trailfire

harleysportster · Post by **harleysportster** » Sun Dec 02, 2007 3:29 pm

The fuel pump works by a combination of pressure and vacuum. The line connecting the fuel pump to the crankcase is the impluse line. The diaphram in the fuel pump is moved back and forth which pumps fuel, from the combination of the pressure then vacuum repeatly.
As the crankshaft rotates the piston downward a presure is created pushing on the diaphram of the fuel pump, then as the piston comes back up, a vacuum is created pulling on the diaphram of the fuel pump.
This impulse action of the fuel pump moves the feul from the tank to the carb whe neverything is working properly.
I believe the ports on the pump have a directional arrow stamped on them. If there is a arrow pointing towards the pump, that is the inlet port of the pump from the tank. The impluse line port would be on the top or bottom side when holding it flat.
To test the diaphram, a carb tester or shop-air regulated to 7 lbs is needed. Connect the air to the impluse port of the pump and charge it with 7 lbs and valve it off. If it will not hold air, the diaphram is bad.
To check the pump, remove the supply line to the carb and place it in a jar and pull the recoil rope over. You should see impluses of fuel fill the jar.

smitfire · Post by **smitfire** » Sun Dec 02, 2007 5:20 pm

i disconected the line from the crankcase and it shot fuel out of the line not out of the pump --is this right, and then the line to the carb also shoots pulses

Danzig · Post by **Danzig** » Sun Dec 02, 2007 5:44 pm

Nevermind.

Deere or Nothin' · Post by **Deere or Nothin'** » Sun Dec 02, 2007 6:24 pm

Once more. Make sure there is gas in your tank. Make sure your shut off valve is open, if in fact, you have put one on yet. Take the pulse line off at either the pump or the crank case. Never mind about the line going to the carb. DON'T turn the machine over. What you're looking for is whether or not gas is coming through the pump from gravity alone. When you take the pulse line off, the gas that comes out of the crank case is gas that shouldn't be there. Just let it drain.

Better yet, just take the pump off.The diaphram is probably torn around the edge of the plate. Replace that diaphram and you should be good.

harleysportster · Post by **harleysportster** » Sun Dec 02, 2007 6:25 pm

smit-trailfire wrote: i disconected the line from the crankcase and it shot fuel out of the line not out of the pump --is this right,? and then the line to the carb also shoots pulses

If you disconnected the impluse line at the crankcase and then pulled on the recoil and the fuel shut out, the crankcase is flooded. If this is the case, you still need to figure out how the extra fuel is getting in there. It is either a bad diaphram or worn,dirty needle/ seat in the carb.
Is this the fuel pump you have...
The directional arrows are cast on the top side. The top center port is for the impluse line.

Mr. Deere · Post by **Mr. Deere** » Sun Dec 02, 2007 8:17 pm

Its a 10 Dollar pump JUST REPLACE IT!!!! BOB

smitfire · Post by **smitfire** » Sun Dec 02, 2007 9:36 pm

where do u get it for 10bucks

Metallica19991 · Post by **Metallica19991** » Mon Dec 03, 2007 12:06 am

try ebaying it. you just need to find the right pump... its easier if you know the #'s on the pump...

tieszo6 · Post by **tieszo6** » Mon Dec 03, 2007 1:07 am

Central Snowmobile has the pump for 20.95 or a rebuild kit for 3.95.

Mr. Deere · Post by **Mr. Deere** » Mon Dec 03, 2007 8:13 pm

DK has them for cheap also. BOB

smitfire · Post by **smitfire** » Thu Dec 13, 2007 11:18 pm

well i took the engine that was flooding and put in in another trailfire with a different carb and fuel pump, had backfiring problems at first then we gave up, today i walked up to it gave it some new spark plugs and away i went, still needs some adjusting as it dosent want to idel well and doze bog up alittle but a great day for me, hope i get more than today out of it