[Gearbox Paul]

I am looking to buy a 98 GSXR 750. According to the owner, the bike has been sitting for 2 years and now the fuel pump is not working. I really don't have much more detail than that at this point. The fuel tank is off and the owner has pulled the fuel pump assembly off. I assume the issue is the pump is not getting power as opposed to it being fouled up and trying to pump but unable to generate any flow/pressure. If the issue is excessive fouling and/or plugged fuel pump strainer, I can deal with that and I'll likely buy the bike. If the fuel pump has failed, I can rebuild it with an aftermarket fuel pump rebuild kit - that's not too expensive. If the fuel pump relay has failed, that's a cheap fix. But if the issue is the ECM, then I'll walk away. So, when I go to inspect the bike, if the owner will allow me to do that, I'd like to do a little trouble-shooting with a pocket volt tester. To that end, I'd like some advice as to what to check. Again, my motivation is to confirm the ECM is not the culprit.

I found this handy wiring diagram on this forum. If I turn the ignition on, the fuel pump should be getting power for three seconds. I would confirm this by checking voltage between the yellow/red wire at the fuel pump and ground - is that right? If there is no voltage then I will go to the fuel pump relay. Checking the fuel pump relay is easy, as per the service manual. But if the fuel pump relay is not defective, then either the ECM is defective or some input signal to the ECM is defective. The tip over sensor can be easily checked and the side stand switch/relay can be easily checked as well. Assuming none of these are found to be defective, then it can be a wiring issue or an ECM failure. Does that make sense?

I'll also put the FI self diagnostic into dealer mode (using a paper clip jumper) to read any codes. If it reads "CHEC" that would be a good indication of a problem with the ECM unit or wiring - right? And if it reads C41, that would indicate a problem with either the fuel pump relay or power source to the fuel pump relay - correct?

Sorry for asking so many questions. I'd like to be well prepared when I inspect this bike, so that I don't end up buying something that is expensive to fix. Thanks.

 

[peter079]

Key switch ON, Kill switch ON, Engine in Neutral and/or Side Stand Up. The CHEC should disappear and the dash should show "engine temperature" or blinking "FI" if a sensor is disconnected. Then you can put it in dealer mode and it should show C00 or perhaps an error code. (Eg C41 Fuel pump relay).

If you get to this stage then I would say the ECU is good.

If you still have CHEC then one of the above conditions is not met. (Eg. Kill switch still Off, bike not in neutral, etc). It could also be faulty wiring to one of the above components, but how much time have you got?
The Ignition Fuse and/or Fuel fuse could be blown as well. So check the fuses.(Take some with you?)

Once CHEC has disappeared and dash is showing the temp or C00, you can do the other tests
that you mentioned.

You may want to take a battery as well, if the bike has been sitting for that long.

 

[Gearbox Paul]

Good ideas, thanks.

 

[TwistedMister]

it could be more than that, loose wiring corroded wiring broklen wiring, dig this my 600 low level light stayed flashing all the time, annoyed me.. so i check and I check, nothing..

so I remove fuel pump about to test resistors and I notice one of the resistor wires was pinched behind the mount post.. relieve it and its fixed.. sometimes it's the goofiest thing, maybe wiggle the forward looms left and right sides, wiggle me good, my 750 had a bad connection, if I wiggle it would light up and start, bought new right side controls and problem solved, for me too lazy to overhaul the controls and test wiring, simple but lazy.. a new control was what $20 shipped?

maybe pull all connectors and inspect for corrosion, clean and inspect pins are healthy and making good contact.. if it's nothing simple then you have to begin testing leads so forth?

 

[Gearbox Paul]

it could be more than that, loose wiring corroded wiring broklen wiring, dig this my 600 low level light stayed flashing all the time, annoyed me.. so i check and I check, nothing..

so I remove fuel pump about to test resistors and I notice one of the resistor wires was pinched behind the mount post.. relieve it and its fixed.. sometimes it's the goofiest thing, maybe wiggle the forward looms left and right sides, wiggle me good, my 750 had a bad connection, if I wiggle it would light up and start, bought new right side controls and problem solved, for me too lazy to overhaul the controls and test wiring, simple but lazy.. a new control was what $20 shipped?

maybe pull all connectors and inspect for corrosion, clean and inspect pins are healthy and making good contact.. if it's nothing simple then you have to begin testing leads so forth?

Agreed, but remember that I am going to look at someone else's bike to see if I want to purchase it. I won't have much time, if any, to do any trouble-shooting. The only thing I'd like to determine before I commit to buying the bike is if the ECM is faulty or not. If the ECM appears to be functioning properly, then I'll likely buy the bike. Once I bring it home and have lots of time to trouble-shoot, I'm pretty sure I'll figure out what is stopping the fuel pump from running. But if I suspect the ECM is faulty, I'll walk away. I assume an ECM failure is unlikely and that's all I'm trying to determine at this point. Hopefully that makes sense.

 

[TwistedMister]

not that easy unless you turn the key and everything fires up, clock sweeps all that, pump whirrs.. if pump is faulty everything else should work, it just wont whirr, prolly not start, should turn over..

its best to tell said seller not knowing what's wrong I cannot pay this price or we need to see if we can get it fired up and going? maybe you both can work on it to get it going or at least see what its going to take to get it going?

if he cannot do that at the very least check the timing and do a compression test?

 

[TwistedMister]

you can hit the pump leads under the tank with 12 volts if it works it will pump fuel?