25 replies to this topic

[timmy850]

When mine was that low on 2 cylinders it’d blown the gasket between the cylinders. It wouldn’t start no matter what I tried

[gazza82]

I had a Midget engine running on just 1&2 as the exhaust valves were burnt so low comp on all four should fire. Pour some fuel down the carb .. small amount!

[Mattnumber2]

Whilst the cylinder pressures do look a bit low on 2 & 3, I would expect the engine to at least try to fire, especially if 'Instant Start' (or equivalent) was sprayed into the carb wit the throttle fully open.
Personally I suspect the timing is incorrect by at least 90 degrees.
Best plan might be to get it running, even if it runs badly, the address the compression issue. Re-set the valve clearances then re-time it.

So I ran out of time yesterday to work on the mini, and I'm at work today, but I did want to say, the distributor hasn't been removed since I've owned the car, and it ran for over a year. So unless something inside it broke, or moved somehow, it should still be in the same basic position. I have removed the cap, rotated the engine to TDC on compression, and aligned the distributor rotor with the post for cylinder 1. I checked that again yesterday. The only thing left untested now is the distributor itself. All I know is that it rotates with the engine, is always in the same place at TDC, and a spark tester says I have spark at all cylinders when cranking. Using a timing light while cranking verifies with the pulley mark that timing is set correctly.

[gazza82]

Fuel is still good and clear.

Doesn't mean it's still good enough. The ethanol in the fuel goes off and takes the octane rating right down. Plus it can attract water moisture.

[Steam]

If you have a good blue / white spark at each plug and the firing orderis definitely correct then 5 to 10 mls of fuel down each cylinder will make it fire. If not then it is mechanical (ie valves, compression etc) rather than fuel or ignition.

[alpder]

...and aligned the distributor rotor with the post for cylinder 1...

 

I know so many of us keep banging on about timing that it's getting boring/insulting so I apologise for piling on, but you have a complete mystery here of why absolutely nothing is going 'bang' even with sparks and engine-start squirt. Low compression could well be an issue preventing ignition of (old) petrol/air, but some kind of a kick should still be happening when you mix the volatile squirt stuff with good sparks.

 

So the wording of this statement caught my attention. I'm probably reading too much into one active verb but... how did you "align the rotor", please? The rotor goes on in one place on the shaft which either is the right place or it isn't. It can't be aligned by the fitter except by moving the distributor or (rarely - though I have done this for particular reasons) by changing the distributor's driveshaft gear mesh with the camshaft.

 

Also, it is still in theory possible to be 180 degrees out with the timing, even using a timing light that's sync'd to #1. To be absolutely bet-your-life certain requires checking that the rotor is pointing to the lead of cylinder #1 when #1 (not #4) is TDC on its compression stroke. The most direct way to check which cylinder is on compression TDC (and which is on exhaust TDC) is by viewing the rockers.

[bpirie1000]

Head off i would say.. get the top off. Can then see bores, gasket, valves, cylinder walls, piston rings, piston tops, valve seats, any cracks in block or head..

Engineers blue is your friend with this kind of situation.

[Lplus]

A couple of questions - I'mm assuming the car ran fine before this problem occurred, so how long ago since it ran properly?  Secondly, I don't see any mention of checking valve clearances, so have these been checked?

[Mattnumber2]

...and aligned the distributor rotor with the post for cylinder 1...

I know so many of us keep banging on about timing that it's getting boring/insulting so I apologise for piling on, but you have a complete mystery here of why absolutely nothing is going 'bang' even with sparks and engine-start squirt. Low compression could well be an issue preventing ignition of (old) petrol/air, but some kind of a kick should still be happening when you mix the volatile squirt stuff with good sparks.

So the wording of this statement caught my attention. I'm probably reading too much into one active verb but... how did you "align the rotor", please? The rotor goes on in one place on the shaft which either is the right place or it isn't. It can't be aligned by the fitter except by moving the distributor or (rarely - though I have done this for particular reasons) by changing the distributor's driveshaft gear mesh with the camshaft.

Also, it is still in theory possible to be 180 degrees out with the timing, even using a timing light that's sync'd to #1. To be absolutely bet-your-life certain requires checking that the rotor is pointing to the lead of cylinder #1 when #1 (not #4) is TDC on its compression stroke. The most direct way to check which cylinder is on compression TDC (and which is on exhaust TDC) is by viewing the rockers.

Yes. I removed the rocker cover and turned the engine to TDC on compression stroke. Verified by the rockers on cylinder on both being closed. Where the rotor was pointing, I turned the distributor housing to match up with cylinder 1, the same way I adjust the timing when it is running. I checked the spark with a spark tester that lights up when the plug is firing. Whether or not the plug is actually firing I don't know. Is there a way to actually see the plug sparking, to be sure it is? I'll try the fuel directly into the cylinders suggestion when I get a chance, hopefully today.

[alpder]

To see a plug(s) sparking: remove it, plug on its lead, strap/clamp/tie-wrap the plug so that the metal body is in good contact with the engine (best not to try holding it... can get a nasty shock). Then turn the key and crank, and see if you get a spark at the electrodes. A strong spark should be easily visible indoors, but rather less-so outdoors in strong sunshine.

[bpirie1000]

Any joy with the spark today?


Progress no matter how small is still progress..