Electric Fuel Pump Relay Wiring Questions

[kray-z-1]

My electric fuel pump decided it didn't want to play anymore. In checking the existing wiring, it appears the trigger wire is not sending power to the relay. Rather than take the harness apart, I've decided to bypass the existing wiring and run the fuel pump on all new wire. I still want to have a n/o relay in the circuit but I'm not sure of the correct wiring or my options.

Here is my thinking:

1 - Power lead direct from the battery with in-line 20 amp fuse

2 - Ground wire

3 - Positive lead from the fuel pump (the negative from the pump is grounded on frame)

4 - a trigger wire that operates with the ignition.

The three questions I have are

a) is the above layout correct?

on a n/o relay - which wire is going where?

c) can i run a wire from the positive on the coil as a trigger wire? I would rather use new wire and a new source than tap into existing if possible.

My thinking would be the ground to 85 - the pump positive lead to 30 - the battery to 87 - and the trigger wire to 86.

I wish I had better knowledge of auto electrical and being color blind isn't helping any either!

Any help would be appreciated - Thanks!

[260zCaliCar]

There are a lot of people on this site with more knowledge on this subject then I have, but... On mine at least... The electric fuel pump doesn't get power until the engine is above 400 rpm. Did you test yours with the engine running? If you did and it still doesn't work, replace the fuse even if it looks okay, it's the easiest first thing to try and has solved (again in my case) 99% of the electrical problems.

[kray-z-1]

I have a 73 Z - and only has an electric fuel pump. There isn't a mechanical pump and doesn't appear that it ever had one.

I know that many had the electrical fuel pump as a booster - but in my case it is only the electrical pump for fuel.

Thanks for the idea though!

[zKars]

Jim

First check the fuel pump fuse. Its not on the fuse panel in the console, it's a white inline fuse holder and can be found behind the heater control/fuse access area. Try reaching around behind the console on the passenger side to find it. Take the console out to get better access from underneath if you have to. There is also a rear defrost in-line fuse back there too, so look for both to be sure you find the right one.

There is no stock fuel pump relay on a 73. Only FI cars (74.5-78 26/80) have that.

Many of those little universal relays have the wiring diagram right on them, cast into the plastic. The terminal numbering is universal. 87 and 30 get connected when you apply 12volts across 85 and 86. (ground either one, +12 to the other) I'm doing that from memory, do a little googling to confirm.

And of course before you do anything, run a temp wire from the battery directly to the pump and make sure it still CAN work! Might be the pump itself. Sounds like you might have already done that test, just be a shame to run all that wire than still not have it work.

Also check the harness connector to the fuel pump and fuel level sender in your hatch. You have to take off the plastic panel in the back over the taillights to get to it, on the pass side. The ground side of that circuit is harder to get to. The terminal is under the hatch floor, well hidden by the gas tank. Not likely the issue but you never know.

Changing to use just a mechical pump is another possibility. Simple, quiet, no wiring or fuses. KISS.. Just laying out the options.

Jim

Edited June 28, 2010 by zKars

[kray-z-1]

Thanks Jim

I did check the elec fuel pump. I removed it and connected directly to the battery and it works fine. I also checked the existing in line fuse and replaced and tested...its fine too. It seems that there were a lot of variations on fuel in the 240Z - both in 72 and 73. I remember when I bought the 72 new - it only had an electrical fuel pump - I can still remember the clicking sounds at start up. As I recall, the 72 didn't have a mechanical pump either....but then again...I'm old!

I also replaced the relay with a Bosch relay pinned as in the diagram just in case the relay failed.

Thanks for double checking my work.....I always seem to miss the obvious!

Jim