fuel pressure low
Old School Hot Rodder
Joined: Feb 2006
Posts: 6,472
Likes: 11
From: Exmore, VA
scratch, did you get the diagram off my site? If you look at it, the blue wire bypasses the relay and resistor. It is to prime the carburetor when cranking. Once the engine starts, the oil pressure switch closes the circuit and powers the relay coil.
If you go to the relay, you should have power to the yellow wire at all times. If you do not, then go look inside the cab on the passenger side near the heater duct. You will see a switch (black with a white button on top) with two yellow wires. First see if the button will push down and latch, if it does you may be good to go. If it is down, then check for power on both yellow wires, one should be hot, if it isn't, then you have to follow it through the firewall to the gray fusible link in the right side harness.
If you have power at the relay yellow wire, jumper the oil pressure switch (small switch with a 2 wire plug) jumper the plug and turn on the key, the relay should close (small click) and the pink with black stripe wire should receive power. If the doesn't close, check that you have power on the red with yellow wire to the oil pressure switch (fuse #18, 15amp) and that it does get to the relay coil. The other side of the relay coil is a black wire to ground.
If you go to the relay, you should have power to the yellow wire at all times. If you do not, then go look inside the cab on the passenger side near the heater duct. You will see a switch (black with a white button on top) with two yellow wires. First see if the button will push down and latch, if it does you may be good to go. If it is down, then check for power on both yellow wires, one should be hot, if it isn't, then you have to follow it through the firewall to the gray fusible link in the right side harness.
If you have power at the relay yellow wire, jumper the oil pressure switch (small switch with a 2 wire plug) jumper the plug and turn on the key, the relay should close (small click) and the pink with black stripe wire should receive power. If the doesn't close, check that you have power on the red with yellow wire to the oil pressure switch (fuse #18, 15amp) and that it does get to the relay coil. The other side of the relay coil is a black wire to ground.
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New User
Joined: Mar 2013
Posts: 8
Likes: 0
well gentlemen, my truck is back to normal after running a hot wire for the fuel pumps for 2 weeks. The problem was i had a 15 amp fuse blown, so replaced the fuse while the hot wire was still connected and I went to shut the truck off and guess what? The engine kept running with the key off and out of the key cylinder. I then pulled the 15 amp fuse and the engine quit. Today i decided to disconnect the hot wire and put fuse back in and walla it works. Thanks again gentlemen, without your input I could not have figured that out.
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