Not firing on cylinder 1 and 2

[Graeme]

Hi I have a morris 1100 running a 1098 with extractors and a single hs4 su. Have an issue as cylinder 1 and 2 are not firing. Have spark, fuel and compression. New plugs poits leads ect. I have found intake manifold leaking so fixing that . Am I right in thinking a leak in intake manifold could be cause of 2 cylinders not firing.

[woodypup59]

yes, not enough fuel and air being sucked in.

[Alex]

Pretty basic, but check the leads are on the correct plugs...

[68&86auto]

Why do you say they aren't firing, how do you know?

[111Robin]

Presumably pulling the plug leads and making no difference to the rpm. If there's spark, fuel and compression then the mixture isn't igniting, possibly due to the air leak weakening the mixture.

[CooperTune]

The last three power units I have assembled suffered vacuum leaks on the test stand. The 998 Cooper rebuilt with flat top press pistons and surfacing 295 head to reach 10.2 t0 1 CR. The new Maniflow Cooper type center header flange had not been ground to clear a std 998 Cooper intake crossover tube. The other two were a result of cyl head intake ports being so large the intakes required welding the lower edge of flanges to cover the gasket fully. Steve (CTR)

[Graeme]

Cheers for the tips ended up finding valve clearances out and she is now behaving

[Graeme]

Why do you say they aren't firing, how do you know?

Colour tune and when I removed plug wire there was no change on cylinder 1 and 2 but 3 and 4 there was and had fuel and spark

[Peter Laidler]

Is it fixed and running correctly now then? You don't make it clear......... Can we assume that you had a visible spark when you used the colourtune thinggy. If so, that'll narrow it down to two things instead of three. Now it's just fuel and/or air

[Graeme]

Yes all running and fixed sorry was a bit vague. But yes turned out to be valve clearances causing the issue.