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Discussion Starter · #1 ·
Hey experts...got a problem. Bike died while riding, total instant cutout of the engine...like what the kill switch does. But it's not the kill switch.

When turn it on, everything lights up, secondaries cycle, fuel pump primes. Dash lights all good.
Cranks fine...but doesn't get going.
  • does not show any code after cranking but failing to start (checked it with dealer mode...shows c00)
  • not the kill switch, not the kickstand switch
  • turned on and checking voltages, I see that there is no 12V to the injectors, and not the fuel pump either
  • I checked the power right after I turn the key on...pump and injectors have power for a few seconds and then no power, the fuel pump relay is getting turned off.

- I haven't check the Tipover sensor yet... that's next on my list.
After that, no idea other than (horrors) a bad ECU

Any thoughts?

thanks
-Jim
 

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hmm... ignition, but pump primes, odd, coils? you could get a brand new OEM suzuki ignition off amazon for 174, just plug it into the connector to see of its the culprit, if not send it back? pulse generator issue?

check troubleshooting in service manual go over the steps "bike cranks but wont start"

I dunno check all your sensors, side stand, clutch so forth, starter wont crank on those tho.. odd

maybe replicate issue with airbox off or unbolted tank loose and immediately pull a spark plug is it wet or dry?
 

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Never had this problem, so I can only give suggestions.

The crank sensor can cause stalling and no start. It's not very common for them to go out though.
But, if you run out of ideas, it might be worth checking. It could also be faulty wiring or bad connections at the ECU too.

Or, could it be Fuel Pump failure? They don't often fail instantly. But, it could be faulty connection or wiring inside the tank. Or loss of pressure? I did hear of one person who had the pressure regulator fall off.

Put a couple of drops of fuel in each intake and crank it. Does it fire?

Edit: Just thought of another thing. You could also check for spark while you're there.
 

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This is a bit unorganized but may help.
The fuel pump relay controls power to the fuel pump and the injectors. So both are either on or off.
The service manual is vauge about exactly what happens in a tipover condition other than, obviously, power to the fuel pump & injectors is cut. But I've tried manually tipping it on my K6 and it also causes a C23 error to appear. It can only cleared by correcting the tipover condition and cutting and restoring power to the ECM.
Camshaft sensors rarely fail but several crankshaft sensor failures have been reported here. But it will produce a C12 error and you don't have it.
I like priming the engine with some gas in the throttle bores to see if it will briefly run. Something in the fuel pump has failed if it runs because you said the pump will prime.
Unplug the ECM and check the condition of the contacts. There's also one between the main harness and the injectors/secondary throttle/IAP sensor but you say that the STV cycles and there's power briefly to the injectors.
The ECM, fuel pump relay, and the coils get power from the kill switch via an O/W lead. It sounds like it's good.
The kickstand switch and interlock relay control power to the kill switch vis O/B lead. You could check for power on it at the right handlebar connector but it sounds OK.
The STV cycling and fuel pump priming are caused by the ECM during its power-on sequence. So that suggests that the ECM is OK, though it could obviously fail later on.
The absence of fault codes and things acting normally when power is turned makes me wonder if there's some sort of wiring issue.
I assume that you've checked all the fuses.
 

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Discussion Starter · #5 ·
Hi Billv,
Checked all fuses. I get no codes and power goes to fuel pump, injectors, probably plugs too for about 4-5 seconds then the fuel pump relay clicks off. I can hear it, and see that the control signal from the ecu flips from on to off. I checked TO sensor resistance and voltage plugged in, all in spec. It cranks and kill switch would prevent that. Kickstand switch couldn’t cause this in neutral could it? Neutral indicator works. I checked operation of kickstand switch and gear position by watching the fuel pump relay output with kickstand down and in gear. Like that, relay never turns on at all. Kickstand up in gear, it’s on for 4 sec again then turns off. Kickstand down in gear, relay coil gets no voltage like you expect. In neutral, kickstand up or down the same. On for 4 sec then off. The kickstand relay isn’t messing up because it still is supplying power to the fuel pump relay and it still cranks after the fuel pump relay shuts off. I checked the ecu connectors, both look fabulous. The power inputs from fuel fuse has power all the time and the one from kickstand relay has power when I turn the key on.
everything looks good outside the ecu 😕.
Any other thoughts?
 

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You could also check for 12 V to each coil on a Gr (grey) lead. Similary there should be 12 V to each injector via a Y/R lead. However note that this is the same lead that powers the fuel pump so it's only hot when the pump is priming or when the engine is running. I still like priming the engine.
 

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Discussion Starter · #7 ·
Well Billv, doesn’t appear to be the ecm. Used replacement does the same thing. I checked crank position sensor resistance and harness connectivity, it’s good. I don’t have a peak voltage meter to check that. So maybe the fuel pump relay is supposed to shut off ~4 sec after turning on key, and then start again once you crank? Anyone know? If that’s true I’ve chased a ghost. More digging.., I’ll need to jump the battery because it’s drained now. Need to check spark stuff (yes you pointed me there true). And see if the relay pops back on when cranking. I haven’t checked that.
 

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"So maybe the fuel pump relay is supposed to shut off ~4 sec after turning on key, and then start again once you crank?"
Yes, but it's more like three seconds. The prime pressurises the fuel line and there's a check valve in the pump to prevent back flow, thereby maintaining pressure. This is done to reduce the electrical load on the battery during cranking while getting the fuel system ready to immediately inject fuel. The ECM turns the pump back on once it sees that the engine is rotating. As priming is controlled by the ECM, it's an indicator that the ECM is working.

You seem to be resisting manually priming the engine as Peter and I have suggested. What gives? This is a well known and fairly easy procedure.
 

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Discussion Starter · #10 ·
Well Billv I have no good excuse, I misunderstood that the fuel pump relay was supposed to shut off, and I led myself down a wrong path.
So, following your advice, I checked fuel pump output. It’s pumping fuel when the relay is on. Could have power when ignition is on. Dropped some fuel down the throttle bores and when I crank, engine fires until that fuel is gone. Then stops of course.
So I’ve got spark but injectors not injecting. Injectors do have power. I have a PC, I had already tried taking it out of the circuits and it made no difference, just tried again no change.
So the computer is good since replacement didn’t fix, I’m getting spark, fuel pump makes pressure, PC isn’t the problem, the computer connection looks good and no codes. Any ideas now? Could it be my ignition switch to the computer?
 

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Discussion Starter · #11 ·
That doesn’t seem right either… the taillights, turn signals and license plate light all work. The computer is providing that power through the ignition switch ok, and everything else the ignition switch is supposed to turn on seems ok.
is there a separate power or ground to the computer that is connected inside to the injector control circuits?
I just checked continuity from one injector to the ecm connector, and it is good. Something is telling the ecm not to fire the injectors?
 

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Your igniiton circuit seems fine as it will run when you prime it. That also rules out the TOS as it cuts both the spark and the injectors. I think it also means that the CKP and CMP sensors are OK. You could check the wiring circuit through the injectors by unplugging the larger ECM connector and check for continuity through the injector to the fuel pump relay. The injector circuit for cylinders 1-4 runs from the Y/R lead on the relay to connector pins 4 to 7 (Gr/W, Gr/B, Gr/Y, Gr/R leads). Each should measure about 12 ohms, the injector resistance.
 

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Discussion Starter · #13 ·
checked the injector continuity like you suggested, all 11.6 ohms. Both ckp and cmp resistance are good and show continuity to the ecm connectors. It has to be detecting crank or it wouldn’t turn the fuel pump relay back on, right? Or fire the plugs? I checked grounds connectivity to the ecm, all of them are good. Some input to the ecm that it doesn’t like..,.
Again, no codes at all.
When I disconnect the cmp, I get that code. Same for ckp
 

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so when you crank it to start it do you hold the throttle open a quarter or so? do this then pull the plugs quickly.. are the plugs wet or dry? this should isolate fuel delivery or ignition, that's if your timing isn't just stuffed, cam chain in tact and timing all good there? take a peek if plugs are wet and all 4 spark good.. it's possible it jumped off bad enough to where it wont start but you should have felt a lil something a lurch or something, unless the chain dropped then it just shuts off.. isiolate, is it spark or fuel delivery?
 

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Discussion Starter · #15 ·
@Twisted: It’s fuel delivery. Just repeated the experiment with putting some gas down the throttle bores and it fires nicely. Until no more of the fuel. Fuel pump primes though and pumps. The fuel relay does exactly what it’s supposed to. On to prime, off until cranking, then I again, and I’ve verified that it pumps fuel.
 

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Discussion Starter · #16 ·
Checked gear position voltages. They’re not in spec quite. Supposed to be greater than .6v in all gears except neutral. I see .3v in 1st, 2nd, then going up above .6v in higher gears, and 5v in neutral. Could that be related?
seems a stretch.
 

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Discussion Starter · #17 ·
nope, I forgot to raise the side stand. Now it reads in spec. When I crank, every once in a while a cylinder must get a drop of fuel…I get a rumble then nothing again. (But if I drop fuel in the throttles, fires up like expected.)
 

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Discussion Starter · #18 ·
Another question. The fuel pump does pump fuel, I verified that by removing the fuel feed from the tank and watching it pump out a tube. Is it possible though that pressure is too low? Is there a min pressure needed for the fuel to squirt out the injectors?
 

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It's a stretch but there's a fuel puressure regulator in the fuel pump that conceivably could have failed. You could check the output pressure to confirm that it's working. Should be 43 psi.

I have a 12 V LED (LTH5MM12VFR4600) that I attached to some 12" red and black leads with sewing needles on the ends. I can slip the needles beneath the insulation on an injector connector to monitor the injector. The LED flashes brightly when the engine is running. It really cuts through the crap about whether or not the injector is being pulsed. It draws about 12 mA when on, which is small relative to the injector current.
 
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