Fuel Pump Testing

longrider · Jun 9, 2006

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My 1980 GL1100 standard started sputtering, even after it was warmed up, when I would get going from a stop. Prior to this the bike was running well. It was smooth as a good wing should be.

I did the Sea Foam treatment with only a slight improvement in starting and performance. I cleaned the tank and the internal filter. Changed the Fuel filter and checked the hoses. Nothing else made sense except that the bike seemed to make the same noise, and act like it was going to choke and die unless I gave it a lot of gas.

I broke down and bought a vacuum gage to test the fuel pressure. Followed the instructions and low and behold it seemed to be showing substandard pressure.The Haynes manual says I shoud be showing 1.5 psi or .18kg/cm(squared). I got 1 psi or about .08kg/cm(sq).

Is it time to replace the pump? Is there a way to fix the pump? Honda says no user servicable parts and the unit must be replaced.

firefitr@cxp.com · Jun 9, 2006

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You need to do a flow test. Run a fuel line from the output of the pump into a container that has good measurements on it. Engage the pump for exactly 5 seconds. Multiply the amount by 12 (12x5=60 seconds) This gives you a flow capacity for one minute.

The min flow capacity is 500 cc or 16.9 oz for the 1200. I am not sure about your 1100.

Hope that helps you.

longrider · Jun 10, 2006

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Haynes manual says it should be 150-250 in 30 seconds. It did about 150cc in 30 seconds.

One interesting note about the pressure test. As soon as the engine was shut off, the pressure in the system dropped rapidly. According to the manual, the outlet valve is leaking if the pressure drops rapidly.

Any more thoughts on this? Is the outlet valve repairable or is it part of the pump itself?

longrider · Jun 17, 2006

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Here's another fine example of "live and learn." I have a Clymer manual for the GL1000 and 1100. I read in the troubleshooting section that the fuel pump pressure should be "about 1.5 psi" with the rpm at 5,000. However, in the fuel specifications section it says the pressure should be at 2.0psi with the engine at 5,000 rpm. Flow test results in the fuel system sectin of this book also has the pump doing 450cc or 15oz in60 seconds at 3,000 rpm.

Of course, this is further evidence that I need to replace the pump. When I get the pump from Service Honda, I'll see if the fuel starvation problem is alleviated.

Fuel Pump Testing

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