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97 vfr750 spark mystery.


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Hi, I have 97 vfr750, I got the bike in pieces and got it all back together. When I went to start it turns over but no fire. I checked all the plugs and I’m getting spark  at all cylinders except #1. Then I replaced  all coils, plugs, wires. Still no spark on #1. Did a complete Ignition check. Coils are good, reading 12v+ at each coils. Pulse generators check out too. Power to cdi 16p connecter. Still no spark # 1. I moved around coils, switched wires from coils 3 to 1. Then I got spark on number 1 but not 3. What ever spark plug I hook up to the blue/black wires no spark. So then I got a new used cdi and still the same, no spark. Then I got a new harness, and still nothing. Has anyone ever had this problem? Spark to all cylinders except #1. With new coils, cdi, plugs, harness. The works. Just seems very odd the that two different cdi boxs have the same problem with. No spark to #1 with all All ignition checks are OK. ???

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Just wondering if the ignition pulse pickup is positioned correctly, it might be just on the hairy edge!. Can the pickup be moved closer to the spinning magnets or reluctor points. Is there a magnet/reluctuor perhaps missing or damaged for number 1?

 

Sorry don't have a 97, just thinking outside the square a bit!

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I haven’t tied that just because the one gen sparks 1 and 3 ant the other spark 2 and there. And I have spark at all or there coils. I could make sure the gap is correct. .0015” Is the correct gap. One business card. It’s just very odd.

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10 minutes ago, Dougwfresh said:

I haven’t tied that just because the one gen sparks 1 and 3 ant the other spark 2 and there. And I have spark at all or there coils. I could make sure the gap is correct. .0015” Is the correct gap. One business card. It’s just very odd.

And you definitely have good continuity of the wires of number 1 coil back to the ICM? Pins, sockets and wire crimping of these is all good?

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Use noid-light to determine for sure 100% if ICM is or is not triggering coil#1. 

Even easier if you have oscilloscope.

 

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Maybe a close inspection of the starter clutch outer with the pickup magnets, actually, they may not even be magnets, just metal. Check that none are damaged.

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27 minutes ago, Dougwfresh said:

 does anyone know the correct ohm/v readings for the pulse generators?

 

so you don't have the fsm ?? 🤫  about 400 ohms, and both should be close to the same.

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2 hours ago, Dougwfresh said:

I moved around coils, switched wires from coils 3 to 1. Then I got spark on number 1 but not 3. 

Which wires did you switch?

The hi-ten leads between coils & plugs?

Or the trigger wires between ICM and coils?

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Dan, the leads between coil and plugs are new. For instance so on the back right next in front of the  battery there’s the two coils for number one and number three cylinders. number one has the blue with black with the black and white(12v)and number three has red and blue with black and white.(12v) If I take the red and blue and switch it over to coil number one with its black and white cable. I will get spark on coil one and if I hook the black and blue and black to coil number three then I get spark on number three. so it has something to do with the black and blue wire. But it  has continuity between the icu and the coil.

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Did you buy these items as brand-new OEM parts from authorised Honda dealer?
 

- ignition coils

- ICM

- plugs

- harness

 

 

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You've done great troubleshooting so far with boolean-logic process of elimination. You need better diagnostic tools to answer most important question:

 

Is ICM triggering #1 coil on bu/bl wire?

 

To do that, we need to measure actual signal on that terminal at ICM itself. You'll need one of these noid-lights to see trigger signal. It has duration-extending circuitry so human eyes can see flash (duration is extremely short). Also handy are some test-leads with alligator clips.

 

Or you can use oscilloscope. You should see identical signal coming out of each coil-triggering terminal at ICM and at coils themselves.

uc?export=download&id=1fVydY7P-5ZSoHI6T6

 

 

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Dan, plugs are new. Coils are oem(stock) because they are all good and test great. Better then the cheap ones I picked up. Coil leads are new. Harness is used but it looks brand new, I Have the stock one to. Both don’t get fire on #1.  ICM is a used one. They both are mz7a,s icms. The new used one and the stock one. They both don’t get fire on #1.

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1 hour ago, Dougwfresh said:

Dan, plugs are new. Coils are oem(stock) because they are all good and test great. Better then the cheap ones I picked up. Coil leads are new. Harness is used but it looks brand new, I Have the stock one to. Both don’t get fire on #1.  ICM is a used one. They both are mz7a,s icms. The new used one and the stock one. They both don’t get fire on #1.

Problem with replacing perfectly-working parts with brand-new (or used) perfectly-working parts is that they haven't been pinpointed as actual cause of problem. And after swap, nothing changes. So original parts AND replacement parts must be tested to determine if they're good or bad. Sure we can assume new plugs are OK. But others needs to be tested. Swapping coils into place and verifying you have spark works on existing 2-4 circuits. But that still doesn't help us identify where on #1 circuit is problem. Possible issues at this point:

 

- bad ICM

- bad harness

 

There was massive flood onto market of bad capacitors in mid-90s. It affected everything electronic from radios, TVs, computers, microwaves, and ECUs. It very well could be you've got 2 ICMs with same circuit-board defect that failed over time. Seen it tonnes of times with auto ECUs from Toyotas all way to Porsche/Ferraris. Crack open case, look at location XYZ2 and ahAH! Burst capacitor!

 

So at this point, it's best to test ICM output signal on coil#1 terminal directly. 

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20 minutes ago, Dougwfresh said:

Dan, I just ordered a noid light. How do I use it?

Use some alligator test-leads and connect noid-light to each of ignition-coil terminals directly first:

 

- coil-power terminal Bl/W. Is there identical voltage going to all coils? Measure when bike is running

- coil-trigger terminal. Can test at coils themselves first. Then test at ICM connector (back-probe connector).

 

Would be interesting to see if ICM is actually triggering coil#1 on Bu/Bl wire. If it is, there may be problem downstream. I usually prefer to test upstream first, then if OK, move down circuit to downstream components and see if signal disappears somewhere.

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Another test is oscilloscope view of waveforms coming off pulse-generators. Should be something like this:

 

uc?export=download&id=1pMlv8iPXpq23LWala

 

It may very well be that one pickup is OK and fires #2 & 4 properly. But other may be marginal and ICM only gets enough signal to fire #3 and not #1. Can't really say until waveforms are seen.  

 

I had one extremely puzzling case where everything tested OK. All wires connected to proper terminals and have continuity in between. All sensors and pickup-coils have proper resistance at room-temperature. Only when looking at oscilloscope trace did problem jump out at me!

uc?export=download&id=178yo_LgcX9YIBryY8

 

Someone had replaced pickup-coils and when wiring into connector, they got wires reversed! So signal waveform sent to ICM started on negative slope instead of positive like earlier picture! ICM was blinded and didn't recognize signal.

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Ok, and when the noid comes in, simply pull the rubber boots back from the connecters on coil #1. Connect noid light to A-clips and then to the blue/black and black/white wires. Do I keep the connecters/wires connected to the coil for testing or just the wires them self.

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Trick to testing electronics is to not change circuit by disconnecting anything. You can slide coil connectors  off 1/2-way to leave them connected to coil. Should be enough to get alligator-clips on terminals. I'm not sure how ICM reacts to no load on trigger line.

 

Yup, power-wires are Bl/W on all coils and triggers are:

#1 = Bu/Bl

#3 = R/Bu

#2 = Y/W

#4 = R/Y

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