Motor that does not run smoothly

[Ghaur]

Hello everyone,

 I am writing these few lines to explain my problem to you.

 I have a 1959 TR3A that I am tuning and I am having great difficulty doing so.

 The engine only runs on cylinders 3 and 4.

 I just replaced the standard ignition with an Accuspark electronic ignition.  Both the ignition harness and the spark plugs are new and I now have a nice spark.  My advance is well tuned.

 Regarding the carburetion, I cleaned all of the jet elements and changed the gaskets.  The level of the tanks is good and the gasoline arrives well.  The sync of the two carburetors is also good.

 And yet I have cylinder 1 and 2 that don't give.  I think the gasoline isn't  going to the cylinders.  I'm sure of it because when I unplug the coils from spark plugs 1 and 2, there is no reaction from the engine, which knocks very hard.  Also if gasoline got into these cylinders without an ignition explosion, it would explode in the exhaust under heat, which it doesn't.

 Could there be some other reason a valve problem?

 What do you think ?

 Thanks for all your suggestions.

[RogerH]

Hi Ghaur,

welcome to the forum,

First simple check - did you put anything in the inlet manifold to blank it off - this has been known to happen.

 

Roger

[billy l]

Hi Ghaur, Remove the air filter from the front carb, run the engine holding the throttle open slightly and look into the intake,  you should be able to see petrol coming out of the jet and being fed into the inlet manifold, if not happening put the palm of your hand over the carb inlet to check for suction, this should give some idea  of what is wrong, either a blockage in the carb or for some reason no vacuum. just a thought' some time ago I replaced the seals around the shouldered bolt  that secures the float chamber to the carbs, one of the seals was too long and was blanking off the feed hole for the petrol to get into the carb, this was gave the same symtoms as yours,Cheers, Bill.

Edited October 25, 2021 by billy l

[Lebro]

1st check you have the HT leads for 1 & 2 the right way round.

 Then check there is fuel in the front float chamber,

Bob

[iain]

34 minutes ago, Lebro said:

1st check you have the HT leads for 1 & 2 the right way round.

 Then check there is fuel in the front float chamber,

Bob

+1.
Also check firing order is correct for anti clockwise rotation for distributor. 

[boxofbits]

If you are running it with air filters on, worth checking the front one is not installed upside down as this will block the inlet. 
 

Kevin

[Lebro]

And check gasket is not upside down, as it will block the 2 upper holes

Bob

[Ghaur]

Thank you for all your answers.  my ignition wiring is correctly assembled in order.  I did these tests with the air filters removed.  there is gasoline in both tanks.  I will focus my diagnosis on carburetor number 1 because I think my problem is coming from this side.

[mikej]

There are two "top hat" shaped black rubber seals between the float chamber and the carb main body. These can become soft due to fuel attacking the rubber. When soft they squash and extend up the securing bolt until the small cross drilled hole (where the petrol flows though the the bolt) becomes blocked. Worth a check but if you have fuel in the float chamber this may not be the cause.

Remove the SU piston pot (3 screws) and remove the piston. You should be able to see fuel in the jet, just below the top surface.

Have you done a compression check?

With the spark plugs in and your hand over the carb air intake is there any suction?

Is the distrubuter Advance pipe connection OK on the front SU? if this is not sealed or missing it will be a huge air leak!

Mike

 

[Lebro]

Remove the SU piston pot (3 screws) and remove the piston. You should be able to see fuel in the jet, just below the top surface.

Agree, also easier to see if you pull the choke right out to lower the jets.

Bob.