Hey guys! Still working on 78 F150 351M. First, background... Started resurrecting dad's old Ford this summer. It sat in a field for about a decade after he died, until I dragged it home. Since then, and with the help of some REALLY smart dudes in this Forum, I've got it running AND moving without being pushed, pulled, or dragged. But she won't quit tooting! Little toots, but kinda stinky. I've already...cleared out of fuel, Replaced fuel pump (twice actually &#128580and filter, of courseRebuilt carb according to the specifications and the much more useful post by fmc400
Plugs and wires
Cap and rotor
timed to 8°BTDC
checked for vacuum leaks
Changed oil and filter after the first replacement fuel pump crapped out and puked fuel into my crankcase
coolant flush (because it needed it)
Pcv valve
Egr was already deleted

I forgot to add that the backfiring gets more frequent when it's in gear. Even before it got ditched in a field, it leaked so much type F that (i'm pretty sure) my dad was buying tranny fluid in bulk, so after I got the motor running, I didn't put it in gear for the first time until a week ago. As soon as I did, the truck bogged down and sputtered out like it was starving. It took me a bit to find the fuel pump problem because I'd only installed it a few months before, when I first brought the truck home, so it had manged to dump a lot (like, A LOOOOT) of fuel into the oil before I realized. Even after the oil and filter change, I can still smell gas in it. I thought that might be the problem, but I'm just not convinced. So, I thought I'd ask the experts before dumping money into an issue that isn't the issue.

I'm open to any suggestions. Thanks guys!

 

Mechanical fuel pumps can fail and let fuel get into the oil. And the gas breaks down the oil and you can wash out your crank bearings. Investigate that ASAP.

 

Change oil again, it doesn't take a lot of gas to kill oil lube properties.

A toot can be leaking head gasket issue, or loose plug.

 

What are you putting in the gas tank? Refried beans?

 

Mmm-hmmm, and what might that investigation look like...? If my crank bearings were in the beginning stages of crapping out, what symptoms might I experience, do you think?

Yeah, I'm going to do it again tomorrow afternoon. Was just hoping to get a diagnosis on the root cause in the meantime.

 

Wait... is that an option???

 

I suspect extremely low oil pressure could be a sign.

When you mix gasoline with engine oil in your crank bearings, it significantly reduces the oil's lubricating properties, leading to increased friction between the moving parts of the engine, which can result in rapid wear and damage to the crank bearings, potentially causing engine failure if not addressed promptly.

Key points about mixing gas and oil in crank bearings:

• Reduced Viscosity:
  Gasoline is a thinner fluid than engine oil, so when mixed, it significantly lowers the oil's viscosity, making it less effective at creating a protective film on bearing surfaces.
• Increased Friction:
  With a thinner oil film, more friction occurs between the crankshaft and bearings, causing excessive wear and potential scoring.
• Deterioration of Additives:
  The additives in engine oil, designed to enhance lubrication and protect against wear, can be compromised when mixed with gasoline.
• Potential Engine Damage:
  Continued operation with a mixture of gas and oil can lead to significant damage to not only the crank bearings but also other engine components like cylinder walls and piston rings.

Causes of Gas Mixing with Oil:

• Faulty Carburetor:
  A faulty carburetor can allow fuel to leak into the crankcase, mixing with the engine oil.
• Fuel Pump Issues:
  Problems with the fuel pump can also lead to excessive fuel delivery, causing fuel to mix with the oil.

What to do if you suspect gas in your engine oil:

• Check Oil Level and Appearance:
  Regularly check your engine oil level and observe its color and consistency. If it appears unusually thin or has a strong gasoline odor, it may be contaminated.
• Change Oil Immediately:
  If you suspect gas in your oil, change it immediately with fresh, clean engine oil.
• Investigate the Cause:
  Identify the source of the fuel leak and have it repaired by a qualified mechanic.

 

Ok, that sounds reasonable. And a bit less freaky. I was worried that some fatal damage may have been caused during the time before I caught the defective fuel pump. I wasn't even thinking there could be a problem with the fuel pump that I just installed, and I hadn't checked the oil since I'd already changed it, so I was running it on and off, for just a few minutes at a time, for a couple months while I was trying to find the problem. I changed the oil immediately after changing the pump, but it does still smell like gas a bit, though not all thin and watery like it was. The oil pressure is OK, too, and there aren't any funny noises or smells or other abnormalities aside from the tooting. I'll update tomorrow after the oil change. Hopefully the toots will subside once she's a bit less gassy.

 

Toot toot

 

Gotta say, that was not the video I was expecting 😁