2003 SV650 fuel pump issue?

[rama]

I have a 25k mile garage queen that's taken out once a month and brought up to freeway speeds to get up to temperature, but otherwise sits a lot. While I use a fuel stabilizer, it does take a few months to empty the tank. Recently it started having an issue with cold starts, stalling on the first and sometimes second start. It also has issues with low RPM bogging even while warm, hesitating to rev up from idle 1300k to about 3-4k before it suddenly becomes responsive. While riding at 6-7k and low speeds (or maybe thats the only time I can hear it), it will sometimes backfire even with an even throttle input. It sounds a bit like popcorn, 1-2 per second in spurts.

The throttle bodies are synced, the TPS sensor reading is good, the air filter is clean, and I just replaced the (normal looking) plugs which made no difference. Fresh fuel hasn't helped. HOWEVER a full tank does, though not completely. The hesitation improves a lot, but it still backfires. Today as I was starting it on the sidestand with 2 gallons in the tank, I noticed the fuel pump making an unusual sound, like its cavitating and pulling air. Standing the bike fully upright (or with a full tank), the fuel pump sounds normal. Here it is on the sidestand, 2gal in the tank, when I flip the kill switch to on:

My theory is its a partially clogged fuel filter and/or reservoir cup inlets, but before I pull the tank wanted to float that with those more experienced. Thoughts?

Also if I do pull the fuel pump assembly, which parts should I have on hand to replace regardless? I'm thinking the sock filter and o ring.

Thanks all.

 

[dmfdmf]

That sound may be normal. The way the pressure regulator works is it dumps gas back into the tank to control the down stream pressure. With the lower fuel level you might be hearing the fuel splashing on return.

I don't know if this is a fueling issue but might be so step one would be to measure the flow rate. On the DL650 there is a test in the service manual measure the flow rate which would tell you if the inlet or high pressure filters are plugged up. There is also a test to measure the pressure which is supposed 43 PSI but most riders don't have a fuel pressure gauge but that could reveal a bad pressure regulator. Pressure regulators are a dead-simple spring loaded valve so they rarely go bad unless rusted. You also might check out svrider.com or post it over there.

 

[Lucytriple]

it’s probably not this, but on every SV, I always check the vacuum caps on the carbs/ throttle bodies. For some reason, more than any other vacuum caps, they are often cracked. Replacing them is one of my favorite things to do. Secondly, I agree that your fuel pump seems suspicious. If you can handle the downtime, an inspection might be worth it. Hoses get old and tired in there as well. I often buy replacement fuel pumps for Quantum, and if they make one for your bike it usually comes with everything you need.