yet another electrical fuel pump issue

[3ryce]

Ok, so i recently acquired a 73 240z 4 speed. I have been doing some fuel things and other things.

ive replaced the voltage regulator, alt, mechanical pump, fuel lines, electrical fuel pump, vent hoses, gas tank, belts. Also, I put some heat wrap around the fuel lines to help prevent vapor lock. No not exhaust wrap but I have that to and will be wrapping the exhaust manifolds later.

After getting the car to run, I do not have the tank installed so ive got the lines running to a gas can haha, well I went to check the electrical fuel pump to see if it was working and it was not. The relays in side the cabin seem to be working, ive tested them too. I had to pour gas down the lines leading to the carb's and I used a pump to pull gas threw to hopefully save some strain on my starter.

Now I know the 73's did not come with an electrical one from the factory, yet my car has been to the dealership and been recalled. I know cause I have the seven bladed fan and the old electrical pump was there when I had gotten the car. Didnt bother to see if it had worked or not, car had been sitting for 5 yrs.

I would think that if the car had been properly recalled and worked on the mechanical pump would not be there. However I still have mine. So my question is what are other things to check? I have come to learn that there are two relays, one is a relay coil? however, maybe I have not located this one and maybe it is my problem! Ive checked the inline fuse and have made sure everything is plugged in. Ide like to resolve this issue so I can get rid of the mechanical pump. Please help! and Thanks for any and all help!!!

[Pat Carr]

3ryce,

Other than checking all your connections, I don't have much advice on your problem. However, the presence of the mechanical fuel pump does not indicate the car wasn't properly recalled. My '73 has every factory recall "fix" for vapor lock, including the electric fuel pump, insulated fuel lines, and the "competition" hood, and the mechanical fuel pump is still there. So is the vapor lock.

[3ryce]

Hmm. thanks Pat that actually helps alot. The one relay in the car on the passenger side kick pannel, I jumped the two green wires and the fuel pump worked. so im not exactly sure what to do. The car is not at my house so im not able to run out and check on things asap. But I have been reading that there needs to be a oil pressure switch so ill check for that, I dont think its there, and go from there. I just got new insulation wrap for my fuel lines they were previsouly wrapped in foil. bleh.

thanks pat

[SteveJ]

The factory modification attached between the alternator and voltage regulator to pull power from the yellow wire. There are two relays for the fuel pump. One is energized by the starter. The other is energized by the yellow wire from the alternator.

Diagnostics:

1. Bench check the relay coils and contacts. Energize each relay coil with a 12 VDC source and verify the contacts are closed.

2. Verify you have voltage at the correct terminals in the car. You have to check this while starting the car and while the car is running.

Note: If key is in the ON position with the engine not running, you will NOT have voltage at the fuel pump.

[3ryce]

Will check into that today also steve. But both fuel relays are in fact inside the car on the passenger side correct? I'm positive I've found one as it has black yellow blue and a white with blue stripe wire. The other relay I'm not sure where that's at.

[SteveJ]

Both relays should be on the passenger side at the kickpanel. There is another thread on this board with PDFs of the Nissan documents for this.

[3ryce]

Both relays should be on the passenger side at the kickpanel. There is another thread on this board with PDFs of the Nissan documents for this.

Wow fast reply. Ok ill look for the other thread. And do u have a picture of the other relay? I turn the key and here one relay click and I tried to hold the other one while I turned the key and I didn't feel it click on.

[SteveJ]

Wow fast reply. Ok ill look for the other thread. And do u have a picture of the other relay? I turn the key and here one relay click and I tried to hold the other one while I turned the key and I didn't feel it click on.

The second relay is only energized when the alternator is putting out enough voltage. That is the engine is running and turning the alternator fast enough for the alternator to energize the coil.

I was wrong earlier. It wasn't a PDF. It was a JPG. Here is the thread: http://www.classiczcars.com/forums/electrical-s30/47253-fuel-pump.html.

[3ryce]

Thanks man. So much help.

[3ryce]

I here the relay b click when I turn the key but that I guess doesn't mean much. But its just odd that everything is plugged in and I here one at least click but the pump doesn't come on. Also I've noticed my tach isn't workingand have read somewherr that the relay clicks on at about 400 rpm and maybe if that's not working it could be a problem, though I don't think that is the cause.

[SteveJ]

Have you downloaded the FSM? If not, it would benefit you to do so. While the fuel pump wiring is not in there, it does have a wiring diagram for the rest of the electrical system.

The tachometer does not trigger anything.

Also, make sure you do the tests I listed earlier. The components must be functional for the fuel pump to get power.

[3ryce]

yes I have the fsm. I was on my phone earlier when looking at this fourm. I will do the test mentioned, gotta wait to get my dad to help, im not so good with using an ohm meter. His old one ya, but the new one I have I do not know what setting to switch it to too just test continuity.