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1989 Isuzu Trooper RELAYS WILL NOT ACTIVATE

Tiny
MTINEZ
  • MEMBER
  • 1989 ISUZU TROOPER
  • 4 CYL
  • 4WD
  • AUTOMATIC
  • 220,800 MILES
#14 FUSE SHOWS 12 VOLTS WHEN IGNITION BUT RELAYS DO NOT ACTIVATE. I NEED TO KNOW WHERE IS THE DIODE THAT IS IN THE CIRCUIT TO RELAYS. RELAY WILL ACTIVATE IF I JUMPER 12 VOLTS TO THE COIL. VOLTAGE IS NOT PRESENT WHEN TURNING ON THE KEY AND SCHEMATIC INDICATES THAT FROM THE IGNITION TO COILS ON THE THE RELAYS IS DIRECT FEED
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Tuesday, November 25th, 2008 AT 6:16 PM

10 Replies

Tiny
MASTERTECHTIM
  • MECHANIC
  • 4,749 POSTS
What ray are you talking about? I see fuse 14 goes to alternator? Explain as detailed as possible what your problem is so we are both on the same page.
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Wednesday, November 26th, 2008 AT 5:27 AM
Tiny
MTINEZ
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Schematic from Mitchell web site shows the coils activated from #14 fuse. There are symbols of a diode before the feed to the circuit after #14 fuse but I cannot find the location of the diode on the vehicle.
I checked the coils voltage with a volt meter with the key off and on same results. The coils only activate if I jumper 12 volts around the fuse.
Problem has been intermitent. Isuzu will run but next time will not start. Change ECM, Speed sensor, TPS, Oil pressure switch. I checked wiring continuity to ecm from each component thru the harness and all fuses, wire and regular continuity
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Wednesday, November 26th, 2008 AT 7:15 AM
Tiny
MASTERTECHTIM
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The diode is in series with the ground, just make sure you have a ground at the black and green wire. When turning ignition on you get power to the black and yellow wire and the ground from the black and green wire which will energize relay. If you think its a diode problem you can eliminate it by running a wire directly to ground at the black and green wire and install your own diode. Also double check the white wires at the relay, they shoud be hot too. There is a fusible link that powers them and you might have a partially burnt fusible link
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-1
Wednesday, November 26th, 2008 AT 9:57 AM
Tiny
MTINEZ
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I went to try the wiring change and after removing the main relay the fuel pump relay coil went from zero volts to 12 volts and activated the fuel pump. These relays are in the same 12 volt circuit. The fuse at # 14 still has 12 volts and when the main relay is inserted the fuel pump relay coil goes to zero volts and the main relay has only 2.0 volts at the coil. What can cause this change? Are the diodes still suspected? Reverse polarity on volt meter to check diodes to ground and found no difference from in ohms reading as if diodes were not in the circuit.
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Wednesday, November 26th, 2008 AT 10:48 PM
Tiny
MASTERTECHTIM
  • MECHANIC
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I need wire colors on wires you say are going from 0 to 12 volts, its really hard trying to follow what you are saying because I cant see what your doing. Be as descriptive as possible. Did you add the ground? Was it good? Is the main power feed staying at 12 v? When the coil switches over is that where your losing the voltage?
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Saturday, November 29th, 2008 AT 5:05 AM
Tiny
MTINEZ
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The blk/yel wire has 12 volts from the ignition switch goes to the altenator. The wht/grn wire that goes to the engine relay coil from the altenator has 2 volts even when when trying to start the engine. Should the wht/grn wire be 12 volts?
The fuel pump relay Wht/red goes to 12 volts with ig tion on but drops to 9 volts when trying to start engine Fuel pump starts when ignition is on position.
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Sunday, November 30th, 2008 AT 6:47 PM
Tiny
MASTERTECHTIM
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Are we looking at the same relay?


https://www.2carpros.com/forum/automotive_pictures/139033_no_17.jpg

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Monday, December 1st, 2008 AT 6:41 PM
Tiny
MTINEZ
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No. That is the main relay and I need information about the engine relay. The schematic is
https://www.2carpros.com/articles/mitchell1eautorepair-car-repair-manuals
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Tuesday, December 2nd, 2008 AT 8:08 PM
Tiny
MASTERTECHTIM
  • MECHANIC
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Ithe mitchell schematic it shows power going directly to the ignition coil from fuse 14 and it shows the relay powering the fuel injectors. This is a four cylinder engine right? 2.6l 1989 isuzu trooper
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Wednesday, December 3rd, 2008 AT 6:49 AM
Tiny
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The Mitchells schematic does not show this breakdown only the Autozone site. The engine is 4 cyclinder 2.6 1989 isuzu trooper etex motor.
Aurozone has page of schematics and #58 and #61 show the wiring diagram of the engine relays. I also have a Mitchells schematic.
I trace the wiring continuity and the and the coil feed does come from the altenator but has only 2 volts. The plug to the altenator has a white wire and a blk/yel with 12 volts. The wht/grn wire to the engine relay from the altenator plug has 2 volts. With the key on and when trying to start.
Is this normal for the lower voltage on wht/grn wire?
Thanks
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Wednesday, December 3rd, 2008 AT 7:50 AM

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