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Discussion Starter · #1 · (Edited)
I ran into a no start issue,
And as most people would have done I started scanning the web for troubleshooting tips
I found that the icm appoxy was melting out

-rotor,cap, plugs wires changed. Ran ok
- timing belt and tensioner changed and it ran abit better.

Then it got shipped and now won't start.

-icm has been remounted and replaced and still no start
-replaced ignition coil still no start
Pulled out my multimeter and started checking things.
Found a issue with voltage at fuse
8,10,11,12 almost no voltage
Pulled the engine relay and jumped it
Got 12v to those fuses but still no start
Fusible links are all good read 12v going to both sides.

Ecm won't go into diagnosis mode light bulb is good no engine light on but I'm hesitant to think there isn't one being that it clearly has an issue

I don't know where the engine relay traces too as I don't have a manual or schematic or the next step to take .

Do I replace the alternator maybe or do I go after the ecm as a possible issue, I did open the ecm up to check nothing looks burnt and looks actually in good shape
 

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lot of stuff replaced, but no basics. Pull a plug, find a way to secure it to a ground, crank and watch for spark. Start there. Dennis
 

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Discussion Starter · #3 ·
Sorry i failed to specify that,
*I did pull a plug no spark when cranking over and holding it to ground before and after
*Also fuel lines build pressure, seems like it is getting fuel.
*Air no restrictions.
*Vacuum lines have been checked nothing that stands out that would cause it not to fire.

*Grounds have been checked even used jumper cables to make shift a ground just in case befor deciding to installing new ground cables

There was a little bit of oil residue in the dizzy cap so good chance the optical sensor could be done for,
But uncertain it would cause the fuse issue causing the 4 fuses to drop voltage sounds like a alternator but without it running I don't think I could do a function test I may need to remove it and check
Also has a new battery so I know that isn't the issue.
I have 4 possible concerns
Dizzy optical sensor cam position sensor I guess in these
Alternator blow diode causing it to trip and shut down
Ecm error that isn't visible
Or short somewhere in the engine relay circuit but don't have a diagram to know where the wires run to check

Any help on determining the fault would be greatly appreciated
 

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1989 Trooper R/S
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Assuming all 2.6's are the same then no spark may be the ignition module (igniter) which is under the lower intake and is often overlooked because it's out of sight.
Auto part Font Electronics accessory Plastic Magenta
 

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That's the icm/ ignitor, I replaced that.
didn't help unfortunately.
But i did confirm power is getting to it
Sorry i failed to specify that,
*I did pull a plug no spark when cranking over and holding it to ground before and after
*Also fuel lines build pressure, seems like it is getting fuel.
*Air no restrictions.
*Vacuum lines have been checked nothing that stands out that would cause it not to fire.

*Grounds have been checked even used jumper cables to make shift a ground just in case befor deciding to installing new ground cables

There was a little bit of oil residue in the dizzy cap so good chance the optical sensor could be done for,
But uncertain it would cause the fuse issue causing the 4 fuses to drop voltage sounds like a alternator but without it running I don't think I could do a function test I may need to remove it and check
Also has a new battery so I know that isn't the issue.
I have 4 possible concerns
Dizzy optical sensor cam position sensor I guess in these
Alternator blow diode causing it to trip and shut down
Ecm error that isn't visible
Or short somewhere in the engine relay circuit but don't have a diagram to know where the wires run to check

Any help on determining the fault would be greatly appreciated
Cam position sensor. I drove me crazy for awhile because it was intermittent when it first started going out. It
 

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1993 Trooper 5spd
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Pulled out my multimeter and started checking things.
Found a issue with voltage at fuse
8,10,11,12 almost no voltage
Pulled the engine relay and jumped it
Got 12v to those fuses but still no start
Fusible links are all good read 12v going to both sides.

Ecm won't go into diagnosis mode light
Sounds like you are close here. You say you jumped the relays so the load circuit has power at the relay and continuity to the load. So the engine relay has no power to the control side, or is not being grounded? Assuming it is ground controlled, you need to confirm what grounds it if there is power. If no power, need to find out why. Not sure how much more you could do without the schematic. May be worth tracking that down. A power probe would help here. Did you try starting it with the engine relay circuit jumped?
 

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Discussion Starter · #9 ·
Sounds like you are close here. You say you jumped the relays so the load circuit has power at the relay and continuity to the load. So the engine relay has no power to the control side, or is not being grounded? Assuming it is ground controlled, you need to confirm what grounds it if there is power. If no power, need to find out why. Not sure how much more you could do without the schematic. May be worth tracking that down. A power probe would help here. Did you try starting it with the engine relay circuit jumped?
I think I'll be buying a dizzy next as it's the next in the ignition side that could cause an issue with spark. Kinda interesting that the ignitor started to go same time as the cam sensor
 

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1993 Trooper 5spd
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I would definitely look into the engine relay issue. It will supply power to you components, not the other way around. Also, have you swapped the relay. I’m not sure what a dizzy is. I’m Isunew.
 

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Cam position sensor. I drove me crazy for awhile because it was intermittent when it first started going out. It
An 89 2.6 does not have a cam position sensor.
 

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Discussion Starter · #13 ·
An 89 2.6 does not have a cam position sensor.
Yes your correct, now that i look at it. it's a crank position sensor not a cam position sensor.

My question I guess is the sensor able to shut down the relay system when faulty and is there a way to test it before buying the part. If not I guess I'll need to buy a new dizzy
 

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Discussion Starter · #14 ·
I would definitely look into the engine relay issue. It will supply power to you components, not the other way around. Also, have you swapped the relay. I’m not sure what a dizzy is. I’m Isunew.
That's what I thought too.
But when I jump the relay system bypassing the relay and getting voltage to the circuit. It made no change.
The alternator has a circuit if faulty will cut power
and I'm wondering if the distributor does the same thing.
If so it would be a good place to start is replacing the distributor as it's the last thing in place of stopping voltage from the coil going to the plugs that hasn't been replaced
 

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The only "position sensor" on an 89 is the distributor. Before you go buy a distributor, pull the cap, spray some brake cleaner or carb cleaner in there, and Lightly blow it out with compressed air (there might be a cover over the window / disc). Then give it a try.
The only thing I could see the alternator having with this were IF it started, a bad circuit in the alternator could cause the fuel pump to shut down. Dennis
 

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1993 Rodeo 2WD 4ZE1/T5 CA Spec - 2016 RAM1500 Pentastar (22mpg) - 1986 RockZuk on Toyota Axles
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Before buying a distributor I'd definitely go on eBay and buy the actual Isuzu dealership paper copy of the Electrical Troubleshooting Manual for your exact model and year, it costs next to nothing compared to the service manual. It's almost a waste of time trying to track down any electrical problems without knowing what wire colors were used between the ECM and the components in question, you can't assume it'll be the same as a different year or a different model of the same year, there's differences for no apparent reason.
 

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Also criticisms of the OBD1 CEL codes are valid and often the codes you get don't match the indicated codes in the manual where it lists the actual fix to your problem, still worth it to tear the dash apart and put in a new CEL bulb . I got 4 seperate codes just because the harness to the igniter wasn't tight. There's no procedure for those 4 codes simultaneously, nothing to suggest unplugging the ignitor can cause that many codes in the manual, but Dennis knew to point me to it anyhow based on those codes, and the truck started soon as I relocated the igniter and ran new wiring to it. I broke a couple things immediately after and it's not running again, but still, CEL codes even OBD1 are useful if you post them here.
 

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Discussion Starter · #20 ·
Thank you for the diagram. Very helpful. I did end up ordering a Reman dizzy, I did check the wiring and no breaks but now I can test the circuit with resistance which is very helpful. I'll post my findings either way
 
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