Briggs Fuel issue

[Fix'em all 49]

I have a later style Merry Tiller with a 5hp Briggs I/C engine that is refusing to start & is stretching my normally good diagnostic skills now. It is fuel related as it will start when I tip fuel in via the air filter but once it stops it will not draw fuel into the carb. It is pumping up into the raised chamber in the tank but that is as far as it will come. So far I have cleaned the carb thoroughly including under the mixture screw. When you blow through both the pipes on the bottom of the carb it is all clear with no obstruction. I have fitted a new diaphragm and there is a good seal between the carb & inlet manifold. Any ideas what I can try as I am stumped now

[nigel 1,877]

I can’t see that it can be anything other than diaphram  I would check that again and also start it by chucking carb cleaner down the air intake a couple of times I’ve found sometimes doing that will clear things out and carry on running

[Fix'em all 49]

Am I correct in saying that the diaphragm only draws fuel up from the main tank to the upper section in the  tank. If so then it is doing that, but is it the vacuum of the intake stroke that draws it up into the upper part of the carb.

[nigel 1,877]

[Reiver 14]

Is the choke working properly?

[Fix'em all 49]

Nigel, thanks for the parts breakdown. I wondered if I am getting a good enough seal between the tank and the carb, so I ordered a new gasket first thing this morning. Only trouble is I have ordered  part no 272996 & your breakdown shows 692241. They look the same but not sure on dimensions.

 

Reiver - the choke does fully close, but I did notice that if the screw fixing the air filter base plate to the choke lever plate is too long it stops the choke lever before the choke flap is fully closed.

[Wristpin 400]

Take the air cleaner off and put your hand over the intake while pulling the rope. That will tell you whether it’s a choke problem. 

[Fix'em all 49]

The choke flap is fully closed so I don't believe it is the issue with this. The tank to carb gasket does seem to weep a spot of fuel so my thinking is that it is also sucking air and preventing the fuel from being drawn up from the upper tank chamber. Am I right in assuming this ?

 

[Wristpin 400]

Still try the hand over the intake and see if it makes a difference.

[Reiver 14]

Any luck getting your engine started?

[Fix'em all 49]

I took the air filter housing off & put my hand over the carb & fuel came up straight away. I have put it all back together and put the air filter cover on  but it still takes about 10 pulls on full choke to get it to start from cold. Runs lovely when it it starts. The only thing that is different is there was a foam & mesh filter in the air filter cover that was rotten so I removed it. The paper filter is all good so don't know if not having the additional filter is enough to cause this. The new tank gasket should arrive in the week. It does weep a bit so it may be sucking air in & preventing the fuel drawing up.

Edited September 1, 2018 by Fix'em all

[Wristpin 400]

The fact that the "hand over"  treatment worked suggests an air leak somewhere.

The gauze ore cleaner shouldn't cause a problem as it was a standard fitment on Industrial Commercial spec engines. 

[Fix'em all 49]

Fitted new tank gasket & still the same. Looked again at the choke & although it looked closed there was a tiny gap both sides of the flap. Slight mod to the set up and it closes tight now & started second pull. I should have checked it properly, thanks guys

[Reiver 14]

Good to hear you got a result.

[Fix'em all 49]

Have now finished the  Merry Tiller Spartan & looks so nice it will be a shame to get it dirty

[Stormin 4,458]

Looks better than new.