Horrible misfire - where do i start?

[super trimbo]

Out of the blue, my marina 1275 engined van developed a really bad misfire today.

It started intermittently and now its there all the time with the occaisional back fire? I weas thinking of raplacing the leeds one by one and testing after each replacement, as well as looking the points etc

Any other ideas?

[izzi]

hi,
Sounds daft, have a look at the engine when its dark, it may show a few sparks when ticking over.
Could be cracked distributor cap or rotor arm. look for simple things first.

Good luck


Roy.

[hanvyj]

Is it running on all four cylinders? Take the leads out one by one (careful not to get shocked) and if it doesn't change you have spark not getting to that one cylinder.

[simmitc]

Try the condenser.

[bmcecosse]

Sounds like head gasket to me - feel the compressions with the handle.......or better still - do a compression test.

[super trimbo]

Hi all

Thanks for the replies. Going to go thru things methodically this morn on the elctrical side, if it's still missing think i'll do a comp test.

What PSI should i be looking for on each cylinder on a marina 1275 engine?

[bmcecosse]

Actual figure not too important - they all need to be pretty much the SAME as each other. Check/set the valve gaps before doing the test.

[Dominic]

I had a similar problem a couple of weeks ago. Was about to embark on a week's holiday in the Morris, starting off by driving 250 miles down south so that my daughter could have a proper stylish car for her wedding. After sitting in a traffic jam for an hour just a couple of miles from home in monsoon conditions, it started losing power along with a loud and raucous noise. Sadly the car had to miss out on it's wedding duties.
First thing I checked when we got back after the holiday was the cylinders. All ok there at 175lbs on each cylinder. Turned out to be the condenser causing the misfiring, and the garage when they had replaced a front tie-plate forgot to tighten a couple of bolts at the lower edge of the radiator front panel. It did sound just like a head gasket had gone! 15 mins work was all it took luckily!

[super trimbo]

Right then:

Rep all the leads with new - still missing
Points at correct gap of 15thou not pitted or rough
Spark plugs, 1,2,4 all orange in colour on the lectrode with soot around the base. Number 3 plug very,very oily.
Oil/Water do not seem to be contaminated at the minute.
Changed oily plug for new, still misfiring but did check spark before i pujt this in and there IS spark to ALL plugs

Any suggestions?

[Biggles1957]

Sounds like exactly what I had with my traveller last year - it was the head gasket.

[simmitc]

So you haven't tried the condenser yet? Also, although very unlikely, it really could, just this once, be the coil. Really the advice is already there - the whole electrical side and a compression check. Of course, you don't have to take any notice of the ideas put forward.

[simmitc]

You could also have a quick look in the carb to make sure that there is no blockage in the jet.

[izzi]

Head gasket test,

Did we used to take the radiator cap off (carefully), then rev up the engine a few times and if there were lots of air bubbles coming up, it meant the gasket was gone.

Also white smoke from the exhaust pipe was a indication of head gasket problems.

Roy.

[bmcecosse]

Only if it's blowing into the water-----usually it blows between cylinders without going anywhere near the water......

[super trimbo]

replaced condenser and coil still the same, thats the enitre electrical system replaced piece by piece and tested in between replacements. The carb seems to be fine and given the below i don't think it's that.

Dry Compression test gave the following results:
1: 170 psi
2: 165 psi
3: barely read 20psi? did this 3 times to make sure it wasn't me! (incidentally same cyl as the very very oily plug)
4 : 175 psi

Am i right in thinking next step would be head off for insepction or am i skipping a step?

[mike.perry]

Off with its head - gasket or valve although if it was the gasket I would have expected low compressions on ajoining cylinders. Could be piston or rings

[super trimbo]

Cheers mike, i'd rather it be something in the head!

I'll try and get off tomorrow night after work se what i find...........

[izzi]

Looks like that's what you have to do,hopefully bmcecosse should give you best advice shortly .

Good luck.

Roy.

[bmcecosse]

It's 'NEVER' the coil !!!!!!!!!!!!!!!!!!!! Head off - but since only one cylinder down it' s probably not the gasket - and the 'oil' does rather suggest a piston/ring problem.......

[IslipMinor]

Without wanting to be dramatic I would not run the engine any more until you have taken the head off. A sudden misfire and virtually no compression could be a valve dropped (or at least the valve head) - they do, I have had it happen with No. 4 exhaust valve! It brought a very enjoyable track day on the Silverstone GP circuit to a rather abrupt end.
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As a plug for Norton Heritage Insurance, they were in the pits at the circuit with the recovery truck no more than 40 minutes after calling them - excellent service!