No power to fuel pump or rear lights

Asked by Feb 23, 2017 at 01:00 PM about the 1989 Chevrolet C/K 1500

Question type: Maintenance & Repair

89 k 1500 i recently changed the clutch and all drive train seals as well as
oil pan and rear main, put it all back together and it worked perfect no leaks
however the brake was very spongy and i found a pin hole right next to the
wiring harness of the fuel sending unit, so i removed the bed and dropped
the tank fix the hard line and now i have no power to the rear end of the
truck, i checked grounds replaced relay and inspected the wires, I have a
volt meter but im not good with it this i my weakness, ive owned this truck
for 26 years second owner and ive done all the work on it which was all
basic nothing major shes been great in fact the clutch i just replaced was
original, I can only think a wire is cut grounded or pulled out

2 Answers

17,725

May can locate it or get a rear harness and replace it, but before that recheck those fuses under dash and hood and be sure the all grounds to frame are in place. Recheck the relays. See if you have a good ground and no blown fuses at the ECM. Looking for bad wires. Disconnect the power source to the vehicle or piece of equipment that contains the wire you need to troubleshoot. Use a wrench if you need to disconnect a battery cable. Inspect closely the connections at both ends of the wire for damage, if they are readily accessible. Slightly pull at the wire ends, where they hook to the connectors, to make sure that they are firmly attached. Trace the length of the wire with your index and thumb, paying special attention to any imperfections around the wire insulation. If necessary, use a small mirror and a flashlight to reach around spots where you have minimum access. You can suspect any problems if the insulation shows signs of damage, including darkened spots that may indicate overheating, which might have caused the wire inside the insulation to break. Unplug the connector to which the wire is attached, and check for damage. Get your digital multimeter and set it for continuity, or the lowest range on the Ohms scale. Turn on the multimeter and touch one of the probes to the metal terminal that holds the wire to the connector, and the other probe to the exposed part of the wire, where it enters the connector. Wiggle the wire to check for a false connection as you probe the terminal. Your multimeter readout should show zero resistance. If the display shows infinite resistance, the wire is not properly connected to the terminal. Test the terminal at the other end of the wire as well, if equipped with a connector. Connect one of the meter probes to one end of the wire and the other probe to the other end of the wire. Use alligator clips on the probes to keep them hooked to the wire ends. Wiggle or carefully bend the wire at various points. If there is a break at any point along the wire, your readout will display infinite resistance. Insert a pin about two or three inches away of the point on the wire where you suspect there is a break. Insert another pin on the other side of the wire, where you suspect a break. Connect the multimeter probes to the pins and wiggle the wire at the break point. If the multimeter display reads infinite resistance as you wiggle the wire, you have found the break in the wire. Check some none good wires so you know what average readings look like. Infinite readings will go really high and back down or fluctuate never zeroing on a specific reading. Sometimes, especially if you are working on an automotive electrical circuit, you will not be able to reach each end of a long wire with the multimeter probes at the same time. In this case, you can use a jumper wire between one end of the wire and one of the probes. Another alternative for use in a vehicle is to connect the jumper wire to chassis ground and then connect one of the multimeter probes to the chassis ground and the other probe to the other end of the wire to check for continuity. If you use pins to probe through the wire insulation, make sure to seal the punctured spot(s) with electrical tape to keep moisture out of the wires. This could create electrical circuit problems later on, if not fixed. Looking for power. On Volts DC find ground wire/ Negative terminal or frame and positive wire then use probes, black to ground and red to positive.

It was the fuse for the sending unit I just missed it all is perfect now ty, Ps I've owned this truck for 26 years and never new that fuse was there make sure you let others know about it it's not something that jumps out at you and says hay I'm a fuse

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