51 replies to this topic

[KernowCooper]

I'm just going to whip the head off I think

The reason I said it again is above, I didn't want the OP whipping it off and not being able to do the full compression tests you mentioned and narrowing down the fault.

[Outofthegame]

I'm going to take the head off, if there no head gasket issue I will come back and do a compression test. 

 

The fact that it is cylinder 2 and 3 only makes me think that it is this. 

 

No matter what the cam or ignition timing were set at it wouldn't ONLY not fire on those two cylinders. 

[Outofthegame]

I believe there was oil between the two cylinders and it hasn't set properly at all, or at least I'm hoping hugely

 

Cam timing, is there a way to tell if it is 180 degrees out? such as when no1 is cylinder is firing so both valves are on the rock, there should be a certain valve doing what. 

Edited by Outofthegame, 26 May 2014 - 10:21 PM.

[dklawson]

When #1 is at the top on its FIRING stroke, the rocker arms above it will be loose and can be wiggled by hand (the valve springs are not compressed because the valves are fully closed).  If your timing marks say #1 is at TDC and the rocker arms are tight (valve springs being compressed) then you are at #4 TDC on its firing stroke (rocker arms above #4 will be loose to wiggle).  

 

Turn the engine over by hand to make sure you have #1 at TDC on its firing stroke as I describe above.  Then remove the dizzy cap and look at where the rotor is pointing.  That cap terminal should have the plug wire for cylinder #1 and the others follow around the cap counterclockwise in the order 1-3-4-2.

 

EDIT:  I also was curious about how you determined 2 and 3 are not firing.  How did you determine that?

Edited by dklawson, 26 May 2014 - 11:37 PM.

[Captain Mainwaring]

I'm going to take the head off, if there no head gasket issue I will come back and do a compression test. 

 

The fact that it is cylinder 2 and 3 only makes me think that it is this. 

 

No matter what the cam or ignition timing were set at it wouldn't ONLY not fire on those two cylinders. 

 

 

Pointless

 

Think it out for yourself what will happen if you put the cam timing 180 degrees out.

Edited by Captain Mainwaring, 27 May 2014 - 01:35 AM.

[Yoda]

What you need to do ( as suggested above by Doug and captain Mainwaring), is work through the firing order logically and check that each pot has all it needs to fire. On each ignition stroke per pot you need three things. 1, compression, 2, fuel and 3, a spark. If any one of these things is missing, it will not fire. First to check is compression. make sure the cam has closed the valves at the right time. If so and all is sealed, you will have requirement no 1. Convince yourself that each pot is getting fuel, you now have 1 and 2. all you need now is a spark to ignite the explosive compressed mix. If the dizzy is pointing the spark at the compressed pot full of explosive compressed fuel when the valves are closed, it WILL fire.

 

As Captain Mainwaring said. sit down and work out what will happen if the cam is out! what pot is under compression when each plug is firing in the order of 1 3 4 2.

 

An easy way to see what is happening is to remove the rocker cover ( Gasket cost £2, two minutes work ) and spin the engine with no plugs in. watch the rockers while poking thumb over each plug hole. if the valves are up but your thumb is not pushed away from the plug hole, you have no compression. If you find this, you then need to go deeper and investigate why. ( cost, Nothing, ten minutes work )

 

This simple check can tell you something before you remove the head gasket. ( cost £20, and two hours work )

 

Shame, i cant just pop round, we would have a diagnosis within ten minutes.

 

We dont wish to sound like we are having a dig at you, but a few simple tests with minimal tools ( most people have at least one thumb! ) can reveal a lot. If you need anything explained on the Otto cycle and positioning of valves at a given part of the cycle, just ask,( we all have to learn at some point.) but i am sure you already know this having built the engine yourself.

 

Edit. Under no circumstances, re use a head gasket if you do take it off to have a look. Always fit and torque a new gasket to avoid disappointment later. 

Edited by Yoda, 27 May 2014 - 04:46 AM.

[Carlos W]

Remember firing order is from the radiator side (i think)

[Outofthegame]

I'll check the compression using the thumb method, thanks for this, it's a great idea. 

 

Doug: Thank you for your explanation of the what should be doing what. I can confirm that when the timing marks on the front pulley are aligned the rockers on number 1 cylinder are on the rock, and when this happens the distributor rotor arm is pointing at the two o'clock position. 

 

Thanks for your help and I understand your frustration. 

 

Dizzy is set 1-3-4-2 starting at 2 oclock and finishing at 11oclock anticlockwise. Number one cylinder being closest to the radiator end and 4 being on where the heater take off is. 

 

With the cam I've got on, there is going to be some valve overlap 

Edited by Outofthegame, 27 May 2014 - 08:59 AM.

[Yoda]

I assume you are using a 1275 gasket with the pocketed block?

[Outofthegame]

I am using a 1275 gasket an old BK450 I had lying around (not used obviously) I believe. 

Edited by Outofthegame, 27 May 2014 - 09:12 AM.

[Outofthegame]

I used to use copper gaskets back in the day, looks like things have moved on

[Yoda]

I only ask about the gasket as with most A+ mods these days, a BK450 is the only one to use. If you had used a cheap one then maybe you would have been correct in your diagnosis. Do the compression check i mentioned and make sure that the firing order is maintained and you should have an answer. 

 

 

Dizzy is set 1-3-4-2 starting at 2 oclock and finishing at 11oclock anticlockwise

 

 

This bit bothers me. If you are going anticlockwise, surely you will end up at 4 o'clock.

 

I think maybe we have found the answer!

 

check and double check what you have done here. Make sure you have gone round the dizzy the right way. Its an easy mistake and i have seen it many times when out on call.

 

Pop the dizzy cap off and crank the engine with the coil disconnected. watch which way the rotor arm turns. this is the direction you need to go with the leads in order 1342.

 

2 o'clock to cylinder one, 11 o'clock to cylinder 3, 8 o'clock to cylinder 4 and finally 4 o'clock to cylinder 2 

 

Fingers crossed, we have found your problem.

 

Please let us know what you find.

Edited by Yoda, 27 May 2014 - 09:32 AM.

[Outofthegame]

11 o'clock maybe was a bad choice of clock point. Basically 1-3-4-2 with 1 at 2 o'clock and then going round in the above order with 2 finishing said order before 1 starts it again.

[Yoda]

OK.

 

Let us know how you get on then.

 

Nothing else is jumping out at me right now. I need some sleep. LOL

[dklawson]

Doug: Thank you for your explanation of the what should be doing what. I can confirm that when the timing marks on the front pulley are aligned the rockers on number 1 cylinder are on the rock, and when this happens the distributor rotor arm is pointing at the two o'clock position. 

 

I'm sorry, that is not what I said.  I don't want to make too big a deal about wording, but this is an area that is often confused by the choice of words.  I avoid the words rocking, crossing, and things like that.  If I could avoid the words "rocker arms"... I would.  I said the arms should be loose and free to wiggle by hand indicating that the valves are closed (their springs are not compressed).  When people say the arms are rocking, they typically mean one arm is moving down while the other is coming up.  That is a totally different thing/meaning.  It is a totally different period in the Otto cycle.

 

So I am clear on your meaning, when #1 piston was at TDC with the timing marks lined up, were its rocker arms loose or tight and where was the rotor in the distributor pointing?

 

In my last post I also asked how you determined that 2 & 3 were not firing.  What method told you that these cylinders are having problems?