Primer system on newer briggs?

[dart451]

Working on a Briggs 09P702-0211-F1. Installed new carburetor, replaced the primer bulb. Engine runs fine but won't Prime! I have introduced some low pressure air from my compressor and it primes with little pressure but I cannot get the new bulb or old bulb to prime the machine. Gasket between air box and carb is new and in good shape. Anything I'm not thinking of here? Thanks.

[KE4AVB]

There is no check valve involved so only a blockage or air leak can be the problem.

First here is a simple test for primer assembly. Take a gauge on like a Mity Vac tester. put hose over the exit hole going to the carb. Now while holding things together with an eye on the pressure gauge quickly push the primer bulb. If it is working then you should see 3+ PSI on gauge momentary IE a peak reading and then back to zero as you release the bulb. Or at least that how the one here works.

Now I haven't seen this with these primers (mainly because I don't see many of these engines) but the base could be warped causing an air leakage.

Also this is one with the white primer piece on the side the carburetor so make sure it is there in place. Currently all I have is the auto choke in hand which doesn't have this piece.

[dart451]

I cleaned the base out very well before I installed the new bulb. However, the White Primer piece...yes, it has it in the carburetor but I'm thinking I don't know how this works?

[KE4AVB]

It just a metered air flow ie an open vent.

Kinda wish I had more experience with this system but walk behind mower are far and few in between repairs here.

But I am fixing to get some experience on my 2000 chevy S1500 transmission. I lost drive on it this morning so now it is for me to figure out how to get it out for an overhaul. Gesh if it isn't one thing it is another this year.

[dart451]

Ok, thank you...it has the little white meter...made sure it had a hole in it...still no worky though...

[bgsengine]

try plugging the little white nipple - piece of small 2-cycle gas line hose that fits, plug off the hose, see if it makes a difference.. got an air leak somewhere that the metered vent is combining with.

[dart451]

try plugging the little white nipple - piece of small 2-cycle gas line hose that fits, plug off the hose, see if it makes a difference.. got an air leak somewhere that the metered vent is combining with.

That did it bgengine! Primes beautifully now...thank you for the response! I did order a new air box so this should work for awhile...

[KE4AVB]

That would been my next suggestion as a work around but I kinda frustrated right now with my truck. I have lined up some support from one of my customers since this is my only vehicle.

This carburetor priming system looks to be quite simple but of course a 2 cycle engine looks simple too but everything got to be just right.

As I said all I have here to work with currently is the auto choke version which does not have the white nipple, Now I have work on engine that had it but never had a priming issue to resolve.

This is why this forum is here as we must share our experience and knowledge with each other. Usually one of us have had the problem that drives other nuts at times.

I did gain a little from this too as I now know what the system is producing pressure wise from the primer assembly and can use that to help trace the root failure. Basically it appear the system requires about 3 psi of pressure to prime. Anything greater test pressure wise would mask the problem as it over condensate for a leaky area. I just got to remember to test my theory when I do get in the next carburetor with the nipple to see if I can come up with a reliable test procedure for all of us to use. I also would need to verify the nipple is truly a metered source or if it has a check valve. Something that I will need to verify personally before I can say definitely which way it is. I will do a write up with I do get the need info and put it in the Briggs downloads for everyone to view.

Too bad Briggs doesn't document this in the repair manual. Here lately some their repair manuals looks like a grade school student done them. Actually that one my complaints about the manual and that is lack of basic info.