# Fuel problem with B&S 18hp engine 422707



## res7788 (Aug 15, 2009)

Initially it would only run if fully choked. I cleaned the tank, filter, and added a new line. Fuel flows good to the pump. Still same problem. I pulled carb and sprayed all orifices with carb cleaner from both ends. I put some new gaskets in the pump (vacuum type built into carb). The diaphram was firm but not hard so reused it. I blew into the vacuum line input to the pump and coiuld hear the diaphram working. Reassembled and installed it. Now it won't run unless constantly primed. It did shoot a lot of black colored gas out of the vent pipe from crankcase for awhile. I am stumped. Help!


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## brokenknee (Dec 13, 2008)

http://www.briggsandstratton.com/maint_repair/manual_and_more/ 


Should be able to find some information there. They have free PDF manuals for download. 

You may also find this useful, (or not)


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## Thurman (Feb 9, 2009)

Don't know if this will help but maybe: A customer came into the auto parts store (sometimes coffee shop/male gossip center) the other day and was telling us about having his 18 hp B&S engine in the shop for the third time with similar problems. Does yours have something like a fuel pump attached to the outside of the starter rope shroud? I'm not sure I totally understood this but it was electrically operated and was just for getting the motor started. This was his problem. The local "authorized service center" had it twice and could not fix this somewhat new engine. Customer called the 1-800-B&S give a shoot line and talked with a phone tech there who knew what the problem was. Customer had the techy call the repair center as he drove over. The ARC had a different tune this time, it was Mr. this and Mr. that, and a lot of "Yes Sir's". The part was UPS RED shipped in, and that was the problem. This may help, or may not. No charge, David


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## res7788 (Aug 15, 2009)

Thanks for the responses guys! Looks like mine is a 91 model. I finally got it running although with a little white smoke - a little rich I guess. It has an electric starter and the fuel pump is built into the carburetor and uses engine vacuum to work. I mowed quite a bit today and when I shut if off it backfired??? Thats never happened before.


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## Thurman (Feb 9, 2009)

Now, I do know something about B&S motors backfiring when you shut them down after running them enough to get them to "operating temperature". I own a TORO Z-turn type mower with a 16 hp motor. The day it was delivered and I cut grass for the first time it backfired when I shut the motor off and scared the hell out of me, I was not expecting that. I though maybe it was the gas the dealer put in it, so I ran all of it out and used different gas, same thing. This went on each time I cut grass and one day the local County Police pulled up investigating a call about firearms being discharged in the neighborhood. I demonstrated the motor backfiring for them, they were not amused, at all. When I called the dealer to come get it to see about what I thought was a problem they told me that it was not a problem, it was built into the motor. I didn't, and still don't like it. It has something to do with built in advance on the camshaft for easier cranking. HECK, it's electric start, how much easier can it be to crank? I've learned that when I'm shutting it down to let it idle for a few seconds, then turn the key off, and right back on maybe twice. This usually works. Thanks, David


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## res7788 (Aug 15, 2009)

Well i don't think mine is built in since it never happened before. I will try your cut off solution.
Thanks


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## 47_47 (Sep 11, 2007)

Let the engine idle for a little bit, slightly open the throttle and then turn the key off.


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## res7788 (Aug 15, 2009)

Well, it ran great for a day! Today it started out surging a bit. A few minutes later and I had to use some choke, and then later full choke and back off on throttle. Then it won't run unless primed - same as before I cleaned the carb and rebuilt the pump. Checked fuel flow, good. Removed gas tank cap and air filter, still no go. Help! Only thing I know for sure is that its a carb or pump (built into carb) problem.


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## Charlie1101 (Jul 22, 2009)

I had an intermittent problem similar to this on my B&S 18HP OHV. The problem was with the anti-afterfire solenoid. This is on the bottom of the carb bowl. It's normally closed and blocks fuel flow with the key off to prevent backfiring. 

My problem was actually a bad connector feeding voltage to the solenoid. I simply spliced a wire in to bypass the connector.

If this is the OHV, be careful with use of starting fluid. During diagnosis of this problem, I used starting fluid. This blew out the head gasket requiring replacement.

good luck


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