05 NPR "Fail-Safe" mode fuel problem-...

05 NPR "Fail-Safe" mode fuel problem--no throttle response

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Atlanta, GA

#1 Nov 29, 2011
Bought a used 05. At random times, goes into "fail safe" mode where the engine continue to run but no throttle response. If you pull over, turn off the truck, then crank back up the computer resets and you can continue driving. The computer code is supposedly a fuel problem. The dealer mechanic replaced injectors, filters, dropped the fuel tank to check for rust, did almost everything to do with fuel. Got it back, drives fine for a day or two and then does it again. Went to another dealer--they had it for 5 days and couldn't fix it. I am frustrated! It will run fine for 2-3 days and then do it 5 times in five miles. There is no consistency--sometimes under power, occassionally at idle. Sometimes with full fuel tank, sometimes with 1/4 tank. The truck runs fine otherwise, but it is certainly dangerous when the throttle suddenly stops working in the middle of an intersection.

Sierra Vista, AZ

#2 Jan 1, 2012

Has this issue been resolved? It sounds like a connector problem. Has the engine been cleaned? Isuzu has a bulletin concerning under cab connectors and the need to use liberal amounts of silicone dielectric on all weather exposed connectors.

Atlanta, GA

#3 Jan 2, 2012
No, the problem has not been resolved. We are going through a period now where it is running fine--hasn't done it in two week (same tank of fuel it was doing it with a lot before). Considering that the computer error code is supposedly a fuel related issue, can you tell me what connectors might be most likely to be the issue? Is there any way to determine what connectors might be malfunctioning? Corrosion? Thanks for your help.

Sierra Vista, AZ

#4 Jan 16, 2012
There is a bulletin TSB SB08-J-003A
Symptoms are:
Lack of Power
Engine will not rev up
Idle vibration
Sometimes engine starting concerns

It turns out to be the fuel pressure regulator
It affects all models from 2005-2010
The suction valve control(in the FRP) is faulty.
Testing is monitoring the "Actual vs Desired" pressure stability during idle and wot conditions.

New Castle, DE

#5 May 16, 2012
sounds like your problem is the fuel suction control valve. it is located on the fuel pump. has a white electrical connector. green one is fuel temperature sensor.
Pat at The Parkway Crew

Vancouver, Canada

#6 May 28, 2012
2005 Isuzu NPR Intermitant code p0087 with no throttle response. Dealer has replaced suction control valve 2 times. Problem is still there.Can be fine for days or act up multiple times a day?

Spring Hill, FL

#7 Oct 12, 2012
2001 NPR diesel Isuzu . Engine recoup out of control, ignition switch won't stop it. Hard to start. Any ideas or solution welcome

Olympia, WA

#8 Jan 18, 2013
Pat at The Parkway Crew wrote:
2005 Isuzu NPR Intermitant code p0087 with no throttle response. Dealer has replaced suction control valve 2 times. Problem is still there.Can be fine for days or act up multiple times a day?
Has anyone ever figured out what is going on with this truck? I have one doing the exact same thing. Very frustrating because I have no codes but the temperature light flashes and the alarm for over heating goes off just before the problem happens. I read the scan tool and the temp is right at 187 degrees when it happens.

Atlanta, GA

#9 Jan 18, 2013
My 2005 NPR is still doing it. We limp through the day and I dream of when I can sell the darn thing. Still no insight.

Bremerton, WA

#10 May 14, 2013
Chris wrote:
My 2005 NPR is still doing it. We limp through the day and I dream of when I can sell the darn thing. Still no insight.
I've got the identical problem... between 3 shops scv, fpr,rail pressure sensor, isuzu fuel filter, drop tank check fuel supply lines,performance test pump (oregon fuel injection), no problem in reverse select drive and problem occurs randomly ( drove vehicle in reverse selected drive within 20 feet limp mode happens

Detroit, MI

#11 May 21, 2013
change fuel filter housing, they leak and you dont know it. try bypassing filter, if truck runs ok, you know thats your problem.

North Fort Myers, FL

#12 May 24, 2013
buy a new pig tail for the suction control valve that should fix your problem

Littleton, CO

#13 Sep 19, 2013
2003 W4500 Isuzu cabover. Throttle control dies periodically, where it won't operate over 5 mph. Very dangerous situation. Sometimes lasts for days and then operates fine. Have had gas pedal, throttle and battery clamps replaced. Entered new computer updates and recoded. Works for day or two and symptoms return.

Bixby, OK

#14 Sep 28, 2013
(3)2005 npr's (2)'06 npr and (3)'08 npr's all running rough,limp home mode P1093 code.local dealer replaced turbos, injectors,scv's,fpr's fuel filters and housings, air filters,intake tubes exhaust filter and manifolds,fuel tanks electrical connectors and pigtails.they run good for a couple weekes then back down again with same code.isuzu will no longer help with warrenty.its clear everyone haven the same problem.has anyone fixed one yet..
dealer alternative inc

Hollywood, FL

#15 Oct 25, 2013
i have fixed 4 of these so far with a fuel filter head this is where the manual pump is and f. filter is atached to there is a restriction you can test it by holding the engine at high speed for a few minutes and see if the plunger sucks down (hand pump)





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Houston, TX

#16 Dec 4, 2013
Same issue on mine changed scv and pig tail, frp sensor, fuel limiter, new primer pump (6 months ago) new filter.

Manchester, UK

#17 Dec 10, 2013
iv got 54 plate npr starts fine will rev up to 4000 rpms no problem then after 10 secs it in limp mode soon as I ask for more power wont go above 1000rpms and bellows white smoke out changed filter drop tank airlined fuel pipes same on injector pipes van still the same any help out there

Manchester, UK

#18 Dec 10, 2013
ps its not using water or oil engine light comes for 5 secs then goes off

Garden City, KS

#19 Dec 17, 2013
same problem truck goes into limp mode if you go over 50 mph shuts down to idle and no throttle response. also check engine light comes on right before it happens, been in the hop two weeks and mechanic is guessing

Gainesville, FL

#20 Jan 11, 2014
I've got 9 sweeper on the road 7 nights a week I've been dealing with fail save modes for years
Buy only Isuzu filters
Make shore you have the right fuel caps on
Some trucks have a screen in the fuel pumps that clogg

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