NEXTASEX

was your water temp correct i had a thermostat stuck open and engine would load up @ idle computer stays in cold start mode.

mats

DonMan, I would connect the black/white with the black just beside in the top row. That is where the white black is located on my engine. You may get lucky and find a trouble code that can give you a clue. Still, my experiance is that 95% of all trouble on a marine engine is related to things that do not trigger a troulble code.Then it is back to basics. Would still suggest to check the spark on each plug with a timing light.

DonMan

I have the Cool Fuel system on my boat.
My water temps seem to be right, running about 175*.
I am going to check the spark to each cylinder. If that is good, I`ll check to see if each injector is hitting. I have a feeling that maybe I have a couple injectors stuck wide open.....?
I think I am going to try and retrieve a trouble code with my test light.
Will let yall know what I find.
THANKS!

cobra marty

Turn the key on and check the fuel pressure if it holds then OK if it bleeds down or falls then an injector is stuck.

H2Xmark

on your cool fuel setup it will be the two wires on the end you jump[bridge] black- black/white , [ if you ever need to set your timing you do this step first then hit it with the timing light] after jumping the two wires, then do the test light alligator clip to postive terminal then the pointed tip of light to the brown/white wire with key on, the codes are the same as on an old General motors product from the late 1980's

DonMan

I checked my fuel pressure a couple days ago, it holds rock steady.
I did the test-light trick on the diagnostic connector and it flashes code 12 over and over (no trouble codes stored).
I pulled the map sensor, just to check it out. It was clean did not have any residue on it.
I put about 2 hrs run time on this new set of MR43LTS plugs and pulled them out for inspection just now. All 8 look very good, no wetness and a slight tan color.
I ran the engine again paying close attention to coolant temp, etc...
It runs just fine while cold, it starts to run rough as the temp approaches 150* and fully gets into it`s rough idle condition after the T-stat opens (160*). I am suspecting a faulty coolant temp sensor. I unplugged it while the engine was running (while cold) and it really made the engine run bad. After the engine was warmed, I unplugged the coolant sensor and it made no difference. Is this my problem?
I am mad at myself for my lack of knowledge of fuel-injection and computer-controlled engines. I am ready to swap to a carb just for the simplicity.
I need a good running engine for at least this holiday weekend. Am I looking in the right direction with the coolant temp sensor?
I went ahead and pulled it, hoping to match it up at the parts store tomorrow.
Any other suggestions????
THANKS!!!!

RonS

I would say the coolant temp sender is a good bet, if its faulty it will cause the motor to run rich, but also follow the wires to make sure you don't have a bad connection.

epeek

DonMan, It sounds as if the ecu is commanding to injector
pulse width high. The 2 most likely causes would be the
coolant temp sensor curcuit or the map curcuit. If you have a
volt meter you can easily test these. Both run off a 5 volt
reference signal. Unplug the coolant sensor & turn the key on
test the wires,you should have aprox. 5 volts on 1 of them
Then plug it back in. Back probe the other wire (signal return)
as engine temp rises the voltage will go lower, open curcuit
will be 5 volts. The sensor acts as a variable ground. More temp
lower voltage. For the map,start engine on the signal return
you should be at about 1.2 - 1.6 volts depending on rpm. A open
curcuit would be 5 volts. If either curcuit were open the ecu
would command the injectors open thinking that the engine
was cold or at wide open throttle. Also with the map make
sure you have 18in.of vacuum,less vacuum,high voltage. Again
ecu thinks your wide open. The voltage on the map should rise
as the throttle increases. By the way,stick with fuel injection
its a great setup. Good luck, Rick

epeek

FFT,do you have a schematic for this system, If you do,look and
see if the black goes to ground or back to the ecu.
If it goes back to the ecu you would probe the black. If it goes to
ground you would probe the yellow. You may be right, I"m an
auto tech by trade & am baseing my info on commom gm obd 2
systems. I've never seen a wiring diagram for the merc setup.

DonMan

I swapped out the coolant sensor with a new one ($12, auto parts store). ...No change.
I have a new map sensor, but haven`t tried it. I will check things out with the volt meter.
THANKS!