Isuzu NPR experience ? - PeachParts Mercedes-Benz Forum

Fredmburgess · #1 12-11-2007, 09:07 PM

Sorry to post a non MB subject but more sorry that I've been working in cold rain for two days trying to get a '99 NPR diesel to start and run. I had some of the fuel hoses off so problem is undoubtedly air. I've checked all connections 10 x (will do it again in the morning). Worked primer pump until fuel flowed from opened bleed bolt. Tried cracking injector lines at injectors and cranking with starter. Thought it might be a failed fuel shut off solenoid and removed what I believe (HOPE) is that solenoid, which of course turns out to be functioning just fine except I can't see if it needs to attach to anything or just be screwed back in place. Frustrated...who, me?! I've got 6 diesels and this one - not mine - makes me feel like a complete beginner. Anyone have Isuzu specific experience or a service manual? Snow's coming and I've got to get this thing out of here!! Thanks for any and all suggestions. Nothing too simple - you never know!
Fred

#2 12-11-2007, 09:38 PM

The shutoff should be a remote mounted actuator/servo near the left cab hinge that pulls on a long bowden cable. It pulls the cable to shut it off. If you disconnect the bowden cable from the injection pump that will keep it running without the key and let it start with a bad actuator.

Also check the glowplugs. The NPR's I worked with got very difficult to start if more than one went bad below 40*F.

I'll agree with you though, the NPR's are an unusual breed.

Fredmburgess · #3 12-18-2007, 03:33 PM

Thanks for the reply. As it turned out I had a few things working against me (not the least of which was my own lack of patience!). The truck was facing uphill in my driveway, so fuel had a tendency to run back and away from the IP. I've learned that these engines are notoriously hard to prime if you've had the fuel system open as I did. In any case, I added a Walbro electric fuel pump and was able to purge the air and restart it within minutes of powering the pump. The bad news is that in my haste I removed not the fuel shutoff solenoid (which I can now locate - thanks!) but the cold start solenoid that moves the rack and advances the injection for a couple of minutes when starting at temps below about 25 F. After much inquiry I learned how to remove the operating foot of the solenoid and reinstall it to seal the IP, but of course it is no longer doing it's job. Truck's owner is happy enough as the thing runs fine, however, in order to make it right I'll probably pay an injection pump shop about $1000.00 to R/R the pump and solenoid. Oh well, sometimes you learn things the easy way and sometimes it's a bit harder. On the upside the thing runs like a top on WVO the WVO conversion I installed. Thanks for the feedback!

rbdevries · #4 06-06-2021, 07:31 PM

I have duplicated your problem and actions to the point that I have yet to get the truck started. I too removed the timing advance solenoid thinking it was the shut off solenoid. Just want to know what you finally did to get yours running and did you ever get the timing advance put back into action. Any advice will be greatly appreciated. Thank you in advance. I'm in SE Georgia so am not too concerned about cold start. THANKS!