2000 NPR electrical issue

2000 NPR electrical issue

Posted in the Isuzu NPR Forum

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Scott

Attleboro, MA

#1 May 23, 2010
When I turn on the key, no dash lights, and it won't engage the starter. Headlights, flashers, and horn do work. Before it totally quit working, I could hear a relay click under the dash that seems like it must be some sort of master relay. I've swapped out every relay I can locate (I don't have a manual) and they all seem to be fine (I swapped them with the horn relay, they all seem to have the same part number). Any suggestions on what to check next would be greatly appreciated. Thanks!
Sam

San Jose, CA

#2 Jun 9, 2010
I had the same problem.I checked the fusible link in the fuse box located behind the cab on the drivers side,the one that says NO STEP, to find the 50 amp fuse blown.Got a new one in and dash lights came on. Turned the key to start and the starter was making all these awfull noises then the starter froze and blew my new fusible link. I replaced the starter and the 50 amp fusible link and problem solved.
Scott

Attleboro, MA

#3 Aug 2, 2010
Thanks Sam, but the fuses all seem fine. I've no idea what is going on with this thing. I guess I need to break down and get the service manual for a hundred bucks.
Mike

United States

#4 Apr 3, 2011
Truck turning over no spark replaced coil and modulator are there any fuse behind the cab that could case this
Scott

Attleboro, MA

#5 Apr 4, 2011
Mike wrote:
Truck turning over no spark replaced coil and modulator are there any fuse behind the cab that could case this
Hey Mike, thanks for responding. This is a diesel, so no coil/etc. I have checked the fuse box behind the cab, they all appear fine. Several people I have spoken to (that don't know each other) all seem to feel this is a bad ground issue somewhere, so there's a common theme I'm going to try to check out next.
Scott

Attleboro, MA

#6 Aug 17, 2011
Hi all, I still don't have a solution if anyone has any other ideas. I did buy the electrical troublshooting manual but have not had the opportunity to dig in with it yet. It behaves like a bad ignition switch, but I replaced that. $100 down the drain. I can jumper a couple of contacts on the switch and get it to start...which is why I thought it was the switch.
Robert

Superior, WI

#7 Sep 14, 2011
We were fighting with a problem that sounds exactly like yours on a 1997 Isuzu NPR, 3.9L turbo diesel with the RLW/4BD2 engine. We replaced the ignition switch and the starter with-out solving the problem. We also went through all the grounds, because like you, I thought it was a ground issue. I found a link to a free NPR shop manual of a European version, which wasn't exactly right, but helped and had diagrams of all the grounding points and wire routing and circuit diagrams (don't let the website name fool you, it really is a NPR shop manual) http://www.weatherproof-windows.co.uk/nkr_rep...
Anyway, when WE FINALLY SOLVED THE PROBLEM it turned out to be a break in the wire in the harness between the fuse/relay box behind the cab (the one that says "no step") and the dash. The circuit goes through the 80A fuse, a wire leaves the fuse/relay box and splits somewhere to feed the ignition switch on the steering column and after running through a 30A fuse in the fuse panel on the dash returns to the fuse/relay box behind the cab to feed the hot side of the starter relay. We ran a new wire from the downstream side of the 50A fuse in the fuse/relay box to the ignition switch and also jumpered from the same point over to the supply side of the starter relay. This eliminated the 30A fuse in the panel on the dash, but now the truck works and we did not have to replace the entire wire harness.
Robert

Superior, WI

#8 Sep 14, 2011
Oh, I forgot to mention. One of the reasons that it was so hard to find the problem was that the wire must have still been making some contact, so that the volt meter still showed 12v but when we turned the key the voltage would drop to zero once the load was on it. Jumping the contacts on the back of the ignition switch worked because there is another hot circuit there and you could get power from the wrong place to make the truck start. We did that too.
john

Fredericktown, OH

#9 Oct 2, 2011
just got 98 isuzu w4 diesel.has been sitting for 4 years.clutch and shifting is rough barley able to get in gear.batt,brake and vacume warning and buzzer is on?where can i get a manual?
john

Fredericktown, OH

#10 Oct 2, 2011
Scott wrote:
Hi all, I still don't have a solution if anyone has any other ideas. I did buy the electrical troublshooting manual but have not had the opportunity to dig in with it yet. It behaves like a bad ignition switch, but I replaced that.$100 down the drain. I can jumper a couple of contacts on the switch and get it to start...which is why I thought it was the switch.
where did youfind the elec trouble shooting manual
john

Fredericktown, OH

#11 Oct 2, 2011
any one know where to find manuals? i have issuzu w4 1998
NPR manual

Columbus, OH

#12 Feb 23, 2012
I looked at the diesel, do they have one for a gas engine?
Robert wrote:
We were fighting with a problem that sounds exactly like yours on a 1997 Isuzu NPR, 3.9L turbo diesel with the RLW/4BD2 engine. We replaced the ignition switch and the starter with-out solving the problem. We also went through all the grounds, because like you, I thought it was a ground issue. I found a link to a free NPR shop manual of a European version, which wasn't exactly right, but helped and had diagrams of all the grounding points and wire routing and circuit diagrams (don't let the website name fool you, it really is a NPR shop manual) http://www.weatherproof-windows.co.uk/nkr_rep...
Anyway, when WE FINALLY SOLVED THE PROBLEM it turned out to be a break in the wire in the harness between the fuse/relay box behind the cab (the one that says "no step") and the dash. The circuit goes through the 80A fuse, a wire leaves the fuse/relay box and splits somewhere to feed the ignition switch on the steering column and after running through a 30A fuse in the fuse panel on the dash returns to the fuse/relay box behind the cab to feed the hot side of the starter relay. We ran a new wire from the downstream side of the 50A fuse in the fuse/relay box to the ignition switch and also jumpered from the same point over to the supply side of the starter relay. This eliminated the 30A fuse in the panel on the dash, but now the truck works and we did not have to replace the entire wire harness.
Parts in Columbus

Columbus, OH

#13 Feb 23, 2012
Any idea where I can find parts for my 1999 NPR?
befuzzled

Upper Marlboro, MD

#14 Mar 21, 2012
thanks all, having the same problem. as an emergency/temporary fix
I ran a wire direct from the battery through a standard bump switch to the starter and it starts, so at least that eliminates buying parts for now..
Rcoatings

Emmaus, PA

#15 Dec 24, 2012
I just replaced 2 dead batteries on my 99 npr and after hooking them back up I am getting a click at the starter, but it is not turning over. I have the batteries hooked up in parallel, should I have them in series? Everything else seems to work fine on the truck, lights, horn, etc. It just wont turn over.
Electrical problem

Ardsley, NY

#16 Feb 4, 2013
Hey guys i have a 2006 isuzu npr 5.2l i dont know whats wrong with it, it cranks but does not start, the fuel pump is all okay because diesel gets to the fuel filter with no problems and its clean, but the diesel does not get into the engine for some reason, the injectors are electeic but i dont know which wires to check, oh and when i turn the key the volt meter reads 12v on the wires going to the engine but then it goes to 0 volts right away
ROBERT JOHNSON

Vancouver, Canada

#17 Feb 5, 2013
what scan tool do you need to retreive powertrain codes for a 2004 npr desiel
todd

United States

#18 Feb 23, 2013
I have an 03 gas npr. Getting no power to the 5 fuses on the right side of the fuse panel in glove box. Is thee a fuse or relay that controls power to these? I believe I get no power.to the ecu. As I have no spark and check engine light does not come on when turning key on. Turns over, but no fire.
Jose

Fort Worth, TX

#19 Apr 18, 2013
I have a Isuzu NPR and my dad put the cables (the ones in the batteries) in a opposite ways, so I was trying to find the fuse but I can find it. Some knows where's at?
Jose

Fort Worth, TX

#20 Apr 18, 2013
Some knows where's the fuse battery on a 1998 Isuzu NPR?

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