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1997 VFR will not start. No spark on cylinder one


Dougwfresh

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Hi, I have a 97 vfr that will not get spark to cylinder #1. I get great spark on all other cylinders. I’ve changed all plugs, wires, and all new coils. New cdi box and a completely new wiring harness. Still can’t get spark to #1. I can get spark to that cylinder when I jump it from the other rear coil but it’s the wrong order then. So still no start. I’ve checked all contacts from battery up and all have great connection. I’ve tested my pulse generators and they are producing over 300 ohms each. I just can’t figure out why there’s spark all other 3 cylinders but just not #1.  I would like some help. Do I need to replace the pulse generators or get a higher cranking battery. I just don’t know. Please help.

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Tedious pulling clutch cvr but sounds very similar to an issue I solved on my ‘86 by changing pulsers. With everything else you’re saying there’s not much to lose by replacing them, sometimes the test #’s can be misleading...

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Not sure But does your bike also have the Cam Pulse Generator? I belive a 1997 vfr750f should have it, quite different to airwalk's 86 model. Might pay to do the Service Manual check for this device and it's wiring and connections.

 

As the same Pulse Generator is also used for cylinders 1 and 3, it would seem unlikely to be the issue.

 

The resistance values should be between 450 - 550 ohms. And 405 - 495 for the Cam Pulse.

See attached.

IMG_0973.PNG

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I have not, those readings are from the 4p connecter straight to the gens. You’re saying, plug the 4p back up and take a reading from the gens on the 16p connecter to the ecu. They should be same if there is resistance?

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4 hours ago, Dougwfresh said:

I have not, those readings are from the 4p connecter straight to the gens. You’re saying, plug the 4p back up and take a reading from the gens on the 16p connecter to the ecu. They should be same if there is resistance?

yes, resistance of coils should measure same at ECU connector to verify wiring in between is OK. Should be since other cylinder of pair is firing.

 

So it may be output issue. 

 

1. measure resistance of each trigger wire between ECU and coils

 

2. measure for power at each coil with key ON

 

3. test for ignition trigger signal with noid light. Test by connecting to primary terminals of each coil. This will tell us if ECU is triggering each coil.
 

 

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You can use test-leads with alligator-clips to connect noid-light to coil primaries. In some cases where bare terminals aren't accessible, I poke into wiring with sewing-needles and attach alligator clips. These noid-lighs have duration-extending circuitry to make sure light stays on long enough to see that trigger occurred. You won't see regular power-testing lights flash.

 

Other way is to test coil-primaries with oscilloscope. The grounding-pulses to dump coil are extremely short duration.

 

uc?export=download&id=1NggHYzHkpWu_gzHtX

 

obvious wiring fault can be discovered if you measure coil-triggering pulses at ECU, but they don't arrive at coil.

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