This write-up is for owners of the 1981–1985 Datsun or Nissan 720 pickups with the electrical fuel pump. Top top this page, you will certainly learn how to go beyond the typical business manual fuel shipment problem diagnosis.

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If, prefer me, you have actually trusted in her Haynes manual to troubleshoot a fuel distribution problem, you may have discovered that nothing seems to work and also the trouble persists. You’ve confirm the fuse (#2) and also it’s good! You’ve confirm the output of your electric fuel pump (just in prior of the passenger side behind tire) and find the it works most of the time—or maybe it just works if you power the pump v a jumper wire! Yet, your pump simply won’t put fuel to the carburetor when it’s supposed to . . . Or it will for a while, but then the van dies and leaves friend stranded for 10–15 minutes, or until tomorrow.


It is most likely that the problem lies in your fuel pump relay. Currently I recognize that the book doesn’t to speak anything about a fuel pump relay, and many mechanics don’t also know about it (they’re probably using the same book). I'm below to tell you the the relay exists and also should be dubbed a fuel shutoff relay. Friend will also find that the auto-choke relay is placed on the fuel pump relay. Trust me, it exist (don’t believe Chapter 13, figure 5.2b). I have actually a 1981 Datsun and also a 1984 Nissan and they both have actually this troublesome black box. Your repair overview not only ignores it, however it is conspicuously lacking from the wiring diagrams, making diagnosing and repairing electric fuel pump troubles virtually impossible. I tore apart mine wiring exploit to uncover it and later uncovered other shade-tree mechanics discussing it in a few online forums.


Look Under Here!


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To find it, look under the dash on the passenger’s side. The is just visible above the kick panel in prior of the door and will have the auto choking relay attached, and also in automatically trucks, the fuel reduced solenoid.

Look Closer


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The fuel pump relay itself has actually a 6-pin connector going right into it. Those are six wires the you will not discover on her wiring diagrams. Do not try to remove the exploit from the relay unless you have actually forearm muscles favor Popeye. Remove the attached relay(s) and also then undo the two screws holding the fuel pump relay to the panel. I uncovered it easiest to eliminate the knee bar and heater blower motor first, but if friend have really short screwdrivers and tiny hands, you deserve to probably manage less disassembly than I did.

Wiring chart of Relay


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B=black, W=white, L=Blue, G=green, and also Y=yellow.


These six an enig wires screen several necessary systems in your truck so that if any kind of one of castle fails, the electrical fuel pump will certainly not run. Prior to you unbolt the relay and also spend $50 or an ext to change it, first make certain that this systems are functioning correctly!

They are:

The ignition switch accessory position (power to blue wire as soon as on).The ignition switch start place (power come white wire at begin using fuse #5).The alternator (power come white/blue wire once running).The oil push switch or oil sending out unit (4WD) (yellow/green).

This is a wiring diagram for the fuel pump relay terminal the I created using the Haynes shade codes uncovered in mine harness. Hope yours is the same. Usage this to check continuity in your wiring. It’s better to discover a damaged or corroded wire currently than to change the relay and still have actually the same problem.

Repair hands-on Discrepancies

I’ve listed some imbalances in my Haynes manuals which may or may not apply to yours as well.

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The wire from this relay come the human body harness connector (ultimately to the fuel pump) is white/black. Why Nissan provided a white/black wire from the relay come the human body harness connector (found under the carpet in ~ the passenger’s seat) is a secret to me. All other fuel-related wires throughout the truck are brown as is the connecting terminal in the human body harness connector i m sorry goes directly to the fuel pump.The white cable connects to the fuse block in ~ fuse #5. In my two Haynes books (chapter 13, figure 3.1b), fuse #5 is displayed to be empty. I’m at this time running a 10A fuse in this position and also haven’t had any type of trouble. Also, pulling this fuse doesn’t seem to shut off any kind of start features other than the fuel pump (via the relay).Not related to the fuel pump relay so lot (but due to the fact that I’ve breached the subject) the wire the end of fuse #1 (ignition coil no. 2) should have actually been detailed as WB and also not WY. All various other diagrams it seems to be ~ to show it correctly.

Test her Fuel Pump Again

If you have actually not already tested her fuel pump by running a jumper cable to it, you have the right to do it now. Develop a short jumper wire and connect the blue terminal to the white/black terminal. When you revolve the ignition end to the accessory position, you need to now listen the fuel pump running constantly (not recommended together a permanent fix)!