Ah, ok.  I didn't realize the oil pressure switch was a "three way" switch.  The diagram didn't make sense at first, but i've got it now.  Thanks for the write-up.

Do you know if all late model 240's had that unused wiring in the harness?

Almost finished my electric fuel pump. Had to bypass the oil pressure switch for the time being as I can't seem to get it threaded in.

I wanted to post this video as i purchased yeh same airtex pump, and I just wanted to know if this is normal. The pump doesn't make a continuous hum, but rather a dadada noise with the hum in the back ground.

Anyone else come across this? I have a filter between the tank and pump (pictured) as well as in the stock location.

I should also note, the mechanical fuel pump is still installed, and in the video the car is not running.  Ignition on only.  You may have to turn the volume way up.  Is this cavitation?

Edited July 6, 20159 yr by HuD 91gt

If the mechanical pump is not being actuated then I believe the pump is dead-headed. It will be noisy if it is dead-headed.

Ok, i'll check again.  But I think it made the same noise when the car was running.  I guess an easy way to check would be to disconnect it prior to the mechanical pump into a bucket and see if it continues to make the noise.  I'll report back.

On ‎05‎/‎14‎/‎2013 at 7:10 AM, Jarvo2 said:

The airtex pump I used only produces 4-6 PSI which is fine for the SU's. If you get a higher pressure pump then you'll need to put a regulator in somewhere between the fuel filter and the hard fuel line in the engine bay. I haven't had any issues with my low-PSI pump.

Two questions:

1. WHere exactly is the best place to measure the fuel pressure at the car? On the fuel line that goes to the rear carb or between the fuel filter before the gas gets through the fuel rail?

2. Which of this two pumps can dial approximately between 3.5 to 4 psi and less noisy:

Airtex 8012S

http://www.summitracing.com/int/parts/atx-e8012s/overview/

or

Mallory 4070LP

http://www.summitracing.com/int/parts/maa-4070lp/overview/

 

For the airtex 8012s, i guess i will need a fuel pressure regulator. Not sure yet! Please let me know!! Dont like adding more stuff to the engine bay ie a Holley fuel pressure regulator. I think this is not needed.

1st time poster. Just finished dropping the tank for a cleanup and hose freshen and noticed the extra pair of wires with the fuel level sending unit on my early 71. Back in the day I had a 73 Z and it did have vapor lock problems. The dealer installed an electric pump that you could hear start as soon as the ignition was turned on. I'd always let it pressurize a little before starting and it seemed to make it a little easier to start when cold. I'm thinking of just getting the electric pump, hooking it up as the Datsun dealer did so it runs when the ignition is on. Is there really any big problem with this approach? My 73 ran this way from 74 up until the car disintegrated from rust in the early 90's.

No problem.  I run an electric pump on my '71 and have removed the mechanical pump.  Are you having startup problems with the stock pump configuration?

Dennis

Thanks for the reply! No, no startup problems, but I would have occasional vapor lock problems in really hot weather. The car has been a garage queen for over 10 years now so I decided that since I'm going to keep it, I better get it running again. Initially I'm cleaning the fuel system front to back and doing new fuel rubber that's E85 rated so I won't have to mess with that again. Figure while I had the tank out I'd get the K&N fuel pump and go electric, never had a problem with the electric in the 73 so why not? Also getting the rebuilt SU's from MSA and putting the TBC 6 to 1 headers on. Along with that I'm going with the Champion 3 row radiator and the double electric fans on the shroud with Evans waterless cooling fluid so I'm hoping the vapor locking and heat up in traffic will be no more than a bad memory. The car has original dealer installed A/C so I'm also going to get rid of the York and go with a Sanden compressor and update the rest for R134a. The wife and I are old so we got to have A/C!

Sounds like a perfect plan.  Enjoy the Z!

Dennis

You may find that with the mechanical fuel pump removed that if the car sits for an extended period it may not start or crank excessively long. The electric fuel pump (whether new or old) runs off the safety relay under the dash. This relay is powered by the alternator. When cranking the alternator may not put out enough voltage to energize the relay. I found the relay needs 4.5 volts to energize and the alternator only puts out 3.5 volts while cranking. With no fuel in the carbs due to evaporation you will sit. The safety relay was designed by Datsun to kill the fuel pump in the event of an accident to prevent gas fuled fires.  No engine running; no voltage; no gas. The mechanical fuel pump would provide fuel to the carbs while cranking. My 1973 240 is used sparingly and the Webers go dry. I installed a byass switch ( montentary action) across the relay coil. Basically I hold the button in for several seconds to "prime" the carbs. Starts every time now.

Should the pump be wired to the start on accesories or on start position of the ignition key?