Just bought a '75 MGB, broke down right away

So, my wife and I just purchased a 1975 MGB, which we were told "it runs great". Famous last words. I have only a general understanding of car mechanics, but a very good understanding of many other mechanics (thought this would be my learning car) So I could really use some advise. The first drive I took it on, I only made it about a mile from the house before it broke down. It died, not quite like it was running out of gas, but like combustion wasn't happening like it should. every time the motor would cycle through firing the plugs, it would slow down and speed up, until it it stalled completely. It took about a minute to die after it began sputtering. Towed it home, then it started right up the next day, and the same thing happened in half the time. The major problem is that it was also dumping fuel out of a tube from what looks like a valve connected to the carbon canister- See photo. I'm assuming it is meant to only give off gas vapor. There is an after-market fuel pump also mounted on the wall of the engine compartment on the driver side. I need help diagnosing why excess fuel is not going going back to the tank, and pouring out of this tube which I think is for excess fuel vapor. I was told it had been running fine with this fuel pump until this point, although the seller also said it hasn't been driven much at all recently.

You have a sticky needle in one of your carburettor float chambers, did you get a manual of any kind with the car?

And can you make out a brand and model number on the pump? It may be putting out too much fuel pressure, or it could just be that things have gummed up through lack of use.

Don't get too down, this is an easy fix. :)

adoption pains...I'm familiar 8-)

ps: This only happens when your wife is in the car; really instills trust!

Thank you the Wiz,
I ordered the workshop manual as soon as I got it, it just hasn't come in the mail yet. I assume it can tell me how to clean the carb. Does the carbon canister have to be replaced too, since the fuel must be going through it?

The fuel pump says Carter 5E10A504

The carbon canisters can easily be rebuilt using aquarium charcoal contained in a "flow through" container. A nylon stocking works real well.

Until your manual arrives, you can download on here:
http://www.bmcno.org/tech%20tips/techtip.htm#DL_LIBRARY

Welcome to group. Cheers

OK, on a 75 you probably have HIF carburettors, these have the float chambers built into the bottom of them. To service them you really need to remove the carbs. - This is not a difficult job - Worst case scenario, the gas tank has rusted and the crud from it is jamming your needles. This happened to a new owner not far from me recently, we fitted a new tank. cleaned everything out and it has all been fine since then.

To figure out the problem, first, do you have a fuel filter in the engine bay? If not, you need one, if you do, is it plastic? If it is plastic is the fuel in it clear or cloudy? If it is clear you probably just have some varnish in the carbs.

A can of Seafoam (available from Autozone etc.) in your gas tank, and a couple of taps on the side of the carb with the handle of a hammer will probably clean things up.

If you don't have a fuel filter, or it is metal, go into the trunk of the car and remove the filler hose from the floor of the trunk. If the fuel in the tank is clear do the Seafoam thing above.

If the fuel is cloudy, this also applies if the fuel in the filter is cloudy, replace the tank, remove the carbs and clean out the float chambers, blow out the gas lines, fit a new fuel filter, re-assemble the carbs with a new float chamber seal and put them back on the car with new gaskets (all 6 of them).

Thanks for the tips Ken!

OK, you have a Zenith, not HIFs, just about everything I said above applies, except the number of gaskets. :D

Welcome James!! The carburetor you have in the picture is the Zenith type.
To see if the pump is working you can disconnect it from the carb and use a can or jar and hold the hose
in the can and have someone turn the key on for a second or two.

It apparently is pumping fuel if it is running out of the hose at the charcoal canister.

The Zenith is not too bad to remove and check the float to see if it is stuck.

Be careful with the car while gas is going everywhere. Would be good to have a fire extinguisher nearby
till you get the leak fixed.

Welcome!

On the Zenith-Stromberg carb, the first thing I would check is the rubber diaphragm in the carb. If it's split, the car won't run. Remove the damper, remove the four screws on top of the carb using a POSIDRIVE screwdriver - not a Phillips, you'll bugger the screws - and remove the top. Remove the piston. The rubber diaphragm is mounted to the top of it. Inspect the diaphragm - any splits, even a pinhole, will cause problems. I'd replace it with a new one, anyway. It's only $5, and if it looks old, then it will fail eventually. When you replace it, notice there are two tabs on the bottom. One goes in a slot in the piston, one goes in a slot in the carb body. If you don't put the tabs in the slots, the piston isn't oriented properly, and you'll foul your plugs.

You may also have a sticking water choke. Here's a link to an article on the water choke.

Water Choke Article

FWIW, the device fuel is pouring out of is the anti-run on valve...

James,

There are 3 videos on youtube dealing with the Zenith-Stromberg carburetor.

John Twist Videos

It may help to view these to get an idea of how the carb. works.

Listed as MG Stromberg parts 1,2,and 3.

You can take that fuel pump number down to NAPA and they will tell you whether it is the high or low pressure one. You need the one that says 2 to 4 psi. It also needs to be mounted back by the tank and as low as possible. If they are mounted high then they will not last very long.

Wow, thanks everybody. You guys are my new best friends.

Looks like someone has changed the location of the fuel pump according to James' photo. That one shown is definitely not stock. Now I'm curious what else had been done to the car and I wonder what, if anything, is in the area where the stock pump should be.

I don't have much experience with the Zenith (other than to stay away from them) but as mentioned, fuel leaking out of the anti-run-on valve usually indicates a stuck carb float or needle.