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Ignition problems


coxy123
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Several questions you need to answer to give people half a chance!

1. Points or electronic ignition - does it work? Contacts ok etc?

2. Voltage to coil ok?

3. Plugs ok?

4. Dizzy ok? One way is to see if you have a spark at the centre of the dizzy

5. Rotar arm ok? 

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It may be the multi-way plug and socket in the ignition switch loom. Try cleaning the contacts with switch cleaner or brake cleaner spray.

A high proportion of the electrical problems on the TR7 are caused by corrosion in the many multi-ways in the looms.  

Dave

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If you have a ballasted ignition system the coil resistance should be 1.5 ohms and if non ballasted 3 ohms. The coils are not interchangeable. If your not sure which type your system is you could measure the voltage at the coil to confirm it:

With the ignition turned on but engine not running measure the voltage to earth at both terminals on the coil. The -ve one going to the distributor points should be zero and the other +ve coming from the supply should show about 6 or 12v with the first indicating a ballasted system (a reading of around 8v would be due to having the wrong coil).

If the negative terminal happens to show 12v as well it means the points are open and you need to rotate the engine a little to get them to close. Turn off the ignition while you do this....

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All TR7 have a ballast resistor in the loom and hence use a 1.5 ohm coil.

Some other info - The ballast resistor is bypassed when the starter motor is engaged. The bypass lead come off a connection (relay) on the top of starter motor under the exhaust manifold.

Dave

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If its is a separate block and not in the loom then just bypass the block, a jumper lead across the block. If its in the loom then generally a lead has to be take back to the ignition switch and fed directly to the coil.

There is a way with the 1980 on TR7. The is a a direct feed from the ignition on the left hand side of the coil. This is a simple cable join, you have to open up the joint then solder an additional lead, then re-insulate, to feed the coil.

Dave

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On the TR7 if it looks like there is no 12volts or no connection to the points then its worth checking a number of multi-way plugs and sockets. 

Follow the leads from the ignition switch, first picture and clean the multi-ways on the end of the loom picture 2. The other multi ways are the two on the passenger side down by your right foot picture 3. Leaks through the bulkhead where the heater pipes come into the car can cause problems with these two multi-ways.

Dave

Picture 1.JPG

Picture 2.JPG

Picture 3.JPG

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Thanks for all you're input.it still won't fire.  We think it must be a faulty coil. We've found it is wired as a  US car ,with 4 fuses. It has a white/pink ballast wire. So thoughts are to get a new coil, from the comments i have received, I think a 1.5 ohm unballasted coil is the correct one. If someone can confirm this or tell me different that would be good. Thanks Steve

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