This is a cheap and easy fix on a 2006 Mercury 25 4 stroke EFI that has a bad ECM. This ECU lost power from the ground source to the fuel pump. It happened shortly after an aftermarket (Quantum) fuel pump was installed.
Mercury/Tohatsu 25-30 HP fried ECM from aftermarket fuel pump. CHEAP FIX WITHOUT BAD ECU REPLACEMENT
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2530, Aftermarket, cheap, FRIED, From, Fuel, Mercury/Tohatsu, Pump, Replacement, Without
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I have gotten a ton of messages about more specific questions about wiring. Cut the original plug (2 wires) that plugged into the fuel pump/VST tank. Be sure to leave enough room on both sides to allow for a butt connector. It had a blue wire and a blue/black wire. 86 on the relay should be wired into the blue wire that is on the engine wire harness side (back to the ECM). ANd 87 on the relay wired to the blue wire on the plug side that plugs into the fuel pump. The blue/black wire on engine harness side (back to ECM) will now be left bare. The blue/black wire on the fuel pump plug should go directly to engine ground (use any bolt that's grounded) as well as to pin 85 on relay. and 30 on the relay should go to your constant 12v+ power source (fused of course) and I used the hot side of the starter relay.
What fuel pump should I buy so I don’t run into this problem?
Morning all,
Does anyone have a step by step install video? Please help =)
Did you guys loose the beep when cranking the engine and did you loose spark when it was just cranking? I’m having those issues with mine
Does this have anything to do with the engine not having any spark at all
I just did this to mine and it fired right up. For the guys that did it how did it preform long term?
I need help. I have done the fix that you suggested. The motor now runs but it didn't solve my original problem. The shop had it for 3 months. Ruin my whole summer. I brought it there because it was only doing 7 mph. He gave it back to me with the relay fix but now the engine is still only doing 7 mph and it seems like it's surging at full throttle. So what is the issue with the motor? All my components seem to test good. Is it the high pressure pump is bad?
ECUs usually control the "low side" of the circuits, the ground lead. Aftermarket fuel pumps often draw too many amps compared to OEM pumps, and blow out that controlling MOSFET inside the ECU.
Therefore your fix is best, because replacing the $$$$ ECU with the same fuel pump still there, would kill the new ECU.
You could bench test an OEM Vs aftermarket fuel pump and ensure the amperage draw is within an Amp or so….
How did you test the ground wire?
Do you have a wiring diagram for this motor? I have a 2009 mercury 30hp efi 4 stroke….has electric start and also pull start….so it can run batteryless too…really need to know the colors of the wires coming from ecm etc.
Also another question how does a battery less efi system like mine work in the event that say my battery died? Does the rectifier supply dc voltage to the ecm?
Im curious how things work so im just wondering what's the actual need for the delay?
Also does the fuel pump continuously run? And the mechanical regulator controls the fuel pressure in the fuel rail? Or does the fuel pump driver module in the ecm turn on and off the fuel pump based on sensor readings? Im assuming the pump just continously runs because there is no fuel pressure sensor of any sort to tell the ecm what to do….im really curious on the need for the delay
Does the ecu supply both power and ground to fuel pump or just ground? Im talking in normal operation
Great video, what side is the load wire on the yellow hp pump connector, trying jump the hp pump but not sure of the connector pin out? Thanks
I don't power or ground coming from the e.C.U what could be the problem.
I wasn’t able to see the part number for the relay, could you possibly post that number. Thanks
How much is a fuel pump?
Will a bad ground on the ecu cause the coils not to get fire i changed out the fuel pump now i have no spark
I just used a regular 12V 40 Amp relay on mine and it works just fine. Lot cheaper than the time delay on relay.
My engine was fired up today by following the video. aftermarket fuel pump burned the ECU.
Can you tell me what "gauge wire" Mercury used for those "Blue" and the "Blue/black trace" wires in that 2006 Mercury/Tohatsu 25HP outboard you posted this about?
I am helping an elderly neighbor with this exact same year, make, model, and scenario to boot! Thanks in advance from a former FL LEO and former Master Automotive Technician.
Have same motor but manual start. It doesn’t have rectifier to wire pump into. If I bought a rectifier could I wire your relay setup with + wire going to rectifier output and achieve same results. Can’t see adding a battery if there is no way to charge it with the engine. Thanks for your time sir!