16 HP opposed twin gas dripping from fuel pump vents

Papaw582

Forum Newbie
Joined
Feb 3, 2019
Threads
3
Messages
5
  • / 16 HP opposed twin gas dripping from fuel pump vents
My tractor is always kept in the shed. It has the original B&S 16HP opposed twin with roughly 1100 hours. My last use was mowing in late Oct. 2018. When I finished mowing I changed the oil. I add 4 ozs of MMO to every 5 gallons of gas. The first week of Dec, I started the tractor and drove it out of the shed about 6 feet. She died and wouldn’t restart. I check both plugs for fire. Good to go. I saw there was very little fuel in the filter, so I disconnected and lowered the fuel line @ the fuel pump. I had good flow. Cranked again, no start, no fuel entering filter. Researched the issue, ordered rebuild kit for fuel pump Briggs & Stratton Fuel Pump Kit 393397.
I rebuilt the fuel pump, (used a pocket flat blade screw driver with a dap of grease to place the springs), still not pumping fuel. Removed carb and disassembled the fuel pump. The small spring in the carb body had bent when I put it back together (?). Reinstalled carb and still no fuel. Tried blowing into the gas tank while cranking, still no fuel. Fuel filter gas level doesn’t change. She’ll run putting gas or carb cleaner into the carb throat. I removed the fuel line at the shut off valve and blew air into the gas tank. The gas became cloudy. I removed the gas tank, drained and cleaned it. There was a tan material in the bottom of the tank that looked like sand to me, (but didn’t feel gritty). Maybe enough to fill 1 sewing thimble. I had to use a fiberglass driveway marker pole to loosed a spot the size of a dime in the right side of the gas tank, (there’s a small indentation there), to get it out. I installed new fuel lines, filter and the line that provides vacuum to the fuel pump. All line are clamped with gear hose clamps. I placed my finger over the vacuum line while cranking, but can’t really tell if vacuum is present. I blew into the hose with compressed air and had no back pressure. I again tried to get her started, but no luck. Engine cranks and spins as it always had. I removed the carb, cleaned everything, (carb was not dirty). Didn’t find any issues, everything was clean. Reinstalled carb, but no go. Still not pumping fuel, even while blowing into gas tank. I did notice I have a lot of vacuum down the carb throat. Placing my hand over the throat with no air cleaner while cranking the engine requires effort to get my hand off. I checked the carb throat & vacuum line to fuel pump. Both are about equal. IShe'll run pouring gas into the carb. The air cleaner housing is installed. Something told me to check the oil and it was grey. Maybe I missed the carb and gas went down the breather tube? I changed the oil. I removed the carb, dismantled it, recleaned and used my compressor to ensure all passages I could see were clear. Reinstalled the carb and she started. When I shut the engine off, I noticed gas dripping from the fuel pump vents. When I closed the shut off, it stopped. I have since cranked the engine several times, but not started it. No unusual noises. The oil level is still on the full mark and there's no discoloration to the oil. I also saw oil on the floor. It appears oil is leaking from the oil filler tube o ring and the front cover. I didn't have any oil leaks before this. What is happening here?
 

Attachments

  • 00U0U_8O0WFyHoGdr_600x450.jpg
    00U0U_8O0WFyHoGdr_600x450.jpg
    19.3 KB · Views: 2
  • 00V0V_9sSPqRFK6f_600x450.jpg
    00V0V_9sSPqRFK6f_600x450.jpg
    35.4 KB · Views: 6
Last edited:

Papaw582

Forum Newbie
Joined
Feb 3, 2019
Threads
3
Messages
5
  • / 16 HP opposed twin gas dripping from fuel pump vents
Cold compression is 60 pounds on both sides. Plugs are fouled. I also have blow by in the air filter housing but this condition was present before the fuel pump issues.
 

Attachments

  • L side plug.jpg
    L side plug.jpg
    82 KB · Views: 10
  • R side plug.jpg
    R side plug.jpg
    73 KB · Views: 7
Joined
Jul 22, 2017
Threads
21
Messages
2,154
  • / 16 HP opposed twin gas dripping from fuel pump vents
Something is awry with your fuel pump.......

Marvel Mystery oil is good for a lot of things....... It will separate from gasoline though..... Just like a outboard tank that needs to be shaken after it sits a while......

Plus Tard Mon Ami ~!~!
 

(Account Closed)

Well-Known Member
Joined
Dec 3, 2018
Threads
6
Messages
260
  • / 16 HP opposed twin gas dripping from fuel pump vents
Those plugs don't look bad, a little rich, but not bad.

Agreed with something up with the fuel pump. Do you have a parts diagram and did you follow the parts assembly to the letter?


Also, (for yourself, so you don't keep yanking the carb), hook up a small auxiliary fuel tank (I use a spare, small mower tank with an on/off valve) straight to the carb inlet (by-passing the pump) and see how / if she runs. Keep the tank HIGHER THAN THE CARB as it's NOW gravity fed. I suspect it'll run.

Once running, hook your gas tank line to the fuel pump and see if it pumps- I suspect it isn't. Your issue is between the pump (including it) and the tank.

Cold compression seems awfully low to me, Boud?
 
Joined
Jul 22, 2017
Threads
21
Messages
2,154
  • / 16 HP opposed twin gas dripping from fuel pump vents
Those plugs don't look bad, a little rich, but not bad.

Agreed with something up with the fuel pump. Do you have a parts diagram and did you follow the parts assembly to the letter?


Also, (for yourself, so you don't keep yanking the carb), hook up a small auxiliary fuel tank (I use a spare, small mower tank with an on/off valve) straight to the carb inlet (by-passing the pump) and see how / if she runs. Keep the tank HIGHER THAN THE CARB as it's NOW gravity fed. I suspect it'll run.

Once running, hook your gas tank line to the fuel pump and see if it pumps- I suspect it isn't. Your issue is between the pump (including it) and the tank.

Cold compression seems awfully low to me, Boud?

I was gonna mention the aux tank but I forgot........... BTW Scott his carb has the fuel pump built into it..... Not a separate animal like the newer engines......

Compression is reasonable for that cam he has I think... It's been a while since Iv'e worked on one of those.....I don't have my record/log books from that long ago from my old shop.....

Sometimes I show 35 to 50 PSI on the newer 6 HP's ACR strikes again.....
 

(Account Closed)

Well-Known Member
Joined
Dec 3, 2018
Threads
6
Messages
260
  • / 16 HP opposed twin gas dripping from fuel pump vents
Scratch the aux tank!

Great info Boud!
 

(Account Closed)

Well-Known Member
Joined
Dec 3, 2018
Threads
6
Messages
260
  • / 16 HP opposed twin gas dripping from fuel pump vents
He can still use the Aux tank, but it has to be above the carb..............

Well that will work then.

I suspect something isn't installed correctly in the pump.

A pic of the factory assembly should help (if there's much to the pump)..
 

Geoff813

Member
Joined
Jul 4, 2015
Threads
4
Messages
10
I have the 18 hp version in a machine I built from discarded carcasses and that pump is a yearly battle which I suspect is due to what passes for gas these days plus imported replacement parts being softened/damaged.

I just ordered a real B&S kit and cant wait to see how long that lasts.
https://www.amazon.com/Briggs-Stratton-393397-Fuel-Pump/dp/B000A13FBU

The 28N707 engine in mine is an animal and runs circles around a 15 hp OHV B&S Intek and heavy tall grass doesnt slow it down and require 2-3 passes.
 
Top