4AD Electric Fuel Pump conversion

[ggvette]

I am having some difficulty in obtaining a suitable electric fuel pump.
The pressure regulators are readily available, and I think around 2 PSI should be OK?

However the smaller pumps I have researched available from Holley and Mr. Gasket all state "negative ground only".

These are basically small DC motors, and should not be polarity sensitive?

I would appreciate any info as to what works with the positive ground
on the 4AD.

Thanks!

[BRG]

Grant,

The pump will not operate correctly it will run backwards. Try hooking a blower motor up with reversed leads it will turn backwards. On newer pumps it is also possible that they have a diode in them to cut down on electrical noise (spikes). if you hook them up wrong you can blow the diode and can cause problems.

Two possible solutions are to isolate the pump body from the chassis and hooking a wire from the chassis to the positive terminal on the pump and a wire from the igniton switch with a fuse inline to the pumps body.

The second solution is to convert the car to negative ground. To do this you need to change the ground from positive to negative, repolartize the generator and regulator and if you have an amp meter swap the leads on the back side. One last change is to swap the ignition coil primary(low tension) wires. Then you can run any negative ground pump you want.
The Solex carb should see 1-1 1/2 lbs. 2 lbs should be okay.
BRG

[kabu]

You can get the correct SU fuel pump from several places, at least in the UK. I would guess that Moss Motors have those pumps in the US as well since the same pump has been used in several British cars as well.

Burlen Fuel Systems in the UK has an eccellent stock of SU carburettor and fuel pump parts ( http://www.burlen.co.uk/default.aspx )

It looks to me that MG TC-TF has the same pump as 4AD. Moss Motors seems to have several alternatives for the MG TC-TF pumps ranging from 145 to 335 USD. ( http://www.mossmotors.com/home.aspx )

[kabu]

I looked more into the Singer pump specificaions. The correct pump for the 4AD is the low pressure SU pump, type L. The following page has a good description of different SU pumps, Singer pump is the type LP ( http://www.gowerlee.dircon.co.uk/Pumps.html )

The the following page confirms that the MG T-series has the same pump until the late TF model ( http://www.mgexperience.net/article/su- ... s-101.html )

[Mark Thompson]

An alternate and cheaper fuel pump that definitely works on the 4AD can be found. I have used a Master brand fuel pump, model# E8310, that is designed for a 1982-1985 Honda. The pump is rated at 20 gallons per hour and 2-3.5psi. The pump can be purchased at AutoZone and Advance Auto Parts for less than $70. I have used this pump for three years with no problems. When wiring the pump, connect the black wire to ground.

I have used this pump in series with the standard SU pump on my 4AD. I mounted the Master pump in the rear of the car at the fuel tank and the SU in the original location. I wired the pumps to a three position toggle switch that allows selecting either pump or a neutral position that cuts off the power to both pumps. This provides an additional security advantage against unauthorized use of the vehicle. The pumps can be switched while the car is running without missing a beat. Most of the time, I use the Master pump.

Using the pump at the fuel tank has a distinct advantage in eliminating vapor lock. I live in Nashville, TN and today the temperature is supposed to reach 100 + for the third day in a row. When I drive my Singer at temperatures over 85 degrees I have had problems with vapor lock. Using the master pump to push instead of the SU pump to suck has eliminated the problem. Both of these pumps can be connected in series and will allow flow through the pump that is not running. This means that you don't have to use bypasses and valving like you would use in a parallel piping arrangement. I mounted the Master pump at the tank with a fuel filter in front of it. I did not modify the original tubing that goes to the SU pump. This way, I am able to remove the Master pump and reconnect the original tubing to the tank in a matter of minutes. I have done this twice in order to show my car in a concours. The three-way toggle switch is mounted up under the dash, out of sight.

If you would like any additional information about this pump or arrangement let me know. Good Luck Mark Thompson