few OX66 issues

[Kingfish999]

got dual 250hp OX66. would like some advice on how to proceed

1: our starboard engine has for a long time had issues with cold starting. i have come to the conclusion that the engine is not cranking fast enough and is not firing injectors as a result. winky blink gave a code for pulser coil but the real issue is slow cranking. once started and warmed up, engine runs good and starts up no problem. batterys are new (900CCA starting), battery cables to engine are new, cable from relay to sterter is new and larger, swapped starter with the port engine made no difference. using a jumppack on the battery does help it crank some faster and will fire up but battery tests good. when putting an amp gauge on each starter cable, this engine draws a good amount more amps than the port engine does (i think like 270amps verse 200amps IIRC) like the engine is struggling to turn. recently replaced waterpump to make sure it was not causing extra resistance, shaft spun fine to lower unit

engine was rebuild few good few years ago, not sure when this issue started to occur but it might have been around the same time. is there a spec for how much torque it should take to spin the engine with a torque wrench? anything else i should try?


2: a recent issue the starboard engine, with key on engine off, the fuel pump will occasionally keep running. normally it should stop after a few seconds. i normally take this as a sign of a failing computer in the automotive world. am i right to assume?


3: another very recent issue with this starboard engine that just started yesturday. it started this tendency to diesel after turning the key off. when i turned off the key, it ran for 5 seconds before turning off. it did this 4 times in a row but then stopped doing it. it sounded like the reason it finally stopped was because it lost fuel pressure more than lost spark. this is another indication i might have a bad computer. unless its something like they key switch is bad


4: port engine starts up and cranks great. but it coughs quite abit and dies. usually takes a good 20 keystrokes for it to fianlly warm up enough that the coughing becomes minimal and doesnt die as frequent. idle rpm seems good, throttle blades and TPS adjusted to spec. wondering if possible reed valve issue. recommendations before i take the intake off to inspect them?

[Keithbaja]

Ck for bad grounds and for voltage drop on the pos side. U can check reeds with a sheet of plastic over each intake port. Hold taught and watch action. Those oxxys 66 are damn good motors

[zenoahphobic]

You say engine was rebuilt some time ago. Was the head(s) machined down?

The only relationship with the engine being hard to crank and deiselling is that the compression has been significantly increased.

However deiselling usually happens when a significant heat source remains in the combustion chamber unlike the spark plug electrical supply cannot be switched off.
Usually this is excessive carbon deposits on the spark plug, but can be on the piston head but unlikely on this engine. They retain a glow, that is high heat or a point source of heat.
Again, but probably unlikely in this engine, with a clean plug even of normally correct heat range, can keep glowing long enough to sustain ignition if the engine was revved excessively at extreme high RPM’s.
Just trying to point out a possible relationship, some area to explore (compression, carbon deposits, spark plug heat range, high revving in neutral).

[Keithbaja]

For a engine, any gas engine it MUST have fuel to diesel. Usually cheap fuel or high idle. On that motor a leaking injector can be the issue.

[Kingfish999]

the heads were resurfaced but not significantly milled. i cant imagine enough to raise the compression ratio that much to make a slow cranking. even milling heads a decent amount on a automotive engine will only gain a tiny amount more compression unless the chamber is tiny. for example the heads on my truck if i milled 0.020" off would only gain 0.2 more compression ratio by reducing like 3cc of chamber size. but it has crossed my mind

the dieseling issue is defiantly separate issue than the rebuild. i want to say the engine was rebuilt like 5-8 years ago? hard to remember as both engines were rebuilt (one of them twice) and my concept of time is not great. the dieseling issue is only a very recent occurrence. and i dont think its mechanical because it literally happened 5 times in a row for the same amount of time acting like i never turned the key off. either like a stray voltage kept the computer going

the dieseling and fuel pump running constantly when KOEO is making me suspect the computer. since the computer controls the when the fuel pump is on, fires the injectors and con*****ing ignition i would assume it is the most likley suspect. I might have a friend with a spare computer. but i will check grounds.

the hard cranking has been an issue for years cause i made a post like 4 years ago related to this issue. i originally suspected pulser coil issue but thats when i realized the slow cranking was the issue. never solved the issue but i eventually found a workaround that lets me get the engine started when cold. i realized that when KOEO, putting the throttle to WOT forces the injectors to pulse abit (almost like an accelerator pump on a carb). so when i switch the key to RUN and the fuel pump is running for a few seconds, i pump the throttle to WOT to force the injectors to get some fuel in the engine. its usually enough to get the engine to pop a few times and crank fast enough to ge tthe injectors firing like normal. its defiantly not a fix but it has gotten me by for years now. but i would like to fix it permanently. i jsut have to figure out why the engine cranks soo slow

i did compare voltage drop between the 2 engines. as well as measuring the amp draw. i dont remember the voltage drop but it was not significantly enough for me to say its the issue. the amp draw did make me think that maybe something mechanical with the engine is causing the slow startup

if i remember to, i will put a torque wrench on each crank and see how much it takes to spin each crank. then ill try it with the plugs out so compression is not a factor. i also have the original Yamaha battery cables in good condition, ill run them in parallel to make sure the battery cable is not the issue

[zenoahphobic]

You raised an advantage not available to most: another motor to compare with. I am referring to slow cranking motor.

I don’t think you have swapped starter motors.

Depending how far you want to go, many things come to mind some of which you have ruled out and perhaps you should revisit with a clear mind.
You can swap most of the electrical system: starter, battery, flywheel/coils (or just remove to observe the lessening of friction), LOWER LEG (could even have significant drag from your water pump) and WIRING.

Not being there, I can only come up (with an exhausted list if you want) with random things. If compression ratio is not the culprit then maybe the pistons or rings are different, or your bearings are tight through slight misalignment, your crankshaft could be bent, and if journals were reground maybe irregularly. Some of those possible culprits won’t loose there added friction when the engine heats up. But you may detect a slight loss of peak horsepower. So there is another path to follow if all else fails

[Keithbaja]

Pull all spark plugs and keep in order. Look for any variance. Pull plastic flywheel cover. Spin in clockwise direction. Now starting to turn then rock back and forth, checking for play and rimrock. The bearings in that motor are plastic caged needle bearings. And its very easy to sea if there is a issue. If there is a issue,, pull gear case and recheck. V6 two stroker with A ox Senser... SWEET !!

[Kingfish999]

we did swap the starters hoping it might be the issue (also hoping not because $1k for a starter is kinda crazy). when i first tried to tackle this few years ago we did swap pretty much everything from one engine to the other. did not find the issue. even got a few spare parts like flywheel, pulser coils and such.

we just replaced the waterpump in it couple weeks ago. it was trashed and the housing was melted pretty bad. spinning the shaft, does not feel like the lower unit is the cause of resistance. do have good water pressure now which is good.

might work on it more this weekend

[zenoahphobic]

Check also starter engagement to flywheel, slight misalignment there, or even a buckled or out of round flywheel can cause excessive binding. I think you can check this by manually turning out the Bendix gear for fit around various crank positions.

[Keithbaja]

A starter for 1K is nuts for that motor.. A few weeks ago I R'n'Rd a Volvo PENTA starter. A KAD 43 Super Charged, Turbo, Intercooled Bad boy.. Gave the starter to my custermer at my cost of $1,389.00. Yikes !!