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got a 1997 zr580 efi batteryless my problem is the fuel pump. I checked coil off stator reads 2.0ohms in spec move to plug after ecu unplug it get 15-16 volts when pulled over all time. plug connector back in to fuel pump and pull over and only get 4-6 volts. sled runs like new with battery hooked directly to fuel pump. no codes on ecu. why 15 volts when fuel pump not connected and 6 volts when plugged in. thanks
 

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Just from your description, either a partial break in the harness, or maybe shorting some voltage to ground (either way, voltage supply is dropping off)

May also be a stator gone (or going) bad....

Been quite a while since working on one, but, IIRC, these had an inline reducer for the voltage.....??? I dunno (it's been since 1999 that I last worked on one of these)

EDITED: The ECU is the only thing standing between fuel pump powering coil, and the pump itself (I've had my memory re-booted on this one)
 

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THANK YOU FOR RESPONDING stator is new on sled and did all the ohm checks on it warm and cold all coils were in good specs. fuel pump is a new walbro pump also. been chasing this problem and don't know where to go now. so when pulling it over connector after ecu to fuel pump is getting 15-16 volts on fluke when plugged in only 3-5 volts this is when pulling sled over. what actually regulates and stores voltage to fuel pump? diode or something in ecu? another thing if you know is fuel pump wires have continuity so should the wires from ecu also have continuity? sorry for bothering ya but I'm kinda lost> do you know anybody you could refer me to on this sight that has one of these sleds or might know about my problem? again thank ya sir
 

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Discussion Starter #7
I will try it and see what I get for voltage. I cant thank you enough for your patience and time sir. thank you very much. I will let you know the outcome.
 

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reading the thumbnails you sent I'm assuming the two tests with orange wires coming off stator pump coil are in ac voltage and the one on pump connector after ecu is done in dc voltage? pretty sure that's right but wanted to make sure. thanks for everything
 

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ok sir did some testing today from thumbnails you sent me. orange leads measured 16-24 ac volts first time.let it set a while tried again this time got 17-24 ac volts. all good on that test. put connector back together and started sled took test and only got 1.6 ac volts while running. so when hooked to ecu voltage really drops. now to fuel pump connector after ecu. with it unplugged and pull sled over get 16.5 dc volts. now plug fuel pump connector back up and get 3.5 dc volts pulling it over with plugs out and 3.5 dc volts with it running. so with ecu unplugged the stator checks good and with fuel pump unplugged reads good. so its only bad when one of the two (stator or fuel pump is plugged back in to ecu) so do you think it took a cramp from my readings? also tested pump stator while running it puts out 80-90 ac volts. again thank you hopefully this can help you out. chasing a gremlin would be lost without your help
 

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ok sir did some testing today from thumbnails you sent me. orange leads measured 16-24 ac volts first time.let it set a while tried again this time got 17-24 ac volts. all good on that test. put connector back together and started sled took test and only got 1.6 ac volts while running. so when hooked to ecu voltage really drops. now to fuel pump connector after ecu. with it unplugged and pull sled over get 16.5 dc volts. now plug fuel pump connector back up and get 3.5 dc volts pulling it over with plugs out and 3.5 dc volts with it running. so with ecu unplugged the stator checks good and with fuel pump unplugged reads good. so its only bad when one of the two (stator or fuel pump is plugged back in to ecu) so do you think it took a cramp from my readings? also tested pump stator while running it puts out 80-90 ac volts. again thank you hopefully this can help you out. chasing a gremlin would be lost without your help
Right there in your post is telling us it's the ECU (unfortunately) :(
 

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Discussion Starter #14
ok that's what I thought to. found one that has same cat number and square symbol gonna give it a try. thank you for everything
 

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hello sir me again so my son actually did get a different ecu and we put it in sled. then tested the pump connector off stator. first unplugged 1.9-2.0 ohms then plugged it back in and tested connector on ecu side and readings were the same. thought great we got it. not so fast so went to connector after ecu to pump pulled over sled took reading and it was 13-16 DC volts. all good so far. Then plug fuel pump into connector and BAM voltage drops to 3.4-4.1 DC volts. do you know what could be causing this I'm lost. sled will still run like new when on a battery hooked to pump. all readings are good until pump is plugged in but if pump was bad would it run off separate battery?
 

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Sad thing about electronics (and buying used in particular) is that UNLESS you have the affected machine along to "test" the "said" Good COMPONENT, you can very well be buying another bad component...

Here's my thought.. WHY would there be a unit like this for sale "used".....?
To me, were it CERTIFIABLY GOOD, then it would still be in the unit it was first assigned into, instead of being for sale. Sure, sometimes a sled gets wrecked and GOOD COMPONENTS become available on the Internet....
But, I've seen many folks buy something used that"Truly is not any good", and I'm highly suspecting your case may be "one of those"...?
 

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I say the above based on the fact being, that if everything is "good" going into the ECU, but isn't producing required (proper) voltage as its exiting the ECU, then it makes sense to literally guarantee that another ECU is bad and you got snookered...? Sorry to have to say, but like I've previously posted, I've seen it happen a lot over the years....
 

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I would double check you fuel pump connector. Fuel pump runs when hotwired. Power when fuel pump is unhooked, when connection is made looses voltage. check you ecu connector maybe loose pin on harness side that gets pushed back instead of connecting. (making ecu test fail with two ecu)

just some thoughts good luck...sleds are fun
 

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I'm having the exact same issue with a 98 powder special, the common link seems to be the Walbro fuel pump, I've been an arctic cat tech for 10 years and it has me stumped as well. I spoke to a rep from quantum fuel systems where I bought the pump and he admitted to not knowing a thing about how a stator powered efi works.

My suspicion now is that the pump simply requires more power than the stator is capable of providing, causing the voltage to fall off. Are there any kind souls out there with a running machine and OEM fuel pump that would be willing to test the amperage their fuel pump draws? The Walbro takes 5.7 amps running off a battery.

Side note, which model of pump did you get from Walbro?
 
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