Lotus Elan

I should leave well-enough alone

PostPost by: archigator » Wed Apr 27, 2011 6:23 pm

Do we have concensus? I'm sorry to belabor this... but I don't want to fry my tach or worse. This seems to be the scheme that's agreed upon for an RVC tach hookup. :D

Gary
'71 Sprint FHC
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Is this the correct RVC Tach hook-up?
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PostPost by: collins_dan » Wed Apr 27, 2011 6:52 pm

Frank's right. Here is the wiring diagram. It may be helpful as it does show the white wire connecting to the + side of the coil.

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PostPost by: Frank Howard » Wed Apr 27, 2011 7:05 pm

Gary,

As Ed McMahon said many times, you are correct sir. What really impresses me is your photo with the fancy graphics. :)
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PostPost by: archigator » Wed Apr 27, 2011 7:35 pm

Heeeeeeeeeeere's Johnny!

Gary
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PostPost by: archigator » Sat May 14, 2011 4:34 pm

Well I got to the tach/ignition/coil wiring connections as noted in my previously posted photo/sketch. The ignition light goes on, the engine turns over, but I get no spark. I have checked the wiring and found none of it compromised, the fuse box fuse is not blown, and when I checked the internals of the RVC tach nothing inside appears burned/melted due to my previous mis-attachment of wiring connections. I'm stumped.

I found this sketch on-line and it mirrors the way I have it wired. The White wire goes to ignition swith terminal #2, and the green is power when ignition is lived when switched "on." I have grounded my tach using the back-of-tach pin noted on the earlier posted Speedograph sketch, but have also ground wires at the tach threaded hold-on connectors as with my previous RVI tach.

Could I have fried my tach, although it's not visible to the naked eye?

Any further help would be much appreciated... thanks.

Gary
'71 Sprint FHC
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Tacho RVC.jpg
This is the way I have my RVC tach wired.
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PostPost by: stugilmour » Sat May 14, 2011 4:48 pm

Gary, have you tried disconnecting the tach and see if the car runs with it totally out of play?
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PostPost by: archigator » Sat May 14, 2011 5:02 pm

Disconnect the W/B (Blue on my car) and Green wires totally? Should the W/B (Blue on my car)wire connect to the Green wire then?

UPDATE: I just checked the power to both the W/B (Blue on my car) wire and the Green wire individually. Each has power to it individually when I turn the ignition key to the next-to-last position before turning-over the engine. Should that be happening; should both wires to the tach show power when the key is in the next-to-last position? I also have the original White wire running from the #2 position on the ignition to the positive side of the coil, totally independent of the tach...

Thanks,

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PostPost by: stugilmour » Sat May 14, 2011 7:17 pm

archigator wrote:Disconnect the W/B (Blue on my car) and Green wires totally? Should the W/B (Blue on my car)wire connect to the Green wire then?

UPDATE: I just checked the power to both the W/B (Blue on my car) wire and the Green wire individually. Each has power to it individually when I turn the ignition key to the next-to-last position before turning-over the engine. Should that be happening; should both wires to the tach show power when the key is in the next-to-last position? I also have the original White wire running from the #2 position on the ignition to the positive side of the coil, totally independent of the tach...

Thanks,

Gary
'71 Sprint FHC
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Yes, I would try starting the car with the wires disconnected from the tach to separate any tach issues from the ignition circuit. The car should run without the tach. You should not have to join any of the tach wires together to make this check. See below, but I would first attempt this check with the tach sensor wire disconnected from the negative coil terminal; i.e. only the wire from the -ve coil terminal to the distributor and the white to the +ve coil terminal connected.

Yes, both of the noted wires should be hot in run and start positions of the ignition key. They should be zero volts on off and acc'y positions of the ignition key.

The green wire is presumably the power wire to the tach. Green means "hot in run and start - fused" in the standard wiring schema. The White / Black? or Blue? in your case is the sensor wire from the coil. It is 'seeing' current flowing to ground thru the coil from the positive coil terminal White (hot in run and start - unfused) as the points open and close electrically. The sensor wire 'sees' the on and off of the coil as a wave form which is interpreted by the tach electronics and transformed into a reading on the gauge face.

The ignition circuit should be powered by the White on the positive coil terminal, and should all work with or without the tach. As you are presently unsure of the tach condition and perhaps uncertain of some of the connections, I would try to get the car started without it being in play. You of course cannot fix the tach if the car won't start, so getting the car starting again would be mission one.

The green wire to the tach is probably not an issue for the ignition circuit. If it were grounded inappropriately within the tach due to some sort of failure/damage the fuse would have blown. I am thinking that the tach is potentially interfering with the ignition somehow, perhaps grounding out the ignition circuit (due to an incorrect connection or internal fault) preventing the points from doing their on & off thing. If the coil is not going on & off, there will be no spark, which is what you described as your issue.

Once the car is running correctly you can return to sorting out the tach connections and function. I don't have a RVI in my car, but what you are describing above seems to make sense to me so not sure of the specific issue, or know how to check it further. It could be a minor connection error caused by confusion of the terminal positions on the tach, or it could be internal failure of the tach; the folks with the RVI tach model will know better.
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PostPost by: archigator » Sat May 14, 2011 10:14 pm

I disconnected the power wire to the tach (Green) and disconnected the wire from the tach to the negative side of the coil (Blue on my car)... leaving the White wire from the ignition to the positive side of the coil and the White/Black wire from the negative terminal of the coil to the distributor. I crank the engine, still no spark to the plugs.

I turn the key to the next-to-last position before turning-over the engine and I find:
1. I have power to both sides of the ignition fuse (original two-fuse box configuration)
2. I have power from the white wire to the positive side of the coil.

So, since everything seems to be getting power properly up to this point, I guess:
1. Either my coil has gone bad (doubtful)
2. Or my points/condenser, rotor, distributor cap need replacing

Does that make sense?

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PostPost by: stugilmour » Sat May 14, 2011 11:30 pm

archigator wrote:So, since everything seems to be getting power properly up to this point, I guess:
1. Either my coil has gone bad (doubtful)
2. Or my points/condenser, rotor, distributor cap need replacing

Does that make sense?

Gary
'71 Sprint FHC
Miami, Florida


Both make sense to me Gary, although would not completely dismiss coil being flakey.

Have you checked for spark while cranking to ensure the ignition is at least firing?
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PostPost by: Frank Howard » Sun May 15, 2011 5:40 am

Gary,

I'm not sure where you checked the white wire from the ignition switch to the + side of the coil for power. If you checked it at the switch, it's possible that you're getting power there but not at the coil because before it goes to the coil, it goes through the anti-theft switch in the glove box. This switch has given me trouble in the past. If your car is equipped with an anti-theft switch, I would flip the switch on and off several times to get a better contact and I would try starting the car with the switch in the up position as well as the down position because you never know which way it was installed.

A most basic test you can perform would be to pull a plug and clamp it on to the engine with a pair of Vise Grips. Close the garage door, turn off the lights, and check for a strong spark. Of course, if the car starts, turn it off immediately and open the door :!: If you get no spark, try bypassing the distributor cap by hooking up a plug directly to the coil and clamping it to the engine. If you get spark now, you've narrowed your problem down to the distributor.

One other detail you could share with us is whether or not your car is equipped with a ballast resistor. If you have one, it should be near the coil. We're going to get this, one way or another!
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PostPost by: archigator » Sun May 15, 2011 12:07 pm

No ballast resistor, no anti-theft switch...
I am getting power on the positive (White wire) side of the coil...
I already pulled a plug, connected to its wire, and laid it on the cam cover next to a bolt... no spark when I fire the engine.

I'm going to pop the distributor cap this morning and see if my points may be at fault. I have a spare set of points and a new condensor if need be. I'll also have to track down a spare plug wire to attach directly to the coil to test it. (I've also found some good Moss Motors videos on YouTube on how to check your vintage ignition circuit.)

I appreciate the advice! Thanks. We'll soldier on...

Gary
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PostPost by: Frank Howard » Sun May 15, 2011 2:41 pm

Gary,

I don't think you'll see much while the distributor is in situ. It will probably have to come out. If you mark where the rotor is pointing before removal (or just make a mental note of it), you'll be able to put it back in without upsetting the timing. When you get it out, pay special attention to the small wire that was attached to the negative side of the coil. This wire should connect to one side of the points without coming into contact with anything else that is metal. That's why there should be a plastic insulator where it attaches. Make sure all of this is in order. I inspected an Elan a couple of years ago that wouldn't start. I discovered that the owner didn't think it was important to make sure it was connected to the coil using the plastic insulator. Remember, all the points do is switch the ground to the coil on and off. Good luck.
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