next »

[boxbiker]

Same car, more trouble. I installed an electric fuel pump on my tr last year. I placed it on a flexible mounting on the fuel pump blanking plate on the motor. I continue to have fueling/ carb trouble. I put some clear fuel line between the copper line and the "T" so I could monitor the fuel and I see air bubbles in it when I rev the motor up and let off. The carbs then stumble and almost shut off.

I also had to install a new fuel tank last year and filled it up for the first time yesterday. On the way home fuel started pouring out of what I assume is a vent tube that comes out of the top of the tank. It has a banjo bolt and copper line that goes down by the tank and thru a hole in the floor . I opened the fuel cap thinking it was somehow pressurized but that did nothing.The fuel continued to flow until I crimped the line. Then when I drove home it started stumbling and trying to shut off. To keep it running I had to put in the clutch, pull the choke and feather the throttle. That continued for a mile or so then cleared up. By the time I got home it was running well. That is the second time that has happened.

My questions are: is it ok to put the pump in the engine bay or does it need to be in the rear by the tank ?
                    why am I getting air bubbles in the fuel line ?
                    why did the fuel come out of the vent tube? 

[TR3driver]

The pump should work OK in the engine bay, but you might want to put it away from the engine heat.  One possible source of the bubbles you saw would be the fuel boiling in the lines.

Another possibility would be a leak somewhere, allowing the pump to suck air, possibly combined with a restriction in the line.  You might try removing the inlet line from the pump and blowing backwards into the tank; then inspect inside the tank to see if anything came out or is floating around back there.

I can't explain the fuel pouring out the vent, unless perhaps the tank was just overfilled.  Because of the vent location, you can't fill it until the nozzle shuts off.  I actually blocked mine off permanently, since even with some air space in the top of the tank, a hard left turn will dump fuel out the vent (as the fuel sloshes to the side with the vent tube).  My car already had a vent hole in the cap, but it would be easy enough to add if your car doesn't have it.

[boxbiker]

I reread the Moss cataloge and it said the pump could be used under the hood as long as it did not get too hot. I checked it when the engine was hot and the pump was cool. The air bubbles appear even when the engine is cool. I have checked all the connections and they are all dry , not leaking.

I put a little over 10 gals in the tank when it started leaking yesterday and it poured out about half of that before I crimped the line to stop it. I am calling it a vent but it is a line that is on the top of the tank that goes down into the tank. I put a flex hose on it and blew into it and I could hear it bubbling back thru the gas. The replacement tank had more holes on it than the stock tank it replaced. The original tank had only one threaded hole on the top and I placed that banjo bolt and tube in the only hole in the new tank that it fit. There was another threaded hole in the tank but had a plug in it so I left it. There is another small tube sticking up out of the tank near the filler hole that I plugged. I wonder if i can just plug that hole also. I know it needs to vent to get air to displace the gas pumped out .

[TR3driver]

If there is a tube sticking down inside the tank, then that fitting is not for the vent.  Furthermore, with it sticking down into the fuel like that, once it starts flowing it will keep flowing (forms a siphon).  You'll need to make some alternate arrangement for the vent.

Don't know what else to say about the bubbles, except they have to be coming from somewhere.  Either vaporized fuel, or air getting in.  Although unusual, it's not impossible to have a leak that only passes air, not fuel.

Does the fitting you are using for the tank outlet also have a tube inside the tank?

[boxbiker]

I think I'll plug that "vent" because it was siphoning the gas out. I'll use the pipe by the filler hole and run it out with a pcv valve in it.

The outlet fitting is on the bottom of the tank and has no tube.

Hopefully this will cure the fuel starvation problems.

[motomadness1947]

Make sure your fuel pump outlet (going to the carbs) is positioned so it is on the top of the pump.  That is the only way accumulated air will be forced out of the pump.  If you notice your pump clicking rapidly the problem is air.   I installed my electric su pump with the out let on the bottom and it drove me crazy until I looked at another brit car and noticed the outlet on the top.  Bam it works like a champ now even in hot weather.  I mounted my pump on the front of the firewall on the drivers side and ran a gas hose over the top of the valve cover to the front carb.  This eliminated the steel line that ran around and very close to the cyl head.

Bruce Fahnestock