the barrels and the fuel rack won't move. Sometimes I was able to carefully force the rack to move and with the injector lines loose spin the engine while working the rack and it freed up. Usually happens when they sit for 6 months or more, the fuel now days is garbage, if you keep an additive in the fuel it helps, I usually put Lucas Injector cleaner or Marvel Mystery Oil in every time I add fuel to help prevent the varnish.

 

[R8f1k]

Let me say in advance, I am not a diesel guy at all. I am pretty new to them. I teach auto tech at a local high school, but diesels are rarely seen in our shop, so I am learning as I go. THANK YOU for all of your help up to this point.

First, I am betting that I have a problem with the engine is the fuel shut off. I am wondering if the fuel shut off isn't pushing enough.

Second, I have no idea what the 'rack' is. How do I move it? Is there a way to pour something into the injection pump and let it sit for a while to loosen things up? Marvel mystery? Biodiesel?

Finally, I just bought a manual for this unit so I am going to study that a little to try and get a better understanding of what to do with the pump.

(Side note: once I get it up and running, any thoughts on what kind of diesel to buy and to continue to buy? I have access to a few kinds here in rural Wisconsin)

Any recommendations are appreciated.

 

[Delmer]

If it started, ran, and died three times, then I don't think you have an internal problem with the injection pump, unless there is water or really nasty fuel in it. If it gets air in the lines to the injectors, it will take a while to start, it will start easier if you loosen the injection pump line at each injector and crank until there is no more air bubbles, just fuel. Assuming you can do that on this engine, I believe you can.

 

[heymccall]

Remove water separator bowl, then remove and clean screen in filter head.
Just had same issue on my '00 Npr.

Also had one, years ago, with plugged muffler. Started normal, petered out within 5 seconds, wouldn't restart until it sat for at least 20 seconds.

 

[R8f1k]

If it started, ran, and died three times, then I don't think you have an internal problem with the injection pump, unless there is water or really nasty fuel in it. If it gets air in the lines to the injectors, it will take a while to start, it will start easier if you loosen the injection pump line at each injector and crank until there is no more air bubbles, just fuel. Assuming you can do that on this engine, I believe you can.

I can do that on this engine, however, regardless of how long I let it prime or crank, no fuel at the lines to the injectors. HAS TO BE the fuel shut off.

 

[R8f1k]

Remove water separator bowl, then remove and clean screen in filter head.
Just had same issue on my '00 Npr.

Also had one, years ago, with plugged muffler. Started normal, petered out within 5 seconds, wouldn't restart until it sat for at least 20 seconds.

I am replacing my fuel filters very shortly. I ordered new units, I hope to get them in ASAP. I am pretty sure the muffler is good.

 

[R8f1k]

I was able to get the unit running today, I adjusted the fuel shut off cable, she started up pretty quick and then died after about 5 minutes. Tried again and no start. Checked and there was no fuel in the injectors lines. Bled the system again, started and ran for a while then stopped again. I'm going to wait on filters to try again. Anyone know if I do in fact have a bad injector, will that allow air into the system?

 

[heymccall]

Minimal tools required....
Remove both fuel lines from water separator housing in front of batteries. Unbolt whole assembly, taking care to keep it upright. Carry it away and shake it upside down over a clean pan. Once all the crap is done falling out, take it apart and clean the screen.

And, a faulty injector will NOT introduce air to the system.

 

[R8f1k]

I will do that. I am getting new Baldwin filters on tomorrow, when they show up, I will pull apart that unit, clean it up and install new filters.

 

[R8f1k]

The end plate is right between the bell housing and the injection pump. There are 5 5mm allen head screws that hold the plate on.

After taking a look at the back of the pump, there are about 8 5mm bolts. Not all of them are easily accessible, especially along the bottom. Do I have to yank out the injection pump out to put the solenoid back in? Also, can I run this truck with the solenoid in, but without the little 'foot' on it? It starts without it, but will I have issues down the road?

 

[R8f1k]

Minimal tools required....
Remove both fuel lines from water separator housing in front of batteries. Unbolt whole assembly, taking care to keep it upright. Carry it away and shake it upside down over a clean pan. Once all the crap is done falling out, take it apart and clean the screen.

And, a faulty injector will NOT introduce air to the system.

No screen present. I think this is an aftermarket filter housing. There is a small black flap that seems to act like a one way valve. Not sure what that is for.....anti-drainback?
Below is a photo of a VERY similar unit.

 

[heymccall]

My '99, '00, and '01 NPR all have the separator on left, where #29 is said screen.
You, apparently have a 1(b), the style on the right.

 

[Delmer]

No screen present. I think this is an aftermarket filter housing. There is a small black flap that seems to act like a one way valve. Not sure what that is for.....anti-drainback?
Below is a photo of a VERY similar unit.

that has a primer on it, in order for the primer to work it needs two check valves, the rubber flap could be one of those check valves.

 

[R8f1k]

My '99, '00, and '01 NPR all have the separator on left, where #29 is said screen.
You, apparently have a 1(b), the style on the right.
View attachment 283842

I do have the other unit. I have the bottom section of the water separator. I also have a 2003 NPR which might explain it.

 

[R8f1k]

UPDATE. I installed new Baldwin fuel filters, bled the system and she fired RIGHT UP! No hesitation, nothing. Ran pretty good and I wanted to clean out the mess underneath it. I pulled it outside drove about 200 feet and it died. No restart. I checked for fuel at the injectors, none. I have lots of fuel at the water separator, I have lots of fuel at the bleeder behind the injector pump and I have lots of fuel at the upper fuel filter. WHAT THE HELL IS GOING ON?!!!

I changed the lift pump with a 'new' unit. It is totally a Chinese or similar build unit. Is it possible that the pump is trash? Could it be bad out of the box? Any way to tell? I keep losing fuel/fuel pressure.

 

[R8f1k]

The unit I have is just like this, but I had an issue. It came in the box assembled very similar to this, but it did not fit the engine. The fuel line from the fuel filter was only able to go on the back most right port. Does it matter what port is used for what? Is this just a universal pump and any port works? Do I have things in the wrong spot? Is there a way to pressure test? This is making me nuts......

 

[R8f1k]

Is it possible that the oil pressure switch is no good and causing a situation where it is a safety measure to kill the engine? I changed the oil yesterday, 14.8 quarts and a new filter, I still have the oil warning light on. There is a little box/panel to the right of the steering column that has red lights, one keeps flashing regardless and it is the oil light.

 

[R8f1k]

After doing a little looking on the web, I found that the little panel I have to the right of the steering column is an aftermarket device of some kind, not stock to the truck. I don't see any photos of other NPR's with the panel on it. It has 5 lights on it, indicating oil, temps, etc. It lights up with the ignition switch and seems to be some sort of fleet vehicle monitoring device. Could this thing be malfunctioning and causing all these issues? Could it be shutting down my truck? I will add a photo ASAP. Maybe this afternoon, maybe tomorrow.

 

[Delmer]

Yes, an aftermarket "fleet monitoring" thingy could shut down the engine. I've never heard of a TRUCK that would shut down from oil pressure or temp. Do you know how the injection pump is controlled, I thought that injection pump would have been electronically controlled since the mid 90's, that is, more than just one solenoid to shut it off, a whole wiring harness to control timing etc. If it's only one wire to one solenoid, that's much easier to test for voltage while running, with the key on but not running, and after it dies.

As for the pump, you'd have to pump it by hand to confirm it's working. I wouldn't think there are more ports, but I guess I've never looked that close. I'd think the other ports are access to the valves or mounting holes.

 

[R8f1k]

Yes, an aftermarket "fleet monitoring" thingy could shut down the engine. I've never heard of a TRUCK that would shut down from oil pressure or temp. Do you know how the injection pump is controlled, I thought that injection pump would have been electronically controlled since the mid 90's, that is, more than just one solenoid to shut it off, a whole wiring harness to control timing etc. If it's only one wire to one solenoid, that's much easier to test for voltage while running, with the key on but not running, and after it dies.

As for the pump, you'd have to pump it by hand to confirm it's working. I wouldn't think there are more ports, but I guess I've never looked that close. I'd think the other ports are access to the valves or mounting holes.

What solenoid am I testing? Fuel shut off? There is also the Cold Temp Solenoid that I still have a problem with, but I would think that it should still work regardless. Am I looking for a drop or loss in voltage?