Wisconsin VH4D carb/fuel injection swap

I've come to the end of my tolerance for the modern fuel changes and resulting complications with the carburetor on my OMC 1200.

Every year when the fuel changes for winter here in the Northeast, I deal with rich/lean vapor lock issues and cannot find a balance with carburetor settings. I've replaced the whole zenith carb with a newly rebuilt one 3 times, installed a vapor lock arrestor filter and an aftermarket carb from Amazon, played around with the whole gamut of jets and fuel pressures, etc. etc.

Finally, I removed everything before the intake and ordered a fuel injector, fabricated my own intake from 1" steel pipe, installed the butterfly from the zenith, installed an aftermarket oxygen sensor and air fuel ratio gauge, hooked up all the wiring and high pressure fuel pump, and got the engine running.

Currently, my challenge is that the injector is open constantly, and I adjust the fuel ratio by opening the return fuel valve to decrease the pressure. I can set the correct fuel ratio by setting the throttle, and then the valve while watching the afr gauge and rpm meter. It runs better than ever, but I cannot change the throttle unless I get off the machine and turn the fuel valve as well.

I toyed around with a 12v Pulse Width Modifier with limited success, but burned up a fuel injector as a result. I gather that the fuel injector solenoid overheated. I have looked online for a dedicated fuel injector driver, but all I can find is a fuel injector tester. I ordered one, but I do not have much confidence that the device will be able to handle the longevity I am requiring from it.

What I think I need is a throttle position sensor that works together with an adjustable
rate, 12v full-power pulse sending unit. I am a technical dinosaur with my hand stuck in a computer generation cookie jar. Please, anyone with some smarts in this direction deliver me from what I sense is an obvious answer just beyond my reach!

maybe the thing to do is to get a bulk fuel tank that can provide you the fuel you need thru half of the year, treat the fuel and it should be ok ,just refill when the fuel you decide to use is available. I keep 100 gal. of 100 percent gas on hand at all times.

Thanks for the reply.

This is not a practical for my use. 100 gallons would not be enough, large volumes of gasoline storage would be frowned upon on the property, and the cost and would be prohibitive. Hopefully, someone reading this is experienced with electronics enough to help me with a solution.

Trying to keep this post in the daily feed. Anyone else have an idea to help with these electronics?

Thanks

Can you be specific about what your rich/lean vapor lock issues are?

This is amazing. Where did you find a retrofit for your engine, please. You didn't mention a manifold air flow sensor. I assume you have one, or that the throttle position sensor will do adequately.

During startup and normal running, the jet adjustment is fine. After about 12 minutes of normal load, when the carb gets hot in its position under the exhaust manifold, the mixture changes enough to make it run very rich and the motor bogs down. Several seconds after the engine shuts down in this condition, a loud backfire with flame out the tailpipe results. I have installed multiple newly rebuilt carburetors, adjusted the floats to perfection, installed various vapor lock arresting systems, etc. etc. I have determined that these engines were designed to run with leaded gas, and in spite of the assurance from fuel salesmen that the new formula works fine, I have experienced otherwise. Now she runs indefinitely and strong with the new injection system. My only problem is an adjustability challenge whereby when the governor calls for more throttle, the engine runs lean because the more open throttle changes the mixture. If I can make the injector run more slowly under a low throttle, and faster under high throttle, my engine will run perfectly. I have abandoned any ideas of making the old carburetors work, and if I have to keep running her like she is, it will be worlds better than the Zenith. I just need some help with the electronics to make the mixture predictably variable and adjustable.

Thanks for any help in this new direction!

Dave1234 said:

This is amazing. Where did you find a retrofit for your engine, please. You didn't mention a manifold air flow sensor. I assume you have one, or that the throttle position sensor will do adequately.

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I made my own retrofit. I am pretty handy with the physical aspect of mechanics, I'm just half baked when it comes to electronics. I have no MAF, nor do I know how to make one work with an injector. Any retrofit I have researched is not designed to work with my engine. I would love to work with a budy who knows these types of systems, but so-far y'all are all I have to help me in that regard. Here are a few pictures of the system.

T-rustyfix said:

During startup and normal running, the jet adjustment is fine. After about 12 minutes of normal load, when the carb gets hot in its position under the exhaust manifold, the mixture changes enough to make it run very rich and the motor bogs down. Several seconds after the engine shuts down in this condition, a loud backfire with flame out the tailpipe results. I have installed multiple newly rebuilt carburetors, adjusted the floats to perfection, installed various vapor lock arresting systems, etc. etc. I have determined that these engines were designed to run with leaded gas, and in spite of the assurance from fuel salesmen that the new formula works fine, I have experienced otherwise. Now she runs indefinitely and strong with the new injection system. My only problem is an adjustability challenge whereby when the governor calls for more throttle, the engine runs lean because the more open throttle changes the mixture. If I can make the injector run more slowly under a low throttle, and faster under high throttle, my engine will run perfectly. I have abandoned any ideas of making the old carburetors work, and if I have to keep running her like she is, it will be worlds better than the Zenith. I just need some help with the electronics to make the mixture predictably variable and adjustable.

Thanks for any help in this new direction!

Click to expand...

I should add that if I spray cold water on the carburetor after it begins to bog down, it begins to run better for about a minute. I have gone so far as to install a water injection system that sprays cold water onto the carburetor when I push a button just to get me through a job. Believe me, I have tried everything.

Oops, the pics didn't load…

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I installed the fuel injection system today along with the injector tester.

The tester has a continuous pulse mode which starts when I push the "play" button and runs indefinitely until power is turned off or the button is pressed again. This pulse runs at 50-7 millisecond pulses per every 1450 milliseconds. According to my calculations, this translates to about 34 pulses per second. When I run the engine, I get about 900 rpm at this level of fuel supply. Any higher throttle and it runs lean very quickly. If I could increase the dwell or pulse rate with a variable input from a throttle position sensor or rigged up pot adjuster, I could make it work. I'm just not sure how to do it, or what components to use. Here are some pictures of the installed and running unit

Here is a picture of the tester unit's paperwork description

Here is the guts of the unit. Is there anyone who can help me remake this board or make another one that will accomplish these parameters?

Is there a way to install a variable output and reprogram this board?

At the risk of asking the obvious, did you try to re-route the exhaust and muffler? Try home made double or triple wall ventilated exhaust piping, or ceramic insulation between the heat source and the carb? electric fan to blow on the carb/insulation gap? re-plumb the carb further away from heat or below the fuel source so there is no lift in the lines to get fuel to it? Raise the fuel tank (even if temporary as a test) or add a fuel pump , re-plumb your manual bypass valve up to the driver area so you can adjust it manually without getting out,? Is it possible there is some clogging in the shrouding of the engine forcing too much hot air in the direction of the carb? It seems like getting a fuel injection system to work well automatically is going to take a computer to balance it all out (But diesels and early corvettes ran without all that , so there must be a simpler way that I don't know of.) Ultimately, you know that gasoline doesn't just immediately evaporate whether winter or summer--it takes time at atmospheric pressure. Eliminating fuel vacuum conditions and excess heat in the fuel system ought to resolve the problem. No doubt winter fuel is designed to evaporate at a lower temperature. Your system must have been really marginal even before gas changed with the season. I doubt lead had anything to do with it. If you wanted to check, I think aircraft gasoline still has lead in it, but it might not be adjusted for the season so might no tell you anything definite.

On my 440B I had the same sort of issues. Flooding when hot. Especially when the machine was rocking while in motion. Loud backfire on occasion when shut off.
I lowered the float level a tad. Had to try a few adjustments. And added an electric fuel pump That was a few years ago now and it still works fine

The exhaust manifold on a VH4D surrounds the intake. There is no way to re-route it. Yes, I have tried all of your other suggestions as well as heat shields, fuel cooling systems, extra fuel pumps, cold fuel flow bypass and on and on, all with no long-term success.

Please consider this info regarding boiling points and fuel blends:


Thanks for all of the attempts to get my old, frustrating, non-working carburetor back on the engine. You are all quite persuasive and tenacious. This must be why I love this forum so much! Really, though, who wants to invent a simple system for fuel injecting small engines with me? Let's Go!

I just did a search for DIY fuel injection--seemed to be lots of stuff out there that might be useful--have you been there? This looks potentially doable--https://www.hotrod.com/how-to/budget-electronic-fuel-injection/ or this https://www.hotrod.com/how-to/a-homemade-tbi-conversion-for-904/ And this page has some useful calculators--http://www.megamanual.com/v22manual/minj.htm#size--that define numerically what you seemingly have done seat of the pants with pressure adjustments. As i said originally--what you did from scratch is amazing.

Just to add to the conversation, I am restoring my 2nd old, carbureted 6 cyl Pontiac engine with the exhaust and intake manifold on the same side. I am having the exhaust manifold ceramic coated to keep the heat in the exhaust and reduce the heat rejection into the engine compartment.