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Discussion Starter · #1 ·
Hi all, I have a 2000 Isuzu NPR. When I turn the key, I get nothing. No dash lights, nothing. I can jumper a couple of points at the ignition switch and then get dash lights, glow plugs, etc, as if it was working fine. I can also then turn the key and engage the starter and it starts and runs fine (I think the turbo is stuck, but that's another matter). As soon as I remove the jumper I lose dash lights, etc. I have to manually move the stop solenoid to shut off the engine. This started as an intermittent problem, most notably when I used the left turn signal (almost like that shorted something out). I could hear a loud click under the dash as if it was some sort of master relay misbehaving. I had an automotive electrical guy come out and he thinks it is a bad fusebox (the one in the glove box). He jumpered a couple of points and said "See, it works when I jumper this". But when I remove the key, the dash lights were still on, so I doubt he found the root issue here.

Anyway, I'm open to any suggestion here, I really need to get this thing back on the road so I can stop renting U-Hauls. Any thoughts or suggestions would be greatly appreciated. Thanks!
 

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NPR electrical issue

Hey Soundcheck,
Did you ever figure out what was going on with your NPR? I have one with the same exact issue and the starter and ignition switch have been replaced and the issue continues. Any help would be great. Thanks

-Jase
 

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Discussion Starter · #4 ·
Hey Soundcheck,
Did you ever figure out what was going on with your NPR? I have one with the same exact issue and the starter and ignition switch have been replaced and the issue continues. Any help would be great. Thanks

-Jase
I sure haven't. But I'm going to check out TRUKDOC's idea. I can see this causing the issue, because one thing I didn't mention is that since I started troubleshooting, I've jumpered a couple of fuses in the fuse box so when I turn on the key, the dash will actually light up. BUT, when I turn on my left turn signal, every time the signal blinks ON, the dash lights dim significantly. Unless he is referring to the ignition switch and pigtail assembly, which I have already replaced and it didn't solve the problem.

Also, I can get the truck to start like this, but when I turn the key off, it doesn't stop and I have to reach in and hit the shutoff solenoid with my hand to get the engine to quit. Also, something is "trickle-draining" my batteries and I am recharging them pretty regularly.
 

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Hi Guys,

New member here. I found this site while searching for the exact same problem described above.

I have a 2000 NPR that had an intermittent problem of the power cutting out for just a split second when I used my turn signal. The dash lights would go out, the radio would cut out, then half a second later, everything was fine again.

Well, today it did it and didn't come back. I have no power at all to the dash. The horn works, the interior lights work, the 4 way flashers work. So I know its not a battery problem. I checked all the fuses in the glovebox and swapped some of the relays in the dash and still the same problem. I suspected it was an ignition problem and that is what led me to this site.

My truck is currently parked on the side of a road and I would like to move it. Can you tell me what wires you jumped on the ignition switch to get it started. I would like to try it to see if I can start my truck and move it out of the way.

Thanks in advance for your help.
 

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OK. Small update. I was able to get start it by jumping a couple of wires on the back of the ignition switch. I was also able to jump a couple other wires to get power to the dash. But I couldn't drive and hold the jumper wire at the same time, so I had to drive it in limp mode. I guess with no power to the dash, the ECM gets confused and there is no power in the engine? I was able to drive it slowly home.

So, with my limited troubleshooting skills, If I were to throw parts at it, my first guess would be the ignition switch as I can easily get it to work properly via jumper wires. BUT, I have read many posts about this same problem and several people with the same issue replaced the ignition switch and it did not work.

The post above regarding the combination switch is where I am thinking of exploring. Considering the intermittent power problems I was having before were related to the signal stalk, it makes sense that the combi switch could be the culprit. I found a reasonably priced on on E-bay, but it is in Turkey, so shipping will take some time. Anyone know of some Isuzu parts on this side of the pond?
 

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Problem fixed.

I downloaded the service manual and studied the wiring schematics. I ran through the test procedure to check the ignition switch and it checked out OK. While I was checking for voltage at the switch, I noticed there was only 8v at the main power wire to the ignition switch. That threw a red flag as it should be 12v. So I got a 6' long piece of wire, attached it to the + side of the battery and touched it to the terminal in the ignition switch that was supposed to be fed with 12v. Bingo. Everything worked. So now I had to find where the continuity was being broken. I chased the wire from the relay box behind the cab to the ignition switch and checked the voltage at several places along the run. I had 12v at the 50 amp fuseable link in the relay box. I had 12v just before the wire went into the cab (behind the front grill). But I only had 8v on the wire on the inside of the cab. So the connection from the outside wire loom to the inside wire loom was the issue. After pulling off the protective boot on the harness plug, I found this:



The main power wire to the ignition switch is the white with black stipe and you can see all the corrosion around it. I gave it a wiggle and the wire pulled out of the harness connector pretty easily. So I simply cut the same wire on the inside of the cab, used a couple butt connectors and a 6" run of wire and ran a bypass wire around the connector, into the cab, and connected it to the other side. I flipped the key and had all my power to the dash back again. Flicked it one more turn and she fired right up.

So the good news is, no parts were needed to fix the issue. Although it took me a while to chase it down. Hopefully, this can help someone else in the future.
 

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Discussion Starter · #9 ·
Hi Guys,

New member here. I found this site while searching for the exact same problem described above.

I have a 2000 NPR that had an intermittent problem of the power cutting out for just a split second when I used my turn signal. The dash lights would go out, the radio would cut out, then half a second later, everything was fine again.

Well, today it did it and didn't come back. I have no power at all to the dash. The horn works, the interior lights work, the 4 way flashers work. So I know its not a battery problem. I checked all the fuses in the glovebox and swapped some of the relays in the dash and still the same problem. I suspected it was an ignition problem and that is what led me to this site.

My truck is currently parked on the side of a road and I would like to move it. Can you tell me what wires you jumped on the ignition switch to get it started. I would like to try it to see if I can start my truck and move it out of the way.

Thanks in advance for your help.

Hi,

I first used a paperclip to jumper fuses 15 and 16. Then when you turn the key the dash will light up and supply power to the computers. I also had to jumper (on the ignition switch on the steering column) the White with Black stripe wire to the Blue with Yellow stripe wire. Then when you turn the ignition to start the starter will engage. Now, when you turn off the ignition, it won't engage the engine stop solenoid so you need to reach in and pull the engine shutoff cable with your hand.

A buddy of mine thinks it needs a new fuse box that is behind the front left wheel. I'm not convinced that's it. But, since we are seeing the exact same problem (and I would expect others have, too) I'm hoping SOMEONE has seen this exact issue before and knows what it is.
 

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Discussion Starter · #10 ·
Problem fixed.

I downloaded the service manual and studied the wiring schematics. I ran through the test procedure to check the ignition switch and it checked out OK. While I was checking for voltage at the switch, I noticed there was only 8v at the main power wire to the ignition switch. That threw a red flag as it should be 12v. So I got a 6' long piece of wire, attached it to the + side of the battery and touched it to the terminal in the ignition switch that was supposed to be fed with 12v. Bingo. Everything worked. So now I had to find where the continuity was being broken. I chased the wire from the relay box behind the cab to the ignition switch and checked the voltage at several places along the run. I had 12v at the 50 amp fuseable link in the relay box. I had 12v just before the wire went into the cab (behind the front grill). But I only had 8v on the wire on the inside of the cab. So the connection from the outside wire loom to the inside wire loom was the issue. After pulling off the protective boot on the harness plug, I found this:



The main power wire to the ignition switch is the white with black stipe and you can see all the corrosion around it. I gave it a wiggle and the wire pulled out of the harness connector pretty easily. So I simply cut the same wire on the inside of the cab, used a couple butt connectors and a 6" run of wire and ran a bypass wire around the connector, into the cab, and connected it to the other side. I flipped the key and had all my power to the dash back again. Flicked it one more turn and she fired right up.

So the good news is, no parts were needed to fix the issue. Although it took me a while to chase it down. Hopefully, this can help someone else in the future.

Woohoooooo!!!! I think you nailed it! My truck has the same corrosion in this spot! How the heck did you actually reach this? I could barely get to that bolt to get the loom loose to check this. Did you pull the headlights and grille off?
 

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If you pull the grill off, you can get access to this connector. Pull the rubber boot off and you can see what is pictured. If your wire is corroded like that, you probably have the same issue. Just check it with a volt meter before cutting anything. You can check it right at the ignition. If you do not have 12v at that wire, you probably need to do the same thing I did.

If you want to try something before going through all this trouble, get yourself a 5-6 foot piece of wire and clip it to the + on the battery. Then touch the other side to the power wire on the ignition switch and turn on your key. If everything works with the direct connection, you have isolated your problem.

On the inside, you have to remove the shroud under the dash that covers the duct work, then pull off the main A/C duct. I did not have to remove any screws for either of those pieces. They just pull right off. With the duct work out of the way, you can see the inside half of the connector.

At that point, I located the thick white wire with black stripe, snipped, and used a 6" piece of wire to reconnect the 2 wires with butt connectors. I basically just baypassed the connector alltogether.
 

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Discussion Starter · #12 ·
If you pull the grill off, you can get access to this connector. Pull the rubber boot off and you can see what is pictured. If your wire is corroded like that, you probably have the same issue. Just check it with a volt meter before cutting anything. You can check it right at the ignition. If you do not have 12v at that wire, you probably need to do the same thing I did.

If you want to try something before going through all this trouble, get yourself a 5-6 foot piece of wire and clip it to the + on the battery. Then touch the other side to the power wire on the ignition switch and turn on your key. If everything works with the direct connection, you have isolated your problem.

On the inside, you have to remove the shroud under the dash that covers the duct work, then pull off the main A/C duct. I did not have to remove any screws for either of those pieces. They just pull right off. With the duct work out of the way, you can see the inside half of the connector.

At that point, I located the thick white wire with black stripe, snipped, and used a 6" piece of wire to reconnect the 2 wires with butt connectors. I basically just baypassed the connector alltogether.
Ok, that seemed to work great! Your information has be extremely helpful. My only problem left is that when I turn the key off, the engine doesn't stop. I've checked all the fuses and it all seems good. I'm not sure what to check next to see why the shutoff solenoid isn't engaging.
 

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Ok, that seemed to work great! Your information has be extremely helpful. My only problem left is that when I turn the key off, the engine doesn't stop. I've checked all the fuses and it all seems good. I'm not sure what to check next to see why the shutoff solenoid isn't engaging.

Awesome. Glad I was able to help. Hopefully, this info can help others too. It seems to be a common problem.

As for the engine stop Check fuse #17 in the glove box. That is the fuse that supplies power to the engine stop switch. If that isn't the problem, let me know and I will post up some schematics of the stop switch wiring as well as the testing procedure to test the stop switch. It may just be a bad ground from the stop switch to the frame.
 

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OK, here is the schematic for the stop motor. Use it to trace wires to make sure there are no breaks:




Here is the testing procedure for the stop switch output from the ignition switch. Unplug connector number B68 (the smaller of the 2 plugs coming from the ignition switch). Check for continuity between the positions listed below with a meter. If your results are not as indicated below, you may have a bad ignition switch and its not sending the correct signal to the stop motor.

If you have continuity as described below, then the ignition switch is sending the right signal to the stop motor and the problem is between the switch and the motor, or the motor itself. Repeat the same continuity test on the plug going into the stop motor (plug number J34 in the diagram). If the results are different than the test you did on the ignition switch, there is a problem in the wiring between the 2 plugs (B68 & J34). If the test shows everything is fine, then it might be the motor itself.

I hope that helps. Good luck with the diagnosis.

 

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depends on what 2 terminals you are jumpering. Have you considered a bad key switch? There are 2 accessory power leads going to the switch, you MIGHT have lost power to one of them. The fluttering relay was due to loss of power on the sol. side coming from the switch.
 

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My boss has the same problem on his 2000 NPR. So far we have replaced the 10 amp fuse in the glove compartment and the 60 amp fuse behind the cab. I have got the lights to come on, but the flashers don't flash
 

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I'm having a problem with a 2002 NPR. Fuses and relays are good. Replaced flasher and hazard switch but, the turn signal lights don't work. Any chance someone can post a wiring diagram for this? Thanks.
 
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