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Discussion Starter · #1 ·
First time on any type of forum, so please excuse my lack of knowledge for this computer stuff. When I was doing the volume test to check to see if my fuel pump is working correctly, after I disconnected it, it has a steady drip before and after I put voltage to the pump. I know there is fuel in the line that needs to drain after I disconnect from the F/I rail, but mine seems to drain much more than would be in that short section of fuel line. I'm checking the fuel pump because my bike isn't performing as well as it was a few weeks ago. The fuel volume test was low so I got a new (Quantum) pump to replace the one that has been in it for a few years. The new pump tests low on the volume test also, which makes me wonder if it is 1 of the o-rings or the back pressure regulator that may be causing the problem. I don't have a way to test the pressure at the moment. I did order a new regulator and it should be here in a couple of days. Any help would be great, if someone has had a similar problem and could offer some ideas I would like to hear them. Thanks in advance. Bill.
 

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The K1/K2 service manual has a better description of the pump motor, notably that there's a check valve in it to prevent backflow and maintain line pressure when the pump shuts off after the prime. I'd expect that valve to also provide some resistance to forward flow when the pump is off & fuel line is disconnected. Your dribbling suggests that there's a leak somewhere. That might be the regulator if it has any rust. Otherwise I'd be looking at the O-ring on the regulator inlet or, more suspect, the rubber bushing between the pump motor outlet and the main filter inlet. The standard fuel pump test is the flow test as described in the manual. That ought to be all that's needed. However the ultimate test is to rig up T-fittings, lines, and a pressure gauge so you can observe the pressure while riding, a hassle to do. The only other thing to do is to inspect the injectors for dirt in their inlets or try cleaning them per youtube videos.

My general opinion is that the Mitsubishi OEM pumps are higher quality than aftermarket and suggest that you stay with it unless it dies or you otherwise know that it's faulty.
 

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Discussion Starter · #3 ·
The K1/K2 service manual has a better description of the pump motor, notably that there's a check valve in it to prevent backflow and maintain line pressure when the pump shuts off after the prime. I'd expect that valve to also provide some resistance to forward flow when the pump is off & fuel line is disconnected. Your dribbling suggests that there's a leak somewhere. That might be the regulator if it has any rust. Otherwise I'd be looking at the O-ring on the regulator inlet or, more suspect, the rubber bushing between the pump motor outlet and the main filter inlet. The standard fuel pump test is the flow test as described in the manual. That ought to be all that's needed. However the ultimate test is to rig up T-fittings, lines, and a pressure gauge so you can observe the pressure while riding, a hassle to do. The only other thing to do is to inspect the injectors for dirt in their inlets or try cleaning them per youtube videos.

My general opinion is that the Mitsubishi OEM pumps are higher quality than aftermarket and suggest that you stay with it unless it dies or you otherwise know that it's faulty.
I'm guess I didn't mention what bike I have so here it is, 2004 Suzuki gsxr 1000. I have had it for a little more than 2 years. When i first got the bike it would only rev to about 10,000 rpm. I only ride/race the bike at my local 1/8th mile dragstrip and haven't owned a motorcycle for about 20+ years. I thought this might be normal as the bike ran pretty strong up to 10,000 rpm. I usually had to short shift the bike to keep the front wheel down in 1st and sometimes 2nd gear (stock wheelbase). a couple of months later it stopped running at the track. I did the tests in the manual and found the pump had quit, so I bought the Quantam pump and it tested out at above the required volume and now my bike ran strong all the way to redline. Forward to a few weeks ago, My times had been improving practically every week, then I noticed my times and mph were starting to slow down. I did the fuel volume test and it was at 50 percent. I bought a new pump because I thought that might be the problem (they are fairly cheap so what the hell). I was surprised by how low the output was during my initial check with the new pump (again about 50 percent). I had seen other people that said the high pressure filter may be clogged, so today I rigged up the new pump to 12 volts without the back pressure regulator or the high pressure filter. And it performed well above the required test results (as it should with nothing to impede the flow). So I drilled a bypass hole in my H/P filter (as mentioned in some stuff I read online) and installed the modified H/P filter and the "new" back pressure regulator, and put 12 volts to that and it put out much more fuel than is called for (as it should with a open H/P filter). The stuff I read was for SV1000/650 (same pump and H/P filter as mine) and they were using an inline filter after the pump and before the fuel rail. I don't know if I have room to do this with my setup or not, (I ran out of time at the shop today). I'm trying to NOT spend $345 on a new H/P filter or $820 for an entire new pump assembly. I will try a local salvage yard to see if I can get some used stuff and hope it will do the trick. As for the leaking/dribbling, it is still happening. I will have to look at it a bit more. Thank you for your reply and information.
 
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