Honda 50bfi fuel injected false starts

I have a Honda BF 50hp efi (fuel injected). Many times when I try to start it, it takes 5 to 6 tries to get it to fire up. It sounds like it is going to start but once I release the key it dies. I can advance the throttle in neural and turn the key. That often is a big help, but then it reaves up to 1,500 rpms as it starts. I can push the key down (choke?) when I turn it, but that doesn't seem to make any difference. I do not hear any sound from the engine when I push the key in (should I hear the choke solenoid?).

It idles at about 850 to 950. I have tried to adjust the throttle linkage to increase the idle rpms in hopes that would give it more gas at ignition. I am maxed out on that linkage adjustment and it didn't help much. This is a relatively new problem that is getting worse and worse. It now happens about 80% of the time I start the engine. It runs beautifully once started. This happens in hot and cold weather.

Of course the problem is intermittent and seems to happen more deep in the LA marsh than in my garage.

I have also tried the following:
New water/fuel separator filter
New plugs
New high pressure fuel filter
New in line fuel filter
Fresh gas
Have run several cans of different injector cleaner
High and medium octane non ethanol gas

My other thoughts are:
Some efi sensor is not sending the correct feedback to the computer or the computer is malfunctioning at start up. Any thoughts what sensor I should replace if any? Do you think a computer diagnosis might help (I don't have one). Should I pull and clean the injectors? If so who does the forum recommend.

Or should I just haul it to the shop!?

This forum has been a big help in the past and here I am again. I appreciate any feedback.

Thanks

Did you cleaned the IACV,Throttle body ? This EFI engines doesn't have choke. fuel supply and idle air will control by computer. And should not increase the idle rpm by adjusting throttle link.at idle throttle valve should fully close.
yes one of sensor or computer can be malfunction,did you get any check engine light?for that you can pull out self diagnose code by using short connector.

wajira

Thanks

IAVC throttle body? No I did not clean that. Don't know what that is. Is that the port the throttle valve is connected to?

Well, that makes sense that I didn't get much change as I adjusted the linkage and pushed the key in.

I get 2 beeps when I power the key on and all of the panel lights light up for a second, then only battery light stays on. No check engine light when I kept turning over the starter.

I assume an diagnostic computer would tell if the sensors or control module were bad?

I found the IAVC in the shop manual and will check resistance. I don't think there is any way to clean it.
Thanks
Keep the ideas coming.

Remove it and clean the screens and make sure that the openings into the intake manifold are not plugged up with carbon.

Mike

Thanks Mike
Will do. Resistance checked out at 12.2 ohms. I show that in range.

More discoloration than carbon build up but I cleaned it and may just replace the whole valve in hope of a solution.
Thanks

It might the the valve or it might be the lack of signal to operate it.

Keep it connected electrically, but keep it removed from the engine. Turn the key to on and see if the piston inside moves any. If it does, it is getting a signal.

Then try to start the engine without remounting the iac. Be ready to turn the engine off quickly. If everything else on you engine is working right, it should start right up at a high idle. If you can.... have someone watch the piston inside the iac at the time you are going from on to start. I can not remember for sure if the iac moves when the key switch is turned to on or if it moves when you start the engine ....or both. It should move at least a little at either of those times.

Mike

Mike,
Voltage going to the valve's wire connection while the valve is still bolted to engine is 3 volts with key is turned on. Then it jumps to 13 volts when I crank the engine.

When I plug in the wire connection bu, remove the valve from the engine to observe the plunger the following happens:
Turn the key to on - plunger moves a very small amount but appears to return quickly to its' original position.
Crank the engine - plunger does not appear to move but the engine does start and rpms jump to 2,400.

Not sure what all that means other than it is getting a signal and unfortunately may be working correctly. I would prefer that the value was bad in oder to solve the problem.

Thanks
Any additional thoughts?

start the engine with IACV connected, then remove IACV connector, at that time engine should not go off,idle rpm go down and unstable but it should not go off.then connect IACV again and see whether rpm become stable,So its mean IACV is functioning, still my idea is to clean the throttle body.you did everything so you can try that also.(but i dnt have much experience with BF50 but other big engines it works )

wajira

Wajira

Thanks
I started the engine and idle at 900 rpms. Disconnected IACV and rpms droped to 660 and got 2 beeps. Then engine died. Tried it several time and got basically the same results (some times dropped to 700 or 725). Engine always ultimately died after about 30 seconds to 1 minute after dropping rpms.

When you say clean throttle body I assume you mean the right circle per the picture and not the inlet manifold per the left circle on the picture?


Thanks yet again.

Wajira
Yep, your right - fair amount of build up on the throttle plate, walls and into the manifold. What's the best way to clean? Carburetor cleaner sprayed in the manifold or should I take the whole manifold off to clean?

Yes throttle body is right circle but not plastic thing mettle unit with 4 screw. carburetor cleaner is best,but its better to remove throttle body from the manifold,then you can clean it properly,important part is get clean idle air bypass passage.for that you have to remove throttle body.clean well throttle valve and inside,if too dirty it should make something change at start.

Great, Thanks
I have removed the throttle body and will clean it with carb cleaner. I am leaving the manifold on, unless you advise to remove and clean that as well. There is build up on the inside of the black plastic intake manifold but hopefully cleaning the throttle body and valve will work.