1999 40hp fires over and instantly shuts off

[mjl66o]

I have spent some time trying to wrap my head around this good news is I found C8 and D11. I was looking at a mirror image of the connectors, so I was inspecting the wrong port. Bad news is I am not having any luck with the neutral circuit I have checked the resistance on both neutral switches, and they are zero along with the wring to them. I am getting 10 volts on the brown neutral switch circuit at the ECM while cranking. If I understand you correctly you are saying this is the root of my issue but looking at the circuit design there has to be battery voltage at this terminal while cranking. The brown wire is powered by the white battery positive wire through the ignition switch so the brown wire will show battery voltage on any part of the circuit that is between the power sources and the consumer which in this circuit is the started solenoid correct?

[redlowrey]

When the key is on in neutral, you should have ZERO volts, and five volts in gear, what have you got, on C8

When you crank the engine, the computer wants to see the cranking voltage on D11 it will ignore the cranking voltage it will see on C8 because it seen 0 volts on C8 with the key on, this is how it knows whether it is in gear or neutral.

[mjl66o]

I have zero volts in neutral and 5 volts in gear on c8.

[redlowrey]

Ok that’s what it should be, what about D11 when cranking. It should be cranking voltage, between 8 and 10 volts.

If you get the right voltage on D11 remove an injector plug and connect a test light to battery pos and probe the ground side and crank the engine and see if the test light blinks on and off, the grey wire is battery pos.

[redlowrey]

If you go probing around the computer with a test light, make sure you know the circuit you are on and how much current it can handle, because some of those circuits are only used for voltage reference and only draw a very small amount of current and would not like a test light that will draw an amp or more.

If your not sure use an led light it will only draw around 10 MA. The injector circuit will be fine with a test light that will draw one amp.

[mjl66o]

So power on D11 is at 9.5 while cranking. Injectors are lighting the test light interesting thing is when I started testing the second injector circuit down the engine started and ran for the longest it ever has about 10 seconds plugged that one back in and tested the lower injector and it also tried to run. I went back to it and now I am back to where I started will only run for an instant tried to duplicate testing the second injector down but it does not get the motor to try to run like it did the first time

[redlowrey]

The neutral circuit is doing what it should, you would have no injector pulses or the test light blinking if it was bad.
A few posts back I asked you to check the voltage at the injectors when cranking the engine to see how much voltage drop there was did you.

Connect your multimeter up to the fuel pump and see what happens to the battery voltage on the grey wire, how much it drops when cranking, and also on the ground, see if you loose it when cranking.

[redlowrey]

Have you checked and made sure there is fuel pressure in the rail, I should have asked you that along way back.

[mjl66o]

The injectors have 12.1 volts to them and it drops to 9.9 volts while cranking fuel pump is at 10 volts while cranking and .17volts on the ground circuit fuel pump stays running according to voltmeter while cranking

[redlowrey]

Have you actually checked the rail pressure and checked that the injectors are capable of spraying fuel.

[mjl66o]

I have to get a pressure tester I verified I am getting fuel after the high-pressure filter and when I was testing the spark plugs for spark I was watching mist come out of the spark plug hole.

[redlowrey]

Ok connect up an incandescent test light to ground, probe battery pos to make sure it lights, crank the engine over for about five seconds to prime the rail, leave the key on.



Probe each of the injector grounds for half a second, then lift the warm up lever to open the throttle, turn the key to the start position the engine should rev right up indicating that the rail has fuel pressure and the injectors are spraying fuel.

If the engine does not rev up high it would indicate to me that the either the fuel pressure is to low or the filter baskets are blocked in the injectors.

If I get a problem like yours I check all the wiring, check fuel pressure and connect up an oscilloscope and I can see what I need to see very quickly.

[tommybe1]

Just a thought , did you put new gas in? Check you fittings at the tank and motor for being gummed up. If you can get it started, run a can of sea foarm throught it in a gal gas can. Ask me how I know this, gl.

[mjl66o]

Sorry I needed to step away from it a few days was getting frustrated. I had a different engine on the boat that was running with the fuel system so that "should" not be the cause. When I was following your method, it got me thinking so I pulled the plugs again and now they are soaked. Considering it always wants to start best when I first get out there and unplugging the injectors got it running best. I am pretty confident the system is flooding out. I am not sure why it didnt seem to be when I checked the spark plugs the first time but that's what it is looking like right now, and it is all 3 cylinders that are wet.

[redlowrey]

Surely if that was the case you would have smelt raw fuel coming from the throttle plate, No I think what you have done is kept the ground on too long on each injector and drowned the engine with fuel. At least that tells me the rail had pressure and the three injectors were capable of spraying fuel.
Ok start again, blow the cyls out, install the plugs, don't connect the injector connectors, lift up the warm up leaver and crank it over and let it burn any of the dregs that are left.
Connect the injectors back up and give the engine a good crank and remove the plugs and see if they are wet or dry.

I hope it is running too rich, at least I will know that there is rail pressure and the injectors are opening and closing, which you should be able to see on your sds, if you remove the plugs again and they are wet,
check pin D3 with the key on, light green and white, and pin C9 violet and white and note what the voltages are, if D3 is 4 volts or over we have found the problem, providing you you not in the arctic.