Need Help Bad

[bigturk_80]

Guys, I have a 98 formula 500, at the end of last season, it started acting up. The main fuel lines feeding to the carbs were not getting fuel, and the only way the sled would run was if I manually pumped the primer. It runs OK if I keep pumping primer, but the fuel is not flowing. I assumed it was the fuel pump and purchased a new pump. Put it in, same thing, no flow. I've checked the fuel filter, no prob there, actually if I pull the fuel supply to the pump off, it flows freely. Where do I look next????? Crank seals??? I wouldn't think so, because it runs smooth with the primer. Please guys, i'm hurting on this one.

Kev

[akheloce]

I'm not sure if this will help or not, but this is a troubleshooting procedure relating to ice in fuel. The same theory as having other contaminates in there. I had a 95 summit 670 that the line inside the tank was actually deteriorating allowing rubber chunks to clog it... sounds very similar to your symptoms.


From the NASA Antarctica expedition notes:
15.2a Fuel Flow Problems

Symptoms: Engine cranks but won't run, no fuel present in line from pump to carb. Engine may run briefly after priming.

Diagnosis and Cure:


Check fuel level in tank.
Pry fuel line off carb, pressurize the fuel tank (seal and blow into the vent line) to see if fuel flows out of the end of fuel line. Crank engine and see if fuel pulses out of the end of the fuel line.
If fuel flows and then pumps OK, the problem was probably just small ice crystals in the fuel pump valves. Pressurizing the tank dislodged them, thus solving the problem. Replace the line and go.
If fuel flows when pressurized but does not pump, the problem is fuel-pump-related. First disconnect the vacuum pulsation line from the center of the fuel pump to the engine crankcase. Blow through the line -- if blocked, clean ice out of the line with a wire. Check the nipples on the pump and crankcase for obstructions. If the vacuum line is clear but fuel still does not pump, replace the pump or remove it and let it thaw.
If fuel will neither pump or flow, then either the fuel line or the fuel filter is clogged. Clean the fuel line or replace the filter.
If the tank is under vacuum when you open the filler, check the vent line for obstructions or pinches. Occasionally the line will rub against the exhaust, melting the vent hose. Make sure the tank is venting properly.
If all of the above steps have been tried and still no fuel flows, check the fuel line for cracks or holes, and look for any obvious fuel leaks (i.e., discolored snow) in the engine compartment. Repair or replace the fuel line.
A mixture of 30 mL of isopropyl alcohol per 5 gallons of pre-mixed Mogas will lessen the chance of water contamination and fuel icing.
Pouring fuel through a trail flag or rag placed over a funnel will help eliminate any snow contamination of the tank and will filter the fuel.

[gravy davey]

Check the pulse line from the pump to the crankase. Make sure there are no cracks or a lose fitting hose.

[paul yarek]

have you tried the sled since warmer weather ?

[kragar]

put a new pulse line on and I bet you are good to go.

[Rocketman]

clogged jets?

[bigturk_80]

thanks for all the help guys, I'll try each of those things and get back to you on it, to let you know how I made out. One question, where's the vent line on the fuel tank? I thought it was just a vented cap?

kev

[gravy davey]

I dont think there is a vent line just a vented fuel cap as you said.

[Formulaman]

Nope there's a vent line it usually is hidden by the plastic cosmetics.It'll be a real thin line that will be hooked to a barb on the tank again hidden by more plastic. Usually some where near the filler neck.
As for the pump prob I've seen pulse line that will collapse under vacuum but these were usually thinner walled lines, my vote it's plugged

[30cal4me]

Originally posted by bigturk_80@Sep 30 2004, 08:17 PM
Guys, I have a 98 formula 500, at the end of last season, it started acting up. The main fuel lines feeding to the carbs were not getting fuel, and the only way the sled would run was if I manually pumped the primer. It runs OK if I keep pumping primer, but the fuel is not flowing. I assumed it was the fuel pump and purchased a new pump. Put it in, same thing, no flow. I've checked the fuel filter, no prob there, actually* if I pull the fuel supply to the pump off, it flows freely. Where do I look next????? Crank seals??? I wouldn't think so, because it runs smooth with the primer. Please guys, i'm hurting on this one.

Kev

[snapback]349283[/snapback]

Ski-Doo used a small screen filter in 98. Pull the main fuel lines that are running to each carb off of the brass fitting on the carb body. Inside the brass fitting is a small screen. Remove if it is in place and try again.

Revrnd had problems with his 98 MXZ 500 and Cindy583 had problems with her 98 583 Formula Dlx. Symptoms were the same as you say. Once screens were removed, problem went away.