1989 Isuzu Trooper Fuel Pump, Injectors and Blower not wor

Tiny
MEDMISPRESS
  • MEMBER
  • 1989 ISUZU TROOPER
  • 4 CYL
  • 4WD
  • MANUAL
  • 132,000 MILES
The ignition turns on and the starter cranks, but the fuel pump, injectors, and heater/AC blower doesn't work. No fuel comes through the line from the fuel pump. When I pull out the Engine Relay, the blower works, but most of the warning lights on the dash go out. When I plug the Engine Relay back in, the ECM Relay and the A/C Comp Relay click, as well as a relay behind the left front headlight. With the Engine Relay plugged in, fuses # 8-12 do not show current when a tester that is connected to the ground is touched to them. When the Engine Relay is pulled out, they all (four fuses; #9 is blank) show current with the tester. There is a healthy spark if I try touching a bypass hot wire to the connector for the blk/yel wire going to the fuel pump at the tank (with the connection unplugged from the feed line coming from the front). A black wire with red rings on it connected to the Engine Relay is toasted (insulation is melted), and initially fuse number 13 was burned out. All the above symptoms are with a 10 amp fuse replacement in #13.

Any ideas what is wrong, and how to fix it?

Thanks,
Bob

Next day postscript:
Today I did more checking and it seems that the fuel pump is not working and is shorted out, since I get continuity through the two wires coming out of the tank from the fuel pump, and both sides show a grounded circuit(my expectation is that one side shouldn't). There is no noise of the pump running, buzzzing, or anything when the connection is plugged up and the ignition turned on. If the fuel is bad/shorted out, could that have caused the above problems? And since the engine doesn't run, would that in turn keep the A/C blower from operating?
Monday, July 27th, 2009 AT 9:12 PM

1 Reply

Tiny
KHLOW2008
  • MECHANIC
  • 41,814 POSTS
Hi Bob,

Thank you for the donation and sorry for the delay in replying.

Fuel pump = Fuse # 24 and if fuel pump is shorted, this fuse should blow.

Fuse # 10 to # 16 gets their power source from the ignition switch and the main relay is in this circuit. When main relay is plugged, there seems to be a shorting causing the blower and other items not to function.

Resolving the main relay circuit shorting should solve the problems. The damaged wire of the main relay could be fused with other wires causing a short in the circuit and preventing the engine from starting.

If the fuel pump is shorted, replace it and recheck the wires. Did you test if the blower is working with fuel pump disconnected?

A blown fuse # 13 is a big headache as it involves many different components:
1. OD off indicator.
2. Pattern selsct switch.
3. Clutch switch.
4. Stop light switch
5. Cruise control switch.
6. Chime module
7. Instrument cluster. ( 4 terminals)

Any shorting of above components or circuits would cause the fuse to blow.
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Wednesday, July 29th, 2009 AT 12:33 PM

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