No spark from one coil

[JpRngr]

Hey there!
Just picked up an '88 Vmax that was inop. No back history, got it cheap from an auction for a project. Anyway, put a new battery in and am trying to get it running. Found really old, nasty gas and have drained the tank and cleaned it out. Will be pulling the carbs and cleaning them also. In the process of figuring things out, I determined I wasn't getting spark from the left rear coil. If I swap the connectors between the rear two coils, it will spark and the right one won't. So, don't believe it to be a coil issue.

What should I look at next? Saw something on here about checking resistance at a six pin connector and one of them was lower than the others, but don't have the results here right now. Any thoughts or suggestions as to where to look next?


Corey

 

[MaxMidnight]

Can we assume you have a wiring diagram?

As three of the coils work then that would rule out the pick-up cpils

I would start by checking that I have power to the coil and if OK check that you have continuity back to the ignition unit.

If that checks out OK then I would suspect an issue with the ignition unit

 

[JpRngr]

No, no wiring diagram. Just got this less than a week ago. Google is my friend! LOL.

Anyway, I'll see about checking resistance in the wiring between the ignition unit and coils. If that checks out and I need a new ignition unit, is a stock replacement recommended or is there a better aftermarket unit I should look at?

 

[Fire-medic]

Coil over plugs makes an easy job of switching out coils if one goes bad. One of our members sells a kit to replace yours. I believe at this time Sean Morley is acting as a dealer for him. [email protected]

Wire diagrams:

http://www.vmaxforum.net/attachment.php?attachmentid=28837&d=1337010945 for 1990+ USA

http://www.vmaxforum.net/attachment.php?attachmentid=28836&d=1337010945 for '85-'89 USA

Look in the tech section for the service manual.

 

[JpRngr]

Wire diagrams:

http://www.vmaxforum.net/attachment.php?attachmentid=28837&d=1337010945 for 1990+ USA

http://www.vmaxforum.net/attachment.php?attachmentid=28836&d=1337010945 for '85-'89 USA

Look in the tech section for the service manual.

Thanks for the help!

 

[MaxMidnight]

No, no wiring diagram. Just got this less than a week ago. Google is my friend! LOL.

Anyway, I'll see about checking resistance in the wiring between the ignition unit and coils. If that checks out and I need a new ignition unit, is a stock replacement recommended or is there a better aftermarket unit I should look at?

You can get the service manual here

If the unit is faulty then your choices are OE, Dyna or Ignitech.
However it is most likely to be a wiring or connection fault and if possible I would check the ignition unit by substitution if possible.

As Mr Medic suggests, CoP's are an alternative if you need to replace a coil but that does not seem to be the case here.

 

[effingidiot]

Any chance of a photo of your project,pretty please.

 

[JpRngr]

So, got back to fiddling with the bike today. Had decided to take a break from it due to the newly cleaned tank deciding to leak from the sending unit seal after getting it installed. So, that's now leak free and back in. Now, I'm not getting fuel out of the pump. Tried using a water bottle filled with gas fitted directly to the pump, in case it just needed to be primed. Finally got some fuel down to the carbs and got the bike to fire. Reconnected fuel line to tank. Would only idle, anytime I tried hitting the throttle, it would die. Checked spark again and now all coils are firing. Looks like the fuel pump just isn't sucking any fuel. Don't know if pump had pumped anything or if I just squeezed fuel to the carbs from the water bottle. Anyone know for sure how well these pumps suck? Do I need to prime the pump, or should I look at getting a new pump?

 

[JpRngr]

Oh yeah, and no pics yet, as it's all torn apart trying to get it running. LOL.

 

[MaxMidnight]

Does it run if switched to reserve?

 

[JpRngr]

Does it run if switched to reserve?

???

Am I missing something? I haven't seen a reserve on this bike.

 

[Bill Seward]

Look on the handlebar switch.

 

[vwaxxed]

???

Am I missing something? I haven't seen a reserve on this bike.

There is definitely a reserve switch, but there isn't an actual "reserve tank". When the fuel gets low it shuts the fuel pump off and when you switch it to reserve it overrides it and runs the pump anyways. It's just above the start button (a left to right switch). I believe left is reserve and right is on, im at work so i don't have the bike in front of me but I believe thats the orientation.

 

[JpRngr]

Don't think it'd be the reserve then, cause the pump definitely turns on. Just doesn't suck any fuel from the tank. Guess I'll be getting a new pump. Any suggestions? Saw Chinese cheapos on e-bay for $15-40 and new Yamahas for $250-300. Don't know that I wanna throw $300 into a project bike right now.

Corey

 

[one2dmax]

I've got good used OEM pumps and be cautions of the cheap ones that likely don't have the built in pressure regulator. You may simply have a displaced diaphragm if it doesn't pump. Another thing to make sure is that there is no air leaks on the side prior to the pump. Even a very tiny hole will cause it to lose the ability to suck fluid even if that hole doesn't leak fluid. Picture included of a displaced diaphragm.

 

[JpRngr]

I've got good used OEM pumps and be cautions of the cheap ones that likely don't have the built in pressure regulator. You may simply have a displaced diaphragm if it doesn't pump. Another thing to make sure is that there is no air leaks on the side prior to the pump. Even a very tiny hole will cause it to lose the ability to suck fluid even if that hole doesn't leak fluid. Picture included of a displaced diaphragm.

How much for a good used one? I don't really want to put another cheapo Chinese one in, cause that looks to be what's in it.

 

[sdt354]

Make sure your tank vent line is clear and not pinched.

 

[vwaxxed]

How much for a good used one? I don't really want to put another cheapo Chinese one in, cause that looks to be what's in it.

I'd email Sean and see how much he can get one shipped to you for. [email protected]