Austin Seven Engine Test

Using a Colortune Glass spark plug to test the firing patterns of each cylinder to help diagnose a problem with cylinder three.

Category:

Autos & Vehicles

Tags:

• ausitin
• seven
• colortune

[antonywardle]

you sound like you know what you are talking about! I'd have thought that if you had good mix in one cylinder with a single carb, then all the cylinders will have a good mix. If it isn't then as you say, I'd have thought that either the spark isn't so good, or there is a leak changing the mix. I guess an easy test is to swap around the spark plugs and if there is no difference, the leads, then check that distro cap is ok. I guess an easy check for leaks is a compression tester.

[balbertn]

@antonywardle I have checked all of those things-compression OK-no stuck valves-leads and plugs swapped-disttributor changed-if you look at the valve opening seuence, when cyl 3 is on input, cyl 4 is on exhaust. Therefore if there is a leak between 3/4 combined inlet and 4 exhaust, exhaust gases from 4 can be mixed with input from3 thus diluting the mixture. This suspected leak will only affect cyl 3. This theory will not be proved until the engine is stripped down.I am reluctant to do this now.

[balbertn]

@antonywardle Yes the only effect is that it sounds lumpy when ticking over. Otherwise it is OK. It is great fun. A 1930 Austin Seven RL Saloon.

[antonywardle]

@balbertn They look nice. Just looked them up. Makes my 1967 Datsun Fairlady look modern! Tuning the carbs with colortune is what I was looking up when I found your youtube.

[balbertn]

@antonywardle Anthony-Thanks for your interest. It has been nice to talk. I shall probably leave the engine until it is necessary to dismantle.

[antonywardle]

Looks like you are running a good mix on all four cylinders. Do you have the one carb or is it a duel setup? Is this the 14mm gunson colortune? Thanks for the video, I can now see how they work.

[balbertn]

@antonywardle Only a single carb. The plug is 14mm fitted with an 18mm adapter. My problem is that plug 3 is not firing well at low revs. No change in engine revs when lead removed. However the performance of the engine when reving is OK. The test shows that no 3 is not sparking well at low revs. I suspect a leak betwwen the combined inet for 3 and 4 and the exhaust from 4. I think cylinder 3 is getting exhaust gases from 4 when idling and sucking greatest. I have yet to take the engine apart.

[antonywardle]

@balbertn bummer. You might get lucky and find its only a head gasket. Maybe just keep driving it.

Is it a bit of fun?

[antonywardle]

if the pressure is down on one pot, compared to the others, put a small amount of oil in it. If the pressure goes up, then it is likely your rings are worn. If it doesn't then it is most probably a sticky valve. This is what I've been told in the past, but you might want to check with someone who knows what they are talking about!