• 4 Stroke Husqvarna Motorcycles Made In Italy - About 1989 to 2014
     TE = 4st Enduro & TC = 4st Cross

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Fuel startvation on down-hill?

MorrisBetter

MorrisBetter

Husqvarna
AA Class
I'm getting a fuel starvation problem when on steep down-hill sections and/or under deceleration. Is this normal? Is there a fix?
 
Hey Morris, sorry don't know how to paste the link but here is where it is: Discussion in 'EFI/carb' started by firebolter, Feb 2, 2011 should help
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I don't believe the "moving/slipping up" fuel pump problem is what he is describing. I think he is describing having a gallon of fuel (half a tank in the stocker) and then going down a hill and the engine dying. I think the fuel pickup on the FI bikes is sorely lacking.
 
Yep. My new SM was cutting out from new, mainly under braking/stopping - thought I was stallling it. Dealer adjusted the EFI and it was better but I was told it would improve as the bike ran in. Now (and wiser, mainly thanks to here and SMJ) I've realised that are pump issues for several reasons, ie low level ind/pump slipping/wires coming off. And my first EFI bike too
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OlderHuskyRider said:
I don't believe the "moving/slipping up" fuel pump problem is what he is describing. I think he is describing having a gallon of fuel (half a tank in the stocker) and then going down a hill and the engine dying. I think the fuel pickup on the FI bikes is sorely lacking.
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Yeah, that's it. This is an '08 TE 510 with the stock tank BTW. It happens way before the low fuel light comes on. At about 40 miles I start to get a rough idle going down steep hills. Eventually it turns into a stall. Is this normal? This is a real PITA. I resorted to coasting down about a quarter mile of hill yesterday.

I haven't opened the tank yet, but I think the fuel pick-up at the pump is unporting and sucking fumes. I'm guessing that an internal baffle would help but would be difficult to install. I think the real solution would be to get the pump out of the tank and into a small accumulator mounted lower on the bike with gravity feed from the tank to the pump.

The external pump setup (George @ Uptight if I remember correctly) that we saw a few months ago would be a great solution. I'm picturing adding a petcock to the tank and plumbing it to the pump mounted behind the cylinder. From there to the throttle body. This setup would also accommodate a second tank.

George, I really need that external pump.
 
It's an '08 and you haven't fixed the fuel pump issue yet? Take the fuel pump assy out of the tank and tug vertically on the fuel pump. If it moves when you tug up and down, you've got the problem. See various threads on repair methods, most notably pay attention to not breaking the plastic elbow on the fuel pump when you have the tank off and fix it better than adding another cable tie in the original location.
 
My thoughts: It could be the pump migrating upward due to the loose or swelled OEM cable tie causing more of a problem. I think more have experienced this which is why we keep mentioning this. Beyond that- I am Sure there could be a hill that is VERY steep and LONG that you could find that causes a problem with less than 1/2 tank. You'd have to run the lines and fuel filter out of fuel for the most part.But the pump sliding up Magnifies if not simply creating this issue. I am thinking Maybe somewhere like MOAB Utah may present the test site... Not sure. I have never ran into this problem with my bike. Based on the terrain I've ridden and heavy braking I guess I should have.
 
This pic shows what I think we are dealing with: 1 gal left in the stock tank, a 25 degree downhill, if long enough, the fuel pump pick-up will go dry and the bike will run out of gas.

HuskyTankStockInclined.jpg
 
Nice illistration- I agree its a poor design, the 2011 bikes are in much better shape here.
Maybe its because I wheelie and accelerate downhills sometimes that I don't have this problem... there's your solution
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Or maybe the IMS tank helps a little bit. But I use the stock tank too. I never had the problem but I wired my pump before I did since the pump migration is so common.

This has been a topic for awhile: check out this thread.
Fuel tank volumes and pressure tests
Overloadtt's post from his tests would suggest that the hill would have to be in the area of 7 minutes long and be so smooth of a surface that the fuel would not slosh around- this could offset by on and off braking or accelerating. because it does not take long for fuel to replenish. Also the tank would have to be low on fuel at the same time.
 
OK, I guess it's time to pull the tank and crack it open. Thanks for all of the help. I'll update here when I have more information.
 
"Fully primed pump allows engine to idle for 7 Minutes (tested at 1,750 RPM)" per Overloadtt tests

I think in the field, going down a long, mountainous, rocky downhill, like a pass in Colorado, with the bike in first or second, the revs are more than idle, plus you might be blipping it on small "less downhill" areas without moving any gas to the rear of the tank, I think the 7 minutes is drastically reduced.

I am pretty sure that the design of this tank/pump/frame is only meant for track-like conditions, up/down, left/right, and has problems with isolated type scenarios in trail riding/dual-sport riding, like long downhills and sustained highway riding.

HuskyTankLowered.jpg
 
I agree its a poor design. You are right.
Just suggesting:
> it is worsened if the pump migrates or moves Upward any ammount. And we shouldn't rely on the stock single zipty.
> the half tank downhill senario is possible- but the conditions have to be just so. And trying to discuss all the factors that create and alieviate the issue. Personally- have not experienced it.

ON a side note/ story time :popcorn: : you know how we fully accept that we don't use all the fuel in our 08-10 tanks- we accept the fact that we "can run out of gas" but there be gas left in the tank. Because ofthedesign flaw as above. SOmething like 8cups or x ounces or x/10 gallons. When I did Lab2v and my buddy shattered his foot. We got him to the Hospital in Barstow. This was all off course and extra milage toward the end of the day. Well we got him there and back to the motel- the whole time I wondered how much gas I had and hoped I wouldn't run out. The next morning ready to ride out- I started my bike. It quit after 20 seconds or something and would not start. I though- I am out of gas confidently. Everyone was like... "what are the odds of that- no something is wrong..." Well, I was condfident, so I pushed it to the gas station. I put in just over 3 gallons. Primed the pump and it started right up. No problems. Question is- did I use all 3 gallons because of the varried terrain and sloshing? because I was being a good semaritan so I had a HuskyAngel looking over me? Or was the gas station's meter off. (I actually couldn't hear any gas sloshing). I swear- I am pretty lucky- or something.

I think the tank's are at their worst on flat ground or flat hills with no sloshing. I think on rough down hills (or if the rider is braking and accelerating) if the fuel gets sloshed around with variation- the fuel gets replenished into the system pretty quicky: so a couple slosh's of gas and it starts that 7 minutes (or whatever time period based on rpm you want) over.

Running out of gas downhills: Is this happening to anyone that has checked and secured their pumps? Seriously- didn't know it was an issue anymore? I thought it was a symptom of the pump being loose.
 
I think the key to Morris's problem is the length of the hill. I've ridden long downhills like he is probably talking about, and the steep ones, my motor is revving pretty high as I use gearing to maintain a safe speed. Look at the position of the fuel pump in my pic, whether or not it is tied to the flange is not a big help since the pump is almost parallel to level. The problem is the design of the place that the pump sits. If there is enough fuel to keep the level above the red dot, there is no problem.

HuskyTankStockInclined.jpg
 
I had the broken pump tie and "ran out of gas" twice before i new about it and fixed it. Both times the bike was running with out the low fuel light on but would not restart after I turned it off. The low fuel light was now on. Maybe it takes more fuel in the tank to start um than to keep um running. When I fixed the tie, the engine would not start until I had 3 cups in the tank. 8 to turn off the low fuel light.
 
Elimination has got to be the answer here. Quarter fill a coke bottle, even with the slightest movement the water sloshes around. I totally agree, the fuel pump should be at the lowest possible point, or if outboard, then then the feed to it. You'd have to be on a perfectly smooth slope with no suspension and no tank movement at all to eliminate sloshing of fuel. I really think the pump mod is the quickest/cheapest/easiest fix - took me one hour max, then if prob still persists you've def got a hunt on for the cause. Be really interested to know what you find. Cheers
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Problem solved. Thanks for all the help.

The fuel pump was about 1.25 inches up from the bottom of the mount. I cut the zip-tie and replaced it with a SS worm clamp. Safety-wired the clamp and reapplied a zip tie for the wires. I put 1/Gal. of fuel in and went up and down the problem hill. Idles smoothly on the down-hill even under braking.

BTW...The hose connection to the tank looks like a likely failure point. Does anybody know if the red plastic ell is a pipe thread on the tank end? If not, how does is it fastened to the pump plate?
 
Congrats Morris. There is a post re the red elbow bend where it has been snapped. I think the fix was to thread the pump plate and fit a brass outlet then fuel hose onto that. Happy downhills
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Congrats-

for future reference- >this thread "Fuel Pump Mod"< is a good thread for pump securing.

I think the red Plastic elbow is a fitted "snapped in" piece- that is not made to be replaced.
I have been very careful and lucky- worst is when people don't know how delicate they are and end up breaking them the first time they take the tank off.
These two threads go into the plastic elbow and some fixes.
>Fuel pump plastic elbows<
>another EFI plastic elbow solution<
 
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