3 cylinder 1500

[iainbja]

I have a strange issue with my engine. its a rebuilt unleaded head bottom end had piston rings re bore new shells etc and it drives normally fine I even tow a  caravan with it. all four compressions are equal but only 140 on my compression tester. New rocker shaft and the tappets are set cold to the correct gap.

When the car has not been used for say a week or longer sat in the garage. When I start it it is on three cylinders the one nearest the bulkhead not firing. give it a few revs up maybe drive up the street goes back to 4 and will remain like that all the time until another long rest period,

Got electronic ignition Power Spark the non Lucas one AC Delco I think it powers the rev counter from a cable drive. 

 

[johny]

wonder if a valve stem is a bit tight so it sticks open when left a while but luckily frees off when run for a bit....

[Clive]

I would try a few simple checks. Maybe swap the plug and leads around, see if the issue moves with it. 

(for a moment I tjough you may have swapped a modern 1500 3 cylinder engine into the car. That would be tasty!)

[NonMember]

Does it always do this after a week in the garage? Is it always the same cylinder? Something like johny's idea seems likely but I'd expect it either to move around the cylinders or only happen when it happened to stop with that valve open.

Definitely try clive's idea of swapping the plugs - it may well be that the one in number 4 is a bit damp-sensitive and needs to be warmed up before it works.

[Clive]

2 minutes ago, NonMember said:

Does it always do this after a week in the garage? Is it always the same cylinder? Something like johny's idea seems likely but I'd expect it either to move around the cylinders or only happen when it happened to stop with that valve open.

Definitely try clive's idea of swapping the plugs - it may well be that the one in number 4 is a bit damp-sensitive and needs to be warmed up before it works.

Or one of these, dead handy for diagnosing issues

[johny]

7 minutes ago, NonMember said:

Does it always do this after a week in the garage? Is it always the same cylinder? Something like johny's idea seems likely but I'd expect it either to move around the cylinders or only happen when it happened to stop with that valve open.

Definitely try clive's idea of swapping the plugs - it may well be that the one in number 4 is a bit damp-sensitive and needs to be warmed up before it works.

Apparently some engines do have a tendency to stop in the same place everytime and its why their flywheel starter ring gear can wear in one place☹️

Certainly worth checking everything else first though and then if nothings found remove the rocker cover after the engine has been left a long while and turn it by hand to see if a valve stays down....

[dougbgt6]

Yeh, I've got 3 of those, somewhere! But they are very useful I put them in the East Berks Christmas party crackers one year.

Don't worry about 140, I've got two meters one says all around 140, the other, all around 120! It's how close they are to each other not what the actual number is, within limits!

What colour are your plugs? The rear carb might be leaking? So 1,2 start up 3 joins in but 4 has to wait?

Doug

[Pete Lewis]

i would make sure the sprung rotor contact is in contact with the carbon in the dizzy cap 

check for any side float on the dizzy spindle (less of aproblem with elctronic)  but lack of oiling causes delco to wear badly in the top bush 

dont use any spark plugs with a R in the suffix 

Pete

[daverclasper]

On 29/11/2022 at 14:26, clive said:

Or one of these, dead handy for diagnosing issues

I've got one of those though (fortunately) not had to use it yet. I guess they show that every working generally ok, up until the plug ( which could have failed)?

[Clive]

1 hour ago, daverclasper said:

I've got one of those though (fortunately) not had to use it yet. I guess they show that every working generally ok, up until the plug ( which could have failed)?

They show if you arer getting a spark at that cylinder, but if no spark you don't know if it is cap, lead or plug. But easy to swap stuff around. Thet are a simple but useful diagnostioc tool. I carry one in my toolbag.

[PeteH]

Hi

"A long long time ago" (that bloody song again!). I had a similar problem with a Pinto (Ford) engine. One cylinder would stop firing. I found the problem by accident as it was a dark evening, one plug lead was tracking and in the dark I could see it!, but every time we disturbed it when checking the sytem the leads moved and it would start, as it settled back it was tracking to earth. Replaced the lead and the issue was solved.

Pete

[iainbja]

always the same cylinder tried different leads these are new ones from the Club the Magnicor ones. could be a sticky valve i guess. 

[Clive]

To check the sticky valve theory, next time you start and it misfires, stop immediately and do a compression test on that cylinder. That should tell you. 

[Pete Lewis]

a short spell of misfire on start up indicates a head gasket is letting coolant into the bore 

may not show up as a coolant loss till it gets more silly  but a top up that you have not done before points you in this direction

the coolant gives the misfire till its burnt it off 

a head stud re torque may help  back off each nut 1/2 turn and re torque  do one at a time 

Pete

[iainbja]

Pete your reply makes sense. I have just had the head gasket fail after 5k miles since rebuild.. ran ok but clouds of steam out of the back and it was on three cylinders at times when started from cold. I purchased  payen gasget set and replace it. Did not get the head skimmed because it had never got hot the water and oil also never mixed but of course replaced both.

done about 500 miles since. I have ordered those flange nuts for the A+engine and will replace one at a time retorquing it down.

Hope that sorts it rather than taking the head of again.  

[Pete Lewis]

that seems a good plan   

let us know how it works  out 

as you use washer faced nuts will you be removing the old fla ( or now deformed ) Washers

so make sure the stud threads are clean /no crud binding the nuts 

Pete

[johny]

Strange that the compression is good though. I suppose one of those leak down tests where you pressurise each cylinder stationary and then see if it drops would be more useful? 

[Clive]

26 minutes ago, johny said:

Strange that the compression is good though. I suppose one of those leak down tests where you pressurise each cylinder stationary and then see if it drops would be more useful? 

Even better is you can pressurise a cylinder at teh top of compression stroke, and listen for where air is escaping. ie bore next to it, inlet valve, exhaust valve, water bubbing etc. Far more useful than a basic compression test. I made one from a braken compression tester, attached to my compressor and set at 80psi. Diagnosed a blown head gasket that a compression tester failed to show.