Oil in plenum

[deetes]

TVR390 with MS and wasted spark

Took the plenum off to remove the injectors and found a small pool of oil at the back of trumpet base. Would appear to have come from the breather which is attached to the RH rocker cover.

Had the plenum off a short time ago and there was no oil then and it's done very few miles, as it's running like a bag of s***e.

Doesn't appear to be a lot of blow by with the filler cap off.

No significant smoke from the zorst.

Compressions OK. Maybe a little high on that side on one cylinder.

[ramon alban]

Had the plenum off a short time ago and there was no oil then and it's done very few miles, as it's running like a bag of s***e.

Doesn't appear to be a lot of blow by with the filler cap off.

No significant smoke from the zorst.

I dont think a small pool of oil is a problem, but it seems to me that if the engine is running badly, you should fix that problem, then deal with the oil issue.

The way you describe it, gives no clues for diagnosis, so can you explain the symptoms.

Something to be going on with:

Check the condition of the breather system and to ensure the flame trap filter of chicken wire is in good condition.

http://www.vintagemodelairplane.com/pag ... hers01.pdf

Also check for air leaks in and around the plenum in case it is not sealed when last fitted.

Likewise for all the pipes and orifices that connect to the plenum.

This link may help in fault diagnosis:

http://www.vintagemodelairplane.com/pag ... num01.html

[deetes]

Ramon,

Thanks for your reply and sorry for my late reply to you.

I've been have a lot of bad running issues since I converted to mapped ignition using Ford coil packs.(Megasquirt) It ran Ok, last year, with Megasquirt running the injection and Lucas running the ignition

There's been a misfire at higher rpm and after a good run, there's been one spark plug that was always black(number 6). I've checked everything I can think of, including the compressions. The aforementioned cylinder(6) had a very high compression(250psi) compared to the rest of the cylinders(210psi). In fact if I remember right there was a couple of the cylinders on this bank(RH) that were high.

Possibly oil in the bores??? But no significant smoke from the exhaust

One of the suggestions was to get the injectors, especially number 6, out and have them checked. This is how I discovered the oil in the plenum, this puzzled me as I had the plenum off a couple of months ago to fit new rocker gaskets and it was dryish.

On the subject of having the injectors checked, I can only get them ultrasonically cleaned, as I couldn't find anyone around Aberdeen that could test them. Something to do with the old flapper type injectors not fitting their test rig. So I'll still have to figure out a method of testing them when I get them back

[dnb]

I believe a little bit of oil in the plenum is normal. My Griff has done it for at least the last 100,000 miles...

The best bet is to follow the advice of the first reply - fix the bad running then see what the oil problem does.

It sounds like you may have induced a rich misfire in the tuning somewhere along the line, or even a stuck injector.

[ramon alban]

There's been a misfire at higher rpm and after a good run, there's been one spark plug that was always black(number 6).

One of the suggestions was to get the injectors, especially number 6, out and have them checked.

I can only get them ultrasonically cleaned, So I'll still have to figure out a method of testing them when I get them back

Yup, A probable No 6 injector weeping.

Go here for home brew help.

http://www.vintagemodelairplane.com/pag ... tor01.html