Plug lead ordering & compression

Post by **dplant_uk** » Mon Oct 08, 2007 11:22 am

From the distributor cap what is the order of the spark plug leads? I am also assuming it runs 1 thru 4 from front to back, please confirm.

Also, what is the compression reading I should get from the engine, I will stick a compression measure on later to check. The engine is trying to get going but not quite there so wanted to check these things.

Post by **Welung666** » Mon Oct 08, 2007 11:27 am

Number 1 plug is closest to the radiator and the firing order is 1342. They run anti-clockwise round the distributor.

Post by **dplant_uk** » Mon Oct 08, 2007 2:00 pm

Hi, don't mean to sound thick BUT... is this the order of spark plugs from front to back based on the firing order in your answer:

RAD 1 3 4 2

or do they simply run like this:

RAD 1 2 3 4

and that the firing order relates to the order driven by distributor?

Post by **MoggyTech** » Mon Oct 08, 2007 2:02 pm

Dizzy rotation is anti-clockwise, firing order 1342 with plug lead one nearest rear firewall.

Compressions depend on engine size CR and engine health.
Difference between cylinders is more important. (10% max)
My 1098 returns 12BAR (174PSI) on all 4 cylinders. (Newish engine)

Anything above 130PSI is good going on a tired engine.

Cylinder Numbers are 1234 with 1 closest to radiator

Post by **bigginger** » Mon Oct 08, 2007 2:40 pm

dplant_uk wrote:Hi, don't mean to sound thick BUT... is this the order of spark plugs from front to back based on the firing order in your answer:

RAD 1 3 4 2

or do they simply run like this:

RAD 1 2 3 4

and that the firing order relates to the order driven by distributor?

The leads need to be arranged so that the first goes to 1, the second to 3, third to 4 and fourth to two. It's how the engine is designed - do it differently, and the spark will happen at the wrong point of the piston cycle, thus not running the engine

MoggyTech wrote:Dizzy rotation is anti-clockwise, firing order 1342 with plug lead one nearest rear firewall.

Conventionally, plug 1 is nearest the radiator, not the firewall.
a

Post by **dplant_uk** » Mon Oct 08, 2007 3:05 pm

bigginger wrote:
dplant_uk wrote:Hi, don't mean to sound thick BUT... is this the order of spark plugs from front to back based on the firing order in your answer:

RAD 1 3 4 2

or do they simply run like this:

RAD 1 2 3 4

and that the firing order relates to the order driven by distributor?
The leads need to be arranged so that the first goes to 1, the second to 3, third to 4 and fourth to two. It's how the engine is designed - do it differently, and the spark will happen at the wrong point of the piston cycle, thus not running the engine

MoggyTech wrote:Dizzy rotation is anti-clockwise, firing order 1342 with plug lead one nearest rear firewall.
Conventionally, plug 1 is nearest the radiator, not the firewall.
a

Thanks guys for quick responses. Great forum.

I will now have to clock watch until I can get out of work to play with the moggy.

Post by **MoggyTech** » Mon Oct 08, 2007 3:32 pm

quote]

Conventionally, plug 1 is nearest the radiator, not the firewall.
a[/quote]

But isn't the plug lead from the dizzy for #1 cylinder closest to the firewall? e.g. the rotor arm points to the firewall (10' O'clock roughly) on #1 firing stroke. Sure is on my car. #1 spark plug closest to radiator.

Post by **bigginger** » Mon Oct 08, 2007 4:24 pm

Not on any of my cars, it isn't - bottom right, nearest the rad, arm @ 4 or 5 o'clock
a

Post by **Axolotl** » Mon Oct 08, 2007 4:29 pm

Not on any of my cars, it isn't - bottom right, nearest the rad, arm @ 4 or 5 o'clock

Ditto.

I think it is possible to assemble the distributor with the offset key drive 180 degrees out, which would give the firing positions you have, Moggy Tech.

I seem to recall a thread on here where somebody had bought a reconditioned distributor like that, and couldn't work out why their engine wouldn't run with the leads in the old "correct" positions.

Post by **bigginger** » Mon Oct 08, 2007 5:05 pm

It is simple to replace them 180 degrees out

a

Post by **MoggyTech** » Mon Oct 08, 2007 6:44 pm

Looks like I have two distributors with the offset key assembled 180 degrees out.

Oh well, something a bit different. Both are 25D4 units.

Very strange having two the same (I haven't rebuilt either of them)

Post by **dplant_uk** » Mon Oct 08, 2007 7:09 pm

Oh bugger, my compression readings are thus:

60, 38, 60, 80

advice sought please.

The moggy is 1950 MM, the manual states 918cc, so it won't hit 175 PSI ever!

Post by **MoggyTech** » Mon Oct 08, 2007 7:19 pm

dplant_uk wrote:Oh bugger, my compression readings are thus:

60, 38, 60, 80

advice sought please.

The moggy is 1950 MM, the manual states 918cc, so it won't hit 175 PSI ever!

Not good. Looks like worn rings/bores on all 4 as well as possible burnt/leaking valves on the cylinder giving 38 PSI.

You could try a wet test. Squirt a little engine oil into each cylinder through the spark plug hole and retest. A large improvement = worn pistons/bores, little improvement = valve problems, but could still be both.

Post by **bmcecosse** » Mon Oct 08, 2007 8:56 pm

These compressions are desperately low - but are you doing the test correctly? You need fully charged (good) battery and hot engine - all spark plugs out, and throttle wedged open slightly. then crank the engine over until a steady reading appears on the gauge.
And -re plug leads - ANY lead can be made #1, the rest just need to follow on in order.

Post by **dplant_uk** » Mon Oct 08, 2007 9:24 pm

MoggyTech wrote:
dplant_uk wrote:Oh bugger, my compression readings are thus:

60, 38, 60, 80

advice sought please.

The moggy is 1950 MM, the manual states 918cc, so it won't hit 175 PSI ever!
Not good. Looks like worn rings/bores on all 4 as well as possible burnt/leaking valves on the cylinder giving 38 PSI.

You could try a wet test. Squirt a little engine oil into each cylinder through the spark plug hole and retest. A large improvement = worn pistons/bores, little improvement = valve problems, but could still be both.

Thanks for the lead MoggyTech, will have to give it a go.

Post by **dplant_uk** » Mon Oct 08, 2007 9:29 pm

bmcecosse wrote:These compressions are desperately low - but are you doing the test correctly? You need fully charged (good) battery and hot engine - all spark plugs out, and throttle wedged open slightly. then crank the engine over until a steady reading appears on the gauge.
And -re plug leads - ANY lead can be made #1, the rest just need to follow on in order.

Agreed, they are desperately low. Thanks for the advice on pressure testing. I have a pressure gauge that I screwed into each plug hole one at a time, full battery and turned the engine over for 3 seconds - my brother-in-law's advice, he is the tech - a beetle enthusiast.

I will follow up on yours & MoggyTech's advice from way up there in Bonnie Scotland

Cheers, Darren

Post by **Matt** » Mon Oct 08, 2007 10:05 pm

Whereabouts in S'oton are you? its one of the most active areas on this forum and someone will probably be able to come and give you a hand

Also feel free to come and join the SADMOG group, we meet at a different pub every week around the Southampton area (see "Sawfampton taawn" thread in off topic)

Post by **overider** » Mon Oct 08, 2007 10:06 pm

My screw in comp tester says remove coil + connection remove plugs one at a time screw in tester throttle fully open and turn over for ten seconds.

Post by **bmcecosse** » Mon Oct 08, 2007 11:09 pm

I have only ever seen it done with ALL plugs out. Gives the starter motor a chance to spin the thing up.

Post by **dplant_uk** » Tue Oct 09, 2007 7:16 am

Matt wrote:Whereabouts in S'oton are you? its one of the most active areas on this forum and someone will probably be able to come and give you a hand

Also feel free to come and join the SADMOG group, we meet at a different pub every week around the Southampton area (see "Sawfampton taawn" thread in off topic)

Helpful assistance would be great. I'm based Locksheath, work in Hedge End.