BJ8 Fuel Pump

Hi, Guys,

I just fitted the new fuel pump with no real issues. However, when I applied electric power (turned battery switch on and turned ignition switch on) it is running really fast, but no fuel appears to be pumping. How long does it pump before getting fuel into the lines downstream? I let it run about 30 seconds before turning off power. There is a quarter tank of fuel in the car. Does it need to be primed? Thanks!

You have air in the line. Take gas cap off and blow into the fuel tank. Don't run the pump with out fuel or you could burn it out.

The electronic SU fuel pumps do only pump up until pressure is attained and shut off until the pressure drops and then pump....like the old points operated pumps, correct? The pump engages and the sound it is making changes to a lower pitched sound and fuel is pumping into the carbs, but it isn't shutting off. I did blow into the fuel tank and noticed this change in sound after I did that.

stever said:

The electronic SU fuel pumps do only pump up until pressure is attained and shut off until the pressure drops and then pump....like the old points operated pumps, correct? ....

Click to expand...

Correct.

If fuel is going into the carbs, but the pump isn't shutting off, is fuel coming out somewhere? Carb overflow?

Hello, John, I do not see any fuel dripping anywhere. I see fuel has increased in the fuel inline filter I installed just ahead of the carburetors and I noticed ONE air bubble entering the filter when I had the pump going. I checked the fittings from the fuel tank to the pump and everything is tight. What are the odds that the pump's check valve shutoff isn't working?

Pump run-on is more often than not due to an air leak on the inlet side (the fact you saw a bubble in the filter indicates this). The joints can be 'tight' without sealing, and the fiber washers are often a pain to get to seal properly (try soaking them in oil or gas to soften them up a little). If the inlet side is properly sealed and the pump is pumping rapidly you will have a fuel leak somewhere (possibly a stuck float valve; this is why you have two small drain pipes on either side of the intake manifold).

SU pumps--points-based or electronic--don't have a shutoff valve, only a valve that permits outflow and one that permits inflow. Pressure is created by a spring pushing fuel through the system; when the spring is extended to a certain length either the points or electronics triggers current flow through the pump body, which is essentially a solenoid. The energized solenoid pulls the diaphragm, and hence the spring, back for another cycle. The valves in these pumps are small one-way 'flapper' type (not unlike valves in a heart).

Maybe I should purchase new fiber washers and replace the old ones before purchasing and replacing the fuel inlet line?

Stever,

disconnect the fuel line and draw fuel from the tank. The pump is fed by a line that comes out of the tank, passes through the boot bulkhead and travels between the seat pans across the center support high above the pump before dropping down to it. This means there will definitely be air in the line before the pump that must be purged.

With a new pump installation, you will need to pull fuel into the pump intake line. This can sometimes be accomplished by pressurizing the tank with air from a compressor or even by manually filling the pump with fuel. Also, by disconnecting the first carburetor during this procedure and running the line into a container, you will be reducing any resistance to pump output flow and also allowing air to escape.

… And, you thought your installation was going flowingly (great),
Ray(64BJ8P1)

I just went to the Moss catalogue and was ordering some flat gaskets and noticed that there are "O-Ring Gaskets" for "recessed seating surfaces" and a note "for current SU Pumps". The new pump has these gaskets in the inlet and outlets. Do the old stock banjo connectors work OK with these O Ring gaskets? Do you use both a flat washer and the O-Ring washer? Or, just connect up with the old connector with only the O-Ring?

Sorry, didn't think of this wrinkle. Older SU pumps have a flat seat on the inlet and outlet ports, where the banjos sit and are snugged up with banjo bolts. On newer pumps there is a recess on these seats for an O-ring. Take a look at your pump's ports, if they're flat they need the washers if there's a recess you need O-rings (which should have come with the pump; if not, you want a correctly-sized Buna-N or nitrile ring).

The fiber washers, over time with tightening, will actually deform to match the seats and, generally, you don't want to reuse them (but can in a pinch). O-rings should be reusable. The flat washers are sometimes a bear to get a good seal, the O-rings can get pinched and torn on installation but, generally, I think they're easier to get a seal. I have both types as spares, and carry a half-dozen washers and O-rings in the boot.

Edit: Be careful, the pump body is a crappy, soft metal (zinc?) and you can cross-thread them (someone, er, told me this once).

I was also not aware that the electronic pump had a different connection sealing system ("O" ring) and definitly could be causing your air leak and lack of fuel draw. I would install the appropriate gasgets and, if still not drawing fuel from the tank, suggest you consider filling the pump with fuel so the pump can pull a small vacuum on its inlet.

good luck,
Ray(64BJ8P1)

I think even the newer, points-switched pumps have the recess requiring an O-ring.

But, do the old banjo joint connectors work with the O Rings? In other words, you still use the same fuel line connections, just not the flat washers where the fuel pump inlet and outlet have the O Rings? Thanks, Steve

stever said:

But, do the old banjo joint connectors work with the O Rings? In other words, you still use the same fuel line connections, just not the flat washers where the fuel pump inlet and outlet have the O Rings? Thanks, Steve

Click to expand...

Yes. But, it's possible to pinch the O-rings if you're not careful (not that I would EVER do that).

Edit: Slip the O-ring over the banjo bolt, all the way to the shoulder of the bolt, then tighten as usual. Probably wouldn't hurt to put a teensy bit of silicone grease on the O-ring. Unless the fuel system has been molested, the banjos are soldered to the hard lines and requiring a new banjo to accommodate O-rings would be a real PITA (I've not seen any other types of banjos). Note you still need the fiber washers on the banjo connections to the carbs