2000 Mercury 200EFI intermittent loss of power, SN 0T158142

[EuropeanAM]

Fuel is a year old, all 75+ gallons of it :) However, it is REC90 with Stabil and Seafoam added. In my experience, while not ideal the fuel should still be good. I seems that bad fuel should cause the motor to run poorly all the time - slow to get on plane, etc.

Why not plug off your fuel line, and connect a PORTABLE fuel tank, with known-good FRESH fuel, of the correct octane?

Quick way to confirm or rule out what's going on!

[SouthernNarwhal]

Thanks for the suggestion Don. I will try running it on a portable tank. I may also siphon some of the fuel from the main tank into my truck and jerry cans and fill up with some fresh REC90. I will keep updating this thread until the damn thing is fixed.

[EuropeanAM]

You keep referring to Rec-90. Unless something has been done to this engine to modify it, I would recommend you use 87 Octane fuel, from a Top-Tier, High-Traffic Station.

ESPECIALLY for this test, but preferably always.

[SouthernNarwhal]

Don, REC90 is what I use because it is what is typically sold on the water where I boat. While I am skeptical about 3 octane points having any negative effects on the performance of a properly running 2 stroke, I will try 87.

[EuropeanAM]

[EuropeanAM]

Fellows- Please take a moment to review the Announcements at the top of the Forum, then open a separate thread for your (separate) engine. Be sure to provide the required info- one of us will be happy to assist you!

[Coxwain]

Did you ever get this issue solved?

[SouthernNarwhal]

I wanted to update this thread - better late than never :)

I ended up borrowing a known good ECU and that seemed to solve the problems. Since that ECU was a loaner, I ended up buying a Brucato ACU (aftermarket ECU replacement) and so far have not experienced any issues. It appears something was intermittently failing in my original ECU as it got hot.

[buster502]

i was thinking there is a place that can test the ECU and tell if its bad and repair the old one,i thought they was real costly

[EuropeanAM]

Simon Technologies repairs them.

[SouthernNarwhal]

I claimed victory too soon...The saga continues! Please help!

I spent a long day on the water on Sunday and for the most part the motor runs great! Starts quickly when cold, has excellent power and response throughout the RPM range, and it even idles well! No excessive smoke. However, if I shut the motor down while hot - it is very difficult to restart. Sometimes, I can bring it back to life by opening the throttle half way but on at least one occasion it would not restart at all. I confirmed fuel pressure (34psi) and good spark on all 6 when I have the no-start condition. The only way I was able to re-start the motor is by pulling all the plugs and wiping them clean. All the plugs were wet with fuel. After the plugs were clean, the motor instantly restarted and idled/ran great.

Background:
This spring, the injectors were sent to Brucato for cleaning (Don was not taking on work at the time). The injectors came back with a clean bill of heath. The fuel rail and the VIS were cleaned and reinstalled with fresh o-rings. All the fuel lines and bulb are relatively new, installed last year. The fuel filter was replaced in the spring at the same time as the injectors. Engine compression is good and even, all between 120-125psi. Fuel is fresh 90 octane non-ethanol (added 30 gallons on Sunday to a month old 10 gallons already in the tank). Tank was completely pumped out in the spring.

Several weeks ago, the I experience the no-start condition just like Sunday. I took the boat to my local Mercury dealer for diagnostics (Duskin Point Marina, Mercury Outboard Premier). The technician was not able to replicate the problem, but had several findings:
Idle was a bit low - and he bumped it up to spec.
He said that the fuel pump supply current kept increasing as the motor got hot - he suggested replacement of high pressure pump.

Based on his recommendation - i replaced the high pressure pump with an aftermarket pump (reused the original o-rings). I also replaced the VST float and valve with OE parts while I was in there. The VST was perfectly clean with no visible debris.
Sunday was my 1st outing after installing the new parts. Motor idles even better, but the no hot start condition persists.

Fuel pressure readings
key on: 35psi,
key off - 34psi,
15 seconds - 31psi,
30 seconds - 30psi,
1 minute - 29psi
2 minutes -28psi
5 minutes - 25psi.

The problem manifests itself as I am coming in to dock after running for a while. Come off plane, idle for a bit, a little back and forth to dock, and shut it off. After sitting for a few minutes, the motor does not want to restart. Pumping the bulb does not help (bulb is full, I can hear the hi pressure fuel pump running, have verified 34psi while cranking, and there is spark on all 6). Opening up the throttle helps sometimes but not every time. Spark plugs are wet with fuel.
On Sunday is was pretty hot (90F + and Sun was blazing).

Please help! What can I check? What can cause the motor to overfuel/flood during hot start?

[lpugh]

Got to admire you vigilance on this matter
Were the fuel pressures taken while the motor was in a fault condition, especially the leak down portion
Check the TPS, CTS and IAT sensor also while in failure mode
Check the VST vent line for fuel dripping at this time as well while applying pressure to the bulb, does the bulb slowly sink with pressure applied
Check the injector driver side wiring for pinches, chaffing or shorts all the way to the ecm. Look very carefully for copper contact with anything

Are there any signs of heat damage to the wiring harness, I have seen motors overheated enough to actually melt the wiring insulation inside the harness causing cross shorts intermittently. Should be able to see signs of this on the outside of the harness though and usually there will be paint burnt off the block as well. Did this to one myself years ago when I picked up a plastics bag on the lower, stuck a piston as well. This would probably only apply if you ever had a power head failure in the past due to a serious overheat condition

[SouthernNarwhal]

Leon, thanks for the feedback!
Yes, the fuel pressure measurements were taken as I was trying to troubleshoot the no-start. I am running around the lake with a full tool kit, fuel pressure gauge, spark tester, etc...
The IAT and CTS are new last fall. When the boat was at the shop just 2 weeks ago, I specifically asked them to monitor all the sensors and the feedback from the tech was that all sensor readings were normal. The ECU I am currently running (Brucato ACU) does not reed the TPS at all, it uses RPM and MAP sensor for fuel delivery calculations.
I have never had an overheat with this motor, and the harness appears to be free from damage. I feel like I have opened, cleaned, lubed and re-connected every damn connector on this motor...several times over.

I am starting to think that for some reason the VST vent line is leaking gas into the intake for some reason. I just changed out the float and needle, is there any adjustment? Can the oiling system be pressurizing the VST after engine shut down and causing the leak?
I am going to pull the vent line, install a long clear tube and see if I get any fuel in it.

[JOE54]

if you advance throttle wot( lots of air ) will engine eventually start smoke real bad like its flooded , made sure recirc check valves are working correctly

[SouthernNarwhal]

If I advance the throttle, the engine starts some times. It usually takes several tries and it does not want to idle. On the occasions when it does not start, it just keeps turning over with absolutely no signs of life. I have confirmed that there is spark and fuel pressure while this is happening. If I take out and clean the plugs (they are wet with fuel), the engine starts immediately.

I have purchased both the engine block check valve as well as the check valve on the bottom of the VST, and will replace them this weekend.

I will also take one more look at the timing at idle. Is there a setting that may be better for rich hot starts? Idle timing is currenlty 4 deg ATDC (if I set it right to begin with).

Any other suggestions?

[JOE54]

back it up to 8 will be leaner at idle open throttle shutters if you need to up rpms , try this , any chance you could borrow ecu again for test, wonder if your having RFI PROBLEM here

[lpugh]

back it up to 8 will be leaner at idle open throttle shutters if you need to up rpms , try this , any chance you could borrow ecu again for test, wonder if your having RFI PROBLEM here

Interesting you mention this Joe as I have seen issues with incorrect plugs, plug wires and alternators that have bad stators or diodes cause some really unusual symptoms, raise hell with the ECM.

[JOE54]

yes sir me too

[SouthernNarwhal]

One step forward, two steps back.

I replaced both the engine block check valve and the check valve on the bottom of the VST. The check valve on the bottom of the VST was definitely not working as I was able to blow through it in either direction. I was quite exited that perhaps I was getting close to getting this thing sorted out and moved on to checking and adjusting the idle timing.

I verified the .462 mark, and the pointer was spot on. I checked idle timing and it was at 0 deg. I previously set idle timing to 4 deg ATDC and so I suspect that the Mercury technician messed with the idle timing setting in order to bump up the idle speed slightly. Isn't there a separate idle speed adjustment screw on the top throttle plate?
I re-set the idle timing to 8 deg ADTC and verified WOT timing is still 24 deg.
All of this was done on the hose, with the ECU disconnected, throttle cable disconnected, all the spark plugs except #1 cyl out, and all the coils grounded (through a spark tester) to the block.

Unfortunately, once I plugged everything back in and put everything back together - the motor would not start. No signs of life whatsoever. Just keeps turning over. Verified good strong spark on all 6, verified fuel pressure, and even moved the idle timing all around in an effort to get it to start. Not even a burp.

I did not have much time to troubleshoot, but am pretty sure that now the injectors are not firing. Spark plugs were dry. I either fried something when setting timing, have a bad connection somewhere, or whatever was intermittent before finally broke all the way. Can't seem to win with this motor, and its not for the lack of trying. Frustrating to say the least.

Any suggestions? What could cause the injectors to not fire? I am thinking of taking it back to the Mercury dealer, but want to check the easy stuff first.

[buster502]

back it up to 8 will be leaner at idle open throttle shutters if you need to up rpms , try this , any chance you could borrow ecu again for test, wonder if your having RFI PROBLEM here

i think i would try another ecu if you can get one like joe said