Gas in Oil

[rydog1130]

Soo I’ve noticed a small leak under the green 70 bronco. It looks like really thin oil dripping from the rear main seal area. Further inspection it’s oil and gas mixed which is NOT GOOD! Reading up on this I found a few causes, bad fuel pump (just replaced it and this leak was happening before this so it could’ve been the old pump) and badly tuned carb. The car was taken off and cleaned out due to bad gas. I’m not sure if my dad adjusted the jets properly after reinstalling it. Any other areas of concern? I changed out the plugs as the other ones were laden with soot and heavy build up of carbon. I’m also def changing the oil immediately

 

[Apache Bronco]

If it runs good it is not a badly tuned carb. The diaphragm in the fuel pump had a tear or hole that allowed fuel into the crankcase. You should have had way more than 5 quarts of very thin gassy oil drain out. This happened to me on a Jeep. It does clean out the oil passages though.

 

[B RON CO]

Hi, a bad fuel to oil problem could raise the oil level on the dipstick. How did you figure the drip is oil and gas mixed?
A rear main seal leak is a big headache, and gas in the oil is a bigger headache.
It may be time for a compression test and more a engine evaluation.
Good luck

 

[Local Boy]

An excessively rich condition, as your plugs may indicate, can lead to raw fuel being pumped (fuel wash) past your rings into the crank case...If this is condition is prolonged, it can lead to loss of compression due to ring/cylinder wear as the oil is "washed" off the cylinder walls in the process.

Let's hope it was your fuel pump leaking fuel...

Aloha

 

[Broncobowsher]

Also a fuel leak washing oil down.

Gas in the crankcase is the bigger issue. Gasoline is not a lubricant. If the crankcase level is rising, that is gas diluting the oil. Even if it isn't rising, you can still have gasoline contamination (gasoline taking the place of oil as it is consumed). Start by checking the oil, smelling it, feeling it.

 

[rydog1130]

Ok, I’m going to change the oil and keep an eye on it

 

[rmk57]

Most of the mechanical fuel pumps on the Fords I've owned have a weep hole to prevent filling up the crankcase with gas if the pump does bad.

I would check fuel pressure at the carburetor or a sticky float, needle and seat not sealing. I've had them where it's so bad when you shut the engine off there's gas pouring out the boosters, flooding the engine.

 

[blubuckaroo]

Modern fuel has a lower vaporization point than when these cars were built. This leads to vapor lock and float bowl percolation problems with carbs. The ARB Edelbrock carbs in particular have this issue because of the position of the float bowl.
Sure you can open the throttle a bit when starting a warm engine, but the real problem is the oil contamination. Problems like this need to be fixed, not just avoided. Sometimes a carb spacer and/or lowering the carb's fuel level are needed. Either that or plan on changing oil really often.

 

[rydog1130]

Most of the mechanical fuel pumps on the Fords I've owned have a weep hole to prevent filling up the crankcase with gas if the pump does bad.

I would check fuel pressure at the carburetor or a sticky float, needle and seat not sealing. I've had them where it's so bad when you shut the engine off there's gas pouring out the boosters, flooding the engine.

I think I found the issue ...sticky float!

 

[Tjmiller]

I have the same problem. I first noticed it last year. I replaced my fuel pump and made sure the gas cap is vented but I still have the problem.
I have a newly rebuilt 347 (4 years ago but it only has 2-3 hour of total running time) with a brand new holly 4 barrel carb.
I've been working on some final details to get everything running over the past week. It is hard to start when cold and I've been trying to adjust the electric choke. If I manually close the choke all the way, it starts right up. It also starts easily once warm. But it does seem to run rich.
I've been running it for 5-10 minutes every couple of days for about 1 week.
Last night I drove it about 2 miles to my friend's and it was running bad. It would not go above 40 MPH. It would rev up fine with the clutch in, but had no power. When I went to leave, the engine was still hot, but was struggling to crank. I knew the battery should be fine but tried jumping it any way without success. I checked the oil and it was about 1" above the full mark and smelled like gas again. I drained the pan and got 2.5 gallons of dilute oil/gas out.
I'm starting to think I have a problem with the carb but ignored it so far because it was brand new.
What do you all think?

 

[bronkenn]

You may need to put a vacuum gauge on it and make sure you have the right power valve. The vacuum is what keeps it closed until you need it. A vacuum gauge is your best friend for setting up a Holley. If it has the 4 corner idle circuits you can use the gauge to adjust that as well. The power valve shouldn't affect it too much at higher speed but if the engine got loaded up at lower speed it could have fouled up the plugs and caused it to run lousy.

 

[Broncobowsher]

Since I have had this multiple times after putting stuff together, check the float level. Holley has sight plugs or sight glasses on the fancy stuff. The glass should have fuel half way up, the plugs should be slight dribble out the threads after you remove it.

What happened to me a couple of times is a sliver of rubber fuel hose gets caught in the needle and seat (for some reason always on the secondaries) and causes that fuel bowl to over flow. Look at the venture boosters (all 4 of them) while the engine is idling. If you see fuel dripping off them, you have a hung float and the bowl is overflowing fuel into the engine. If you pull the sight plug like this be prepared for a LOT of gas to come running out. It's a few ounces but you will feel like it is a quart when it happens. Outside, fresh air, no ignition sources, etc.

 

[oldiron]

Here's another culprit to the "sticky float" problems several of us have had lately. In a lot of the new rebuild kits (I'm talking about the 2100's here) the needle and seat assembly are the type that have a slot on the top of the seat meant to use a large screwdriver to install. Problem is that when installed everything looks great...but on occcasion (or all the time) the needle can't seat properly because the clip that holds the needle to the float will hang in the top of the slot and not go all the way closed. I chased this one for about two months before I found it. Replaced it with a seat that is hex shaped to use a socket to install, no more engine flooding, or occasional spill over.
Hope this helps you.
Greg

 

[Tjmiller]

Do you think I've already ruined my new motor?

 

[oldiron]

Do you think I've already ruined my new motor?

Not likely.

 

[Tjmiller]

I have the Street Avenger Holley so the needle isn't actually connected to the float. However, I took it apart last night and found a few interesting things. There was a lot of brown deposit inside the bowl and the needle was kind of sticky inside the assembly. There were also a few pieces of aluminum millings(from factory?) on the gaskets. The fuel screen on the inlet was somewhat dirty with tiny rust chips.
I cleaned it up and put it back together (nobody in town had the rebuild kit). I changed the oil and filter.
I also adjusted the float down a lot because the gas level was about at the middle of the sight glass. When I started it up, it ran great at idle and warmed up nicely. The exhaust smells much leaner. I did't smell any raw gas at least. When I rev'ed up the engine, it had a 1 second hesitation at the start of a quick acceleration but recovered. If I rev'ed it slowly it did not hesitate.
On a test drive the hesitation was present on take off and every time I shifted gears. Other wise it was running very nicely. Plenty of power. The hesitation only presents with a quick acceleration and is at the 1000-1500 RPM range.
What is causing that hesitation? I contemplated raising the float level more, but I don't want it to start flooding again.

 

[bronkenn]

Could be your accelerator pump.

 

[Tjmiller]

Could be your accelerator pump.

I thought about that too but it didn't hesitate before I took it apart yesterday. Are there adjustments to the accelerator pump?

 

[bronkenn]

There are adjustments for the accelerator pump.https://www.bing.com/videos/search?...357E2F4F597483526706357&view=detail&FORM=VIRE