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Crossflow Misfire
The Doc - 20/4/08 at 08:36 PM

Hi,
Ford X flow 1600.

Starts fine, runs great then after about 10 miles mising and lumpy. Checked the usual stuff and all seems well when cold/rested.

Added a tank breather just in case of an air lock being developed but still the same.

I guess it could be dirt in the carb, but it seems too consistent - always around 10-15 miles. Always fine starting and initial running.

Not overly hot. Any ideas?

TA

Mike

DavidM - 20/4/08 at 08:46 PM

I had a similar problem with my 1300 crossflow. It was dirt (actually fluff) in the needle valve filter gauze. It would be ok when cold as the float chamber would fill during cranking and initial tickover. Once driving the float chamber gradually emptied as fuel was exiting faster than it could enter. The engine would then start missing and spluttering for some time before dying.

David

bilbo - 20/4/08 at 09:03 PM

What type of carb and choke do you have?
I had this sort of problem on a pinto running a Weber DGAV. Found it was a failed diaphragm within the autochoke mechanism. Basically, the choke stayed on once the engine was hot.

clairetoo - 20/4/08 at 09:24 PM

Have you got a spare coil to try ? I had a similar sounding problem with a crossflow - as soon as I swapped the coil all was well .

graememk - 20/4/08 at 10:10 PM

must admit it sounds like coil to me.

madteg - 20/4/08 at 10:37 PM

Sounds like ballast resister or ballast resisted coil

britishtrident - 21/4/08 at 07:17 AM

quote:
Originally posted by madteg
Sounds like ballast resister or ballast resisted coil


You might well be right with that --- could be a coil that requires a ballast but hasn't got one fitted.

02GF74 - 21/4/08 at 09:01 AM

coil/leads breaking down once hot?

David Jenkins - 21/4/08 at 09:28 AM

quote:
Originally posted by britishtrident
quote:
Originally posted by madteg
Sounds like ballast resister or ballast resisted coil


You might well be right with that --- could be a coil that requires a ballast but hasn't got one fitted.


I think you'll find that your coil will be a molten heap after quite a short time in that situation. You could try to touch the coil can CAREFULLY to see if it's getting hot, but most coils would have boiled over fairly soon.

If you've got points I'd have a good look at the state of the contact breaker electrodes - if they're severely burnt maybe your capacitor has failed.

If you've changed to a Valencia electronic dizzy then make sure that you have some heatsink compound between the little amplifier module and the dizzy body (available from Maplins).

You could also check the state of the rotor arm, and the dizzy cap - look for burns, tracking and cracks.

And if this is like teaching granny to suck eggs then many apologies!


David

Oh... one more thing... I know that you've fitted a tank breather, but humour me with just one test. Next time it coughs and splutters, stop the car and undo the petrol cap. If you hear a whoosh of air, you have a tank vacuum problem - which is what this problem sounds like, and would have been my first thought up to the point when you said that you had a tank breather fitted!

[Edited on 21/4/08 by David Jenkins]

MikeR - 21/4/08 at 12:03 PM

I was just thinking tank vacuum as well.

The Doc - 25/4/08 at 04:15 PM

I forgot to mention,

My initial thought after fittin a breather was coil and/or condenser. I did change these, as well as the points.

The original coil was with ballast resister which I replaced with a standard 12 volt coil and no ballast. Is it possible I have the wrong condenser, as I guess this would have been chosen to match the make and year (with ballast etc.)?