fuel loss mystery

[Bobacuda]

I filled my B4B, drove about 150 miles and ran out of gas. The truck has been gettin about 15-18 mph, so this should not have happened. 
 

I found a minor weep at the rubber line from the steel line to the fuel pump. Fixed that. Float working fine, can’t find any other leaks and it’s hard to believe that could have weeped about 7 gal unless it was really squirting out at 50 mph.

Another thought - I have never experienced a Mopar fuel pump diaphragm leaking back into the crankcase. Have any of you experienced this?  What symptoms did you observe?
 

I checked the oil after the truck had set a couple of days. No gas smell and about the level is about where it normally is. I would assume the engine heat would vaporize gas if it got in the crankcase. 

Otherwise, if that weep was not the culprit,I’m stumped.
 

Thoughts?

 

Edited October 4, 2023 by Bobacuda

[bkahler]

I don't know that fuel will evaporate once it gets into the crankcase, at least that wasn't my experience recently with my Cushman Truckster that recently suffered this malady.  I do know that if enough fuel gets into the crank case the bearings will eventually fail. 

 

 

Edited October 4, 2023 by bkahler

[wallytoo]

you are positive you filled the tank?  i've done that once (in my cj5) where i thought i'd filled it, but it was well short of full.  ran out of gas later that day.

 

on my b-1-f, i know it's full when i can see fuel in the filler neck.  that's where i always fill to.

[Bobacuda]

A friend of mine that lived in Alaska told me they would put diesel or kerosene in the crankcase to thin the oil in winter. As the engine warmed, the diesel or kerosene would burn off. On this, I only know what I was told. But i also know gas would burn off faster. 
 

I will gas can it enough to get back to a gas station (using non-alcohol gas) and will keep working on it. 

[Los_Control]

Just now, Bobacuda said:

A friend of mine that lived in Alaska told me they would put diesel or kerosene in the crankcase to thin the oil in winter. As the engine warmed, the diesel or kerosene would burn off.

IMHO, comparing Diesel/kerosene to gasoline is like comparing apples to oranges.

Diesel has oil in it, it is a lubricant. Gasoline is a cleaner and cleans oil up.

 

I understand in Alaska why they would want to thin the oil in winter, but the diesel still brings a certain amount of lubrication with it.

 

Too much gasoline in a cylinder could be bad as all of it will not burn and it could "wash out" the cylinder .... meaning clean away all the oil on it the rings need for lubrication.

Same as if it gets in the oil, the oil loses effectiveness and the bearings do not get the same protection they should be getting.

 

I never ever heard gasoline will burn off from the oil. I only know it is bad and problem should be corrected as soon as possible.

 

Story time 

When I was 22 years old, I hooked up with a divorced girl with a child .... we have now been married 35 years.  ?

First I bought a single wide mobile home, then I made a deal on some property, then I bought a old county 2 ton 1961 Dodge truck to move the mobile home.

Typical 22 year old with no brains. The truck was overloaded with the mobile home .... could not drive over 35 mph .... front tires were barely touching the ground.

I had no trip permit or license to pull the trailer .... pulled it 30 miles on the freeway and all went smoothly  .... Wife following behind me in the Hot Rod with the 4 ways on.

 

Just saying I bought the truck for a purpose, later it was used to clean up the property, at times it was our only running vehicle and hauled me to work every day and to the grocery store. My wife drove it all the time, the old slant 6/4spd. ...... The carburetor was always junk on it and leaked gas into the oil. Idled And accelerated fine .... but leaked gas into the oil.

 

One day while driving it on the freeway, it was payday and wife was coming to meet me at lunch to get my check and go shopping. She heard a loud explosion.

She pulled over right away thinking a tire blew. The truck was idling fine, she walked around the truck and all looked fine. So she went on her way.

I told her I would look at it this weekend .... What happened is the excess gasoline in the crank case ignited and it exploded.

The dipstick was 1" short & all curled up. I had to stand on the fender and uncurl the dipstick as I pulled it out. It was 1" shorter then before the explosion.

 

I must have been 24 or 25 years old and much wiser, so I changed the oil & installed a used dipstick ... then drove it another year or so before trading it off.

Thats my only real life experience with a engine with gasoline in the oil, it did not kill that slant 6, but it was not pretty either.

[Bobacuda]

Los - your story is why I’m trying to find if anyone has experienced the fuel pump on a Mopar flathead dumping fuel in the crankcase. 
 

I have no symptoms of gas in the oil that I recognize, but since that may be a possibility, I figured I would ask.
 

I plan on putting more gas in the tank, checking the oil level, then going to the gas station (20 mile round trip) to fill up.  I will check level with a rubber hose. As soon as I get home, I will check the oil level and look for leaks. I will check gas level with a rubber hose. 
 

 

[Los_Control]

Sounds like fuel in the oil is not a issue in your case ..... I also would not feel comfortable thinking it was a non issue. In case you did.

 

Sounds to me you need to keep searching to find the real issue. ..... The joys of being a mechanic & testing your detective skills.

[LazyK]

I found a minor weep at the rubber line from the steel line to the fuel pump

if this was on the pressure side on the fuel it is entirely possible that was you fuel loss. Suction side of the pump would have sucked air and acted like you were out of fuel.

[ggdad1951]

A diaphram leak (at least my experience) also dribbled a line of gas as you drove/puddle inder the pump sitting as the weep hole drains outside the engine area.  But to be safe I pulled the plugs, drained and replaced the oil.

[JBNeal]

A diaphragm leak would definitely leave some residue below the pump body, on the block, and maybe on the side of oil pan.  Even after a few days, the gasoline-thinned oil would have a different odor than non-thinned oil, even feels different between thumb and forefinger.

 

A rubber fuel line leak would dump some fuel out for sure...I had a hose that leaked at the crimp, was not dumping it out but it leaked more when I got off the throttle, kinda like when coasting downhill after climbing a grade...enough of that high-low throttle movement, and ya just might be dumping gallons out of a tankful.

 

Was the fuel gauge telling ya any whoppers?

[Bobacuda]

No large, observable leaks. I did find that small weep on the input side of the fuel pump. Can’t see anything obvious. Oil smells like oil - can’t smell gas in it.
 

I’m going to reflare the steel line, reattach the brass fittings that allow the rubber hose to fuel pump and replace the rubber hose. After that, I am pulling the top off the carb and checking the float level (I noticed the top gasket was fuel soaked, but no major outside leaking.)
 

Back to snipe hunting. 

[Ivan_B]

If you are talking about misplacing gallons of gas, it is not in your crankcase, otherwise you would see it. Don't worry about that.

Are you sure that the tank is currently empty? Are you going by the dash gauge or manual check? I, recently, had a false running out of gas issue. Turns out, it was not running out of gas at all, but got extremely rich and stalled, under certain conditions. And, of course, would not start afterwards. I did not have time to investigate that, so far, but it looks exactly like when you are running out of gas, except that the tank is full

 

Alternatively, you could've just had increased fuel consumption, since the last time it was getting 15-18 mpg.

 

[Bobacuda]

Tank was empty. Put 4 g in, primed carb, it started.  I gues. It is just trying to keep life interesting. 

[Ivan_B]

How about you do a metered run - drain the tank (or attach the pump to an external container), put one gallon in, take some spare gas with you, and drive it off to see how far you can get? If you cannot see puddles of gas underneath the car, or smell leaks, it is probably all burning up

Once I removed the air filter and saw how much gas it squirted into the carb from the accelerator pump, once you press the pedal, I was very surprised...

[Bobacuda]

Before I go the Roadkill method with the small gas can, I’m going to see how much difference fixing the weep in the fuel line makes. It’s possible the weep was stronger when driving 50 mph for several hours. 
 

Anyhow, the weep is fixed, the float was set correctly and the float’s needle valve is working properly. 

[1949 Wraith]

Just wondering if the fuel pickup in the tank has a hole in it? Sucking air instead of fuel for the last few gallons?

[Bobacuda]

Filled the truck with gas about 10 miles from the house. Checked with rubber hose, way up near top.  Due to its recent problems, I kept it running while I filled it.
 

It was then I noticed it was dripping oil in the area that rear main seals leak - that was new. As I got near home, oil pressure dropped below 40 and would go down to about 10 or 20 at a fast idle- that was new. 
 

Parked in shed, can’t smell or see gas.  Used the rubber hose and the gas was much lower. 

Oil is full on the dipstick, does not smell like gas, but looks and feels thinner than 40w. 
 

I am starting to think the fuel pump is leaking into the engine at speed.  There, it thins the oil and either leaks out the rear main (or other seals), or is evaporated off. 
 

Other than that, I’m stumped.  I have an old fuel pump to try next, as soon as I fix its “drift pin” issue. PITA. 

Edited October 19, 2023 by Bobacuda

[Ivan_B]

If the oil level is still the same, I doubt you are leaking gas into the engine. Hot oil will feel thinner

How much lower was the fuel level once you got home? If you've pumped like a gallon into the engine, your oil would be coming out of the fill tube by now...

I forgot, did you already check the plugs? Do they appear normal or black?

Edited October 20, 2023 by Ivan_B