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BF150 no start condition

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Big Ed

New member
While trolling the other day my Honda BF150 sputtered and died. I figured it loaded up and fouled the plugs. I changed the plugs on the water they looked like they were due, but it made no difference. The motor will start and purr on starting fluid, so I figured with 350 hours it was probably due for a high pressure filter. I ordered new filters, high pressure pump and regulator thinking it had to be one of those things. In the meantime I did pressure test and flow test on pump which tested good. I cleaned out water separator, changed out low pressure filter, changed high pressure filter and pump, cleaned the screen under the pump, changed the regulator and checked that injectors were firing and spraying good cones. Still no start. Jumped the two top connectors on the red connector the MIL stays on. I unplugged the tps, maf, and baro sensors one at a time. When I unplugged the baro(map) sensor the MIL flashed a 13 code but it stopped when I plugged it back in. I'm not sure which sensors will cause a no start condition or if I am barking up the wrong tree but any help would be appreciated.
 
Not sure how you did the flow/pressure test on the high pressure pump. Did you put a pressure gauge in the fitting on the vapor separator or did you do it with the pump external?

Generally, the sensor that would keep your motor from running is the crank position sensor. If the other sensors go bad, they revert to a preprogrammed setting....the motor will run but not efficiently.

You said that the engine will run on starting fluid. It sounds like you are getting spark, but not fuel to the injectors. I assume you tested injectors externally?

Have you disconnected the connector going to the fuel pump and jumpered it directly to 12v to see if the motor would run then? Get the pump running and try to start the engine. If it runs, then most likely, you have a bad main relay module. The fuel pump relay is in the main relay module.

Of course, check the fuses before you go too far with things.

Mike
 
First off thanks for the reply Hondadude. I tested the pressure with a gauge at the fitting on the vst. It showed 47 psi when I cycled the key. I checked the flow with a line hooked to the return line off the regulator into a small measuring cup which showed 45cc's per 2 second cycle. I checked the injectors by pulling the fuel rail assembly, unplugging the coils to the spark plugs and having my wife crank the motor while I watched the injectors spray. I forgot to mention in my original thread that I did check the fuses also. I have not hot wired the pump but I left gauge connected to vst port while cranking and shows 47 psi continuously until key is cycled off. It then drops a few psi. I wouldn't think the thing would run on starting fluid if the crank sensor didn't show position, but I honestly don't know much about Honda controls. I was thinking maybe the tps wasn't giving the correct feedback or something and therefore fuel air/mixture wasn't jiving. Should I hot wire pump even though it holds 47 psi while cranking and running on starting fluid?
 
I agree on the crank position sensor.

I would go ahead and directly power up the fuel pump. During starting, the fuel pump is powered by the start relay. Once started, the fuel pump relay takes over.

You did say that you got good fuel pressure with the key turned to on for two seconds. I am pretty sure that comes from the fuel pump relay....so that may disprove my theory. I do not hace a wiring diagram handy.

Let's see what happens with the direct power.



Mike
 
Thanks for the quick response Hondadude. I went ahead and hotwired the hpp it sits right at 47 psi on the gauge but still no start. I'm usually pretty good at troubleshooting but this thing is kicking my rear end. I hate to start ordering sensors and hanging parts. Not sure how the Idle Air Control works in theory but it seems like it has to have something to do with some type of air fuel feedback or something.
 
The iac adds air to the intake manifold. If it is not working...there will not be enough air to start.

If you put the shifter in throttle only and advance the throttle when trying to start....That will simulate the action of the iac.


I agree with you...this is odd.

One last basic thing...make sure your safety landyard is attached to the kill switch.

Mike
 
Mike - as I read this thread that was exactly my thought - kill switch possibly activated. Is the test for that to disconnect it?
 
I went ahead and double checked the kill switch it is good. I tried starting with throttle cracked but it made no difference. I made sure it would still start on starting fluid which it did. Hopefully tomorrow I will have time to check continuity and signal for the kill switch. I started trying to work thru the ecm troubleshooting in the manual but ran out of time today. I am starting to wonder about the ecm. I will update as soon as I get some time. If you guys happen to think of anything else let me know. Thanks again for the help.
 
Open the throttle almost half way. Just to be sure.

As Chawk said, if you disconnect one lead going to the safety switch, it will take it out of the circuit.

In two strokes and smaller four strokes, the safety switch cuts the spark, however, I am not really sure what it does on the 150. When the key switch is turned off, it turns off the main relay and shuts down the ECM. It also has contacts that does the same as pulling the safety landyard.

You obviously have spark and compression, if it runs on starting fluid. You also said that the injectors sprayed when cranking. That is very puzzling.

As an experiment, you could pull the landyard off of the kill switch and see if the engine hits on starting fluid. If it runs, then the kill switch circuit might be the problem.

Also, in checking the fuses, use a test light to be sure there is voltage on both sides of the fuse. Sometimes just looking at them is deceiving.

Since you are using the manual, I am sure you have already seen that the flow chart defaults quickly to "replace ECM with known good one". If you have a friend with a 150 that you could borrow, that would eliminate that question.

One last thought.....what is the quality of your fuel? Did you recently fill up? Have you tried flushing the fuel system and just using a portable tank with fresh fuel? I know it is a way out there idea, but whatever is the issue, it will turn out to be obvious.....once you figure out what it is.

Mike
 
Big Ed, you are far deeper into troubleshooting than I've ever been. It's curious that everything is checking out, and still nothing. You have the basics of spark and fuel, but no start!? Swapping out the ecm would be the next logical step.

A few years ago I had a new boat to me out on the bay for the first time. After turning it off it wouldn't start.......not even a cough. I had to get towed. Shortly after, I learned that the control throttle wasn't exactly in neutral. I was new to boat mechanics at the time. Arrghh!!
 
I posted a thread on this problem just a week or two back hoping that the next guy wouldn't go through what we went through. BF175 wouldn't start, but started on ether and ran perfectly after starting. We went through pretty much the whole list of things that you have been through (sensors, fuel pressure, filters, VST etc). Your logic and our logic about this problem are very similar. Finally we swapped the ECM out of the other engine and that was the problem. An obscure ECM fault that no one seems to have ever heard of. Picked up one of Honda's Oxygen sensor upgrade kits which is a cheaper way of buying a new ECM (with free extra O2 sensor) and all is good in life once again. Upside is that every sensor, pump, filter etc has been serviced. Downside was lots of manhours and $'s.
The only difference between your problem and ours is that we have BF175's and we didn't get the failure whilst running. We had an initial slower to start symptom which then moved to a won't start without ether condition. If you have twins, try swapping the ECM's.
 
hondadude said:
Open the throttle almost half way. Just to be sure.

As Chawk said, if you disconnect one lead going to the safety switch, it will take it out of the circuit.

In two strokes and smaller four strokes, the safety switch cuts the spark, however, I am not really sure what it does on the 150. When the key switch is turned off, it turns off the main relay and shuts down the ECM. It also has contacts that does the same as pulling the safety landyard.

You obviously have spark and compression, if it runs on starting fluid. You also said that the injectors sprayed when cranking. That is very puzzling.

As an experiment, you could pull the landyard off of the kill switch and see if the engine hits on starting fluid. If it runs, then the kill switch circuit might be the problem.

Also, in checking the fuses, use a test light to be sure there is voltage on both sides of the fuse. Sometimes just looking at them is deceiving.

Since you are using the manual, I am sure you have already seen that the flow chart defaults quickly to "replace ECM with known good one". If you have a friend with a 150 that you could borrow, that would eliminate that question.

One last thought.....what is the quality of your fuel? Did you recently fill up? Have you tried flushing the fuel system and just using a portable tank with fresh fuel? I know it is a way out there idea, but whatever is the issue, it will turn out to be obvious.....once you figure out what it is.

Mike
Click to expand...

How was this bf150 problem resolved?
 
It would pay off getting yourself a HDS and plug it into your DLC as it has got more codes on than the current MIL. You can also use a SCS short connector and plug it into the DLC one of these methods may point out the fault for you
 
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1 & 1/2 year old thread. But it sure would be nice to know what the solution ended up being. ECM?
I don't like starting fluid for several reasons but mostly because it is so volatile. Good in an emergency but.....

I wonder if this engine would have lit on propane?
The hot starting fluid can mask a weak spark condition.
Anywho...I guess we'll never know.
A shame.
 
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