*In dire need of help* Intermittent stall and no start

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*In dire need of help* Intermittent stall and no start

Postby rabman369 » Fri Aug 23, 2019 11:28 pm

Intermittent stall and no start

I apologize ahead of time for the short novel i just want to try and be thorough in my explanation.

1990 FZR600. 32000 miles. (Note: the run/stop switch has been modified with a killswitch to the starter where the original start button was. The original start button itself was removed from its little hole on the assembly and replaced with an after market one that bypasses the starter solenoid straight to the starter. Anytime this button is pushed it will crank the engine whether the key is present or not or the run/stop switch is in the run or stop position. The reason being is that the previous owner tried to install a new starter solenoid and the engine would crank every time he attatched the leads to it due to the starter circuit side of the relay assembly having failed into a permanent closed state that he was unable to diagnose)

Okay so the bike will start and run great and then die after 30-45 mins of riding and then fail to start up again until after sitting for inconsistent periods of time and then act like nothing ever happened and repeat. Always cranks and accessories have power but engine doesnt fire.

Usually when it does this it kind of bogs down and loses power as if it is running out of fuel until it dies.

Originally when it did this the very first time i suspected the fuel pump as it (the fuel pump) did nothing when attempting to start. Fuel pump then performed as it should when given direct power from battery so i ruled that out.

Next guess was the relay assembly. Inspection revealed that it made a rattling noise when shaken so i assumed it was completely junk at the time. I replaced the relay assembly with a known good one to no avail. I later discovered through probing it with a mutimeter that it was only the failed starter circuit side of it that i described earlier because the fuel pump side read the same as the new one.

I began to think maybe it was a power supply/resistance issue due to the fact that when the problem occurred one time i was able to just temporarily rig a wire directly from the battery to the fuel pump harness for a quick fix to get it started so i wouldnt be stranded. I thought maybe the heat of the engine made the resistance too high and prevented the pump from getting adequate voltage from a weak battery or something. I had a little spot where i closed the circuit anytime it would bog down so it would fuel it back up and get me home. Well by the time i got home that had stopped working as well. When i connected it directly to the battery it would either give one weak click or nothing at all opposed to the usual strong clicks every couple seconds.

I didnt have any specs to go off of for voltage readings from wires but none of them read diferently between either relays or from when the problem was occuring to when it wasnt

I then discovered through research that i had one of the cheap chinese replacement voltage regulators that are presumably garunteed to fail and thought it couldve had something to do with it seeing as how its readings for charging the battery were on the low side so i checked the voltage output of the stator to make sure it was good and then swapped the regulator with the suggested r6 upgrade. This didnt remedy my issue but needed to be done sooner or later regardless so oh well.

I began to think maybe the fuel pump was really the problem again. I went ahead and took the back off and on the part between the two pieces that "click" together it was a little dark and worn looking so i brass brushed it clean and put it back together. Now anytime it is given direct power from the battery, whether the problem is occuring at the time or not, it functions just as it should (nice and stern clicks) but still weak from the harness itself when the problem occured the next time it stranded me again and didnt have my wire handy to jumper the pump from the battery. So this time after i let it sit and (idk cool down?) I had my girl come bring me my tools and as soon as i put the jumper cables on it and switched it into the run position the fuel pump clicked away strong and fast and the bike started right up when i hit the start button. Im now starting to think its simply been a questionable battery the entire time even though it always reads over 12v even when the problem occurs.

So im not sure if the battery was /already/ toast from the very start or not but by this point it definitely was from dying so many times from attempting to start it and killing it with no luck so i got it tested. It was bad so i replaced it with a new one.

Problem happens again. This time though it seemed a bit diferent. Normally it would do the whole bog down lose power like im runnin out of gas thing. Im not sure if its because i was going up a fairly steep highway on ramp or what but it was going fine then kinda misfired once abruptly then continued normally for a couple seconds then a couple quick little misfires and shes suddenly dead.

Fuel pump is clicking as it should and its cranking nice and strong but no attempt to fire. Towed it home 30 mins later and same thing. Popped fuel line off just for re assurance and pump shoots fuel. Went ahead and tried some jumper cables real quick for the heck of it and still no fire. Let it sit for the night because a storm came through. Went out to start it today and instantly fired right up first try

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Re: *In dire need of help* Intermittent stall and no start

Postby Mouser » Sun Sep 01, 2019 1:44 pm

Hi rabman,

I had a similar problem with my race 400 Fzr at some time....I have high volatge coils mounted and they didn't want to work anymore as soon as they got too hot....misfire ore most of the time bugging like yours like not gatting any fuel anymore.....

check your coils....if they are not too near anything hot, water circuit etc. Eventually replace them, it's possible that they have nearly come to life end and the internal resistance got high and with higher temperature in that area (which would be normal ) the resistance gets bigger and they refuse to work !

Let me know....


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