OutdoorKing Repair Forum Forums Repairs and Maintenance Questions on Engines Questions On Briggs & Stratton Engines Difficult Starting Quantum

Hey guys, suggestions urgently required on this one. I have a Briggs Quantum 5 engine that has an issue starting, when started it runs perfectly. I have replaced the coil, the spark plug, the air box gasket, the carburettor 'O' ring, the air filter, the primer, carby has been thoroughly cleaned and checked, there is no sediment or crap covering the mesh filter behind the primer. I can prime it 3 times or 12 times and set the throttle to various positions but it takes about 6 or 7 pulls before it will start, does not blow fuel smoke when it does start. I'm stumped.

Most likely a choke problem, they have to shut fully

It only has the primer.

Hi MickyD,

Can you post a picture of the area where the primer is please. Note that if the primer is part of the air filter mount bracket it could be warped causing the primer not to work properly.

Hi MickyD,
Have you done a visual check of the primer function. Does it give a good squirt of fuel when you push the primer? Is the manifold loose or leaking? When you prime it with aerostart or something similar does it still need 6 or seven pulls to get going? Is the plug gap set correctly?
If all of the above is working correctly then i would suggest checking the valve clearances and adjusting accordingly. Checked cold, Intake 0.05-0.07, exhaust 0.07-0.09 inches.
Try that and let us know how you go.
Cheers, Ted

Okay here is probably what going here as I have seen this a lot. [quite common issue] Either the air cleaner base is warped from heat or a heavy hand installer over torquing the mounting screws. Once warped is nearly impossible to get a good seal; unless, you make up a modified air cleaner base gasket.

Once you verify that it is not priming remove the new gasket and look that contact area of the primer air channel. Now using a second gasket shave it as to apply more in the non contact area and remove the un-needed gasket in the other areas. I usually bevel cut the second gasket and use light application of wood glue to hold in place until things are assembly as the pressure will bond the layers together later. May take a few test fits to get it right so don't glue until your know you got it right.

Now you might ask why not just use 2 full gaskets? Well I seen it tried and I have tried it too. It simply does work the same as beveled gasket setup.Thin one side and thick on the other.

Hopefully this makes sense.

Yup, AVB has nailed it, I'd say.

Sounds very much like a priming issue, and the most common cause of this on these Quantum engines, is a warped air filter base.

The primer bulb pressurises the carby float chamber, so as to push a shot of fuel through the main jet into the venturi.
If the air filter base to carby joint leaks around the primer gallery, it won't prime.

I have a Quantum XTS50 on a Masport, and it's a 'first pull after 3 primes' start, from cold. Easily the easiest starting Briggs I've owned.