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2004 Honda BF115 crank no start

Ok. I got it to idle and rev. I disconnected the MAP sensor and the sensor on the side of the throttle body. I believe the TPS. Then once it’s idling, I can plug them back in and it stays running.

When I do this, I can ease into the throttle and it will rev up. But if I give the throttle and bit of snap to rev it, it shuts off.

Maybe weak high pressure fuel pump? I haven’t swapped it yet
 
Disconnecting sensors just causes more problems because it sets codes

With MAP disconnected the ECM might go into a default setting which may allow for more fuel

Don't know what a Throttle Angle is

If it's low pressure it might be the Reg and not the pump, only way to know is with a gauge and testing
 
I know disconnecting sensors is not ideal. And yes it is giving the the codes even when I plug them back in. But it is the only way I can get it started and idling.

Disconnect both sensor, start it, let it idle til handle starts beeping. Then reconnect map. Then reconnect throttle position sensor.

Has to be in that order to keep it running
 
Disconnect fuel line going to fuel rail. Find something to get a fuel pressure gauge connected. Cycle the key on/off a few times bleeding the air out and see what the pressure is. I don't know what it should be but need to start somewhere. Finding a place to connect direct while running would be better
 
I think I found the connection you are talking about in the end of the VST.

But my buddy that is fluent in most of the other outboard brands but not much with Honda seems to think it’s the throttle angle sensor
 
My VST is different than that one. I have the high pressure pump in the front of the the VST. Trying to upload a pic but site isn’t letting me.

I also don’t think I have that bolt on the fuel rail. But I’ll check when I get back home
 
Confirmed. I do not have any bolt holes of locations in the fuel rail to hook up a pressure guste. I think I can find an adapter for the bolt on the end of the VST past the high pressure pump.

I’m also going to try to talk a buddy into letting me borrow his throttle body to test the throttle angle sensor since he has the same motor
 
I would suggest, disconnect linkage
Turn key on
There should be 3 wires, one is 5V, another is ground, and other is sensor feed
Place meter between ground and sensor feed.
Rotate TPS and watch the change in voltage
 
Verde2186 said:
You happen to know how to test the throttle position sensor in these 115s? Or the resistance variances?
Click to expand...
ok figured out the test. Just need the resistance readings during the test.

I am getting closed at 0.49 ohms (online says .4-.5). So that’s good

But wide open I am only getting about 2.6 (online says 4.2-4.5).

The resistance goes up linearly but jumps a little and idk if I would call it smooth.

Note: these online readings are from Google not directly from the manual. Trying to find it in the manual that I found online
 
I like voltages more than resistance, but that said there should be not be any jumping around. If it jumps around the wipe in the variable resistor is not making good contact
 
Sorry. My numbers in the previous post were voltage not ohms.

It’s not jumping around. I was just moving the throttle body too fast. Slowed it down and seems smooth. But would the low voltage at WOT cause it to not start? And is the 4.2-4.5 the correct voltage? Can’t find it in the manual
 
The 0.49V at idle should allow the motor to start. The 2.6V at WOT is to low.

What is the reference voltage, is it 5V or something else?
 
Pulled the plugs. They are black and look carbon fouled.

I cleaned the throttle body and IAC. And it was pretty nasty. Could carbon buildup there have fouled the plugs?
 
AllDodge said:
Carbon usually builds up from to much fuel.
Fuel is controlled by TPS, MAP and fuel pressure
Click to expand...
Ok so that included with the sensor disconnect that I did yesterday for both those sensors is telling me that something is wrong with one or both of those sensors.

I swapped the map with another on that I have so it’s pointing to the tps in my opinion
 
Merc TPS is around 0.45 to 4.7WOT

As before disconnecting sensors and reconnect is bad and the ECM may be all messed up and needs codes cleared
Pulling MAP tells the ECM your at WOT and to give the motor a lot of fuel, which can be part of what your seeing
 
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