38 replies to this topic

[james962]

Hi all,

All of a sudden, my engine has starting pinking ever so badly. It is a metal on metal sound. It was fine one minute, put it in the garage, then the next day when I went to drive it, it was pinking under load in all gears?

It has been getting progressively harder to start in the morning, however I have put this down to the cold weather...

The car will idle perfectly fine, and will rev freely under no load with no pinking. I took the vac advance pipe off the carb and created a vacuum and the dizzy plate rotates fine. I have the aldon electronic ignition which rids of the points and condensor).

The clamp is tight on the distributor so it is not as if it has rotated.

I don't have a timing light to hand at the moment so have been unable to check this.

I have richened up the mixture slightly (by one flat of the nut), but this has made no difference.

The only thing could be dodgy fuel, however what I don't understand is how it was fine when I was driving it, then the following morning, it was pinking like a

It is a 998 engine.

Any thoughts or ideas is appreciated.


Thank you in advance (excuse the pun )

James

[KernowCooper]

Air Leak on the inlet track? Difficult starting and pinking underload could well be, I's still check the timing though, and are you sure the base plate is returning to its neutral setting with no vacuum?.

Something which nowdays is overlooked is the mechanical advance mechanism, the old cars had a small felt oil reserve which you oiled with your oil can under the rotor arm and this went down the shaft and lubricated the mechanical advance. Worth checking as this could be semi-siezed? I have stripped some down covered in a thin film of red rust and not working corectly.

[smartie93]

what carb are you using? Does it knock with the choke out? is it straight from cold or when up to temperature?

Edited by smartie93, 04 March 2013 - 11:33 PM.

[james962]

I will have a look at the inlet and see if it is leaking. I will also check the dizzy drive.

The carb is a HS4, not tried it with the choke all the way out. I haven't had the engine up to operating temperature, I was paranoid about the pre-ignition, so stopped the engine, however, I will warm up the engine to operating temperature at idle to check.

Thank you for your suggestions so far.

[smartie93]

When I had an air leak the car would backfire instead, you'd get a loud pop/bang through the carb and the engine really struggled to stop stalling. so if your problem is an air leak maybe it's only small and therefore hard to find, change the gaskets just to make sure, they're really cheap anyway :)

[KernowCooper]

You could always spray some easy start around the intake manifold to head and if it revs up theres you leak, then whip it apart and replace the necessary.
Be careful though not to spray it directly onto the hot exhaust or near the car inlet as this could mislead you as well as worn carb spindle.

[jaydee]

Also check tappets clearance and spark plugs
Crap fuel can cause this but if you're running an high CR

[KernowCooper]

I was just mentioning it as I have seen people spray it around all over the place and it gets drawn into the inlet of the carb and people think they have a manifold gasket leak.

[KernowCooper]

Isn't hindsight a wonderful thing and men who never say anything wrong very gifted in their own mind, you never miss a dig

Shame on you

[KernowCooper]

Commonly known as the WD40 test ? where ? ask around the world and I bet you find its not that commonly known, people use what they have to hand and as long as its a spray which will indicate where the air leak is job done

[jaydee]

I think its called the WD40 because its less inflammable than any other spray thingy and you're spraying just above a hot manifold which is dangerous.

[smartie93]

Ask any rolling road operator worth his salt...........

That's quite a small amount of people then......

[james962]

It does not have an air leak from what I can see, squirted wd40 along the inlet manifold gasket and the carb to intake gasket, no change in idle speed. It also doesn't change whether the engine is hot or cold.

If I have the choke all the way out, it doesn't pink. Ie in second gear at 10mph foot down it pinks, but 10mph pull choke out then foot down it doesn't pink. This make me think that it's a fuel mixture issue rather than ignition timing?

As it was running fine last week, this is leading me to dodgy fuel rather than a carb mixture problem?

What are your thoughts?

Thanks James

[smartie93]

take the carb inlet elbow, cone filter etc off and see if the piston moves up and down easily.

what fuel did you use? mine runs fine on supermarket fuel that has sat in it for a few weeks no problem so I wouldn't think it was fuel... is your engine modified? I mean internally not exhaust filter etc

[james962]

Thanks smartie, I will check the piston in the carb tomorrow as it is a bit dark now! In the mean time, I drained the entire tank of fuel and put in 2 gallons of decent RON97, but this has made no difference.

I took a short video, I will see if I can somehow upload it.