68 Unimog 404.1 and Ethanol

[Karl kostman]

Hello Folks I have an aiisue that I would like some suggestions/ideas on how to best fix! I have a 68 Ex Swiss Army 404.1 Unimog and when I bought it it ran well but started kind of hard, it needed more cranking than I thought it should, well in looking at the problem I found the fuel pump was very weak and the hand primer lever on top the pump did nothing, well definitely rebuild time. Ordered the rebuild kit and got through that just fine and after install the truck started instantly like It should, all if good! Well this lasted for about a month and a half and it was back in the crapper again, it displayed ALL the same problems it had in the past prior to rebuild including the lever on the pump not working anymore. I asked around on this site and a very nice fellow popped up and said that its an Ethanol problem, according to him he does not know of a rebuild kit available today that will tolerate the use of Ethanol fuel, even 10% is TO MUCH for the rubber used in these trucks fuel systems. Well it made sense to me and he seems to be a pretty reliable source of information concerning this. SO here I am and the way I see it I have three choices. 1. find a rebuild kit that has all the pieces that can and will work with Ethanol laced fuels? 2. convert the fuel pump to a 24 volt electric type and depend on a good fuel regulator to keep the fuel pressure low enough to work with the carburetor? 3. quit driving the truck (BAD OPTION)!
Any Ideas or thoughts you may have concerning this would sure be appreciated, and I sure with I had this information BEFORE I rebuilt the pump, as always its that HINDSIGHT thing we all run into one time or another.
Thanks again for your time and I sure look forward to some Ideas!
Thanks much
Karl

 

[Recovry4x4]

How much do you drive it? You can purchase fuel that is sans ethanol. All of my small engines run on this. Should be referred to as REC90.

 

[Karl kostman]

I drive the truck about 2000 miles a year partly to truck shows and parades and the rest just my own personal use, it is greatly my preference to be able to drive the truck and fill with fuel when I need to and if I can get non-ethanol fuel use that but there are times when that is just not possible, like when I am in MN, is this a solution, maybe it is but certainly not my first choice. Can I haul all my own fuel to all these shows, yes but we all know the hassles and potential liabilities involved in that. My first choice is to fix the truck so that it is usable under normal conditions, and that means filling from a pump at a gas station.
KK

 

[m16ty]

Stay-Bil makes a marine formula fuel stabilizer that claims to combat the effects of ethanol. I have used it in my small engines but I have no data to say if it actually works as advertized.

If you've got a small airport around, you can also use aviation fuel. It's kind of expensive but is ethanol free.

 

[ducer]

Stay-bil blue marine formula is what a lot of people are using in their small engines. Sta-brite I believe also makes a concoction. You also could try washing your fuel with water to remove the alchohol.

Denny

 

[kipman]

Or store the fuel in a 5 gallon glass jug, let it sit for a month and see the ethanol seperate. Then siphon off the gas, this works better for small amounts but you get the idea.

 

[andy3]

I used to have issues with Ethanol in all of my small engines and several Onan generators. I started using Star Tron fuel treatment and (knock on wood) have not had an issue in 4 years. The problems were constant before.

 

[tennmogger]

Hello Karl,

The pump lever on the fuel pump works only if the shaft of the fuel pump, from the engine, is not operating the pump. Since most engines tend to stop at about the same rotational location every time, the lever may be fine, just being rendered inoperable by engine position. A bump of the starter to rotate the engine might show a perfectly fine manual priming pump.

I have been using ethanol gasoline in two 404 trucks since ethanol was mandated. The ethanol has not caused any problem with the original fuel pumps. Is it possible that the ethanol is simply dissolving deposits from your tanks, and contaminating the pump and carb? One of the first maintenance jobs on a 404 is to completely clean out both tanks. There are those huge drain plugs to facilitate the job. With the plugs out you can reach up inside and pull out the tank filters from over the ends of the pickup tubes, if they are still there, and clean them.

Slow starting in a 404 could certainly be lack of fuel, or it could be poor starting fuel mixture. The carburetors on 404's have a special choke mechanism that behaved quite differently from most. Rather than reducing air flow through the venturi to richen the mixture, the air is metered through separate choke openings. With choke applied, the correct mixture of air to fuel is achieved without depressing the accelerator. In fact, pressing the foot petal or pumping the pedal will almost guarantee a flooding engine and slow starting. The procedure that works best in both my trucks is to not touch the accelerator pedal but simply pull the choke out all the way. Crank the engine and it starts right up. That works even if the trucks have been sitting for months. Then push in the choke knob as you take over maintaining engine speed with foot pedal.

But, there has to be fuel in the carb so we're right back to your fuel pumping situation. When a 404 is shut down after normal use, the carb soaks up heat from the exhaust manifold and the fuel evaporates out of the bowl. The highly volatile gasoline we get today exacerbates the evaporation. Be sure there is the fiber isolator spacer under the carb.

An electric priming pump is a good accessory for a 404. Not only can you refill the carb before starting the cranking, but an electric pump helps avoid vapor locking on hot days (again, very volatile gasoline, especially winter mix 'left over' into Summer). An electric pump can be installed in series with the fuel line out of either tank. I installed a new banjo fitting at the small plug in the bottom of the rear tank, left front corner. That little drain plug is hardly noticable if you have not looked. By taking gas out of the bottom of the tank, directly to a filter and electric pump, the gas is never 'sucked' out the top of the tank and that helps avoid vaporizing.

Good luck,

Bob

 

[Karl kostman]

Bob Thank you very much for the information you have certainly given me a new direction to proceed on with this project, and as far as the choke goes I new nothing about this and just thought it worked like every other choke assembly I have used in the past. Thanks again Bob, your suggestions are highly appreciated
Karl