98 VMAX Tach Stopped working, but once in a while kicks in

[takedowntheccp]

Hi, I am new to this forum and Im hoping someone has the solution to my problem with a 98 vmax tachometer. I have checked all wires, ground, fuses. and no signs of any problems.
Since the tach kicks in once in a while assumes theres a connection problem, So I thought. Anyone had this problem before?
Thank you for your time.
matt

 

[Fire-medic]

Follow the leads from the lands on the tach, flexing the lines individually as you go, until you find the break(s). I usually begin with the grounds in any electrical issue. You can also parallel-run new wires and connectors, just be sure to use different color wires for each run. Sometimes a connector which appears 'good' from casual observation, is corroded enough to cause problems, upon disassembly. Clean connectors to shiny-bright metal, and use a daub of dielectric grease on the connectors.

A carelessly-run wire can chafe-through the insulator jacket where it makes a bend, especially a sharp one. Inspect the crimp connections to a wire, as that is a location where the strands can fatigue-wear and break, another likely place is just under the insulation next-to the crimp connector, where you cannot see the break, but flexing the location, you may discover intermittent contact.

Resources for you. http://vmoa.net/VMX12-Service-Manual01.pdf


NOTE: there is overlap between the diagrams

 

[Dansmaxresto]

Hey FM, I am having the same problem. Is the wiring diagram the same for an 86?

 

[Fire-medic]

Hey FM, I am having the same problem. Is the wiring diagram the same for an 86?

Here you are, it's different ('85-'89), though the primary difference lies in the ignition having two pick-up coils generating signals for the ignition box to sense and trigger sparkplug impulses. It has 5 wires: (below) Look to the left of the fusebox, in the lower right of the diagram. It's labelled 'alternator/pick-up coils'

black
white/red
orange
white/green
gray

The 1990 has one pick-up coil which is only two leads. (last attach.)

Again, note the overlap between the two diagrams.

 

[Dansmaxresto]

Thank you so much!!

 

[jamie g]

question i dont want a locking gas cap but having hell of a time find just twist on one ??? any help thk you

 

[Fire-medic]

Where in Florida are you?

You have to change the tank neck to accept a twist-cap. Some solutions below.

Some people with Corbin seats use an extension to put the gas cap closer to the top of the hole in the seat, and then use a screw on male & female gas cap and tube. The tube attaches by fabric reinforced rubber gas line rated tubing to the OEM gas tank neck w/hose clamps.

Here's something you would need to attach a piece of tubing to. They have aluminum, stainless steel, and steel bungs (the female threaded part).
https://www.ebay.com/itm/2214289770...a7BYg3-rBmcnb31o58QUFQ08QoJ86R0RoCrqwQAvD_BwE
You could also hit your local parts yard and remove a neck and screw-on cap, just find something the same size as the VMax neck which is just-over 2" o.d. Take the rubber tube too, as that material is expensive if you want to buy a length. I think I paid $20 for a foot at NAPA, years ago.

 

[jamie g]

yes im in florida just north of orlando , thank you so much for all the help will keep you in formed wish me luck.

 

[Fire-medic]

You are welcome. Post up whatever you decide to do.

 

[takedowntheccp]

Follow the leads from the lands on the tach, flexing the lines individually as you go, until you find the break(s). I usually begin with the grounds in any electrical issue. You can also parallel-run new wires and connectors, just be sure to use different color wires for each run. Sometimes a connector which appears 'good' from casual observation, is corroded enough to cause problems, upon disassembly. Clean connectors to shiny-bright metal, and use a daub of dielectric grease on the connectors.

A carelessly-run wire can chafe-through the insulator jacket where it makes a bend, especially a sharp one. Inspect the crimp connections to a wire, as that is a location where the strands can fatigue-wear and break, another likely place is just under the insulation next-to the crimp connector, where you cannot see the break, but flexing the location, you may discover intermittent contact.

Resources for you. http://vmoa.net/VMX12-Service-Manual01.pdf

View attachment 85218View attachment 85219
NOTE: there is overlap between the diagrams

Follow the leads from the lands on the tach, flexing the lines individually as you go, until you find the break(s). I usually begin with the grounds in any electrical issue. You can also parallel-run new wires and connectors, just be sure to use different color wires for each run. Sometimes a connector which appears 'good' from casual observation, is corroded enough to cause problems, upon disassembly. Clean connectors to shiny-bright metal, and use a daub of dielectric grease on the connectors.

A carelessly-run wire can chafe-through the insulator jacket where it makes a bend, especially a sharp one. Inspect the crimp connections to a wire, as that is a location where the strands can fatigue-wear and break, another likely place is just under the insulation next-to the crimp connector, where you cannot see the break, but flexing the location, you may discover intermittent contact.

Resources for you. http://vmoa.net/VMX12-Service-Manual01.pdf

View attachment 85218View attachment 85219
NOTE: there is overlap between the diag

Thank You! I will print this and work through it thoroughly. I Appreciate your help.

 

[Sniffbooger]

I was riding my Vmax to work this morning, all of a sudden for no reason the tach stopped working and the idle went bad like it was missing on a couple cylinders...I pulled over, took off the seat and found a loose connection on my spark wire to the left rear coil and some corrosion at the connection of the wire end...I bit off some rubber and exposed the wire a little better, screwed it in and off I went to work! I'll have to get these wires clipped and cleaned up ASAP! I think the tach is connected to one of these coils for signal...

 

[Fire-medic]

.I bit off some rubber

That's MacGyver shi_ right there. Don't you carry a Leatherman or some kinda pocketknife?

 

[Sniffbooger]

That's MacGyver shi_ right there. Don't you carry a Leatherman or some kinda pocketknife?

Im gonna have to put together a little tool kit under the seat ..my teeth are still complaining this evening...that spark plug wire is some tough sheeite! MacGyver rocks.

 

[Bill Seward]

Don't bite the wire with the engine running...

 

[Sniffbooger]

Don't bite the wire with the engine running...

LOL

 

[Sniffbooger]

Now mine is starting to have tach issues also ...tach is dead upon starting, then begins to work after about 20-30 seconds with engine running....any thoughts?

 

[Fire-medic]

The first thing I start with is proper voltage from the battery, clean, shiny grounds, tight and shiny connectors, and continuity in the wires of that circuit. Sometimes flexing the wires/connections, and watching the needle will reveal an intermittent contact.

 

[Sniffbooger]

Which coil does the tach lead attach to on post '93 models? Does it come from the front or rear coils? I think I see a brown wire from the front right mounted coil behind the CDI unit. And there's a yellow wire from one of the rear coils.

 

[Fire-medic]

Leads to the tach:

grey
brown
black

The coil with a yellow wire and the red/white wire to it, appear to connect to the grey tach wire; the grey tack wire connects to the yellow coil wire.

The same circuit for the yellow wire also connects to the ignition control unit. Follow the yellow wire from the far-right high tension coil and you will see where it connects to the grey tach wire.