Fuel / Pump / Throttle issue? - Suzuki Volusia Forums : Intruder Volusia and Boulevard Forum
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post #1 of 16 (permalink) Old 07-10-2018, 03:47 PM Thread Starter
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Fuel / Pump / Throttle issue?

Hey all

So I've been chasing this problem for about two years now. It's one of those sporadic issues that the bike does it, you take it to the shop, they have it for a day and it never shows up. Then I take it home and two days later it happens again.

The main symptom is the bike running sluggish for a period of time. now for the details.

Picture yourself having a drink from a bottle, the contents of which, I'll leave up to you. Bottoms up, that glug glug when you drink, let air in, drink more, let air, etc.

  • With the throttle open that is what the bike feels like: rev, pause, rev, pause. It migt be subtle enough not to hear it much but you'll feel the bike rocking a bit forward and back as it pauses for the slightest moment. If it's bad enough it might sound like I'm running on one cylinder even.
  • When this happens, if I clutch all in or leave it on neutral and rev it up maintaining for a few seconds I'll get a couple backfire pops
  • If I engine brake I might get a few backfire pops
  • If I'm slowing down and let the throttle hang around between just before accelerating and letting the throttle go, it might get a few pops as well
  • Sometimes this will clear it up and I can keep going with no issues, sometimes I'll need to pull the choke out to alleviate until it gets over it.
  • If it is in the middle of this ... asthma atack, for lack of bettter description, and I need to come to a stop, sometimes it will just die on me unless I pull the choke out to keep it alive.

Recently I took the Carb out and had it all cleaned up. Since then it feels like it picked up a new symptom. Lets say im doing 50mph
  • it's having the fit
  • Throttle down
  • Throttle up, nothing happens
  • throttle reaches about where it was to maintain my speed and it kicks back

While it'll do the other symptoms, after having the carbs cleaned, it feels like the symptoms are more organized with the addition of the new symptom.

At this point the shop has mentioned that it might be a fuel pump issue. That, with a full tank, bypass the pump and go to the carb. It should let me ride around for about the first gallon or two aided by the weight of the gas before needing the pump. If the problem doesn't happen then I might have the issue there. The only problem is that the symptoms can show up every day this week on my way to work, and just the one day next week. I might go a full tank with the issues not showing up and next fill up, it might show up after a few days of riding. My paranoid self at this point has started to, probably falsely, notice that if there is a crosswind, chances are higher for the problem to occur.

I've cleaned carbs, changed vacuum lines, put a fuel filter between tank and pump. I' had to even swap out the engine (completely different issue), and the problem survived en engine swap. Needles to say, this is a frustrating problem and I'd rather not keep swapping $100 parts to go deeper down the rabbit hole of an elusive problem.

/rant

Thoughts? Ideas?

2002 Suzuki Intruder Volusia VL800
1978 Honda Hawk T2 CB400TII
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post #2 of 16 (permalink) Old 07-10-2018, 04:00 PM
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The fuel pump in the Volusia is vacuum operated. If you are getting intermittent fueling, then the issue is either with the vacuum source or the fuel pump itself. Inside the gas tank is a vacuum operated diaphragm. These do wear out with time and can cause issues similar to what you are experiencing. Since you have already ruled out vacuum by replacing both the lines, remaining source would be the diaphragm in the fuel pump or possibly a vacuum leak in the carb itself.

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post #3 of 16 (permalink) Old 07-10-2018, 04:07 PM Thread Starter
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Any way to further diagnose which side of the equation is most likely to be the problem? I've browsed around for a used fuel pump that i could cheaply drop in and test but not sure if i would trust a used one if age is a factor.

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post #4 of 16 (permalink) Old 07-10-2018, 04:23 PM
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The fuel pump operates under positive/negative pressure caused by the crank case.

Info is found here:


Current Bikes -->
-1969 Indian MX125 -10-2009 to Present
-2014 Honda CTX1300 - 05-2015 to Present

Past Bikes ----->

-1973 Yamaha RD350
-1991 Harley Sportster 883 XL
-2000 Yamaha XV125
-2003 Piaggio Fly
-2004 Suzuki LS650 - 04-2005 to 07-2008
-2005 Boulevard C50 - 07-2008 to 5-2012
-2012 Vulcan 900 - 05-2012 to 05-2015
-2008 Yamaha FZ6 - 11-2008 to 04-2017
-2006 Star Virago - 05-2011 to 06-2017


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post #5 of 16 (permalink) Old 07-11-2018, 08:51 AM Thread Starter
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Seems like I'll be vacuum testing this weekend. I really hope this is it.

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post #6 of 16 (permalink) Old 07-15-2018, 10:49 PM Thread Starter
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Alright. So I did some testing and sadly I'm at the same spot.

Tested vacuum lines to the pump and petco with bike running and there is pull.

Tested the vacuum on the pump before the carb, it holds the vacuum. Tested it at the petco valve and it holds.

Tested fuel flow at the petco with the vacuum connected and disconnected and it flows and doesnt flow respectively

Havent tried testing with the hose disconnected from the carb see how the flow is there so I'll probly try that next but it doesnt seem so far that the issue is fuel pump related. I did remove the inline filter from petco to pump cuz it did seem a bit cracked and its been there for a while anyhow, will see if that makes any difference on a ride longer than a few miles.

The hunt continues.

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post #7 of 16 (permalink) Old 07-16-2018, 10:10 AM
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Didn't I read about a fuel cap issue causing similar problems?
if you've swapped engines, and the problem still exists, it most certainly lies in the bike, and the tank would be my first inclination. Cap, pump, lines, float etc.

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post #8 of 16 (permalink) Old 07-16-2018, 10:46 PM
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How about riding with the gas cap loose and see if the problem is still there?
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post #9 of 16 (permalink) Old 07-16-2018, 11:20 PM Thread Starter
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Quote:
Originally Posted by bbqjoe View Post
Didn't I read about a fuel cap issue causing similar problems?
if you've swapped engines, and the problem still exists, it most certainly lies in the bike, and the tank would be my first inclination. Cap, pump, lines, float etc.
Quote:
Originally Posted by toekneedee View Post
How about riding with the gas cap loose and see if the problem is still there?
You know, I've thought about it that the cap might be the issue. It's just one of those things that seems odd to ride with the cap loose but I might as well try it

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post #10 of 16 (permalink) Old 07-17-2018, 07:52 PM
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Quote:
Originally Posted by Conquest5H View Post
You know, I've thought about it that the cap might be the issue. It's just one of those things that seems odd to ride with the cap loose but I might as well try it
I'm running low on popcorn here.

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