Is there an easy way to check fuel pump operation?
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Thread: Is there an easy way to check fuel pump operation?

  1. #1
    Member
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    Philip E Miner
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    Is there an easy way to check fuel pump operation?

    The bike has sat for some 5 years--with fresh gas and a new battery there is no firing or even a sputter; The motor spins freely and all the electrics work OK. When the key is turned on there is a faint noise coming from the gas tank--possibly the pressure regulator? If I disconnect the fuel line on the tank I suppose that when the key is turned on that fuel will spit out. Messy but seemingly effective Is there an easier/cleaner method?
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    Senior Member Engenia's Avatar
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    Errol Kowald
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    The pressure regulator is simply a release valve. It releases into the tank and it's unlikely you will hear it. You should hear the pump running for a few seconds when you turn the ignition on. If the engine is not turning, the ECU by law has to switch the pump off after a specific time. Three seconds from memory.

    Try putting slips of copy paper down the throats to see if the injectors are firing while cranking. If they get wet you have some fuel pressure, but maybe not sufficient.
    Make up a hose with a pressure gauge, that you can put in-line from the tank. Easy if you have a quick release fuel line connector. The pressure should be around 50 psi.
    hooroo, Errol www.engenia.com.au [139,200 km - and counting .....]

  3. #3
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    Following up

    I'll try the paper in the throat.

    I placed my hand on the bottom of the fuel tank when the ignition was turned on--there was a vibration that--hopefully!--was the fuel pump spinning.

    I also checked the stepper motor--it vibrates when the ignition is turned on. Is that sufficient to verify that it is OK?

    Life cotinues!

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  5. #4
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    More follow-up

    I can see fuel spray while looking down one of the throats while the engine is cranking. Assuming that the engine is getting good fuel--that leaves spark.

    I can't imagine that all three ignition reels and plugs would fail simultaneously--what is/are the common denominators?

    I'll pull one of the plugs to check spark.

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    Senior Member Rick67's Avatar
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    Check the fuel pump relay of fuse .
    You should easily hear the pump priming the system .
    The faint noise you can hear is most likely the stepper motor getting into position ready for a start . .
    You can unplug the pump and attach a 12volt line to it directly to test it , even while it's in the tank .
    EDIT....
    if your now seeing spray in the intakes it may be that the stepper motor is stuck in a closed position flooding the spark plugs.
    Try adding a tiny bit of throttle while starring to let more air in as a test.
    You can then take things apart to clean afterwards .
    Hope this helps a little.
    Rick
    Last edited by Rick67; 11-06-2020 at 05:33 PM.

  7. #6
    Senior Member Engenia's Avatar
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    Errol Kowald
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    Quote Originally Posted by philinnc View Post
    ... checked the stepper motor--it vibrates when the ignition is turned on. Is that sufficient to verify that it is OK?
    Like Rick says, the stepper might be fouled. Only way to know for sure is to dismantle it - DON'T twist it when you remove the piston! Push it out if it is stuck.
    It should be close fitting but able to move easily. The stepper isn't very strong. Use carby cleaner to free it up, or if that is not enough, 240 grit on the piston, not the cylinder.
    I can see fuel spray while looking down one of the throats while the engine is cranking
    You have proven that the injectors operate, but you don't know if the pressure is correct. Only way to be sure is to install a pressure guage.
    hooroo, Errol www.engenia.com.au [139,200 km - and counting .....]

  8. #7
    Member
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    Quote Originally Posted by Engenia View Post
    Like Rick says, the stepper might be fouled. Only way to know for sure is to dismantle it - DON'T twist it when you remove the piston! Push it out if it is stuck.
    It should be close fitting but able to move easily. The stepper isn't very strong. Use carby cleaner to free it up, or if that is not enough, 240 grit on the piston, not the cylinder.

    You have proven that the injectors operate, but you don't know if the pressure is correct. Only way to be sure is to install a pressure guage.
    The stepper motor was replaced with a Triumph one (Part #T1240888) and with new plugs it fired up and runs fine. I had read in another post that his spark plugs went 'bad' when not used for several months. New plugs were a small investment and although the old ones had less that 2K miles and looked fine they weren't. Back to being happy!

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