R12 1250cc coil specification?

R8 Dream

R8 Dream

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Fellow Frogger
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Having some trouble with keeping the engine going, as after starting from cold and running Well for about 5mins then for no reason the engine just dies.
After trying to get it going for nearly 30mins it just wont start.
Fuel is new and pumping, and running a Weber 32/36.
There is spark.
Notice coil was getting quite warm.
Just want to check specs on the coil. Mine reads +/- 2.5ohm; and 9080ohm (+ to centre of coil)
Are there figures normal?
looked in the manual just can’t find and specs.
 
It is a 12v and used to run some 10 years ago.
I heard that they can diminish somewhat, effecting the spark quality.
I have recently changed from a generator to a alternator, could this have any effect on the coil?
Electrics is not my strong point 😬
 
I think my coil is about 3.5 ohms, if you suspect the coil change it and see if it fixes the problem.

Coils have been known to have shorted turns and may effect the spark when coil heats up.
 
Also forgot to mention that the R12 engine (842-01) sits inside my R10 with 330 gbox.
 
Replacing the coil may not solve your problems.

You say you still get a spark. Is it a fat blue one or weak and yellow-ish?

Your condenser may also be a culprit and can give the same symptoms.

When you say the coil is getting warm, is it just warm or is it getting too hot to touch.

Fitting a 6v coil without a ballast resistor could cause it to heat up.

Did that motor run okay before you changed from a generator to an alternator?
 
Exfrogger said:
Replacing the coil may not solve your problems.

You say you still get a spark. Is it a fat blue one or weak and yellow-ish? (Fat blue)

Your condenser may also be a culprit and can give the same symptoms.

When you say the coil is getting warm, is it just warm or is it getting too hot to touch.

Fitting a 6v coil without a ballast resistor could cause it to heat up.

Did that motor run okay before you changed from a generator to an alternator?
Click to expand...

My responses:

Replacing the coil may not solve your problems.

You say you still get a spark. Is it a fat blue one or weak and yellow-ish? (Fat blue)

Your condenser may also be a culprit and can give the same symptoms. (Will test it today and confirm result)

When you say the coil is getting warm, is it just warm or is it getting too hot to touch. (warm, I can hold it easily)

Fitting a 6v coil without a ballast resistor could cause it to heat up. (Its definitely a 12v coil)

Did that motor run okay before you changed from a generator to an alternator? (yes perfectly)
 
A flat blue spark suggests there’s nothing wrong with the coil. However...
If the problem starts after warm up, check you’re still getting the same healthy spark. A faulty coil and condenser can work when cold then fail when warm. Check again for that spark when the car stalls.

I’m thinking the fault is related to the conversion from generator to alternator. Did you do that yourself?

Check you got the polarity right on the coil when rewiring for the alternator.

Does the car usually start when cold?

What type of choke is on it?

Under the fuel line spigot there’s a brass nut, undo that and remove gauze filter and clean.
 
Check venting of fuel tank, will probably find vent is blocked.
Run 30 mins, sucks fuel, creates vacuum in tank, runs no more
Remove fuel filler cap and try again
 
Exfrogger said:
A flat blue spark suggests there’s nothing wrong with the coil. However...
If the problem starts after warm up, check you’re still getting the same healthy spark. A faulty coil and condenser can work when cold then fail when warm. Check again for that spark when the car stalls.

I’m thinking the fault is related to the conversion from generator to alternator. Did you do that yourself?

Check you got the polarity right on the coil when rewiring for the alternator.

Does the car usually start when cold?

What type of choke is on it?

Under the fuel line spigot there’s a brass nut, undo that and remove gauze filter and clean.
Click to expand...

A flat blue spark suggests there’s nothing wrong with the coil. However...
If the problem starts after warm up, check you’re still getting the same healthy spark. A faulty coil and condenser can work when cold then fail when warm. Check again for that spark when the car stalls. (engine ran for about 8mins until fully warmed up and then just died, will try again today to see if it starts up and will check spark)

I’m thinking the fault is related to the conversion from generator to alternator. Did you do that yourself? (I am fairly confident about this, I bypassed the regulator, as the Alternator has one in built. I will check whether or not the alternator is charging the battery as it should)

Check you got the polarity right on the coil when rewiring for the alternator. (yes again confident this is right. The engine runs very well for a while, then dies at full warm up temp)

Does the car usually start when cold? (Yes, will try again today and see if it does)

What type of choke is on it? (carb is a weber 32/36 twin throat with manual choke. This is fully open (ie disengaged) - so its not this I am sure)

Under the fuel line spigot there’s a brass nut, undo that and remove gauze filter and clean. (Thanks, I need to find this as the motor has been sitting idle for 10 years)
 
driven said:
Check venting of fuel tank, will probably find vent is blocked.
Run 30 mins, sucks fuel, creates vacuum in tank, runs no more
Remove fuel filler cap and try again
Click to expand...

I run only for 8 mins, then it dies - so 30mins it won't do. I'll see if taking the petrol cap off helps when it is about to die again.

I am going to check the condenser to see if that has failed or not?
 
When you say the motor has been sitting ten years or so, did you have it running well - since its recent resurrection - before you did the conversion to the alternator?

How long do you have wait after its started (and stalled) before you can start it again?

Does it have an inline fuel filter?
 
Exfrogger said:
When you say the motor has been sitting ten years or so, did you have it running well - since its recent resurrection - before you did the conversion to the alternator?

How long do you have wait after its started (and stalled) before you can start it again?

Does it have an inline fuel filter?
Click to expand...
Exfrogger said:
When you say the motor has been sitting ten years or so, did you have it running well - since its recent resurrection - before you did the conversion to the alternator? (It was running well 10 years ago and in a different body (R8) was running well with an Lucas alternator. When i resurrected the engine I put it in a R10 body that was running an old 1108 engine with a generator and external factory regulator. I am not using the external regulator, just using a pole to connect the the Batt terminal. I reused the Field wire and connected it to the IND terminal on the alternator and connected it to the ignition light wire. I believe it runs as kit should because the green light comes on at ignition, but when it starts the green light goes off. I have not yet measured if the battery is charging - I should do this, but battery is healthy).

How long do you have wait after its started (and stalled) before you can start it again? (Until it goes cold - maybe around an hour).

Does it have an inline fuel filter? (Yes)
Click to expand...
 
Could be needle and seat in the carb. Fuel slowly pushes through the needle and seat and eventually floods the car. Then it won't start for 30 mins because it is flooded??

Frans
 
If you've had the manifolds off at some stage it would be worth checking the nut torque in case the new gaskets have compressed a bit. Don't ask me how I know enough to make this suggestion. :rolleyes: :rolleyes:
 
Frans said:
Could be needle and seat in the carb. Fuel slowly pushes through the needle and seat and eventually floods the car. Then it won't start for 30 mins because it is flooded??

Frans
Click to expand...

Just tried to fire it up. Now it starts, splutters a bit and then dies. I spray some 'start ya bastard' in the carbie, starts runs for 5 seconds then stops. I suspect it is a fuel problem, maybe a blockage in the carbie. I'll try cleaning it out as I will replace the fuel filter too, as there must be crud stuck in the system somewhere that is blocking the free flow of fuel.
If it was flooding, normally I could smell burnt fuel and vapours, but no smell at all?
I suspect not enough fuel getting in. The fuel is fresh 98octane, so it should be easy to fire under normal working conditions.
Frustrating!
 
Another check.
Run the car on a battery only.
Take alternator out of equation as this was your mod
 
Well I have turned my attention to a possible fuel problem.
I disconnected the fuel line into the carby and placed it into a bottle as I wanted to measure what the flow rate was.
I cranked the engine for 10 secs and collected 2.5ml (15ml/min x 60 = 900ml/hr.)
This converts to around 0.9lit/hr.
Looking through the manuals, I see no specifications around mechanical fuel pump flow rates, only pressure (2.5-4psi).
Searching the web, I can't find anything similar, but have picked up some specs for Carter mechanical fuel pump for 351 Cleveland which quotes a rate of 80gal/hr (= 363lit/hr) at 6psi.
Even assuming the flow capacity of my weber 32/36 is 1/10th of the carby used on the 351 V8, then my pump should at least be 40lit/hr?
So at 0.9Lit/hr, I think this must be the issue I am experiencing - ie fuel starvation.
So I am not off the planet with my reasoning, does anyone know what the flow rate specifications for a R8/10/12 mechanical fuel pump?
I have ordered a replacement mechanical pump as well as an electric pump (at 70lit/hr) just in case - cheap really - keep it as a spare!
If this doesn't work then its a carby tear down and checking all the jets so they are not blocked!
 
With old fuel tanks in theses vehicles rust and crud can block the end of the fuel pick up in the tank making it impossible for the pump to suck up the fuel. Father in law has just coated an R8 tank this week that was quite rusty inside. Hadn’t caused problems, but I expect it would have.
 
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