Spitting back

Could be many things, start with some fresh fuel as unleaded goes off after afew months...

Tim..

Timing out?

Can't be the timing adjustment as such, these engines use all electronic adjustment free ignition.

Could be the ignition module itself (situated on near side inner wing) or vacuum pipe from inlet manifold to ignition module.

Only other timing-related item is the crankshaft position sensor but if this is shot, then you will not get a spark at all.

Luke

The engine

Any ideas what

inner wing)

sensor but

I would have thought timing initially as well. If the timing is not adjustable then is there a chance the current is leaking between the HT leads / tracking in the distributor cap / Rotor ? Possibly putting a weak spark into another plug to the one being fired ? Just a thought.

Other than that the fuel delivery / condition (e.g. water in it) seems possible. If you can, disconnect the fuel pipe at the carb and pump some fuel into a clear clean dry glass jar. Leave it to stand for a while and see if there is water in it (the water will be at the BOTTOM of the jar). If there is you'll need to drain the tank (not down the main sewer either!) and possibly get it flushed out but I have no experience of this so don't know what's involved / cost.

Regards, Steve

Also if it's been left for a year, I would check for corrosion on the electrical leads where they plug in to each other, and if the carb uses a rubber diaphragm, check it hasn't perished.

Stuart.

Ok Story so far....

Head had been decoked...New plugs, new leads, new Coil, New igntion module. Still the car backfires thro the carb. Only thing I haven't changed is the crank sensor?...Any other ideas?

Describe the set up. With only one coil, there's usually a distributor of some sort. Sure you've got the plug leads right for the firing order?

Dave...This system is a distributorless system with a double enbed coil utilising a wasted spark system (2 cyplinders fire a the same time). Cylinder number are stamped on the coil...

Cam timing, leaky or sticky inlet valve.

Right - helps when you say, as you didn't give the car make or model, and carb cars with this arrangement aren't exactly common. What is it? Things like Montegos had distributors with flywheel triggers.

You can still use old fashioned methods to check modern ignition systems, though - a dwell meter might well show if you've got cross firing, and an inductive coupled timing light will still show when the spark actually happens. Mark up TDC on the crank pulley with some Snopack etc and make a wire pointer fixed to a convenient bolt. This will allow you to check the firing point (roughly) of two of the cylinders, and do another mark at 180 degrees on the pulley for the other two. With a wasted spark system, obviously two cylinders should fire at the same time, but this might show if they're cross firing.