3.5 Efi - Not turning under compression

rod_922 · Post by **rod_922** » Thu Jul 05, 2007 1:36 pm

Hi all

Would like your expertise on this problem if i may:

I have a 3.5 Efi (flapper) engine which was bought from a guy already fitted to kit car i bought, he says it has been totally re-built and was running. I'm now very close to starting it but have come across this problem.

When turning the engine with the spark plugs out everything is fine, as soon as the spark plugs are in it doesn't want to turn, it does a slow quarter turn and then stops (as if the battery were flat, which it isn't) it tries very hard to turn until the main power wire starts to melt. not sure if it's timed right but I’m not getting sounds from valves hitting pistons. Also you can hear compression sounds, starter seems ok as it fly's round when spark plugs are out.

Any advice??

ChrisJC · Post by **ChrisJC** » Thu Jul 05, 2007 2:18 pm

Timing - it's firing before the piston has reached top-dead centre, and firing the engine backwards!

Turn the distributor clockwise a bit and see if it helps....

Chris.

rod_922 · Post by **rod_922** » Thu Jul 05, 2007 2:34 pm

Chris - I'll give it a go tonight and see what happens, thanks again.

rod_922 · Post by **rod_922** » Thu Jul 05, 2007 4:00 pm

We havn't got the fuel hooked up yet so it won't be firing yet

Just trying to turn it under compression - Could it be the exhuast valves not opening for some reason?

Post by **katanaman** » Thu Jul 05, 2007 4:07 pm

can you turn it by hand with the plugs in? With the plugs out how hard is it to turn my hand?
Always test turn an engine by hand and not by starter motor. Its possible the engine is hard to turn by hand but the starter will turn it easy enough trouble is the starter will also break stuff.

rod_922 · Post by **rod_922** » Thu Jul 05, 2007 4:27 pm

With the plugs in it can't be turned by hand.
With the plugs out it seems to turn ok by hand.

??

Post by **katanaman** » Thu Jul 05, 2007 5:18 pm

something isn't making sense here. You should still be able to turn the engine with the plugs in by hand. It wont be an easy turn but it should turn. Valves stuck shut, engine wouldn't turn by hand as the cam would lock so plugs wouldn't make any odds. Same open valves would hit pistons so plugs wouldn't make any odds. If its turning easy by hand with plugs out but locked with them in the only thing I can think of is silly high compression which is doubtful as you would know about that.

Actually just thought if there is something wrong with a rod or bearing its possible it could be locking with compression??

Ian Anderson · Post by **Ian Anderson** » Thu Jul 05, 2007 7:41 pm

Piston hitting the bottom of the plug?
See what the electrode looks like - squashed etc?

Ian

The Original Tom · Post by **The Original Tom** » Thu Jul 05, 2007 10:55 pm

Following from Ian's comment, I read somewhere that some heads (maybe old ones) have shallow plug holes. In later heads these were made deeper (maybe to protect against threads stripping by having more thread to bite to?)
If the engine's an old one that's been rebuilt with new bits, or is just a bit of a 'bitsa' (like mine

) with bits from loads of different engines and eras, he could have unwittingly fitted old-style heads with shallow threads, that you're fitting with long threaded plugs. These will protrude further into the cylinder than they're meant to and as Ian says, hit the piston as it comes up.

Tom.

ChrisJC · Post by **ChrisJC** » Fri Jul 06, 2007 7:08 am

I go with Toms suggestion.
It should be easy do to a visual check on the plug hole thread depth in the head.

Chris.

rod_922 · Post by **rod_922** » Mon Jul 16, 2007 3:48 pm

SORTED

Sorry didn't get back to you all earlier have been away.

The problem (thankfully) was nothing major at all, the main loom wire which was supplied to me just wasn't thick enough, I tried a nice think wire and round she went!!!

Problem now is fuel pump has packed up so still not started it yet.

Thanks for all suggestions anyway, appreciated.