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New to forum - need help finding support for Isuzu NPR

Discussion in 'Trucks and Trailers' started by spray_man, Nov 2, 2006.

  1. spray_man

    spray_man LawnSite Member
    Posts: 176

    There is plenty of support for all other diesel trucks. Most of the posts here (I searched) touch lightly on mechanical/electrical issues for the Isuzu/GMC NPR. Does anyone know of a site that has more members with NPR trucks? I only count a few owners here with NPRs. My current issue is with a broken exhaust break. Does anyone with NPRs have experience with the exhaust break system? I have a 95 1/2 model year. Your help will be greatly appreciated.

  2. vntgrcr

    vntgrcr LawnSite Senior Member
    Posts: 282

    spray man
    I also have a 95 that has a exhaust brake that does not work. The switch on the stalk works, and the light illuminates but it does not activate the vacuum solenoid. Checked the relay and no luck. I need to do some more electrical diagnostics. Let me know and I will see if I can help you. Good luck finding a shop/ owners manual. I havn't been able to locate one yet. Tom's Trucks has one, but it is around $ 180.
  3. spray_man

    spray_man LawnSite Member
    Posts: 176

    Do you know if the brake will activate at idle/stop? This would help troubleshoot the problem. I know were some of the parts of the system are. But, I don't know if I have all of them. I might do some work on it this weekend. I will let you know what I find.
  4. allinearth

    allinearth LawnSite Senior Member
    Posts: 609

    I have a 95 with the same prob. Let me know if you find a fix.
  5. RockSet N' Grade

    RockSet N' Grade LawnSite Silver Member
    Posts: 2,454

    I do not have a NPR, but I did install an after market exhaust brake on my bob-tail. My experience with the International truck staff left alot of unanswered questions, so I talked with the exhaust brake manufactures/reps directly and they dialed me in within minutes.
    My suggestion would be to call a specialist in this area, not the truck dealer, and my sense is you will get diagnostic information pretty darn fast and accurate. Some of the top dogs with aftermarket stuff: Banks, BD Diesel, Pac Brake and Jacobs. You can find all their sites and numbers on the web.
  6. Ax Man

    Ax Man LawnSite Senior Member
    Posts: 446

  7. spray_man

    spray_man LawnSite Member
    Posts: 176

    Thanks for the great advice. I looked at my exhaust brake system yesterday. As far as I can tell, there are four components. The electrical relay (working), A vacuum valve (working) next to the third item, mounted on the rail, the butterfly actuator (not working ?) in line with the exhaust pipe. The fourth Item is what appears to be a vacuum reservoir tank (I think is working - I didn't think to test it - after I found the actuator not working), mounted on a cross rail behind the muffler.

    I was hoping it was the valve, because it only costs $150. The actuator is $350. The valve is easy to test. It is better to remove it and test it on the bench (easy to remove). There are three inputs to the valve: one to vacuum, one to the actuator, and one to the reservoir tank. When idle the valve is open from the reservoir tank to the actuator. When activated (apply 12vdc to the two pins) the valve is open from the vacuum source to the actuator.

    Before I buy the actuator, I am going to do the same test on the actuator I have on my 1994 truck, which has the same actuator.
  8. spray_man

    spray_man LawnSite Member
    Posts: 176

    I forgot to mention, to test the actuator, use a vacuum pump, and see if it actuates. In my case the actuator was leaking pretty good.

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