Small Engines (Lawn Mowers, etc.): Flymo B&S 380 wont suck up fuel, briggs and stratton, metal mesh

Question
QUESTION: Hi. I have a Flymo 4 stroke mower, using a B&S 380 engine.
Model: 98902, Type: 0385 01, Code: 96110154.
Firstly, can you tell me what information is contained in those numbers ? Like what year it was made, etc. ?
Mainly: if I put a little petrol into the carby, with the air cleaner off, it runs ok.
If I push the primer bulb (a newly fitted one, as the old one was developing cracks on the inside, and nearly breaking through to the outside
of the bulb, and it'd take about 4 seconds to fully return to it's normal shape), it doesn't suck up petrol from the tank.

I've been told it needs a new diaphragm. But the current one 'looks' ok. Not sure how to tell.
The new one comes in 2 parts, they're overlapping in the plastic bag, so I can't tell.
Cost me $12. Not sure if I got 2 diaphragms or a diaphragm & a gasket.
There is a fold in one of them. Is this meant to be, or is it simply a case of bad packaging?
The B&S part number of this is: 795083.
The existing diaphragm has a spring pushing against it. What does this do?
Thanks.
-Joshua

ANSWER: Number identification link:

http://www.outdoordistributors.com/Briggs_And_Stratton/briggsmodelid.html

Most likely there is some debris clogging the fuel pickup screen.  Removing, dis-assembling and cleaning with compressed air from an air compressor and replacing the diaphragm and gasket should solve the problem.  There are no folds in the diaphragm or gaskets.

Diaphragm goes on the metal tank, then the gasket. You engine was built in 1996.

Let me know if this helps.
Eric

---------- FOLLOW-UP ----------

QUESTION: Thanks Eric, that helped!
And your reply was so quick!
The cylinder of metal mesh is in good condition. Not blocked.
Could there be a blockage above that (in the carby) ?
When you say to replace the diaphragm & gasket, can I use the current ones ?

I just managed to separate the 2 new ones, and yes, they are different to each other. So one must be the diaphragm & the other the gasket.
What does the spring (that pushes against the diaphragm) do ?

1996, interesting.

So, this uses a pressurised fuel tank, right ?
If so, does that mean that there NEEDS to be a tight seal between the carby & the fuel tank, otherwise no fuel will be sucked up ?

What about if it IS running, and I remove the fuel cap, will that reduce the fuel tank pressure and cause the engine to stop ?

Thanks again.

Answer
Have you checked the online parts diagram on the Briggs site? It is possible the check ball is causing the problem.  There should be a mounting tab on the carb for the spring to sit in/on.

The system is not pressurized.  Engine vacuum activates the diaphragm which pumps fuel from the long tube up into the small resivor where the fuel is pulled up by the small tube with the screen on it.  Excess fuel just flows back into the tank.

The diaphragm is more like a fuel pump.  Did you get the primer bulb to seal when you installed it?
Did you blow the screen off with compressed air?
Eric