Moss Motors, Ltd

I inherited an ’80 MGB roadster that had been sitting in a garage for several years. I did the usual tune-up(points, plugs, oil change) trying to get it to start but not having much luck. I siphoned out the old gas and put in some fresh. I blew out the gas line from the fuel pump to the carburetor but the gas line from the fuel pump to the tank is clogged. I took the gas cap off but can’t blow air through the line into the fuel tank. I am thinking the sending unit is blocked. How hard is it to take off the sending unit? I didn't see any bolts or screws. It looks most intimidating.

Wait up there nativetexan2,

If you think you have fuel delivery trouble, check for these vital signs first before taking it apart. First off, when you turn the ignition on, can you hear the fuel pump tick (assuming it's an SU type)? If so, good if not, investigate this further. You can also disconnect the fuel line where it meets the carburettor. Have an assistant turn on the ignition and see if the pump delivers. A bowl to collect the fuel is a good idea, as is a well ventilated area for work...

But it's not necessarily a fuel problem... The other thing you need is a spark. Ignition/electrical problems are going to stop going anywhere. At least check/clean the rotor and distributor cap and check for a spark. The crudest, but easy way is to crank the engine with one plug out, the lead connected and placed on the engine to earth the plug body. I note you changed the points - are they opening/closing correctly and with the right static timing? If you have a test light, a lot of this stuff can be checked easily.

Good luck,

Ed

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I want my MGB

Native: Fear not. It is pretty easy to remove the sending unit assembly. It sounds like you have a pretty good handle on checking for clear lines and it is quite possible that stuff has grown on the sock filter attached to the sending unit assembly. You should be able to get fuel (or at least air) through the fuel pump inlet line if you pressurize the tank. If not, pull the sender MAKING SURE THAT THE FUEL LEVEL IS LOWER THAN THE SENDING UNIT!!!  Suck fuel out of the filler if you have any questions.

There is a circular ring that locates the sender. The ring has 3 tabs on it. Take a BLUNT screwdriver or punch and locate it securely on one of the tabs. Take a deadblow or brass hammer and tap the punch SMARTLY! to rotate the ring to the left (lefty loosy)  Little taps will only break off the tab without transmitting enough energy to break the ring.

The ring should rotate about 1/4 turn and then fall free. The sender will then be held only by being stuck to the rubber seal. A quick jerk on the outlet and the unit should pop free. The filter has a plastic frame and nylon filter media. You should be able to clean it up.

I ran into the same problem with my 1980 MGB, but the project got sidetracked and I have yet to get it running.

Good ludk

 

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Kelvin Dodd
Global Sourcing Engineer
Moss Motors, Ltd.
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Disclaimer: Working on automobiles is inherently dangerous. Moss Motors, Ltd. is not liable for injury or damage due to incorrect installation or use of their products. All products are sold with the understanding that the safe and proper installation and use of the products is the customer’s responsibility. Follow factory workshop manual procedures and instructions, but use current shop safety standards and common sense. Some tasks will require professional advice or services which Moss Motors cannot provide.

re-reading my post I noted that I made an editing mistake. 2nd paragraph should read: without transmitting enough energy to break the ring FREE.

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Kelvin Dodd
Global Sourcing Engineer
Moss Motors, Ltd.
Helpful Links:
Code of Conduct
FAQs

Disclaimer: Working on automobiles is inherently dangerous. Moss Motors, Ltd. is not liable for injury or damage due to incorrect installation or use of their products. All products are sold with the understanding that the safe and proper installation and use of the products is the customer’s responsibility. Follow factory workshop manual procedures and instructions, but use current shop safety standards and common sense. Some tasks will require professional advice or services which Moss Motors cannot provide.

Just for grins, check out this article.  http://www.theautoist.com/CHECKLIST.HTM

 

Thanks Kelvin,

A quick swift blow and the circular ring came right off. The sock filter was all gummed up and the tube was completely blocked.I have it soaking in solvent for cleaning later this week. Should I try and clean out the fuel tank too? I think there may be more gunk left in the tank. It seems the PO changed out the SU fuel pump with a square electric pump. I'm thinking I will reinstall an SU electronic fuel pump.

 

 

nativetexan2:

Thanks Kelvin,

...The sock filter was all gummed up and the tube was completely blocked.I have it soaking in solvent for cleaning later this week. Should I try and clean out the fuel tank too? I think there may be more gunk left in the tank. It seems the PO changed out the SU fuel pump with a square electric pump. I'm thinking I will reinstall an SU electronic fuel pump.

You should very definitely clean the tank (and the line between the tank and the pump) if you are going to install a SU fuel pump.  Also, don't even think of installing a filter between the tank and the pump.  The SU fuel pumps are very sensitive to clog on the inlet side.  If the clog is bad enough to stall the pump and the power is left on (while troubleshooting for instance) for a period of time it will burn out the internal swamping resistor in the coil.  On a points style SU pump this will cause accelerated wear of the points and any subsequent replacement points.  With the all electronic SU pump, a burned out swamping resistor will shut the pump down completely, even if the circuit card is not damaged (as they often are).  The PO probably did you a favor by switching to the little, square, run all the time, make a lot of noise, Facet pump in that it has a bypass valve in it to establish outlet pressure and because of that, it is immune to clogs on the inlet side.
Cheers,
Dave 

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Cheers,
Dave
http://homepages.donobi.net/sufuelpumps/

Definitely will clean the tank. Has anyone used the three step process that Moss sells? It sounds pretty easy to use and with the weather like it is, I have plenty of time.

Dave, I have been doing a lot of reading about MGs and somewhere I read that I could use a square run-all-the-time fuel pump in line with an SU type and have it wired to a switch to use in emergencies. Not sure how it works but its a thought.

Thanks everyone.

NativeTexan2-

I have used the 3 step cleaning process Moss sells to clean up a tank and it works quite well. Just follow the instructions carefully. Use copius amounts of water between steps to rinse well. Throw in a short piece of chain to remove any gunk that has built up on the bottom. While you have the system apart, replace the 5/16" fuel hose from the sender to the fuel pump. If it has a nick in it, (remember, it has 28 years on it) it won't allow fuel pressure to build at the carburettor. Install a new filter, and keep a spare ready. After you have cleaned your tank and sending unit screen cone, replaced the funky square pump with a new SU electronic pump, you will be getting plenty of petrol. Remove the first fuel filter after a few miles of service and discard, replace with the new filter. You don't want any crud from the lines fouling up your carbs. I'm not sure about the secondary/backup fuel pump, never seen or heard of one yet, anybody?

Mike Mann

Highland Ca

'75 Midget

'78 MGB

'79 MGB