# Briggs 18HP twin, very odd running condition



## fastline (Apr 10, 2013)

First off, I am a mechanic but rarely work on Briggs stuff. I have a Grazer front deck mower with 18HP Briggs V twin flat head. Previously owned by my dad and cared for well. Has always started and ran well, no smoke, no noises, no oil use, just solid. 

I knew the battery was about junk. Been meaning to get to it. I started for me today, got 10min into mow job and engine started to sputter just like running out of fuel. I lowered the throttle and it seemed to want to idle a bit. Usually if out of fuel, that is it. So I killed it, fuel was fine. Went to crank on it and nothing at all. Meter tested battery, 12.6 surface voltage, bumped the starter, dropped to 4V. I knew the bat just dropped a plate. 

Way to the bat store I was puzzled how the bat could have caused this. Never the less, installed bat and fixed that problem. To my surprise, it still would not run. Pulled plug and looked like pretty much NO spark. However, I still could not see how a battery loss could kill spark. After considering plugs dry, I choked and finally got it to half ass idle. Will not take ANY throttle, see a little fuel jumping up out of the carb. 

I verified the fuel filter is fine, comp tested at 110 or so on both cylinders. When running at idle, it seems to sort of knock and sort of act like running out of fuel but when I try to aid with spray, it does not get better. It finally pinned the throttle and it was running exactly the same as idle. Sort of on-off-on-off. 

I have been suspecting the fuel pump but what are the chances of losing a bat and pump at the same time??? Also, I find that the crank case breather is moving a LOT of air IMO. Maybe somewhat normal and I am concerned. 

Every time I pull the plugs, they are dry, NOT wet. The fuel jumping out of the carb and the crank case vent has me worried something went south in the engine but I can hear that it wants to run right IMO. I was also thinking flywheel key but that usually takes one down completely. 

Confused and grass is still growing!!! PLEASE HELP!


I will add that due to the instant nature of this problem, that should rule a lot of "tuning" or "bad fuel" issues out. It was running like a top and as soon as I headed up a small incline, it started coughing and has not stopped since.


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## wjjones (May 28, 2010)

Does it have the tube that runs from either one of the valve covers? It sounds like a fuel issue, and I have seen the internals of those pumps go bad like the diaphragm.


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## fastline (Apr 10, 2013)

After connecting a node light on the ignition, it was obvious the ignition was the source of the issue. I disconnected the main kill wire on the coil to eliminate any other concerns and ran the same. Meter testing the coil also shows bad. I replaced it and runs like a top. 

I did open the fuel pump after not getting much suction but I am now convinced they don't pull very hard. Found nothing wrong in the pump reassembled and regrouped. 

Fnnnn 10hrs later, it is fixed. I hate this mower. Changing the coil required engine removal! I hate working on stuff that was not designed to be serviced. If the engine came out easy, that would be different though.


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