Rebuilt engine running on 5 pots

[Adelgigs]

Hi All,

I need some help trouble shooting a misfire. I have just completed a complete rebuild of my 3.0 SC engine and have got it running, albeit roughly. The static disy timing is set correctly but #5 cylinder is dead cold after bit of run, whereas the other 5 pots are all quite warm. Also the end of the #5 high tension lead is cold whereas the other are all warm. The high tension leads are also in the correct firing order.

First I thought it may be a dead spark plug, so I swapped that out. Next I checked the high tension lead attached to a plug earthed to the engine - a nice blue spark. I also checked the resistance on a couple of the high tension leads, which varied from 1.88 k ohms to 3.2 k ohms. Number 5 lead was about 2.88 k ohms which I believe is ok (< 3 k ohms ??). Next I swapped two of the injectors around and no difference.

The disy cap was replace 2 years ago and looks ok, although the rotor is quite old.

When cold the engine shoots straight up to 3000 rpm and slowly settles back to a rough idle. By just touching the accelerator the rpm shoots back to 3000 rpm before falling slowing. As the engine warms it seems to get rougher (cold start system turning off ??).

HELP - any suggestions where to go next ??

Thanks, Simon.

[slakjaw]

check the compression

i hope the valves on #5 arnt too tight

at least that would be a good place to start
let us know what you find

LATE
Kyle

[Rot 911]

kyle is probably right. check the valve gap on #5

[john walker's workshop]

pull out the injector, plug the hole in the intake with your finger and have someone start the engine. any spray to be seen? aim it at a rag, so it doesn't make a mess. and put out that cigar! be sure the plug wire is still on the plug, we don't need any flame offs.

[Adelgigs]

Would that cause a dead cold cylinder - the valve would have to not be opening at all ? The plug is sooting so fuel seems to be getting thru.

Thanks, Simon

[Adelgigs]

Just an update for those who are interested.
Compression tests (finger over the injector hole / removed spark plug) came up with no compression on #4 (valves are adjusted correctly), so the newly installed engine needs to come out again. What a bugger.

No idea what could have gone wrong (new piston/rings/barrels), but perhaps a washer or something got dropped down there either bending a valve or fowling a valve seat. No metalic sounds so I hope the piston/rod are ok.

Will let you know in due course.

Thanks for all the suggestions.

Cheers, Simon

[ChrisBennet]

Simon,
A leakdown test will tell you where the compression is going. I wonder if having the cam timing wrong can have this effect?
-Chris

[jabb]

I would do a compression test on all 6 holes before taking anything apart .