Weak fuel pump....?

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Baart · #1 Post by **Baart** » Tue Sep 06, 2005 4:38 pm

I have been having trouble getting my bike started and keeping it running. I changed the plug, then checked it after trying to start and found the plug dry. Through a process of elimination I have determined that the pump must be weak. The bike will run fine and rev and run as long as I like when the fuel line is drawing out of a gas can. It will never stay running for more than 5 minutes if even that long while hooked to the fuel tank. With the bike running from the gas can I put my finger over the end of the fuel line for a second to see how strong the the suction was and it was barely noticeable. I put it on a trickle charger overnight and that didn't help. Measured the battery voltage a couple times and got 13.4 one time and 12.6 another. I replaced the fuel filter also even though it didn't seem to need it. Somtimes the pump makes some sick noises and after charging the battery it seemed to go away except for the last time I charged it. I figure its time for a new fuel pump but have heard something about a fuel pump regulator ground wire that could be the problem also. Anyone know roughly how much PSI the pump should be running, and should the suction be significant with my finger over the fuel line? Also is the fuel filter supposed to be full of fuel, because its usually only half full if that. Its odd that it runs from the can and not the tank. Maybe something with the tank but we checked the filter from the tank. To get it started I have to turn the key on and off 3 or 4 times to get enough fuel. Or I can take a screw drive and touch it to the ground terminal on the fuel pump and the outside of the fuel pump and it runs whether the key/run switch are on or not. I think its the fuel pump and think I am going to replace it, but it may be something else. Is it possible to run a fuel pump that is a bit stronger than the original? She runs and sounds so good until I try to go from the tank. Any wisdom would be greatly appreciated.

wistech · #2 Post by **wistech** » Tue Sep 06, 2005 5:20 pm

Sounds like the quick connects have swollen orings. Fuel pump pressure should be around 42 psi. Also make sure the tank screen isnt plugged. If the pump runs its probalbly fine.

cdrider02 · #3 Post by **cdrider02** » Tue Sep 06, 2005 5:23 pm

Check to be sure you have fuel returning to the tank, it should be quite a bit. Make sure that both banjo fittings on the pump each have two aluminum crush washers, and that all fittings/clamps between the tank and the pump on the intake side are not leaking. I ran across one that had a leaking clamp at the filter and it would not leak but allowed air to be pulled in, it was also making the pump make noise and as soon as the leak was stopped the pump got quiet. Also check the quick connects thoroughly both sides have o-rings in them, I know the tank side can be replaced but don't know about the fuel line side, there are many posts on here on the subject. The filter is usually not completely full. I think you should have somewhere around 42
psi. and have to check it between the pump and the regulator. I would be careful about touching those pump terminals to ground, I haven't experienced it but have read here about that burning up ECU's and I believe there was a factory update to insulate both terminals. Check those ground connections at the left headlight and at the regulator, it doesn't ground the regulator but does ground most of the system, it's just attached with one of the regulator bolts.

Canniboomer · #4 Post by **Canniboomer** » Tue Sep 06, 2005 5:41 pm

I have the OEM tank fittings; females, 90-degree males, and have a "gutted" solution for the straight males. Send email with your tank details, both up front? or one front, one rear?

pacrimdm@msn.com

With new fittings, it will run the same as straight from a gas can at the same level.

haydug · #5 Post by **haydug** » Tue Sep 06, 2005 10:51 pm

funny this thread just got started. I have a bike now, I just put together, starts and runs fine, BUT, NO fuel is returning to the tank.
I took the return line off of my race bike at the tank, and when you prime the pump, you can feel the pressure in the line. Then you can push in on the white plastic part of the fitting, and fuel will spray. This bike, I can't even feel pressure on the return line. But, it runs?? :confused:

cdrider02 · #6 Post by **cdrider02** » Tue Sep 06, 2005 11:05 pm

Doesn't the female (tank side) have to open the male side? I had the tank side fitting come apart on a dirt bike and it would not let fuel through the male side. Check that the guts didn't fall out of the female side.

Canniboomer · #7 Post by **Canniboomer** » Tue Sep 06, 2005 11:31 pm

QUOTE

Originally posted by haydug
funny this thread just got started. I have a bike now, I just put together, starts and runs fine, BUT, NO fuel is returning to the tank.

That would mean pump output pressure not capable of exceeding regulator pre-set of about 45psi???? unless regulator clogged and bike managing to run OK at higher rail pressure. Yep, puzzling beasts, always something new and weird.

fig · #8 Post by **fig** » Wed Sep 07, 2005 7:52 pm

QUOTE

Originally posted by haydug
funny this thread just got started. I have a bike now, I just put together, starts and runs fine, BUT, NO fuel is returning to the tank.
I took the return line off of my race bike at the tank, and when you prime the pump, you can feel the pressure in the line. Then you can push in on the white plastic part of the fitting, and fuel will spray. This bike, I can't even feel pressure on the return line. But, it runs?? :confused:

My friend had this happen on his bike, the oring that goes inside the female fitting that stays on the tank came out and turned sideways. This plugged up the return line. His bike ran ok, after 10-15 miles he ate a fuel pump, my guess is it got too hot because it did not move enough fuel.

Baart · #9 Post by **Baart** » Mon Sep 12, 2005 5:36 pm

Well the tank screen wasn't plugged. Also a couple O-rings on the disconnects were looking a bit rough and fuel was dripping, I guess that is a result of repeatedly connecting and disconnecting them while trouble shooting. So I got some O-rings at the parts store and all is good again. I really think that it may have something to do with the pump regulator or the pump itself. I won't be able to look at until this weekend however as its not here at home. It is weird that it draws from a gas can and not the tank though. Maybe that extra foot or so of fuel line is too much for what the pump is currently putting out. Also odd is that the tank is above the fuel line, so gravity would seem to help, while the gas can is on the ground and the fuel has to fight gravity all the way to the pump. Yet it don't have a problem with that. What about replacing the disconnect valves with something like a straight pipe that has no restriction at all?

Canniboomer · #10 Post by **Canniboomer** » Mon Sep 12, 2005 5:57 pm

QUOTE

Originally posted by Baart
..... So I got some O-rings at the parts store and all is good again....

if all you did was replace the male O-rings, then problem is not solved. Our fittings (out and back) have a total of 6 O-rings, and one or both of the "internal" ones on the suction side are swollen/plugged -- congrats, you proved that already with the gas can test. It's just a plumbing decision now, to replace, change type, or try to dissect the fittings.