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MG MGB Technical - no fuel flow

My '76 MGB died all of a sudden this morning, and when I disconnected the fuel line at the carb (Weber DGV) I discovered that there is no fuel flow (yes, the tank is full). The fuel pump still makes noises like it is pumping, so I suspect that I have a bad diaphragm inside the pump. I'm still at work after completing my morning commute on foot, so I haven't had time to tow my car home yet and check things out. The first thing I'll do when I get the car home is disconnect the inlet line into the pump and see if gas is coming from the tank to there. If so, I'll disconnect the outlet hose at the pump and the carb, and blow the line out with air to see if it's clear. If both the inlet and outlet lines are clear, is there something else I should check before changing the pump? My diagram of the pump shows an internal filter but I've never heard of anyone changing it. Could this be the problem? Any other ideas? Thanks for any help offered.
Lou Belby

Lou: Your car should have a filter in the line somewhere near the carb unless it has been removed. If it does you may want to make sure it isn't clogged. Clifton
Clifton Gordon

Thanks for the suggestion, Clifton. I forgot to mention that I already tried changing the in-line filter. The fuel flow is cut off somewhere BEFORE the in-line filter.
Lou Belby

Lou,
When you're done, those glass, see-through fuel filters are great diagnostic tools for assessing fuel problems.

Tyler
tyler irwin

Take a look at the line between the pump and the tank. Any small cracks here will allow air to be drawn into the pump casing and cause a loss of flow.

Inside the tank, on the inlet line, there is a small mesh "sock" that may have clogged with rust/silt. Some low pressure compressed air may blow this clean enough to restore fuel pressure.

If it's heavily clogged, you may want to remove and thoroughly inspect the tank, and replace if necessary. The fuel tanks rust from the top, so if there is enough rust to clog the inlet filter, you might have a large hole in the top of your tank.
Paul K

If the pick-up pipe rusts through above the fuel level inside the tank you get the same sypmtoms as being out of fuel.
Paul Hunt

Thanks for all your comments. I finally got under the car yesterday and blew out the lines. First I disconnected the line from the tank to the pump and blew compressed air through it. The strong gurgle told me that this line was free, so I then disconnected the outlet line between the pump and the inline filter in the engine compartment. After blowing air through this line, for good measure I blew air into the outlet pipe of the pump just in case the internal screen was clogged. I don't know which of these did the trick, but both the pump and car are now operating fine.
Lou Belby

This thread was discussed between 10/09/2002 and 12/09/2002

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