What fuel for 404?

[sluggish]

I am seeing various info on this topic all over the net and would like to get some more current, hands on opinions. I have a 63 with the 6 cyl gas engine and just wondering what fuel I should be using. I see where guys are adding oil or diesel to the tanks, and some who run only premium fuel, etc etc. I am just about to park this for the winter and want to make sure it will start in the spring when I go pick it up. Should I fill the tanks, and if so with what grade of fuel? Should I add some stabilizer to the fuel as well? Looking for some real world input from people who drive these things. Thanks.

 

[elkhtr]

Alcohol free fuel, stabil, and a zinc addative for the oil.
this is the cocktail i feed my older gasoline rigs

 

[sluggish]

Is this just for storing them or is that how you run them regularly as well?

 

[sluggish]

I assume you mean the zinc additive for the oil?

 

[frank8003]

Tell me what a 404 is and I will have the engineers answer

 

[MtnSnow]

Tell me what a 404 is and I will have the engineers answer

http://www.unimogcentre.com/unimog404.html will explain what they are

 

[Recovry4x4]

Does Cananda put methanol in their gasoline? All pump gas in the US has methanol. There is a fuel called REC90 that is ethanol free. It's used for small equipment and such. All of my carts and small equipment run nothing but this REC90. If your fuel supply has methanol, look for this type of fuel.

 

[frank8003]

8.3 :1 compression ratio?

 

[MtnSnow]

Looks like 7:1 or 7.8:1 depending on which engine
http://www.unimogcentre.com/unimog404specs.html

 

[Mercunimog404]

Any gas that will burn. They are not picky.

 

[elkhtr]

Is this just for storing them or is that how you run them regularly as well?

my gas rigs that are not daily drivers get the alcohol free fuel all the time, as well as all the power equipment that might sit a while.
I don't know about your area, but there are only three sources for ethanol free gas in my area.
call around and see if you can find it, you will appreciate the way it stores.

 

[frank8003]

We wish there was more Swift fuel available
View attachment gasoline other sources to get gas.pdf

https://swiftfuels.com/

also http://pure-gas.org/

 

[tennmogger]

I've got three 404 Unimogs with the low compression M-180 engines and they have been burning regular ethanol-additive gas for years. No problems. Sure I prefer ethanol-free gas but it's not always available. A buddy in Knoxville uses a 404 mog as a daily driver and he runs lowest octane ethanol gas too. The additives are fine, and I am one of those who put some Diesel, maybe 10%, in the gas occasionally in hottest weather. The purpose is to combat vapor locking, which these trucks are prone to. The truck runs better too.

The characteristics of today's gasoline are totally different from what the trucks were designed for. For one thing, the Reed vapor pressure is so low that the gas vaporizes easily. Try to run winter gas in the summer and it'll vaporize before it can be sucked out of the tank. Most any additive will help that (motor oil, 2 cycle oil, Diesel) and these engines burn it just fine. Modern cars use a submersed pump in the tank, and maintain higher than expected pressure, to avoid the vapor locking.

Concerning the ethanol additive, we all know it's added for political purposes instead of for performance, but it's not all bad though. If you recall years ago we added alcohol to the gas to draw out the water that's inevitable in gas tanks not used much.

Best advise for a 404 owner: run the wheels off it and it'll be happy.

Bob

 

[sluggish]

Thanks guys.

What is this vapor lock I keep hearing about and what are the symptoms.

 

[Mercunimog404]

Thanks guys.

What is this vapor lock I keep hearing about and what are the symptoms.

Its chugs. All I would do on a hot summer day when it happens is poor water on the fuel line and it would start right back up

 

[tennmogger]

Thanks guys.

What is this vapor lock I keep hearing about and what are the symptoms.

Vapor lock is caused by the liquid gasoline becoming a gas or vapor. The typical fuel pump can't pump it, and the gas cannot be 'pulled' out of the tank. The old gasoline 404 Unimogs have an on-block mechanical fuel pump and the gas has to be pulled many feet from the tanks, through filters.

Fuel vaporization happens just like boiling water but can happen at much lower temperatures. I have had a 5 gallon gerry can of gasoline in a hard boil at 80 deg F. Few older vehicles can handle that! Such a low vapor point can be due to high volatility components being added at the refinery (to get rid of them!). As long as the refinery meets current (seasonal) requirements, they can do that. The problem arises when the season changes fast and formulation can't keep up, or we pull a can of winter gas out of storage and open it at 50 deg higher temp than formulated for.

Or something like that...

 

[sluggish]

Is there a way to reduce the heat getting to it and causing the issue?

 

[Mercunimog404]

Is there a way to reduce the heat getting to it and causing the issue?

People add an electric fuel pump. You should go to Benz world. Lots more knowledge there as it is an Mercedes forum.

 

[tennmogger]

Is there a way to reduce the heat getting to it and causing the issue?

Heat is certainly a factor but the best solution is to pressurize the gas all the way from the tank to the carb. Adding an electric pump at the tank is a start. But, both tanks feed from the top. The gas has to be drawn up to reach the pump and the gas vaporizes right there inside the draw tube in the tank. This can be verified with a clear tube. Been there, done that.

At the left front corner of the rear gas tank on a 404 is a small plug, not the big tank-drain plug. Add a banjo bolt and fitting there, place an inline filter and the e-pump inside the frame rail, low as possible, and gas gets pushed up. No vapor lock.

If you designate the front tank as the primary tank, you then have the e-pump as a backup if needed, and it will draw from the "reserve" in the bottom of the rear tank. That reserve area will be the last gas available. I only use the e-pump if needed. An electric pump of the common pulse type will add heat to the fuel once it has run for a while. The original mechanical pump will not.

 

[sluggish]

I've been on there a few times but unfortunately that site will just not load for me. I don't know if it's my computer or the site but it is the only site that I ever went on that takes about 5 minutes to load a single page, meaning it would take me a good 1/2 hour just to get to the unimog section before even starting a search.

So if the vapor lock is caused by the fuel heating up, what does an electric pump do? It certainly doesn't cool the fuel. I'm assuming it gets the fuel to the carb faster than the mechanical pump and with more pressure so the fuel doesn't get a chance to vaporize.