I posted this in another forum but I think this is the proper place! Sorry. Car is 79 Rx7.

I installed a Mallory 4070M today in a horizontal position basically where the stock fuel pump was. I turned on the ignition and low and behold fuel was flowing to the line in the engine bay (into a jar).

About 15 mins later I tightened everything up and this time there is no hum of the pump and no flow. The pump also gets hot after a few minutes.

It was suggested that I might have a bad ground or pump so I undid the wiring and put the pump directly on a 12V lantern battery. Again, no flow.

I've noticed from other installs that the pump is often vertically mounted. Did I somehow fry the pump???? Could I simply have a bad pump?

TIA

 

Some pumps do require to mounted verticle. The carter I have is this way. Otherwise it
will fry the pump because of the way its designed.

 

I unmounted the fuel pump and tested it on the bench and sure enough it doesn't work.

I called RB who asked me to call Mallory (now part of MSD). I explained the situation to Mallory and their guess is that it's a defective unit and will be covered by warranty. So I packed up the pump and sent it off to them.

 

I always thought the 4070M had to be mounted vertically. With that pump you also have to install a return line unless you are flowing ridiculous amounts of fuel. Otherwise it gets so hot you can't even touch it and will burn it up.

Speaking from experience here.

 

I think the vertical mounting was a fire risk reduction measure although to me a horizontal mount would also keep any dripping fuel away from the motor.

 

The pump mechanism on those is very sensitive to how tight the screws are torqued. I had one seize on me, and the tech rep told me to back off the screws some. I did what he said, and it worked fine.

It resolved the problem, but I my opinion, that's not a very robust design.

 

Do you mean the fuel inlet/outlet fittings? Even with my pump off the car and with no fittings it would not turn. MSD was very nice to me and are sending me a replacement with no hassle.

 

No, I'm referring to the Fuel Chamber Screws (4). They compress the Gerotor (11) between the Port Plate (10) and the Gerotor Housing (13). On some pumps, over-tightened screws will wedge the Gerotor so tight that it can't rotate.

 

And you should mount it vertically. I don't know that horizontal mounting will cause a fire, but is it worth the risk?

 

Got ya. No, I didn't mess with any of that.

Good point but I just can't figure out why is should matter!

 

There are two general types of pump motors:

Flooded: The electric motor is designed to be submerged in fuel, and uses the fuel to cool it. Sparks can't form because there's no oxygen around the brushes. This is the type of motor used in virtually all modern OEM fuel pumps.

Dry: The electric motor is not meant to be submerged, and may create sparks when it operates. To see an example, run your electric drill in the dark; you'll likely see sparks. If fuel gets near the brushes, those sparks will light it off. This is the type of motor in the Mallory 4070.