Hi,

I have a 90 isuzu trooper that I can't get to start. when it was running I was having a condition where the dash lights didn't completely go out. the truck was running ok so I kinda ignored them. Now I have been having trouble with the mechanical timing jumping. On the last repair where I changed the timing belt abd the truck went down for repairs the starter was turning and the truck would somewhat start. Now I have finished the timing belt work but not the trooper doesn't even try to start. I get no response from the starter. I have bypassed the clutch safety swith to take it out of the equation. I have changed the starter relay with no change. The starter relay does click but nothing happens. I took the starter relay out and found which wire goes to the selenoid and I also found out which wire is hot when the key is turned to the "start" position. I jumped those 2 wires and the starter cranked. The engine didn't start I suspect because the fuel pump relay isn't geting power. I suspect something related to the starter relay. I have looked at a few wiring diagrams and I am not sure which wires go where in the whole starting circuit. A basic wiring diagram for the starting circuit would help.

thanks

mike

Fuel Pump Circuit

Hi,

Thanks for the wiring diagrams. Something doesn't match up with the tarter relay. I havve 6 wires going to the relay and not 4 as is shown in the diagram. What has me puzzled is that that the ignition switch has power which gives the starter relay power when the key is turned to start and the clutch is in. From what I am seeing the clutch is the ground to the starter relay which allows power to flow to the relay. That wire is hot when the switch is turned. The wire from the starter relay to the starter checks out and has continuity. The starter relay does click over so there should be power from the wire coming from the ignition switch to the starter but there is not. Is the wire from the engine relay a ground?? It looks like it is a power wire. That being said when the relay "clicks" over the power should flow from the wire coming from the ignition switch to the wire to the starter . This is not happening. What is the "trigger for the relay to "click" over??? What is the story on the 2 extra wires at the starter relay that are not shown on the wiring diagram???? I think I need a simpler wiring diagram. Do you have a picture of the power distribution cell(10)and the ground distribution cell(14)??? This trooper was assembled in China and not Japan. Does that make a difference with the wiring diagrams????

Thanks for the help.

Mike

The diagrams are from the 88 model year Isuzu Electrical Troubleshooting Manual. That might account for the 2 wire difference. Regarding the cell 10 and 14, the book refers to sections or chapters as cells for purposes of the schematic. For example, the reference to power distribution cell 10 refers to several pages of basically every hot wire related to power distribution and cell 14 is several pages of all the ground wires. I don't see it benefiting you to add more clutter to the equation. If you don't get more assistance here, you can also try http://forum.planetisuzoo.com/

It has more activity thus more folks who can respond to the problem.

Hi,

You have really helped me with this problem. Between your wiring diagrams and the ones that I had here I got to the bottom of the problem. I have a haynes manual and a factory service manual for my 87 trooper that I used along with your wiring diagrams to find the trouble. I never got a factory service manual for the 90 trooper. Quite a few jumper wires and few days later I got the trooper to run. I am not sure if the timing belt repair took since I can't yet take the trooper on the road. It idles good though. The way I had the jumper wires done the trooper looked a mess.

I found that the White power wire coming from the battery pigtail was not getting power to the white wires on the starter relay, engine relay and the other 2 relays at the fuse box. I ran a jumper wire from the positive battery terminal to the 2 relays and that got the starter to crank the right way through the relay. Thwe trooper still wouldn't start at that point but it would crank. I then moved on to the fuel pump relay. The White wire was getting power to the fuel pump fuse #24 and which got power to the fuel pump relay. The fuel pump fuse #23 was not getting power to the fuel pump relay. The black/white wire that goes from the starter relay to the starter solenoid also gives power to the one side of the fuel pump fuse #23 when the ignition switch is in the "start" position. The black/red wire on the other side of fuel pump fuse #23 was not getting power to the fuel pump relay when the ignition switch was in the "start" position.

Would you be able to help me find the breaks in the wires so I can do a permanent fix to this problem???? The "white" wire from the pigtail on the positive battery terminal goes to the lights, the ignition switch, the fuel pump relay, the starter relay, the engine relay, the power windows relay and the a/c relay. Power is getting to the ignition switch, lights, and fuel pump relay. This leads me to believe that the "white" wire itself is ok but that the connection in the wire harness that leads to the starter and engine relays has a break in it.

Would you have a wire diagram of the power distribution for that side of the engine near the fuse box that would show the location of where the "white" wire branches off to go to the relays????? That would help to find the break in the connection in the wire harness and I can repair the break. Would you have a diagram of the routing of the black/red wire from the fuel puump fuse #23 to the fuel pump relay???
That would help to find the connection break leading away from the fuel pump fuse #23 on the black/red wire side of the fuse to the fuel pump relay.

Thanks for all your help.

Mike

I don't know first gens very well, but aren't there some fusible links in the system? I know Craig had one blow in Moab this year. They were located in the passenger side front corner of the engine compartment.

Hi,

The 1st generation troopers are the best. I have had a few but his is the first time I've had to deal with this problem. I checked out the fusible links and they all check ouy fine. That is what makes this problem a pain. I have to unwrap the wire harness to find the break in the connection. I don't want to unwrap any more than I have to. Whatever I unwrap I have to wrap back up when I'm done. The trooper has 297,00 miles on it so things happen at that mileage. It did great during this past winter that we had here. Except when it broke down the morning before the last blizzard hit. Thanks for the idea.

Mike

That white wire provides a constant hot from the battery to the fusible links.. Let me see what I have.

Fuse 23 to fuel pump relay: The diagram shows no connection between the 2 other than at each other. It only shows a splice with another blk/red wire to a connector enroute to the ecm. No connector between relay and fuse 23. I'm fixing to view the white wire stuff.