Ignition questions/problem

[johnnyj]

Hi folks, hope everyone is doing ok. I have a question relating to a problem with my ignition, which I will try to keep short:

1977 FHC, ACG series

I recently refitted my alternator and after doing so the car wouldn't start (it started fine before). I noticed that the ignition light in the dash was not illuminating. Checking the alternator connections I noticed the smaller of the three embedded spade lugs within the alternator multi-plug had come loose and pushed itself off the terminal and out the back of the connector, leaving just the other two lugs connected. I fixed this and the ignition light illuminated again but the car still wouldn't start. This is sort of background info regarding the below, and may or may not be relevant.

So, the car won't start and I have established that there is no HT from the coil, so obviously no spark up the king lead and onwards. In terms of voltage/earth checks, the car has 13.5v on the +ve LT coil terminal (white & yellow wire) with the ignition on, which drops down to around 9v on cranking. The white & slate wire from the -terminal of the coil reads closed circuit up to the same wire in the distributor, and the wire which feeds the tacho - which is correct, I believe. The coil itself is grounded to the suspension turret. So, I have concluded that the LT wiring is as it should be, I think.

As the LT circuit appears to be ok, I am leaning towards the coil having gone faulty, as I can't see what else it might be. The coil is brand new and a lucas model, from a reputable TR7 specialist. However, that got me thinking - "why?".

My first thought was that maybe not having the aforementioned alternator wire connected during cranking had some how fried the coil. I don't know if this would happen?

The second thought was around the ballast resistor. In truth I don't know if I have one fitted, but do understand that a ballast system needs a ballast coil and vice versa. Likewise I don't know if the coil I fitted is a ballast coil or not. Clutching at straws, I wondered if - supposing I have the wrong combination of ballast resistor and coil - the coil was ok initially and started the car, but has now burned out due to the mismatch.

Not sure if this helps the ballast theory, but in terms of wiring on the starter I have three wires - two go to the main terminal post on the solenoid and one to a smaller spade/lug terminal. On the coil I have just the two wires mentioned above (one each on the + and - terminals) and the flying wire from the loom which goes to the tacho. That's it.

Sorry, I failed to keep it short but tried my best! Any thoughts very much appreciated.

Cheers

John

[Beans]

Ballast theory:
If the wiring is original you need a 6V coil.
The ballast system will bypass the ballast wire during starting.
This way you will get 12V on the ignintion system during starting, giving a better spark.
With the engine running the current will flow through the ballast wire giving 6V to the coil.

The rest is a bit strange. Have you checked you haven't dislodged a connector somewhere while refitting the alternator?

[johnnyj]

Hi Theo. Yes, it is a bit strange. I thought I knew the wiring loom inside out, so can't think of any wire that could have become dislodged. Three to the alternator, two on the coil (plus the body earth), and the flying lead to the tacho. That all agrees with the wiring diagram and to the best of my knowledge the wiring is original.

I'll have another look, as I must admit my first thought was that I must have dislodged something. If I find nothing, I guess I'll have to swap the coil and see what happens!

Cheers

John

[busheytrader]

Hi John,

It wouldn’t be the first time that an electrical part (coil) has been faulty out of the box.

I had starting issues earlier this year. Luckily it broke down in my garage. The engine would fire on the starter but refused to run after the key was released. The ignition switch module’s casing had fatigued apart after 40 years (the metal tabs had fractured) and after replacing it, I found the starter relay was faulty. Maybe a short in my switch had blown the relay? Might be worth checking these items with your multimeter?

The starter relay shown and supplied by Rimmers is the wrong item and doesn’t work. It’s readily available elsewhere.

[johnnyj]

Thanks Bushey, much appreciated. Definately the thing I have learned during this epic resto is not to jump to conclusions, and to follow a logical approach to fault-finding. Your advice is a perfect example of the logical approach! For example, I realise now the +12v on the coil is a fairly meaningless reading, as it is fed directly from the main 12v rail (so I am just reading the 12v "in"). What I am seeing is the negative side being the main problem, which ultimately goes up through the points. I'll check the areas you mentioned, and then have a look at the dizzy. Could be the points have closed up, maybe?

Thanks for the heads up re the relay. I have a spare one somewhere, so will drop that in as a test at some point.

Thanks again!

John

[Cobber]

Remove the dizzy cap, and check that the rotor arm does not turn on the shaft if it does the drive peg on the arm has sheared off (unlikely but I've known it to happen), while your at it look for excessive scorch marks and errosion on the rotor arm, if in doubt replace it.
Now with the help of a glamorous assistant turning the ignition key, observe that the dissy shaft is rotating, if not the dissy drive gear maybe at fault, now check that the points are opening on the tip of the cam lobe and closing again you should probably see an arc of spark at the points... if so, good.
Now whilst you're there check that the points aren't pitted and check the gap, if in doubt replace and replace the condenser whilst your at it.
And have a look inside the dissy cap if it's eroded or scorched bin it and check that the little carbon bush is not worn, is still in the middle and moving in and out freely on it's spring.

Unless I know for sure that the points, condenser, cap and rotor arm are OK, I bin 'em.....saves a shitload of buggerising about, and gives piece of mind that you wont have to muck about with the dissy again for some time.

[johnnyj]

Thanks Cobber, great minds think alike. The distributor was loose (I always forget to tighten something up!), so I bolted it down properly. Gosh, I had forgotten how hard it is to get to the dizzy bolts. Anyway, after re-arranging the skin on my knuckles I re-set the points gap - gosh,I had forgotten how hard...you get the rest - and hey presto she ran beautifully.

I'm really pleased with that, as it is a newly-built engine. There's always a slight sting in the tail though, isn't there? The rev counter/tacho now takes a while to leap into action but I can live with that. Next for investigation is a nasty squealing when the clutch is pressed. I haven't investigated yet as I don't want it to take the shine off my day of glory with the engine. It's a headache for another day, and another post on here if necessary. If the engine has to come out again to sort the clutch, so be it!

Cheers all

John

[Beans]

Good to see the problem seems to be solved. As you mentioned it pays to work methodical!

... The rev counter/tacho now takes a while to leap into action but I can live with that ...

One of my TR7's has the same problem for as long as I can remember.
The rev counter will only start working after the throttle has been blipped after starting the engine.

[saabfast]

The sticky tach needle is a common phenomenon on the TR7. I am sure there was a fix somewhere but this thread is all I can find at the moment:
viewtopic.php?t=11846

[johnnyj]

Thanks everyone for your thoughts and help. I'll see if I can track down some info on the sticky tacho, but the next job will be having a look at the clutch noise. For that, I'll report in another post so that the post title aligns.

Cheers

John

[FI Spyder]

My tach is the same way but it quickly comes on. There is a bit of solder cleaner that provides some resistance to needle moving (on the counter balance end of needle when it's at rest). Cleaning this solves the problem. That's the theory. Never actually looked at this and might not be for every situation but next time it's out check this and clean the rest stop area any way. It won't take much to cause this temporary hesitancy.

Squealing clutch when clutch pedal pushed a bit sounds like the release bearing. This should be replaced when clutch is changed even if found good. You don't want to be doing this job twice. A good rule of thumb is to start the engine in neutral with out pressing on the clutch pedal. You do have to make sure to check that you are in neutral of the car will jump ahead will potentially bad results. Old cars with old style graphite release bearings found this out and while not critical on roller release bearings, it will put less strain/usage on it. Of course once it's shot, it's shot.

[busheytrader]

Glad to hear you’re sorted...

I’ve had at least 3 Rev counters on my wedge. Each one has needed a prod on the gas past 1,500rpm before the initial stiction point is overcome.

[dursleyman]

Same here with the tacho, it is often sticky on starting but never failed to spring to life - yet!

[alc59]

My Grinnall TR8 tacho also takes time to recognise I am expecting it to perform.