1983 GL1100 Fuel Pump Questions

[piero]

I attempted to perform a fuel pump volume test using an auxiliary fuel tank (cannot use bike fuel tank for a while) as I am currently unable to do a fuel pressure test. However, in connecting the output of the pump to a measuring container, I realized that fuel was flowing to the collecting container at the rate of about 15 ounces in one minute WITHOUT the engine running. Thinking that something was stuck open inside the fuel pump, I repeated the test 3 to 4 times, unfortunately, with the same result. I tried with the engine running, and both the choke and throttle gas on but...no difference. So, the bike pump seems to be stuck open with either the engine on or off.
I opened the top part of the fuel pump expecting to find some damage of the diaphragm but everything looked fine.
Does anybody have any suggestion on what to do next, before I start considering to replace the fuel pump? Besides, in case of replacement of the fuel pump, should I purchase a stock, mechanical pump or a low pressure (3 to 4 psi) electric one? I would like to go for a mechanical one just to keep my old bike stock!

Piero Minneapolis, Minnesota

[Rambozo]

Depending on the fuel level in relation to the pump, it is normal for fuel to syphon through the pump. The pump is not designed to stop the fuel flow, that is what the petcock is for. If the outlet of the hose is above the fuel level it will stop and then you will see what the pump is doing. As long as it meets the specs like that, you are ok. If you do go to an electric pump, the pressure you want is only 1 or 2 psi. Anything more will flood the carbs.

[piero]

Thank you for the suggestion. I'll repeat the test making sure the outlet of the hose is ABOVE the fuel level in the auxiliary tank. However, I am really concerned about the fuel pump as, after a complete carburetors overhaul with a Randakk's GL1100 carburetor kit, the engine runs only with choke and throttle open. After a few minutes I may close the choke but as soon as I release the throttle the engine dies. Carb mixture screws are set to three turns open and they don't take any further adjustment either by closing or opening them and also the idle screw adjustment doesn't seem to make any difference. The fuel pump volume and pressure tests are the last two alternatives...left to check. After that, I'll have to start all over again taking down the carbs bank.
Again, thank you very much for your help.

Piero Bassi, Minneapolis, Minnesota.

[Rambozo]

Since you are running off an aux tank, You can just gravity feed the carbs to test your theory. Just position your fuel about a foot over the carbs and see how it runs. If it runs great that way, your fuel pump is bad. However, if it is still the same, it's time to look at the carbs again. Tuning multi side draft carbs is one of the hardest systems to get exactly right. When they are right, they work fantastic, but it takes good testing and a lot of experience to get them just right. There are dyno-tune places that have all the right equipment if you find it's not something you want to invest the time to learn.

[piero]

You mean the auxiliary fuel tank (one foot above the carbs) directly connected to the carburetors inlet pipe OR connected to the carbs through the fuel pump?

Thanks - Piero

[piero]

Besides, I thought that with the carbs 4 mixture adjusting screws set at around 2.5 to 3 turns from the closed position (all in), the engine should run without choke (after necessary warm up) and minimum throttle help BEFORE starting the final carbs synchronization.

Piero

[Rambozo]

Without the pump, just gravity feed, like most bikes use.

[piero]

Yes! I'll do it as soon as possible and if it doesn't work...I'll take down the carburetors again. it's possible I didn't reassemble them correctly!

Thank you again my dear friend!