• Hi Guest!
    You can help ensure that British Car Forum (BCF) continues to provide a great place to engage in the British car hobby! If you find BCF a beneficial community, please consider supporting our efforts with a subscription.
    There are some perks with a member upgrade!
    **Upgrade Now**
    (PS: Subscribers don't see this gawd-aweful banner
Tips
Tips

MGB Starving for gas?

Share this page

Rut

Rut

Obi Wan
Country flag
Offline
The MGB runs great and has plenty of power, but driving at highway speed, 60-70 for 10-15 minutes gives me a running out of gas symptom. The gas cap is original, the tank and filter are new, the carbs have been rebuilt. If the car rests for a minute or I let off the gas for 15-20 seconds, the issue goes away. Unfortunately it always happens at a really bad time to pull off the road...last night on the way to the local hospital, so I can't pull off and check. Thoughts?
Rut
 
I had something similar in a BMW motorcycle ('73 R75/5) a few years ago. In that case the float levels were set too low. Once I got them set properly the issue went away.

Also had a bike where the gas cap stopped venting properly with similar results. A new cap fixed it.
 
Both good things to check!

Another would be fuel pump delivery but you would have to do it after the thing konks out... not easy if you are alone and under the circumstances. Sounds like a weekend project.
 
My guess would be a weak fuel pump.

If it were a venting issue, I don't think just letting off the gas for a few seconds would restore the car to normal. You can check for a venting problem by driving it to create the problem on a stretch of road where you can pull over without any danger and remove the gas cap to see if the tank is under a vacuum.

If it is a weak fuel pump output, it could be putting out enough fuel at lower speeds, but not enough to meet the requirements at a higher speed...so the level in the float bowls gradually drops. Letting off the gas for a bit allows the pump to catch up with demand.

You can test the pump by putting the fuel line into a container and switch on the ignition...you should see about 2.5 pints in a minute. If it's significantly less you either have a problem with the pump....or possibly the hard line is partially clogged
 
Back
Top