Engine Stop running after about 3 minutes

[4129R]

Have you got a 9v coil being fed by 12v or a 12v coil being fed by 9v?

There is a white ceramic resistor attached to the fibreglass above the chassis by the coil and right hand tank. That resistor, if wired up, reduces the 12v supply down to 9v for a 9v coil. This is only boosted to 12v when the starter is cranking, if the original wiring from the starter straight to the coil, is still wired up. 

If the wrong voltage is going through the coil, it won't like it.

[jrnicl5]

Hello 4129R,

I'm not sure if this is the ceramic resistor you are referring to. This is all I could find that had a connection to the coil. Please see the attached photo and let me know.

I had to bypass a wire as there was no connection at all. I may need to replace it. I was not sure how to with what resistor. Any help would be great.

[jbcollier]

The resistor is not being used.  Measure the resistance of the coil's primary circuit.  If it is 3 ohms or more, you don't need a resistor.

[Dilkris]

Isn't that an ignition module to the left of the redundant resistor? Has this had an ignition conversion?   

[4129R]

Hello 4129R,

I'm not sure if this is the ceramic resistor you are referring to.

Yes, that is the resistor which is only used for a 9v coil.

As others have said, it is not in use, and it looks like you have an electronic ignition pack, so probably no points in the distributor.

[EuropaTC]

Isn't that an ignition module to the left of the redundant resistor? Has this had an ignition conversion?   

It looks like the Crane XR700 module ?  I'm not familiar with this design although you guys across the pond should be fine with it.

Jean,

In the first post you mention replacing the coil. I have no idea if that's causing the problem but it might be worthwhile checking you have the correct one installed because some of these modules are fussy about coil resistance.   I found this guide which indicates that the Crane XR700 is designed for a ballasted system.

https://mgaguru.com/mgtech/ignition/ig207.htm

Bear in mind that could be a complete red herring because I'm not sure exactly what you've got there (other than it's not the same as mine !    )  My advice now would be to do a quick search on the module you've got and make sure it's installed with the correct coil, etc.

Brian

[jrnicl5]

Thank you Brian,

The diagram you provided is very helpful. Yes, This is the  Crane Cams XR700 as per the attached picture. The coil I used is surely not for the car. I borrow one from another car to get the engine started. let me replace it with the same as the original one that came with the car.



 

[jrnicl5]

I will also replace the "ballast resistor". So far I have bypassed it. I'll provide an update by tonight.

[rjbaren]

I also have a Crane/FAST electronic ignition in my Twin Cam.  I didn't do the installation but there is a ballast resister in use and the coil I went with is from Crane/FAST.  Might not be a bad idea to give them a call.

[jbcollier]

The problem is: not running after three minutes.  Will start if he sprays ether down the carb throats.  If there isn't spark, it wouldn't start even with ether.  We need more information.

- When started cold, does it run "well-ish"?

- When it quits, does it just shut off?  Does it splutter?

- When you spray ether down the carbs, does it run "well-ish"?  Or, just splutter reluctantly?

[jrnicl5]

Hello jbcollier,

See below for my response:

 When started cold, does it run "well-ish"? Yes

- When it quits, does it just shut off?  Does it splutter? it shuts off.  no splutter

- When you spray ether down the carbs, does it run "well-ish"?  Or, just splutter reluctantly? After the shut-off, it would crank and not start. I would spray and will run again and shut off after a moment. I would accelerate to give more gas. but it will eventually shut-off

[jbcollier]

Sounds like fuel issues to me.  Unusual that it is only when cold.  A few more checks:

- start it and warm it up until it quits.  Pull the coil wire from the distributor, hold it a 1/4" from the engine (metal part, not carb), crank engine.  Do you have spark? (Im assume yes but worth double-double checking)

- Again, make sure it is in a "will-not-run" state.  Pull the fuel line off the carb and point it into a plastic bottle, crank for 10 secs.  Is it pumping fuel?  Fuel look good?  Ample quantity?

[jrnicl5]

Hello JbCollier,

- start it and warm it up until it quits.  Pull the coil wire from the distributor, hold it a 1/4" from the engine (metal part, not carb), crank engine.  Do you have spark? (Im assume yes but worth double-double checking) ->YES, I can definitely see the spark.



- Again, make sure it is in a "will-not-run" state.  Pull the fuel line off the carb and point it into a plastic bottle, crank for 10 secs.  Is it pumping fuel?  Fuel look good?  Ample quantity? the fuel flow is good. Please note that the fuel pump is new.


I just spent some time troubleshooting the issue. I believe the issue is from the SU. The fuel flow is not constant somehow. Usually, after I start the engine and it later on stops,  I have to wait some time to be able to start again. So, this time I increase the fuel flow from the accelerator cable area and started the car right away. It started. I could not let it run at high rev too long to not scare my neighbors...

My option may be is to order a rebuild kit or any suggestion would be great.

[Dilkris]

Quote: "So, this time I increase the fuel flow from the accelerator cable area and started the car right away."
What does this mean? Sorry, please explain exactly what you did - did you just increase the idle speed by adjusting the accelerator cable at the carburetor linkage?       

[EuropaTC]

If you're getting a good spark and you're certain there is fuel in the float chamber but after 3 minutes or so it stops and you can only start it with one of these "cold start" ether/acetone sprays then it's a real puzzle. You've got the spark timing right otherwise it wouldn't run at all, so in theory you've got everything in place.

I'm struggling. Two things come to mind - firstly the coil overheating and unable to provide a strong enough spark for a petrol mixture, but enough to show signs of life with ether because it's a more flammable mixture.  If it won't run once the ether has burnt off and you should be running on petrol then I'd try touching the coil and seeing how warm it is. Should be warm but not hot.

Another vague memory comes up from years ago when I ran a Mini with SU (not Stromberg)  carbs and the piston/needle kept sticking, usually after some steady cruising then cutting out. Then it would drop and the car run fine again. I only found it by sheer fluke, the piston dropped when I was "waggling wires" by the side of the road. 

I guess the lesson here is to check the carb is functioning properly;  piston moving freely, no nicks in the diaphragms, float heights ok, needle shutoff valve not sticking, etc. That's a desperate hope, but if you're sure there's a good spark & fuel to the carbs then it's the next place I'd look.

Brian