94 150s EFI limp mode

[fob1904]

I am posting here for some help!
I took the boat to a marine dealer 100 miles away they keep it for 10 days called me said they couldn't fix it
In the past two weeks with a complete Suzuki manuals I have done the following;
New parts:
TPS set per manual
CDI
Rectifier
Cylinder temp probe
Gear counting coil
Spark plugs
Both low pressure fuel pumps
High pressure regulator
High pressure filter
All fuel lines and clamps
Primer bulb
Anti-syphon valves

Now, since the following parts have been discontinued or obsoleted
I found used exact part numbers
ECU
ICU
Checked pulse coils the resistance is right in the middle of specs
Used a visual spark adapter all cylinders firing

Although the above parts checked good I replaced them one at a time

Checked fuel high pressure 34 lbs held steady shut down held for about 4 minutes
Checked low pressure fuel line running almost 1" vacuum

It's always the same outcome check engine light comes on for 3 seconds then off for a couple of minutes
If I run above 3000 rpm as soon as the check eng light comes on it drops to idle

Sorry for long post and thanks for any help

[Solarman]

What is the temp of your motor when it drops to 3k?
If you pump the bulb when it drops, does it do anything?
What does your tell tale feel like, temp wise when it drops to 3k?
Does the motor run smoothly over 3k, until check engine light comes on? Idle & higher speeds? What is the present top speed/ rpms?
When you mentioned hp filter, are you talking about the cone shaped filter in the lower line of the VST?
Did you look at the check-valves in the low pressure pumps (not included in rebuild kits)?

The check engine light should give you two sets of flashes, then should pause and repeat the same code, it should show all codes in your manual.

Did this problem start recently? Did anything preclude these problems?

Post back when able.

[fob1904]

What is the temp of your motor when it drops to
3k?
Haven't check with an accurate temp probe but it doesn't feel hot

"If you pump the bulb when it drops, does it do anything?"

Nothing the primer bulb is firm not hard but firm

"What does your tell tale feel like, temp wise when it drops to 3k?"

Cool to the touch

"Does the motor run smoothly over 3k, until check engine light comes on?"

It seems to be a bit of a miss but if I slowly depress throttle it climbs then will jump up in RPM fast then check engine and drops to idle then back up again.

"Idle & higher speeds? What is the present top speed/ rpms?"

I've only had this boat for about 6 months but it would redline at 5900-6000
Top speed around 58 MPH. The Idle I set at 850 RPM or 0.536 vdc from the calculations in the Suzuki supplement manual for this engine.

"When you mentioned hp filter, are you talking about the cone shaped filter in the lower line of the VST?"
No, The filter from the electric fuel pump outlet. When I redid the fuel lines the cone shape inline screen filers were cleaned and inspected before reassembled.

"Did you look at the check-valves in the low pressure pumps (not included in rebuild kits)?"
Yes, as far as my old eyes could tell no cracks in either side of each low pressure pump. I squeezed shut the fuel line on the outlet side of primer bulb while idling and the gauge went into a vacuum 2-3" it would start to die then.

"The check engine light should give you two sets of flashes, then should pause and repeat the same code, it should show all codes in your manual."

This is the brain twister, the only thing it does, it will come on steady for 2 or so seconds then off for a couple of minutes when at idle (850 RPM). Checking the monitor G/W wire with ignition on shows 12 VDC and in manual states sensors are ok or no hard failures. When climbing in RPMS above 2k it will do the same steady on for 2 seconds then drop to Idle then climb slowly again and repeat this cycle every time.

"Did this problem start recently? Did anything preclude these problems?"

Yes, had problem with anti-syphon valves ( 2 tanks in bass boat) changed them, ran it a couple trips no problems then in late May this started.

Post back when able.

Thanks for the Reply!!
This is all being tested in a 150 gallon water tank.
I replied under every question above.
The only Marine dealer that would even look at this in hundreds of miles, threw there hands up and stated that a lot of the parts had been obsoleted. End of story.
After finally finding a used Suzuki DT150S EFI supplementary manual, I started testing, All sensors (except AIR pressure and Intake temp sensors) were tested. I haven't check output of condenser coils on stator yet it's firing though.
After finding nothing I could pinpoint I started throwing parts at it.
The compression is 108 to 109 all six cylinders.
It seems to be a bit of a rough Idle at 850 not smooth as I would think it fluctuates 50 to 75 RPM.
The voltage output from rectifier at idle is 12.89 to 13.05 then above 2k it looks to be 13.5 to 14.30. Battery potential is around 12.71..

Jumpered the oil flow switch since I knew it was getting plenty of oil. Nothing changed. All the lights on monitor gauge work.

I disconnected battery terminals many times to reset. No change.

I have study the manual (schematic) closely and looked for every sensor to test.

LOST.

[Solarman]

Sorry for delay getting back to you.
You really didn't answer my question on "present" high speed/rpms?

Also, 6k rpms sounds too high, the 2 strokes should max at 5600 - 5700 rpms, you may need to change prop to keep top end rpms lower?

Check the readings of your low condenser & high condenser charging coils in the magneto (there is a high & low charging coil). Also, inspect flywheel magnets to see if any are loose/ moving. The low charging coil provides pulses to fire plugs at idle and lower speeds (below ~ 2500rpms), and the high condenser coil adds pulses for higher rpms.

I can't remember exactly how the TVS is adjusted, but seem to remember it requires a special jumper-wire to read voltage, between ECM and TVS, adjusting for low and high speed voltages?

Removing battery leads doesn't reset ECM, correction of problem is only way to reset. Also, look for any loose, dirty connectors around ECM, have experienced strange results cleaning mine (dt140's).

Good luck, post back when able.

[fob1904]

This is a 150S so rpm is 5300 to 6000
The tps or tpv in the manual shows a voltage calculation of V1, V2 = V3 and V4 that was set with the new update one
All sensors have been checked by resistance and voltage
All coils have been checked by resistance
Oil flow switch is good
Thermal imagery on engine block shows 108 to 122 F on water flow
Magnets on flywheel good
All ground points checked for resistance, wiring harness to and from sensors checked
When I said reset I mean by disconnecting battery to remove error code if any.
Since I have no code just a flash of 2 seconds on then 2 minutes or so off.
Then it's hard to find anything wrong of which I have checked and rechecked.

The only parts that are used from my first post are the ICU and ECU
Last thing to check is the stator but resistance wise it checks good and regulator circuit output is 13.01 Vdc idle 14.35 at 1800 rpms

[fob1904]

Follow Up

I replaced all sensors, replaced thermostats and impeller kit.
Replaced the CDI (new) Rectifier (new) ECU (used) ICU (used)
Low pressure Fuel pumps rebuilt, High pressure electric fuel pump checked and tested under running conditions and meets specs.
Stator (new) trigger (new) pulsing coils (new)

Compression on all 6 cylinders 108-110 psi.

High pressure fuel filter (new) High pressure regulator (new) fuel vapor separator kit. Fuel lines replaced.
Checked all grounding points. Harness wiring to and from various sensors all check good.
Sparkplugs new or about six hours of usage while doing the troubleshooting.

The same problem (check engine comes on while idling for 2-3 seconds then off for 30 or so seconds.)

This happens after about 1 minute after starting motor, whether its been off all night or restart warm.

What the heck can I be missing? As stated in above postings no mechanics will look at it.

[Solarman]

Do any of your cylinder heads get too warm to hold your hand on? A good pee stream indicates water pump is working, but doesn't tell you water is flowing around all cylinders, usually the temp light will come on if too warm?

Have you checked the gear counting coil, and it's distance to flywheel? If not correct distance, will not count teeth properly, may turn check engine light on? It does affect timing and tvs adjustment.

I am reading that, the check engine light is the only light turning on? and, it will turn on just idling, after a couple mins? Then after a couple seconds goes off, then back on a couple mins later again for about 2 seconds? If you increase throttle in forward to over 2500 rpms when check engine light comes on it drops back to idle? And, after a couple seconds rpms will pick back up, until light goes on again?

If this is correct, it sounds like there is a temp limit being reached, possibly due to exhaust interfering with water flow? But generally you should see some signs of higher temp? Spitting or sputtering pee stream if related to sub water pick up.
But if related to exhaust cooling plate at powerhead, pee stream may not be affected, but you should see steam spitting and sputtering, hotter water temps from exhaust port at back of motor at higher rpms? This could show up using a laser temp gun pointed at various places around all cylinders. Also, around the exhaust cover plate.

I am trying to feel your motor out, so I'm fine with your longer posts trying to explain things.

I don't want you throwing money at the motor in new parts, but your motor is trying to tell us what's wrong.

Good luck, post back as able.

[fob1904]

Thanks for the Reply,
I ran a temperature scan twice on the heads around 135 F.
I went ahead and changed the impeller and thermostats anyway.

Since this motor only has a temp probe on top of #2 cylinder and that has been changed too, I went ahead and lifted the probe out of the well and ran it at Idle with the same problem occurring again.

The gear counting coil was replaced in my previous post and set at .030.

It is always the same problem the check engine light comes on then goes off as I described earlier. It doesn't matter if its a idle or 3000- 4000 rpm the check engine light comes on in that cycle . When at higher RPMS it will drop to Idle when check engine comes on then raises RPM back up when it goes off.
Since almost all these components have been changed, I'm at a lost.

I'm wondering if primary coils to the plugs could be misfiring and being read by miscounts of the gear counting coil which is an input into the ICU thus signaling a fault?

I agree its telling me something right now its GREEK to me.

[Solarman]

In looking at parts page, it shows 2 temp sensors, one on port head at top, one on starboard head at top, then it shows 2 plugs or 2 plug water sensors at bottom of each bank of cylinders. I don't have your motor, do I don't know if the bottom sensors are just plugged locations, or plug type sensors? But you should have one sensor at the top of each bank of cylinders? Not just one sensor, please check that.

Also, if you're getting 135°F temps anywhere on heads that is too warm. Check temps again around all six cylinders with motor idling from cold start. Try to identify where it is getting the hottest, when the light goes off.

Also you should have 2 thermostats, one at the top of each bank of cylinders.

I will ask if you have the sub-water cooling tube on your motor the parts page is not clear if your motor has it. Doubt it is bad, because my motors both, had bad grommets and I would get steam from pee stream if I went above 2500 rpms, the exhaust pushed water out of water pump, setting off my alarm for overheat.

Generally the gear count coil won't set off check engine light, however the air temp, oil sensor, tvs, temp sensors will. You should be able to unplug all while running (maybe not tvs?) To see if any affect this check engine light?

If you have a spare/ used magneto, it might set check engine light off, if problem with output voltage to rectifier that feeds ECM. I have heard this has occurred, but not sure in your case?

Oh, think I mentioned, disconnecting battery will not reset ecm, or codes. The ECM goes through checks every set amount of time, and if problem exists it does the same thing until it is fixed. Once fixed the routine check clears automatically.

Good luck, post back when able.

[fob1904]

Thanks for some ideas.

This is a 150S or P model. I found a Suzuki supplemental manual just for this model. This is what I am referring to as to troubleshooting.

It only has 1 encased Dual thermistor based temp probe at the top of #2 cylinder.

The temp probe has two thermistors inside the probe casing, One sends signal to ICU the other to ECU. If my thinking is correct and I pull the temp probe out of the well then that temp should be below any high temp warnings/fault while running. Since it is a new probe and I checked resistance at 25 C or around 77 F and that was correct, then those values sent to ICU and ECU should be correct.

I changed impeller and both T-stats. The manual says they fully open at 130 F. Water flow looks good and pee hole discharge slightly warm to the touch..

The manual also states if I remove the battery cables that all errors codes are lost. Granted if the system has a fault it will regenerate that error quickly while running.

The magneto/ pulse coils/ gear trigger(RPM sensor) / CDI and rectifier have been changed too. Charging voltage output from rectifier @ 800 rpm = 12.71 vdc, @ 1100 rpm 13.02 vdc increases to around 14.15 @ 3000 rpm.

FAIL SAFE:
The ICU monitors throttle valve sensor, engine RPM, oil level switch, oil flow sensor, overheat sensor or cylinder temp sensor, pulse coil and oil warning reset switch when an abnormal signal is received then it sends a mask signal to the microprocessor cutting out ignition to cylinders 1,3,5.. When this occurs the ICU controls engine and will not generate a normal revolution signal to ECU causing a malfunction in fuel injection system.

ECU or fuel injection module:
It monitors TVS or throttle sensor, air temp probe, cylinder wall temp, atmospheric pressure sensor and engine revolution signal from ICU output.
The check engine light is controlled by the ECU for this model.

Having checked the output of the atmospheric pressure sensor at around 14.7 PSIG=3.81 vdc with ignition on and checking the air intake temp probe for linearity between resistance and ambient temp scale they both check good.

Now after throwing many parts to this (which I've always hated doing) and only after not finding anything really defective throughout. I'm studying how to monitor the Yellow/Black wire from ICU to ECU that either sends the normal engine revolution signal to ECU or a fault condtion.
Then if not there then ECU inputs from sensors for fault.

If none are found then I'm back to either ICU or ECU modules are at fault since these modules were used when I replaced then I'm not sure of functionality but the same fault was not corrected or changed then I can't see why the would be faulty.

Any other suggestions you might have?

By the way this message header should not only be limp mode but limp/check engine mode problems.

Again sorry for the long post.

[Solarman]

Cannot believe you only have the one temp sensor on #2 cylinder. I have never run across a motor with one temp probe unless all cylinders were in line. Twin banks of cylinders V-4's, V-6's, & V-8's on outboards have always had one temp probe at, or near the top of cylinder #1, and cylinder #2, simply because water jackets around cylinders can get blocked by salts and corrosion, and one sensor cannot read the temp of both banks period.
So either you're missing/ overlooking one temp probe on cylinder #1, or someone may have removed it?
Also, the parts manual calls for a port and starboard temp sensors.

Check the wiring schematic for both port and stb temp sensor wiring. Your problem might be that sensor is missing, and diagnostics is telling you it is not getting that signal.

Good luck, let us know what you find when able.