99 3.1l ox66 wont rev (what am i not thinking of here)

[rjcamel2355]

Hey folks, I have a 1999 3.1l 200hp ox66 engine. A little back story, boat ran last year but a little rough, pulled the kids on the tube fine. Decided to do the LP delete, first time out would surge at mid throttle or under, wide open was okay, but it's cold out so didn't trim up or stay in it long. Figured the surging was a fuel line or air leak in a line. So I replaced it all, tried it out today and experiencing more problems.

Problem: Engine will not rev over 1200-1400rpms in forward. The engine will rev perfectly fine in REVERSE, OR NEUTRAL. I know neutral means nothing, but it will rev fine in reverse under load, strapped to the trailer. It will not rev up in forward, just bogs, fuel pressure at rail reads steady and needle doesn't bounce. It will rev fine out of the water in forward gear on the hose (yes I know this means nothing, but scratching my head on what else to try).

1. Fuel pressure is 35-38PSI and stays steady on the gauge at idle, and under all throttle ranges.
2. Compression is even 100-105ish on my china gauge on all 6.
3. All fuel filters are clean (vst, regulator, and water sep filter).
4. Have tried a remote tank.
5. Replaced all fuel lines from tank to engine.
6. Checked o2 and Barbel, both clean.
7. New spark plugs, cleaned plug boots.
8. Cleaned every ground and added die electric.
9. Did the LP delete with a carter fuel pump and relay, using the hp pump connections to trigger the Carter pump along with the hp pump.
10. I have tried diaconnecting the shift interruption switch.
11. I have tried disconnecting the yellow wire under the ecu. The buzzer does work for overheat and low oil.
12. I have set the tps at .52 with throttle plates closed.
13. Injectors were Cleaned about 2 years ago.
14. Fresh oil and fuel in the tanks

 

[99yam40]

have you monitored spark timing to make sure it is advancing properly?

 

[rjcamel2355]

have you monitored spark timing to make sure it is advancing properly?

No sir, I haven't. Im leaning towards a timing/spark issue though.

I haven't disconnected the O2, to see if it would rev up (I know keep it under 4000rpms).

It's just really strange to me that itll rev fine in reverse, but not forward.

 

[99yam40]

reverse does not load it up as much as forward is my only thought on that.

and a lot can happen in 2 years on the injectors

 

[rjcamel2355]

reverse does not load it up as much as forward is my only thought on that.

and a lot can happen in 2 years on the injectors

Less load in reverse than in forward was not something I thought of or considered. Just assumed since the prop was submerged and loaded it would be the same. Rev in reverse would hit 5k quick and easy.

Forward I could hold it wide open, fuel pressure steady around 35psi, but rpm wouldn't get over maybe 1400 tops.

Absolutely on the injectors, ill pull them and have them cleaned/tested....... id be completely happy if that solves the issue. Just not sure if load and fuel flow would be that different between forward and reverse.

........ill take any tips and try them all though.

 

[racerone]

???----In reverse there would be lots of exhaust in the water and thus less load !

 

[rjcamel2355]

???----In reverse there would be lots of exhaust in the water and thus less load !

That's the only thing that makes a lick of sense to me.

Exhaust pushing water away from the prop thus decreasing load and allowing it to rev.

I plan to:
1. Swap the old LP pumps back on and see if anything at all changes.
2. Disconnect the o2 plug to see if it changes anything (wont go over 4000rpms)
3. Yank the injectors out and send them off

 

[rjcamel2355]

Disconnected the O2 sensor - No change
Pulled the injectors and mailed them off this morning to Injector Rehab
Re-installed the LP system and checked them via the squeeze ball test to see if any leaks...


Really thinking this is an electrical/spark problem under load....

Is there a good test for the Knock Sensor, and Crankshaft Position sensor?

Other thoughts are a weak-failing stator

 

[99yam40]

some motors limit RPM while in neutral, but have no idea if yours is one of them.
I am not sure how the ecu limits the RPM, dropping injector firing or spark on some cylinders maybe.
need to make sure the ECU sees it is not in neutral when in forwad gear

timing light should show if spark it advancing and show good steady spark on the plug you attach it to.
might move it to different plug wires to see if they all get steady spark

 

[rjcamel2355]

some motors limit RPM while in neutral, but have no idea if yours is one of them.
I am not sure how the ecu limits the RPM, dropping injector firing or spark on some cylinders maybe.
need to make sure the ECU sees it is not in neutral when in forwad gear

timing light should show if spark it advancing and show good steady spark on the plug you attach it to.
might move it to different plug wires to see if they all get steady spark

It's a 1999 3.1L 200hp V200TLRX if that makes any difference.
1- Doesn't limit RPM in neutral (will rev in neutral, and in reverse), just bogs and stays steady just under 2000RPMS in forward.
2- Tried to disconnect the shift interrupter switch to see if it would run/get over 2k rpms in forward, but no such luck.
3. Gonna break out the timing light as soon as the injectors get back and see what I'm getting at idle vs under load.

I know you're pretty familiar with these things (been scouring forums trying to find anything similar for a couple days now).

I do plan to try to mist some fuel into the throttle body and see if it "picks up" but not really expecting it to.

I reckon I could pick up a "winky blinky" just hate to spend the $100 and it not be a sensor, and instead be a stator, ecu or pulsar coil.

 

[99yam40]

Yep, think it was the Z motors that dropped cylinders at idle and dropped more if you revved it while in neutral

 

[rjcamel2355]

Yep, think it was the Z motors that dropped cylinders at idle and dropped more if you revved it while in neutral

Yessir I believe that is correct. Making "some" headway I think.
1. Checked the knock sensor: AC volts, red lead to sensor wire, black lead to sensor body I could tap on that thing as hard as I wanted with no voltage fluctuation..... Went ahead and ordered a used one.
2. Pulled the plugs again just to look and clear my sanity. 5 looked normal, 1 looked like it was still brand new (These were changed during this troubleshooting process).
3. Checked the injector plugs for signal while cranking, all injector plugs were getting signal (noid light flash while cranking).
4. Ohm tested spark plug caps 5500-5800 Ohms on each cap.

So at this point I think I have a bad knock sensor, and at least 1 mostly, if not fully clogged injector. This actually makes some sense to me, because rail pressure was good, but still acted like a fuel issue. The knock sensor could be contributing to the issue, I've read that they do some weird things when they fail..... perhaps this is a weird thing.

 

[99yam40]

hard to believe one cylinder would cause that much difference, but who knows for sure.
I am not sure what a non-functioning Knock sensor would cause.
but I would think the ecu would probably adjust (Back off) timing to stop a knock

 

[racerone]

A " brand new " looking sparkplug means ----No fuel.--Too much fuel.-----No spark ----or no compression.

 

[rjcamel2355]

hard to believe one cylinder would cause that much difference, but who knows for sure.
I am not sure what a non-functioning Knock sensor would cause.
but I would think the ecu would probably adjust (Back off) timing to stop a knock

I don't disagree with you at all, 1 cyl being down doesn't seem like it would cause all of the problem.... but we'll see.
As for the knock sensor I really don't have a clue, I've heard they will cause weird issues. I've also read if unhooked they will lock timing at 7* BTDC I believe, and restrict RPM to 4000 or less. Again take this with a grain of salt, as it's just the hours and hours of forum posts I've been scouring.

 

[rjcamel2355]

A " brand new " looking sparkplug means ----No fuel.--Too much fuel.-----No spark ----or no compression.

I compression tested it and changed the plugs during troubleshooting. Compression was all 100-105 on each cylinder with my cheap china gauge. Have good spark on all 6cyl at cranking (Verified this last night), it could be dropping under load though.....

Injectors are sent off to Injector Rehab, so I hope to hear "These things are clogged and suck!"

Leaning toward an injector problem as the cause of the clean plug, Rail pressure 35-36PSI give or take a small amount. If the rail has pressure and the electrical connector is saying "inject" the only logical reason for lack of fuel to the cylinder would be injector clogged/stuck closed.

I will retest compression again today, hopefully didn't screw anything up over the course of troubleshooting this thing