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Thread: Fuel pump relay

  1. #1
    Newbie
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    Fuel pump relay

    Bike: 1985 Suzuki GV700 Madura
    Issue: fuel pump relay

    Couple of questions about the fuel pump relay, which tests bad:
    • On the back it says CF308 / 4.2. I believe 4.2 refers to amperage? Can anyone confirm that?
    • I see a number of these relays on ebay that look exactly the same as mine, and they say CF308 on the back, but the amp rating (or whatever 4.2 refers to) is different on each of them. Is this a case where a higher amp-rated relay can substitute, but not a lower one? Or does it have to be exactly 4.2?
    • Is there any chance that something else in the electrical system fried the relay?
    I don't want to buy a new one, not for now anyway.

    TIA for any help.

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  3. #2
    M-J Lifetime Achievement Award
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    Quote Originally Posted by drenigere View Post
    Bike: 1985 Suzuki GV700 Madura
    Issue: fuel pump relay

    Couple of questions about the fuel pump relay, which tests bad:

    Is there any chance that something else in the electrical system fried the relay?[/list]
    The answer to the last question depends upon exactly what part of the relay tests bad.....contacts or winding......but my guess is probably not.

    On most bikes, that relay is a safety feature to shut off the fuel pump anytime the engine is not running (turning over)......like when it's laid on it's side. You can "temporarily" bypass the relay so that you have power to the pump anytime the ignition is ON.......for testing purposes only, of course.

  4. #3
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    I should just start over with the issue itself: not getting fuel to the carb.

    I tested the fuel pump by connecting it directly to the battery and it seems to work fine.

    Then I tested the relay according to this, and it came out zero for most of that table. (For the hell of it, I switched the test leads and the numbers came out good, but they were all on the opposite side of the table).

    So I bought a relay off ebay, but when I tested it, the results were the same as the bad one

    Did I just get unlucky and buy a bad relay?
    Or are both relays fine (maybe the test in the manual is wrong ), and something else is preventing the fuel pump from getting juice?

  5. #4
    M-J Lifetime Achievement Award
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    Quote Originally Posted by drenigere View Post
    Did I just get unlucky and buy a bad relay?
    Or are both relays fine (maybe the test in the manual is wrong ),
    You need some advice from someone with that same model who has a wiring diagram.......or who is familiar with it.

    Some models are arranged so that the relay will not operate, and thus the pump won't run, unless the ignition system is sending out pulses (engine running). In that kind of system, the "relay" sometimes is just a big transistor and for the pump to work, the engine must be turning over and making spark.

    ANYHOW, in order to find the problem, you need a wiring diagram, then you need to be able to read the diagram and understand what your meter is trying to tell you. I suspect that both relays are good, but that's just a guess.

    If you don't have the experience necessary to follow the circuit out, you need to find somebody who does.

  6. #5
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    Its possible that both are dud...the tests you are doing appear to check resistance through the coil and at the contacts. If possible remove the cover, ( usually a simple task of using a jewellers screwdriver to pop the case past the tiny projections), and check the points of both any sign of heavy burning will indicate a fault. A simple 12 VDC test will show the contacts either working or not. If the case will not come apart then you can still do the test and feel/hear a solid click.

    In reality a solonoid is just an electronic switch and either works or doesn't. Check to see you are getting power to the solonoid by attaching your meter to the imput side of the relay socket and switching the ignition on.

    Another question to ask yourself is are the fuel pump filters dirty/clogged?

    Good Luck
    Smoke me a kipper I'll be home in time for breakfast

  7. #6
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    Thanks, guys; that gives me some things to check.

    By the way, I've posted the fuel system diagrams here, including the wiring diagram that I believe Easy Rider is referring to.

  8. #7
    M-J Lifetime Achievement Award
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    Quote Originally Posted by drenigere View Post
    Thanks, guys; that gives me some things to check.
    Yep, that's one where the "relay" isn't a relay at all.

    It does look like the operating the start button will over-ride the relay and send voltage directly to the pump. That fact can be useful......if you disconnect the starter solenoid input (so the starter doesn't run), enabling you to test the fuel pump itself by pushing the start button.

    If that work, then you're back to the "relay" or maybe even all the way back to the ingitor output. The best way to test that stuff is to get fuel into the carb bowls so that you can get the bike started; a little starting fluid might be required too.

    More later if needed.

    I think this was discussed here before with some detailed test proceedures.


 

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