3.0L 225 EFi Issues

[Z06_jim]

Don, This is in regard to the conversation we had Fri. morning about this motor.
merc 225 EFI
Serial # 0G558772

I have looked @ everything you suggested and more. any other ideas?

Compression 115 x 6
1/2" spark x 6
tps .96 @ close 3.86 @ wide open by volt meter

All 6 injectors spray
good continuity on all sensor leads
No injector fuel leak
38# fuel pressure
All reeds look perfect
Stator looks perfect and tests good
flywheel has no issues.
Crank position set @ .040
New QL77CC @ .035
Tuner will not move on prybar

Same results on different efi and ignition computers
moving cdm does not change cylinder running
unplugging map sensor makes it rougher
unplugging tps speeds it up

Motor idles on #5 & #6 on the hose, disconnecting 1,2,3 or 4 or all 4 doesn't change rpm or pitch of the motor, a dog out of the hole ~ 300 yards to breakover, then ~ 5700 wide open.

Time to pull the heads?
Powerhead/Tuner gasket?

[Oldgeezer]

Impressive diagnostics. I would imagine that most techs would be most interested in the helpful information that has been offered. Will be interested in the diagnosis and steps that Don offers to a solution to the problem(s). For the inquiring minds, what exactly is happening? Perhaps we can learn from this. Thanks.

[Z06_jim]

Unfortunately this motor has never had simple problems only those that make you scratch your head.
Last time it was losing rpm's past 7/8th throttle. Would run 5700 then as you advanced to full it would fall, sometimes to 4400. what was that?


Stator, and blown powerhead/tuner gaskets

[western angler]

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by oldgeezer &raquo;</TD></TR><TR><TD CLASS="quote">Impressive diagnostics. I would imagine that most techs would be most interested in the helpful information that has been offered. Will be interested in the diagnosis and steps that Don offers to a solution to the problem(s). For the inquiring minds, what exactly is happening? Perhaps we can learn from this. Thanks.</TD></TR></TABLE>

Yes it is, but nothing about the cpu modules. Don will most likely be able to tell you.

[EuropeanAM]

Hmmmn- that's a tough one.

Difficult without my hands on it, but I'm suspecting that your issue COULD be a harness issue. Have run across one or two with injector harnesses that had breaks in them.... would function while sitting "stationary", but lose the injector signals when running (intermittently).

Since I recall you saying that you indexed the flywheel for all six cyl's and checked each cylinder with an inductive timing light- that's where I'd be looking. You might be able to monitor the voltage of the injector harness pairs... but if the break is inside the intake, you'll probably not see the issue unless you pull the harness completely out and do a "resistance and wiggle test".

I'm basing this on the fact that you've ruled out compression- you've ruled out spark- and that narrows the field down to fuel. You've confirmed injector function- you've confirmed PRESSURE... flow was address during our phone conversation- so the only thing remaining is the electrical signal to the injectors. Provided your ECU's (that you tried) are good- that leaves only the "electrical path current travels to fire the injectors" (keep in mind, this is simply an educated guess).

A "color read" of the spark plugs might be helpful... both after an extended idle, and immediately following a high RPM run.

Did you inspect the reeds? Current reed standoff?

Another potential issue could be the sealing rings on the crankshaft- damaged, missing (lets hope not), etc.

One other thing you might check- SHIFT SWITCH. Ensure that it is switching cleanly from "open to closed" when moved in and out of gear.

Shift cable attachment stud should have the nut pulled down "snug"... then backed off approximately 3/4 turn (so that the plastic washer will spin freely beneath the nut). Overightening this nut can (and does) result in shift switch failure.

[Z06_jim]

Did the resistance wiggle check yesterday. checked all the way through to the cpu plug could not make it break. swaped injector locations while I was there top to bottom.

Have not pulled the reed block, but they look and feel good, i.e. not stuck.

Was going to ask about the shift interrupt. I can't get it to switch while shifting although it does work if I pull on it by hand. I'll check tightness I may need to replace some bushings there.

Ordered a bore scope today to inpect cylinders without pulling heads.

Ordering exhaust and powerhead gaskets again today.
Going to clean the tuner again.

[EuropeanAM]

If the shift position switch is not changing when you shift in and out of gear- stop and correct this issue before proceeding.

It is imperitive that the ECU's receive the shift signal.