Mercury/Tohatsu 25-30 HP fried ECM from aftermarket fuel pump. CHEAP FIX WITHOUT BAD ECU REPLACEMENT
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- เผยแพร่เมื่อ 26 ธ.ค. 2022
- 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.
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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.
And this setup is still working just fine. Customer uses it almost every weekend.
What size fuse did you use?
@@jasonbower8524 15amp
I just bought a used Pontoon with an 08 mercury 25hp 4 stroke EFI.
I had the issue where it would start up when cold but if you shut it off after running for any amount of time it wouldn’t restart without sitting for a long time.
I got a Tupperware bin full of things with the boat and I noticed an old fuel pump in the Tupperware. I also noticed a ground was teed into the fuel pump connector. I checked fuel pressure and I had 43 psi and figured fuel was fine. If I sprayed carb cleaner in the intake it wouldn’t pop off at all so I figured I wasn’t getting spark. Checked with a spark tester and sure enough no spark.
I figured my ECM was toast after ohming the pulse sensors and getting measurements within specs.
If it wasn’t for your video I never would’ve realized that the previous owner must’ve replaced the fuel pump and when the fuel pump was pulling too many amps and overheating the ECU it was causing a no spark condition.
I added a diode suppressed relay to power the pump and so far it has started up shut off and restarted several times. I’ll have to report back after hitting the water again. Thank you so much for your video! Life saver!!
Thank you for sharing your fix. In Australia I could only get my hands on a redarc tim06 relay timer costs more but works perfect. I fitted an aftermarket pump and didn't know about diodes or potential damage to ecm.
Hope I could help you thanks for watching and commenting.
I'll be darned. I have the exact same '06 Merc with the exact same problem, and process with the meter. Replaced an OEM pump with a new quantum, and the engine failed after 10 minutes of running, and hasn't cranked since. Local mechanic is swamped for months out, so I've racked my brains tinkering with the engine. Will try the same fix . Thanks for posting this.
Good luck I hope this helps you and gets you back going.
Did you ever end of fixing
@cape fear did you fix it?
Worked like a charm! TYVM!!!
Hi Jay,
I have the same problem. Does the 12v positive wire for the pump also come from the ECU?
Should the positive pass through a relay too?
Thank you
I have a 2006 Mercury 25hp EFI with out the starter. My fuel pump does not run when I pull the rope start.
I tested the pump with 12v direct to pump and it runs. I also put a meter on the leads from the ECU and when I pull the rope start I get the voltage readings the will show a ramp up to 15v when I hook the pump back up it does not run. Not sure if I have a ground problem. I am not sure if the pump that I have now is the 5amp pump which I know now is the wrong pump. I ordered a new pump with the low amp draw of 3amps and have not received it yet.
Do you have another way to test it are can I do what you did with the relay (relay timer). Any help would be highly appreciated.
Would adding this relay setup when ECU is still good work as a protection to prevent the pump from damaging the ECU?
where does the wire from bolt ground, hook to on relay and the wire on the trd relay to the ground on pump relay pin?
i have a 60hp 2015 with bad pump , i wanted to bypass the original relay all together , what part number or under what name did you use to get the plug for the fuel pump ( black plug with 2 blue wires going into yellow plug) thanks
i have the 2008 version with no starter set up. used aftermarket fuel pump and have similar problem. can this happen to my setup
I have the same problem with my Tohatsu TIDL 70Hp will this work on my motor.
It also has a bad ground to ECM
Just had the exact same problem show up today, 2nd time running motor after replacing the HP pump. Man I wish I knew this before buying the aftermarket pump. Was your ECM still good aside from losing the fuel pump ground?
What wire from the ecu did you tap into?
im having a issue kinda like this i have 12 volt at ground when the engine is off but when it starts it goes to 9 volts then to -2 volts is this normal for these engines?
Do you know where I can get one of these ECU's used?
It lookes like both ground wire from bolt and wire to pump are on same pin, if so there is no delay on ground.
That's what I'm saying 🤔 Might as well ground it directly. If it's a negative trigger pump, it would have 12volts all the time and closing the ground would kick the pump on, if I'm understanding this correctly.
I have a 2003 60hp 4 stroke mercury motor with a fuel pump that runs str8 through and i can't figure out what could be causing it. The beep that should come on exactly after turning the key on the control starts after like 20 seconds after i turn the key and when it comes on it beeps for a long time stop and starts back again. the only time my fuel pump stops is when the peeping stops and that's because the beeping only stops for a second. what i'm trying to figure out is if the problem is cause by my ECM, the Vevor control i bought off Amazon or is it just my fuel pump. please can someone help me with this issue? i'm really in a bad place right now.
Could you send me the wire diagram for this please , I have the same problem
We’re are you from I’m having trouble with mine
Thanks for the video! How would you conect/wire a diod inn to protect the ecu? Do you have a diagram for that?
you find anything out about a diagram
Is it similar with 2017 4 stroke 25hp?
Thanks for the info! Should the fuel pump be running when ignition is on, prior to starting?
No only when turning over
Where did you read about what diode to use? I have a new Quantum pump only a few hours on it now I’m scared it will do this
you figure this out? i’m in same boat as you i don’t want jt to happen
We’re are you located
Quick question I have the same engine does the fuel pump turn on at key on or only when cranking?
Only when cranking
Wow how am I just finding this video whit all the looking around for a used ECU?
Any chance I can still get the wiring diagram?
Thank you sir. You may have just saved a motor and my sanity.
email me racertjay@yahoo.com ill send wiring diagram
I have a 2007 tohatsu Mfs25b
I bought engine recently. Had it running @ home. First time out on lake it decides to not turn on. Cranks but no fire up.
Replaced kill switch and start switch.
Start switch wasn’t sending 12 volts to ignition on wire.
Now I can’t get pump to prime or turn on.
Does pump prime with key on?
Or does it turn on once engine is running?
Fuel pump doesn't get power with just the key on, only when it's turning over. If you try to crank it and it still doesn't have the power, and all fuses are good, most likely a problem with the ECM
If I’m understanding this correctly
Fuel pump should have voltage only when Cranking engine?
There’s only one 20 amp fuse by Ecm
Is there other fuses I’m overlooking?
So the ECM isnt fried???
Sorry for not understanding fully but my mechanic told me my ECM needs replaced after an issue following fuel pump replacement with a aftermarket pump. Would this work if the "ECM is bad" according to him?
Depends. He needed ALOT of research to figure this out. Its not easy. If you have the identical engine you may do his repair. If not save your money for an emm and fuel pump (or resistor to drop power to pump)
Did the engines oil light and beep sound come on before this fix?
the oil light will come on for a second or two at each startup. Before and after the fix (that's normal). The beep also the same.
I have 2001 Mercury Optimax and the ground wire from the ECU is bad. I had thought it was the fuel pump and replaced it. When I started it up the engine didn't fire up. Like you I checked the power wire and not the ground wire. A new ECU for mine is $1,700. If I can do what you did it will definitely save me a lot of money. So how has your customer's boat been holding up? Let me know cause if it's still good I'll be doing what you've done in this video. Thanks!
Everything is still great. They use it almost every weekend
@@racertjay Awesome. Thanks for the very quick reply.
@racertjay Hooked up the relay. The outboard fires up nicely. But the thing is the fuel pump stays on. Did your customer's boat do the same thing? Stays on even before I turn the key.
@@kisdasenglothnam the fuel pump should run constantly when the engine is running. Is that what you are referring too?
@racertjay I hooked up the 12v power to the wire straight from the battery. So when I turn on the batteries the pump stays on constantly without turning on the motor. How did you hook up the 12v input? You mentioned something about the starter solenoid? That's what I'm trying to find out. Do you have a Facebook?
How has this held up? I’m doing it to mine now the mercury dealer tried to tell me even with a relay I’d kill the ECU that I needed to get a factory OEM even though the last one lasted 10 hours.. I assume he’s just trying to sell his $750 pump
Holding up just fine so far.
@@racertjay thanks for the update. Just wired in a relay and ordered a quantum pump hope it gets me back going. Cheers mate🍻
I'm working with another TH-camr Omie on his repair for this same engine. I have the same one and my fuel pump works but still no start. I replaced a few things but no start still.
Would this relay guarantee engine running if it was ecu or signal related like a ground short
Do you have good fuel pressure at the shrader valve on the fuel rail? If so, have you tried bleeding it and seeing if it will start then
@@racertjay yes I bled it. I also drained vst. Replaced gas tank gas all fresh gas. Also the gas tank float is broken but I still get pressure. At the fuel valve near injectors, I get 45 psi when cranking. I do run water inside the muffs when trying to start. New battery aswell from my truck I use to start it. Idk which kind is original to the craft. But fuel pump I cleaned out with the vst. Someone else did mess with it before me because it wasn't mounted correctly. But I got it all correctly installed again. Cleaned. Pump did spin if I spun the cogs manually underneath so it wasn't seized. I got 15v at vst connector when cranking but only while start was engaged. When it wouldn't start the voltage would drop and starter and everything would just whine without load.
Thank you guys for posting videos because I'm hopeful I can fix my Craig catamaran LP2 I have. I got the bait for $400 ($200 me, $200 my dad) from a 96 yr old who still is as youthful as a frat house. I promised him I'd let him drive it if I got it running and he's about 16 hours away from me but I think I can make it happen. I'd have to set up the day to do it of course but he'd love it because he gave up trying with it over the many years he owned it.
With power going to the fuel pump connector/harness and fuel pressure, this fix is not related to your issue. Have you checked for spark? Are the spark plugs wet? Tried starter fluid? Sounds like you have an issue with spark, timing, or injectors not firing
And it is normal to only have power to the fuel pump when cranking, it has no power with just the key on.
@@racertjay will the pump hold voltage if it's running. And only lost voltage bc it failed to start? I'll try starter fluid soon. I'm wondering what the heck is going on. My filter gets fuel. My primer bulb primes and pumps fuel. Man I know it's something small and stupid but idk what it is. Just one beep when trying to start but nothing except small putter and fail.
I'll try the spray fluid and I was hoping I could do this bypass to try and just bypass ecu and do the same relay you did and give up and do that instead
Tohatsu outboard does not get gasoline into the cylinders. The injector, ecu, spark plugs are intact. When I pour gasoline into the pistons, it works a little. When I press the starter, oily gasoline comes out of the exhaust. Could the high pressure pump have malfunctioned? How can I test it? Greetings from Istanbul, Turkey..
Test your fuel pressure with a gauge at the test port (shrader valve like a car tire) on the fuel rail. If no pressure, test the voltage at the fuel pump wires going into the vst. Don’t use motor ground use the actual wire
If you have fuel pressure, you have a different problem. Could try to bleed it off and make sure it builds back up next time you start it.
@@racertjay In this engine, apart from the normal injector, there is also an air injector. I do not know how to control the air injector. The compressor is very good. What does air injector do? Could the cause of the malfunction be the air injector? Thank you very much.
Hows it going boss quick question how will this work with the pull start edition of this same motor i will have to add a battery since it doesnt have one
You would have to try and find a 12v source (prolly out the voltage regulator, before the ECM) with enough amperage to power the fuel pump. The easiest thing to do would be to add a 12v deep cycle battery in your situation I would thing so you don't burn up another circuit coming from the ECM.
@@racertjay thank you brother i was thinking the same ground fuel to the ground battery and positive to? Would i still use the time delay? Also brother which wire is from the ecm to the time delay
@@christopherquick9707 yes unless you want to have to worry about having to wait to flick the toggle switch to the fuel pump on until after you've started to turn the motor on. The time delay relay eliminates have to have a a bunch of "gotta do this before that" type of stuff to get it to crank
What did you wire your trigger wire to?
The 12v+ (hot wire) at the engine harness that plugs into the fuel pump.
Tjay, sent you an email on this. appreciate the video and hope to hear from you.
Hey man I know this is an old video but I’d greatly appreciate it if you could send me that diagram of you still have it thank you!
Email?
You should redo that video with it wired right
It is wired correctly in the video. Which is why it starts up and runs and still runs now?? Not sure what you mean. But I also see your other comments now. Read the pinned comment on the video I made for specific wire colors to relay pins or if you send me your email I can send you a wiring diagram I made
@@racertjayare you willing to send me the diagram i really appricate your time !! i just put a new pump in and scared it gonna blow it up you know how i can put diode in
Just a hot wire to the Ignition and grown your done
okay do that and tell me how it works out