V6 Misfire mystery: Am I being stupid?

[edmason]

My Series 3 is running a 3 litre Ford Essex V6 from a 1971 Capri as far as I can make out. It’s not the later electronic ignition version.

It’s had a misfire since I bought it, which I’ve not bothered with ‘till now as I’ve been doing bodywork. It runs, and delivers enough power to spin the wheels on my gravel drive, and will run at 50 on the road sounding quite throaty, but at tickover its lumpy & producing oily smoke. If you open the throttle abruptly at tickover it will stall, but otherwise picks up OK.

So, I put new plugs in, adjusted the choke, checked the points & dizzy cap, all seem fine, plug leads look newish. If I pull No 4 plug lead off at tickover no real difference, & plug looks wet & oily but not sooty.

Checked the firing order. According to various online sources the firing order should be 1-4-2-5-3-6. It was nothing like, so just for the hell of it I pulled all the leads off and started again with 1-4-2-5-3-6, (dizzy rotating anti-clockwise). Wouldn’t run, so I put it back as was, and realised that its set up to fire 1-6-3-5-2-4. ie: reversed firing order, unless online info that says dizzy rotates anti-clockwise is wrong?

Am I being stupid? Is the firing order a red herring? What should I check next?

[Johnsboy]

I had one years ago, if I remember right firing order is as you have 142536. Off side bank 123 near side bank 456 distributor goes clockwise.

Does it chuff when you take the oil filler cap off when it’s running, if so your no 4 could have done the rings unless cam is worn.

A compression test made be needed to see what’s going on.

Regards
Johnny

[edmason]

You're right, the dizzy rotates clockwise so the firing order is right. Duff onfo online. Took the oil filler cap off and did the old trick with a rubber glove over it. No +ve pressure at all, which would, I'd have thought, rule out a blowing valve or rings. DO pressure or obvious comtaminants in the coolant either. Don't have a compression tested but perhaps that's the way to go.

[Saltydog]

Compression test of course, will rule out a head gasket issue on No4 too ?

[Johnsboy]

Does it sound ok, ie no popping back in the carb or popping down the exhaust. Don’t think the Essex suffered with scrubbing cam lobes, can you see both no4 rockers through the oil filler cap when it’s running to see lift on the valves.

Are the rest of the plugs ok? Definitely needs a compression check. Other possibilities could be valve guides or inlet manifold gasket.

[edmason]

So, running a compression test. Never done this before so help me out. I check compressions on all cylinders, and from a video on You tube I think the pressures should be between 140 and 180, but critically I'm looking to see if one cylinder is significantly lower. If it is that suggests rings or valves (as I've got no pressure in the cooling system, no coolant loss, and no emulsification in the oil I'm thinking not head gasket. To determine rings against valves I seem to remember you put a drizzle of oil in the plug hole & re-test. The oil will temporarily improve reing seal so reading goes up. If not suspect valves. Is that it?
Thanks