Help.. Boat will not start

[dustinsnipes]

Bypassing the computer could fix the problem if it was the Low Side Driver in the ECU. If it is any other issue in the ECM or something outside the ECM it won't be a long term fix.

There is a reason the ECU turns the fuel pump on. You don't want the fuel pump on at other times. Keep the pressure up and a leaky injector hydrolocks the engine or worse.

I'm betting it's the crank input to the ECU. It needs to see pulses to keep rely turned on. It wasn't clear to me when I read earlier posts, but is there spark at the plugs?

Yeah I have spark at the plugs it was the first thing I eliminated. I'm no expert on electronics or these mefi systems so your saying the pump doesn't run the entire time while the engine is running? if I ground the relay out the pumps will only run when the ignition switch is on.

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[Stingreye]

I dont know what year MEFA system do a 2 second prime or only power the pump once the engine is cranking.

MEFI4b on my 2004 6.0L prime the pump with the key in the on position and not in the crank position if I remember correctly when I was troubleshooting my problem. I think it was enough to pressurize the fuel rail and get a reading... I think. I would think a 5.7L 2006 is also MEFI 4b but I definitely could be wrong.

[ericinmich]

Yeah I have spark at the plugs it was the first thing I eliminated. I'm no expert on electronics or these mefi systems so your saying the pump doesn't run the entire time while the engine is running? if I ground the relay out the pumps will only run when the ignition switch is on.

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The pump runs the entire time the engine is running. The ECM keeps the pump on when it wants to, based on HW and SW. I can't say with 100% certainty, but I think it does a prime when the key is turned on, then will keep it on (or turn it back on) when the ECM is receiving crank position pulses.

I think I have an internal schematic on the MEFI controllers, probably the earlier ones (I spent time in HW design group on other controllers, auto, not the marine). I'll try to find it tomorrow. The fuel pump control is mechanized the way it is for safety. Just like in autos, you don't want to fuel pump to keep pumping fuel unless the engine is spinning. In a crash, the engine usually stops right away, so the fuel pump will as well.

[UNSTUCK]

I found a MEFI diagnostic manual. Going to do some more troubleshooting tomorrow. In the manual it requires a scan tool to check the circuit between ECM and relay by turning it on for two seconds and the test lamp should light up. But I do not have this magical tool.

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Just wondering of you bothered to check that you do have battery power to terminal 30 and 86 with the key turned on? Im reading where you danced around this but am not sure if you did get power to both and not just one or the other?

Next check the ground side of the trigger. Remove the relay. Put one lead of your meter in terminal 85 and the other lead to a known good ground source. With the meter on ohms it should read OFL with the key off. Turn the key on and it should drop close to 0.0 for a few seconds then go back to OFL. Then crank the engine over and you should see it go back to 0.0. Does this happen?

[dustinsnipes]

Just wondering of you bothered to check that you do have battery power to terminal 30 and 86 with the key turned on? Im reading where you danced around this but am not sure if you did get power to both and not just one or the other?

Next check the ground side of the trigger. Remove the relay. Put one lead of your meter in terminal 85 and the other lead to a known good ground source. With the meter on ohms it should read OFL with the key off. Turn the key on and it should drop close to 0.0 for a few seconds then go back to OFL. Then crank the engine over and you should see it go back to 0.0. Does this happen?

I did all that and have power to both sides of the relay b+ is always hot and the other ignition terminal goes hot when the key is turned on. I did that test from the trigger wire with the ohm meter there is a very faint ground but not enough to ground out the circuit and had to set the meter to 200k to get a reading at all when the key was turned on. With the relay plugged in I probed the trigger wire with a test light and it was still hot while the engine was being cranked over. I have spark and the boat will crank up and run fine with the relay jumped from B+ to the fuel pump terminal. Since I'm stuck and not ready to take a chance dropping a $1k on a new ecm I believe for now I'm going to cut the trigger wire and ground to the block since all the computer does is ground the sytem anyways. I just will have to be careful and not leave the switch on while engine isn't running.

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[UNSTUCK]

Ok, that I understood. You say that the ground side was very high resistance, did you notice the number change at all going from key off to key on, then to crank? If it changed quite a bit, but still very high, my guess is the ECU is switching, but you have corrosion in that circuit. If the number did not really change much then I would say the ECU is not switching like it should. I'm pretty sure that system should prime for a few seconds once you turn the key on then turn off if it doesn't see a crank, cam, or maybe oil pressure signal. So if it doesn't do the initial prime you should be able to rule out all the sensors that feed the ECU. If you haven't double/triple checked all the ground wires in the boat, then now I vote junk ECU.

[dustinsnipes]

Ok, that I understood. You say that the ground side was very high resistance, did you notice the number change at all going from key off to key on, then to crank? If it changed quite a bit, but still very high, my guess is the ECU is switching, but you have corrosion in that circuit. If the number did not really change much then I would say the ECU is not switching like it should. I'm pretty sure that system should prime for a few seconds once you turn the key on then turn off if it doesn't see a crank, cam, or maybe oil pressure signal. So if it doesn't do the initial prime you should be able to rule out all the sensors that feed the ECU. If you haven't double/triple checked all the ground wires in the boat, then now I vote junk ECU.

I'm not the best in the world at reading a ohm meter other than checking to see if there is continuity. It never 0.00 it was reading something like 33.2 with it on the 200k setting. I have ran into weird problems like this before on cars and it would not be getting a good ground at the negative battery post. I'm going to go back clean all grounds make sure everything is the way it should first. Even in the MEFI diagnostic manual it says a ECU failure is extremely rare so of course it would happen to me. Know of anywhere that rebuild these ecm?

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[Wakeman22]

Since it seems to be a ground issue with all the trouble shouting you have done then I would check all ground connections. At the battery, or both batteries, all ground blocks, ground to the engine block, and grounds under the helm. Sounds like a ground problem and I know you would have to shell out 1k only to find it was a ground issue to start with. I would also check the connections at the ECM. Remember this is a water vessel and moisture and corrosion is always an issue.

[Stingreye]

I'm not the best in the world at reading a ohm meter other than checking to see if there is continuity. It never 0.00 it was reading something like 33.2 with it on the 200k setting. I have ran into weird problems like this before on cars and it would not be getting a good ground at the negative battery post. I'm going to go back clean all grounds make sure everything is the way it should first. Even in the MEFI diagnostic manual it says a ECU failure is extremely rare so of course it would happen to me. Know of anywhere that rebuild these ecm?

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I would call these guys and see if they rebuild or reflash, if they don't don't they might know who does.

https://www.obd2allinone.com/mefitune.asp



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[UNSTUCK]

A reading of 33.2 is kind of weird. It makes me think that the circuit is going through the coil of another relay inside the ecu. This is the "internal switch" that can be read about in the paragraph under the fuel pump relay schematic, posted above. I'd like to be able to read all of that DTC-81 information. What is it talking about with the different voltage values?

[dustinsnipes]

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[dustinsnipes]

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[dustinsnipes]

I went to all these steps and ended up at step 13

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[UNSTUCK]

What did you get for step #1?

[dustinsnipes]

No I don't have a scan tool for a boat. But the memory was wiped after putting a new battery in it anyways. But I used a jumper wire at the ecm connector and grounded it the relay clicked on with the ignition on. Just talked to my boat dealer and he said I have a faulty ecm. Believe it's time to bite the proverbial bullet

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