electrical gremlin

matt159

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Finally got a trip in this weekend. Awesome snow. Rode 3 days. Built lots of under hood heat & had the sputtering issue trying to come off of idle a few times while in the trees on day 1... had a couple hot-start/no start issues as well. Fuel pressure appeared to be low when it was sputtering at idle/ barely running (35-40psi). I replaced the fuel pump (pump only -- not the assembly) before day 2 and ran great most of the day... but had a hot start/no start issue again on day 2. Pulled fuel line off & pulled it over a couple times to make sure pump was moving fuel... hooked it back up & then it fired right up.
Day 3, I rerouted the fuel line so it ran below the pipe instead of above it as kidwoo suggested.... burned about 8 gallons of fuel & it worked fine. Had a little burble on restart once but much improved.

Still working on confirming my suspicions... but I think my issue is 2-part: fuel vaporizing in the line & low fuel pressure.

My fuel pressure is a little low for sure (even with the new pump) & think the factory fuel line routing along with my non-insulated aftermarket pipe was vaporizing fuel in the line.
My fuel pressure doesn't "build" each time I pull it over when restarting the sled when hot. After each pull, pressure drops to zero... so takes a really good yank to get all the way to 35-40psi where it tries to fire.
Going to do a little more testing to see why fuel pressure appears low... maybe just the gauge... maybe the regulator... maybe a small leak in the pump assembly.
Will update in a week or two after I get a chance to look it over again. --Matt
 

kidwoo

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Similar here. Much much better since rerouting the fuel line but it did it to me again yesterday. Quick burble and then died. Four or five pulls with the hot start switch didn't work either.

I carry little vials of fuel with me now and dumped one in a plug hole and just took off and it was fine. The plug I pulled was bone dry, as usual.

Something worth noting is that when I wasn't getting the problem, I had the stock can on. I put my diamond s ti back on before yesterday and it did it after like a 20minute stop. I think that heat blanket on the stock can helps keep the radiant heat down. I just put the stock can back on and will be trying to get it to do it again. I did have a ceramic coated skinz can on there when the problem started a year or two ago. Like zero radiant heat with that thing so I may be wrong. But then maybe that was causing the pipe to hold more heat, who knows.

I ordered an air temp sensor relocate extension from SLP today. That initial start and burble that everyone gets before dying still tells me it's getting a heat soaked reading from somewhere. And yes I think having an aftermarket can right under the sensor is making things worse.

Thanks for the fuel pressure update matt. Good info.

I know it's a different part number but I wonder if the ascender fuel pump would work. Looks like the same mount and design. Matt: how did you do just the pump and not the entire assembly?
 
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matt159

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----- I carry little vials of fuel with me now and dumped one in a plug hole and just took off and it was fine. The plug I pulled was bone dry, as usual.

Your solution to add fuel directly to cylinders is telling that it is a fuel delivery issue for sure. I am leaning more & more toward vaporized fuel in the line probably in combination with low fuel pressure... or fuel pressure leaking off too quickly between pulls when hot starting. Unfortunately, installing the new pump didn't fix the fast bleed off & out of spec pressure issue for me.

I hope I find the rubber is leaking where the pump goes into the housing... because it is only $10.00. :)
If not, I'll probably replace the regulator & see if that changes my pressure level.

I ordered an air temp sensor relocate extension from SLP today. That initial start and burble that everyone gets before dying still tells me it's getting a heat soaked reading from somewhere. And yes I think having an aftermarket can right under the sensor is making things worse.

I did the air temp sensor relocate about 4 years ago & it did help with the low rpm burble and made the low rpm fueling much cleaner when heat soaked. I just soldered about 2 feet of wire into the middle of the stock sensor lead & zip tied it down in the nose cone so it still comes off with the hood. Not sure how spendy the SLP kit is, but it's a pretty simple/cheap mod to do yourself if you can solder.

I know it's a different part number but I wonder if the ascender fuel pump would work. Looks like the same mount and design.

A new pump didn't seem to change anything for my situation last week... but if you want to go that route:
http://apeusa.com/html/fppumps.html F20000299 I think is the right pump... check the number on the side of yours 1st. $115 is great price for a real Walbro pump.

Going to hook my pump up to 12v & let it run for a while one of these nights & hopefully catch a glimpse of a leak.
Considering an in-line check valve also...but will see how it goes without 1st.
Will update as I collect a little more info. --Matt
 
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kidwoo

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The SLP thing is just a pigtail extension. 30 bucks.

Where does that regulator for the fuel pump mount?
 

sno*jet

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my hood was off a while back cuz i got it so hot it actually melted up by the curve in the pipe. i was lookin at the fuel line thinking how are these guys routing it to where its actually further away from the pipe? granted its above the pipe stock and heat rises, but looked to me you gonna get closer to it in back of the pipe and have to run longer line and get creative as its not coming out of the tank in a good direction to make a 90 degree bend straight down. maybe you clock the fitting on top of the tank? any rate, thought about wrapping some heat tape on the fuel line but i just looks too far away from the pipe to be an issue to me so said f it. good luck, keep on keepin on. i follow this thread incase it ever happens to me. safe to say you could change title to "fuel delivery gremlins"?
one last note, these tanks are not vented well at all, i could go out everyday in my shop and unscrew the cap and it lets out a big ol burb. polaris had problems in past with oil caps not allowing oil to be sucked into the pump...
 

kidwoo

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I can't change the title of the thread or else I would.

I added a piece of fuel line and routed it down by the jackshaft and then along the main wiring harness, more similar to how the m-series sleds did it.

Once my sled gets in this 'condition' I've always burped the fuel cap. It makes no difference. Like matt said, I think the fuel line gets evacuated and the pump isn't pushing any more, or not enough fuel just on a rope pull.
 

sno*jet

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have you tried loosening the cap before shutdown and leave it loose until you go again? i dont know if other sleds burp this much but m-series never did.
 

matt159

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Where does that regulator for the fuel pump mount?

Bottom side of the fuel pump assembly, right next to the fuel pump. It's held in place with a while plastic clip/cover.
Will snap a pic when I replace the rubber seal that goes between the pump & the fuel pump assembly.
 

kidwoo

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Hey matt. Where is your pressure gauge located?

Next time you're out, run up a climb (something to get the motor good and working) and then park it for 15-20 minutes watching the gauge. You already said your pressure is dropping when pulling the rope, it seems like you'd see a rise in pressure if the fuel were vaporizing in the line.
 

matt159

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Hey matt. Where is your pressure gauge located?

Next time you're out, run up a climb (something to get the motor good and working) and then park it for 15-20 minutes watching the gauge. You already said your pressure is dropping when pulling the rope, it seems like you'd see a rise in pressure if the fuel were vaporizing in the line.
Pressure gauge is behind the side panel.
Once my sled has been ridden for an hour & I shut it off, the pressure drops to about 10 psi as soon as the engine stops & is at zero within a few seconds after that.

Here's my whole "theory of what may be happening" part... but no easy way to confirm.
Gasoline will boil anywhere from 100F to 400F at sea level pressure (14.7psi) depending on what component of the gasoline is boiling off.
At 10,000 feet air pressure is about 10 psi... so boiling point has dropped from 100F to about 80F.
Pretty easy to imagine that your gas line by the pipe could be 80+ degrees right?
It slowly starts to vaporize and push back into the pump or through the regulator and my pressure stays at zero because it is pushing back into the tank.
If I start the sled again within a few minutes, not much vapor has formed so it starts fine & I ride away happy.
When I shut off because I need to dig someone out (or take a break) for 20 minutes... then it has had time to make enough vapor in the line & pump.
That is when I can't get it to start consistently.

When I am riding around the fuel pressure is 42psi, the boiling point is pushed up to at least 140F at that pressure so I don't think I am making much vapor in the line while moving & getting air through the engine compartment.

Would be nice to know if this hot start issue is more common with aftermarket pipes (no heat shield like the stock pipe has) & silencers (which have no heat shield like stock either).

Also wonder... does every sled's fuel pressure drop to zero when you turn it off once ridden or is it just mine? or just the problem sleds?
If your sled holds even 15 psi of fuel pressure after you shut it off, the fuel in the line won't vaporize nearly as fast because that 80F boiling point is pushed up to 120F by the remaining pressure.

Lots of theory & several questions without answers. I can't be certain this is the whole issue, but I will try a few things to see if I can keep the fuel line pressurized longer when hot.

Possibly put a check valve in as long as the regulator doesn't bleed off too fast... can't tell if there is one in the fuel pump assembly that isn't working or maybe there isn't one at all.

Got a little wordy, but that's the theory I am pursuing for now. If it doesn't pan out... I will start over with something else.
 

kidwoo

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Got a little wordy, but that's the theory I am pursuing for now. If it doesn't pan out... I will start over with something else.
All good. My background is analytical chemistry so I'm used to it ;)

And yes, that's exactly what I've been thinking. Open injectors would flood the thing and that pressure is going somewhere. I'm thinking it's pushing back into the pump. And yes I think hotter non-insulated exhaust components make it worse.

Telling that the c-tech motors moved the fuel line to where skidoo and polaris have it........NOT over the exhaust. Same with the air temp sensor.

As far as check valves go, I do wonder if something like this would keep the line charged.

 
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matt159

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thoughts? I'm actually worrying that the 2.9psi min to flow might be a problem.

I thought the same thing about the Amazon ones... this one is supposed to crack at 1psi.
This is from the same place that has the regulator & fuel pump rubber isolator.

I think the right place to put the check valve is in the tank under the fuel pump... but I hate to make it that inaccessible if I want to remove it for some reason.
One major drawback is that you definitely don't want to run out of fuel with a check valve in the line under the pump.
It will suck the smart valves closed & if none of the valves have a leak, the smart valves won't reopen until you crack the line between the check valve & the smart valves.

I think I would see a 1psi pressure drop (or more if their claims are exaggerated) pressure drop to the injectors if I put it after the pump.

Hopefully I can solve my issue without installing a check valve. Will probably do a little testing this Sunday with a 12v battery in the trailer.
 

kidwoo

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You're gonna love this:
I just pulled out the old fuel pump I took out last year and pulled the pancake backflow release to see how it's setup. I put it back in the assembly and messed around with pushing air backwards through the system with my compressor.

It won't open until about 40psi. But it will STAY open down to just below 25 psi once it's cracked. I bet that's enough to push a good bit of the fuel back. That kind of jives with what you were seeing with your pressure gauge. Completely replacing my pump assembly seemed to improve things but only for a short period of time before "it" started again. That would explain the fuel evacuating from the line but not why it can't build back up when pulling.


I was thinking about the same thing with a check valve. Since the backflow release is before the pump (flowing backwards here) I'm not sure that would solve the problem. I think it would need to be after the pump if we're correct and it's the fuel line to the rails that evacuating. Putting it between the pickups and the pump would still allow backflow into the top of the pump mounting assembly.
 
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matt159

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Putting it between the pickups and the pump would still allow backflow into the top of the pump mounting assembly.

I agree that it will. The fuel pressure can bleed off (back into the tank) 3 ways:
backwards through the pump itself
through the pressure regulator (what you are referring to as the pancake backflow release)
around one of the seals where the fuel pump or the pressure regulator attaches to the assembly

If any of the 3 let fuel leak back through, then fuel pressure will be lost quickly when the pump is off.

Check valve after the pump will work, but I don't want to do that and potentially drop my fuel pressure at the injectors... unless I can't stop the bleed-off inside the tank.
 

kidwoo

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I just ordered some high pressure/high temp fuel line, an inline pressure gauge and a shutoff valve. I figure the shutoff can do what we're thinking with the check valve.

We shall see!
 
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matt159

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Replacing the fuel pressure regulator seems to have done the trick for my fuel pressure issue.
Ran the pump on battery for about 20 minutes. Ran steady at 42psi. Pressure would bleed off to about 5psi instantly when pump stops & to zero within a few seconds.
Just changed out the regulator (nothing else) and hooked it back up. Ran for 20 minutes at 47 psi. Pressure still held at 22psi 20 minutes after turning pump off.

A few differences I noticed:
There is a second o-ring on the Quantum regulator that had to be removed before installation... apparently it is needed for another application.
It appears that the factory pressure regulator has some white plastic (or maybe white coated) component in the center, but the Quantum regulator appears to be brass.
Quantum regulator is louder for some reason... with the factory one I could hear the pump spinning... now I just hear the regulator sputtering.

I will replace the isolator on top of fuel pump also ($9) since i have one. It seemed pretty soft when i put the new pump in last week.
This fuel pump assembly only had about 800 miles/3 years on it so I imagine it was a barely-in-spec regulator to start with.

Will have to get on the snow to confirm that this helped/fixed my hot-start issue but feels like I am on the right track based on what I saw last trip.
I will update this thread if fuel pressure becomes an issue again. ?

 

kidwoo

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They list two different ones, one for 2012-2013, and another for 2014-2020

What do you think the difference is?
 
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