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Briggs Vanguard 16 -loss of power

Discussion in 'Mechanic and Repair' started by arborguy, Aug 18, 2004.

  1. arborguy

    arborguy LawnSite Member
    from KY
    Posts: 14

    I have a early 1994 Cub Cadet 2165 with a Briggs Vanguard V-Twin 16 engine. This summer I've had a problem that I can't seem to nail down. It starts great, runs great for about 20 minutes at full load and then begins cutting out. Letting it sit and cool will allow me to start and run another 20 minutes. See, we've already narrowed it down to about a dozen things :)

    I've done all the basics, new plugs, fuel filter, air filter, oil change. I suspect it's developing a lean condition since when it cuts out applying the choke helps me get it back to the barn. One consideration was vapor lock since it seems more pronounced on hot days.

    I've tried running the carb a half turn richer but the same symptom occurs.

    I've checked the flow rate out of the fuel pump and it's giving a constant stream about 1/8 inch in diameter, does this seem sufficient?

    Something that has troubled me from day one is that this engine will start with an almost full fuel filter and after 3 to 5 minutes at full throttle the fuel will slowly drop to the bottom and appear to bubble out of the supply hose, is this normal ?

    I've run the engine with no gas cap to rule out a plugged tank vent.

    I'm thinking it may be time to look at the carb but suspect there's probably a bunch of experts out there that know the quirks of this engine.

    Any ideas ? Thanks in advance for your help.
  2. fixer67

    fixer67 LawnSite Silver Member
    Posts: 2,100

    Did you check the fire to the plugs? If the coil(s) are overheating you could be losing fire to one side. If it is only running on one cylinder you will lose a of of power. I see this in the shop all the time. Next time it does that check the fire on each plug. Try not to get "bit" but with it running unplug one side and see whats. If it dies than that side was the running side if not plug it back up and try the other side. Good luck
  3. kkat

    kkat LawnSite Member
    Posts: 62

    If your fuel filter is full and then empty maybe your fuel line is plug up, take your tank off and check the fuel outlet and lines, have seen a buildup of grass/leaves/etc plug up the tank outlet and fuel line all the way done to the filter
  4. arborguy

    arborguy LawnSite Member
    from KY
    Posts: 14

    Thanks for the replies. Unplugging each side did result in one side stopping the engine so I replaced both coils just to make sure. (It's a pain in a shaft drive cub). Bad news is, it didn't fix the problem. Regarding the second, comment, I didn't make it clear but the fuel lines are clear, fuel filter new. Does anybody know if the output of the fuel pump sounds right ? It's about a 1/8" stream... I'm also wondering about vapor lock in the fuel lines, filter, or pump, does that ever happen?
  5. fixer67

    fixer67 LawnSite Silver Member
    Posts: 2,100

    Check the vent on your fuel cap. If the vent has become clogged you will have flow problems.
  6. arborguy

    arborguy LawnSite Member
    from KY
    Posts: 14

    Yup, that was one of the first things I tried, I even tried running with the cap completely removed. Same deal.

    Since you haven't commented on the amount of fuel coming from the fuel pump, I assume it's a reasonable amount. I've only checked that cold, I'm wondering if the pressue coming from the valve cover to the fuel pump is leaking when hot or something causing the fuel pump to lessen it's output.... I'll keep checking. Thanks for all the replies.
  7. fixer67

    fixer67 LawnSite Silver Member
    Posts: 2,100

    Try this, get a "test tank" of some kind. Here is what you do, get a gas tank of some type like a boat tank and place it on a stand or something higher than the carb. Hook the hose from the test tank straight to the carb bypassing the fuel pump making it a gravity feed system. Let it run for 30 minutes or so and see what happens. The fuel pump runs on a vacuum/pressure pulse. As the piston goes up and down it creates a vacuum/pressure pulse in the crank case and this is what runs the pump. Check the pump vent to make sure it is not clogged. If it becomes clogged the pump will not work right if at all. The pump vent will look something like the picture below. Also if the PCV valve (aka crankcase breather) is not working right you will lose part or all of your crankcase pulse and the fuel pump will have nothing to run on. Good luck
  8. fixer67

    fixer67 LawnSite Silver Member
    Posts: 2,100

    Forgot to post pump vent picture

    pump vent.jpg
  9. lonebear30

    lonebear30 LawnSite Member
    Posts: 4

    Hello to all. My mom has a John Deere lawn tractor with a 48" deck that did the same thing. You could run it for about a 1/2 hr and you would have to pull the choke out at times to keep her going. I suspected coils, checked them out and replaced one of them. NO Difference. I checked the fuel flow from the electric fuel pump to the carb. It seemed to have good fuel flow. To make a long story shorter, I removed the electric fuel pump under the seat and found that the small hose from the pump to the fuel line had slipped down off the line going from the tank. I slid the line back up into position and clamped it. Problem solved. My sugestion would be to pull the pump from the tank and check it over and see if that is your problem. Good luck. Let us know what you fine. lonebear30
  10. grass_cuttin_fool

    grass_cuttin_fool LawnSite Gold Member
    Posts: 3,503

    I know im off topic some with this. This spring my tiller wouldnt run very long. I have a 5 hp briggs. The rubber ends on each end off a pipe that goes from the crank case to the carb were bad. Long as the tank was full of gas it had enuff suction to run but after about 10 minutes of running it didnt have enuff vacumn to pull the gas up and out of the tank

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