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MG MGB Technical - fuel problems?? never.....

So i'm driving my MG, minding my own business, when it decides to stop running... luckily, at this time i had enough momentum to get myself off the road. I immediately thought it was out of gas.. the only problem was i filled it the last time it saw the gas station and it only had 140 miles on the tank of gas. t usually gets a whopping 200. I tried to get it started again and it wasn't going to comply.. so much for my theory that the problem was in my imagination. I did notice that my fuel pump wasn't staying on. It's loud, so i can hear it tick, and it usually keeps ticking, but when i turned the key to on, it ticked once or twice and then there was no more ticking. So i walked home convinced my fuel pump had packed it in.

I came back with a gerry can a bit later and put some in and low and behold the thing kept on ticking like it had always done... i took the car to the gas station thinking "stupid kids syphoned my gas".. filled it up, but it only took 30litres. with the gerry can that's 34 litres all together, and i filed it to the point where it wasn't disapearing from the top of the spout anymore. Now this doesn't sound like an empty tank problem to me.. is it a crapped out fuel pump? I was going to get under it to day to make sure all of my connections were still tight and all of that fun electrical stuff...

if anyone has had the same problem or has heard of something similar, i would really appreciate any help.

-Dave
75 roadster
David Ryzuk

Dave. Do you have the original SU pump or an aftermarket model? The original SU will pump a few times when the key is turned, then quit when the fuel bowls are full. The aftermarket types seem to just keep clicking. When, with the SU pump, you run out of gas, the fuel pump begins sucking air and will produce a loud clicking sound that does not stop because there is nothing to pull from the tank. In your case, there are several areas to investigate--the pump, the fuel filter, the tank and the carbs. If the pump is bad, it will not produce the volume and pressure necessary. If the fuel filter is clogged, it will not allow the fuel to flow through it properly and the carbs will not get the gas they need. If the carb fuel bowl vents are not clear, the fuel may not be going in properly. If the floats are sticking or the needle valves are sticking, you can run out of gas because it is not flowing from the fuel line to the carb bowls and then through the jets. You could have an obstruction in the fuel line. The pick up tube in the gas tank may have broken or the in tank filter may be clogged. You need to check out the whole system to find out where the problem is. The fuel tank venting system is another area which can become a problem over time and should be inspected. Les
Les Bengtson

Thanks for helping me out. I have the aftermarket fuel pump that never shuts off. I'm hoping it's something small, and i'm planning, either today or tomorrow, to go through the delivery system and the return line in an attempt to find something. Hopefull i can figure it out no that i have some idea as to what could be wrong, thanks again.

-Dave
David Ryzuk

I have an electronic pump, not an original SU, and mine clicks a couple of times and stops just like the SU did.

Mike
Mike Howlett

Dave, if (or more likely WHEN)it happends again, try giving the pump a sharp whack. It will probably click into life again. 'Most' electric pumps do this a few times before expiring forever. It's trying to warn you!
Ken Lessig

Aftermarket pumps are not inherently inferior to the standard SU, tho they do have some minor problems of their own - such as too much pressure. But that can be handled by a decent pressure regulator, such as the Holley #12-804.

I would also look for poor grounding of the fuel pump, and possibly even poor electrical connections for the switched power from the ignition to the pump. If either of these are tenuous at all, most pumps will not really run quite right and perhaps intermitently. I had this happen to me on my MGA and discovering a poor ground connection suddenly restored proper functioning.

Given the age of our cars, I would, as recommended, also look at the total fuel delivery system for blockages causing fuel starvation. Crud in the fuel lines, or in the tank can cut off or severely restrict the amount of fuel which can be delivered. Sometimes old hoses breakdown or crud in the steel lines can break loose and clog a filter or a carb jet. You can use air pressure to blow back through any part of the fuel lines back into the tank, tho I think you should remove the fuel pump while doing this.

Another problem which can cause a car to sputter to the side of the road is a slug of water sucked up from the gas tank. The water can get in there either by condensation or having pumped it in from a gas station with water in its gas (yes, it still does happen!). Often, the water can be seen in a tank as a "puddle" of lighter material bouncing around like an ameoba at the bottom of the liquids. When this blob floats past the pickup tube in the tank, sometimes enough can be sucked up to kill the engine. Once that has been exhausted as the car sputters to the side of the road, it is replaced in the float bowls with some decent gas and then the damned car starts and runs just fine. Grrr.

Short of flushing the tank, the next best thing to do is to add a bottle of Isopropyl alcohol gas drier/antifreeze to the tank. It will mix with the water and allow a burnable mixture to pass through without killing the engine.

When you find your problem, let us know what you found. It is all good info for future reference. Thanks and good luck.
Bob Muenchausen

If David has a pump that makes a noise all the time, and it stopped making that noise, then either the pump itself is on the way out or the connections to it are dodgy as Bob says. This could be a heat-related problem (when it cools down it starts working again) so I would plump for the pump rather than connections (unfortunately) but still check the connections (by measuring the voltage at the pump terminals) first.

PaulH.
Paul Hunt

David,

I would check to make sure the venting system was open. If not, you will build up a vacuum in the tank that the pump can't overcome. After stopping a while, or removing the filler cap, the vacuum is gone and the car runs. Until the vacuum in re-established.

Just a thought.

Jim
74B Roadster
James Conner

Based on your symptoms, there may be another possibility. Did the B run poorly for a bit before it died? No power? I've seen same sypmtoms when a carb float valve gets stuck closed. Runs the one carb out of gas. Fuel pump won't click because the other carb is full up. Depending on your overall state of tune, your car may or may not run/start on the one carb that has fuel. Once I drove across a culvert, at a 4-way intersection, at an elevated speed. Shortly thereafter, the B started to run poorly. I found the rear float bowl empty, the front was full. Several occurences followed in the next few months. I ended up replacing the float valves. Never had the problem again. Pop your bowl covers. If there's gas in both bowls, and the car still doesn't start, it ain't your fuel pump.
Terrence Goodell

This thread was discussed between 17/11/2001 and 21/11/2001

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