7 replies to this topic

[Hectorfleetsond]

Hi all, thought i had seen an answer to this some where but can't seem to find it now.

I have no combustion in cylinders one and two. I have spark at the plugs. If i remove 1 and 2 plugs it starts no problem just on 3 and 4 but if i remove 3 and 4 plugs it doesn't start at all with just 1 and 2. Any ideas to solve this, what could be causing it. Thanks in advance. It's a 1989 998 engine. 

Edited by Hectorfleetsond, 22 June 2026 - 08:20 PM.

[68+86auto]

Have you checked the firing order?

[timmy850]

Have you done a compression test?

[sonscar]

Inlet manifold gasket or head gasket would be my thoughts.Steve..

[gazza82]

When I had this on an online A-series found exhaust valves on 3 & 4 were burnt so hopefully not as bad as that!

[Earwax]

As above

 

Air ingress - at inlet manifold or elsewhere  - spray some 'start you bastard' or similar near the 1,2 junctions 

 

If it is a Weber carb - one side stuck shut - 

 

It could be worthwhile changing over a lead or two - but less likely

 

Compression down/gasket failure - squirt oil down spark plug hole and it may give enough compression to fire- not  a fix but may help diagnose for the next step

 

Sadly if an older unit -it may actually be having two problems - eg one rocker stuck and down on compression next door - so check operation of lifters , lash - tightness of a stud

 

Hope it is something simple and not too sinister

[68+86auto]

There are many things it could be and with the information available to us, it is impossible to know.

 

If a mechanical fault is suspected, a quick test is to disconnect the ignition and crank it. Make sure it sounds like it has even compression. If it is low enough to cause what you describe, the sound will be obvious.

Edited by 68+86auto, 23 June 2026 - 10:54 PM.

[Hectorfleetsond]

Thanks for all the advice/suggestions and tips. Hopefully get time to have a look over the weekend.