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2009 Honda Bf90D - at the end of my tether

SamBrink

New member
Hi All

my name is Sam and I'm from South Africa. I purchased a boat with a Honda bf90 EFI two years back.
I've done roughly 30 hours. Earlier this year the motor started doing the following:
Sorry for the long post, but if rather give you all the info so that I dont waste your time with back and forth

Motor Starts
Rough idle and dies
When you hit the throttle it dies, if you increase the throttle gradually it sputters and eventually picked up RPM
So it seemed to be a fuel issue I found that the fuel pickup tube on the onboard fuel tank was rusted and that these particles ended up in the fuel system

  • I did the following:
  • Cleaned the fuel tank
  • Replaced fuel lines and primer bulb
  • Replaced the External Filter/Seperator

Cleaned the Onboard Water Seperator
Replaced the HP Filer in the VST
Replaced the HP Fuel Pump
Replaced the Screen holding the fuel pump
Replaced all 0-rings in the fuel system
Had the injectors cleaned and serviced ( One was apparently faulty so they supplied me with a replacement ( refurbed)
Replaced the Mechanical Fuel Pum (Low Pressure)
Replaced Spark Plugs
Oil
Oil Filter
Thermostats
Poppet Valve

After all that I still had the problem, but much less pronounced.

I then removed the Intake and found dust and rust particles combined with what seems like a film of oil in the intake.
It seems that the flywheel started rusting and the particles were being sucked into the intake.
  • I cleaned the throttle body
  • I cleaned the intake manifold
  • I cleaned the airbox

When I assembled everything I noticed the following:


  • No Battery Light on indicator panel
  • No MIL ( Check engine light ) on the indicator panel
  • Double Beep when I turn ignition on.
  • Green Light on the Remote control
  • Engine starter engages but does not start
  • Fuel Pump does not come on when I turn the key
  • Powet trim doesnt trim up ( tapped the PTT relay and it worked)

I checked the fuses and removed the fuse box to check for current with multimeter, Fuse box works.
I checked all the ground connections
I checked the main wiring loom connectors and cleaned them up ( some had green corrosion)

So I'm down to three possible scenarios, and please correct me if I am wrong here:

Faulty ECM
Faulty Main Relay
Or Faulty Wiring loom

I ran the fuel pump direct on battery and it worked.

I would be grateful if someone can point me in the right direction or eliminate any of the three scenarios above

Many thanks

Sam
 
I have just one idea. I was at a similar wits end with a BF50D. Because of something I read somewhere, I tried disconnecting the ground side of the wires leading to the fuel pump and ran the ground wire to the pump directly to ground. In my case, this allowed the fuel pump to run whenever the key is turned on. Worked! Engine would start and run normally. Clearly this patch didn't identify the problem, but it did fix it, or rather allowed the motor to run, without further ado.
 
Alan, the 50D will not run after market fuel pumps other than by the way you mention, just a possibility on that one. Re this issue with the BF90, you mentioned green wires, is it possible this motor has been submerged. The issues mentioned above definitely indicate a wiring issue, either in the boat harness, engine or both. You will need to get a workshop manual and work through the electrical system systematically. This is way too complex to describe in a forum. My go to is my made up control panel that I plug into the engine to rule out the boat side. Alternatively, use a dealer, these engines are not that complex.It's highly unlikely to be anything other than a corroded terminal given the engine was actually running before.
 
The elephant in the room is the ECU. Too many test procedures in the manual tell you that if the test fails try replacing the ECU. I don't know about others, but that part, for what they go for, is not a part I'll have just laying around number one, and number 2, I would hesitate to plug a new ECU into a motor to see if that fixes it - or takes a second ECU out because of an unforeseen issue. That's one hell of an expensive "test".

My favorite saying - "fuel injection is great, until it isn't".

I'll take a carbed motor any day.....
 
The fuel pump should get a 12v. signal for a couple of seconds when you switch the ignition on. You can either unplug or back probe the connector to verify. If the signal is there, then it's probably a pump ground issue. If no signal then you'll need to see if the main relay is supplying volts to the pump circuit.

I don't have this wire diagram so, hopefully, you do.
 
Fuel pump has 12v continuous, switched to ground by the ecu. The problem here just judging by what the warning lights are doing is definitely electrical, there is a bad connection somewhere, trick is to find it. ECU is always blamed, these are rugged, we maintain hundreds of hondas and I think in 20 years I've replaced 4 ecu's, all with rough running issues, not one with complete failure.
 
Agree that the ECU is switching the ground to control the pump. Hot side goes right to the ignition switched fuse.

Will remember the vote of confidence regarding the durability of the ECU's. Thank You. -Al
 
Yes, I stand corrected about the pump being continously powered but the point I was making is still valid. Is the voltage actually there? And...the voltage comes through the main relay does it not?
That voltage is fused prior to entering the relay as well as before being delivered to the pump.

Lots of opportunities to lose that signal.

Although...I do have a schematic of the 175hp system and it shows the fuel pump for that engine being continously grounded at a main ground lug through a black wire. That pump receives voltage via the middle relay in the main relay box and the middle relay is switched via the FL terminal at the ECM.

So, is the 90hp fuel pump circuit completely different to that?

Just trying to help Sam figure out why the pump isn't running.
 
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Thanks for the input: Here is an update
Removed the entire harness, relays, ECU and fuse box.
Cleaned every single connector with Vinegar and after that soaked in a bit of baking sode
I also took a wire brush to all the ground contacts.

Turned the key - Fuel Pump Ran
Started - but was running ROUGH ( seemingly in limp mode)
I still had no MIL Light or Charge Light

I reset the ECU, started again and voila :) It worked
I just want to confirm if there is an error on the ECU, will it stay in limp mode until you reset the ECU/Clear codes?
Before I cleared the ECU i started pulling sensor connectors to see where the problem was causing the rough idle.

The MIL Light and Charge Lights worked again after I did the reset.
 
AWESOME man!

So....resetting the ECM seems to be something that should be done after all.
Good information and great results!

Thank you for updating on this.

P.S. in automotive repair it has been a standard practice to clear codes and reset the Powertrain Control Module (PCM) by removing the battery ground cable terminal and connecting it to the positive cable terminal for several minutes. This discharges the memory "keep alive" capacitors in the processor that can cause a fault condition to remain and be a source of trouble. Although....as systems get more sophisticated and OEM'S attempt to keep independent repair shops "out of our business"....very late model equipment requires a dedicated scanner to perform a "global reset". I don't think Honda Marine is there yet but probably coming soon.
 
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Further to what I've said, go back over the plugs you played with that resulted in the engine running well. if not corrected properly, the problem will re occur.
 
Thanks, I found it strange that the MIL and Charge light came on after I cleared the codes.
The PTT relay definitely needs to be replaced, up trim works intermittently Is there a way to disassemble the two ECU plugs to check those pins?
 
You've done a good job, the only thing I would have done that you haven't done is apply electrolytic grease to all your plugs. As far as the ecu plugs are concerned, I once had a pin push back making bad contact, just check they are all fully seated and apply the mentioned grease.
 
You've done a good job, the only thing I would have done that you haven't done is apply electrolytic grease to all your plugs. As far as the ecu plugs are concerned, I once had a pin push back making bad contact, just check they are all fully seated and apply the mentioned grease.

Thanks again. I went to the water today. Sadly... hard start. Once started buz Buz buz and a solid MIL light..
 
Definitely electrical, no doubt. If you have any corrosion visible in any plug I would recommend relacing the entire harness.
 
Definitely electrical, no doubt. If you have any corrosion visible in any plug I would recommend relacing the entire harness.

Hi all just some feedback:)

The intermittent power trim problem, the rough idle, the stalling, the codes, etc.

I replaced the main wire harness and my Honda is back to its old reliable self again:) This solved all the issues.
Pricey but worth it

Thanks for assistance and advice:)
 
Really glad to see that you GOT IT!
You did a lot of work and now get to enjoy the rewards.
Goodonya!
 
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