'90 4.3 2bl Mercruiser - compression test with various wires disconnected?

[denhajm]

Iboats crew: I've got my exhaust manifolds and elbows off for replacement. Thought I'd do a compression test and leak down test while I have the easy access. Test kits will arrive tomorrow. With the exhaust manifolds/elbows off, there are several electrical ground wires which are currently disconnected from those components. Is there any harm to cranking the engine do do the cylinder compression checks with these wires disconnected? I don't want to fry any electronics needlessly.

Also, is it okay to leave the spark plug wires connected to the distributor cap? Sorry, haven't done this for a while.

Thanks!

 

[Bt Doctur]

I would disable the ign coil to avoid sparks by removing the wires from the coil
there usually are no extra wires connected to the bolts for manifolds and risers?

 

[denhajm]

No Title

The Starboard elbow has some electrical components mounted to it in the front (see photo with wiring harness). Similarly, the port side had a bracket with some electrical items mounted to it on the inside. These are all disconnected at the moment as the elbows are off the engine.

 

[Bt Doctur]

thats better ,there the shift plate on one and the ign module on the other 1 bolt has a ground wire for the module and 1 wire going to the bottom of the dist

 

[denhajm]

So can I leave these disconnected wires 'flopping in the breeze' while I crank the engine for compression testing, or should I ground them to the engine somehow?

 

[NHGuy]

Just make sure you don't ground any positives.
If you really want to isolate it electrically get yourself a start button and hook it to the solenoid. With the button you only spin the starter and don't energize anything else.
Don't forget to open the throttle so there is no suction in the intake manifold as you crank.