Hi All

Brief history of the car: Escort Cosworth pushing around 500bhp, T4, 8 greens, swedish inlet, P8 with pectel, ETC.

I purchased this car a week or so ago with a cold running problem (misfiring on number three) which was supposedly a cold start mapping issue due to the fact the ecu was changed to enable the use of Anti lag (not yet been used). So today i put a resistor in where the E.C.T is to fool it into thinking it was warm, but still the same problem.

so as i was under the bonnet with it running (like shit) i could hear a chuffing noise from the inlet plenum, so i'm thinking valve burnt out, anyway i have to go to work at this stage, thinking i'll do a compression test later.

I get home 5 or so hours later and take out the plugs, start to do the test and (bear in mind its a low comp engine). 1=110, 2=110, 3=110, 4=110 and they would hold pressure forever, so i think cool it's a plug or something basic like that, anyway i was sure it was a valve due to the chuffing.

So i decided to test number 3 again, and there was no compression at all this time. WTF is going on.

I kinda have a theory of my own but don't really want to say just yet, because i don't want to influence your diagnosis.

Please let me know what you think

Regards: Bart

 

loose valve seat ?

 

Sticking INLET valve.
tabetha

 

Hi guys.

Very close but i have fixed it tonight . And it turned out to be the small valve spring on number 3 inlet, I could push the valve down with my thumb easily, so i think the outer spring was so weak it could'nt overcome the oil pressure in the tappet.

Cheers: Bart

 

Valve springs only function is to close the valve, they do NOT overcome any pressure in the tappet, obviously if they are broken/weak they cannot return the valve back onto it's seat (against the inrush of air), they will "STICK" where they/it are ie open.
It's nothing to do with the tappet, unless that is sticking.
tabetha

 

Hi,

I think you'll find that if there is no valve spring pressure the tappet will jack itself wide open under oil pressure and will hold the valve open slightly.

This is exactly the reason you have to squeeze out all the tappets when you remove the cams or followers on any engine with hydraulic tappets, otherwise you can have trouble starting the engine due to lack of compression

When the piston is travelling upwards on it's compression stroke there is no inrush of air due to a higher pressure on the underside of the valve.

Regards: Bart