Slight gas smell on oil dipstick

[Sixpactogo]

Never, ever start a car and let it "warm up". The engine never gets warm enough to burn off condensation. It also runs on the choke which adds to the over rich problem and washes down the cylinders, which puts more fuel in the crankcase that doesn't burn off. If you are going start it, drive it. And not just around the block. It also burns condensation from the exhaust. If you can't do that its better to let it sit. Fog the cylinders for the winter layover.

I never use the red X without an explanation why.
I don't agree with the any claims of this one though. Warming an engine is not hard on it unless the choke is not set up properly. On fast idle the choke should be open giving plenty of air to not be washing the cylinder walls. Also, after it has been idling for 10 minutes try putting your bare hand on any part of the engine then tell me it won't get warm enough to burn off condensation. I don't think I want to grab the tail pipe by then. In my neck of the woods, I put a half million miles on my D150 440 truck from new in 1978 until the late 90's with only a valve job on the engine. When I restored it in 2015 it got a .10 over bore so all those warm-up periods it got in lots of -15F Wisconsin and Minnesota temperatures didn't hurt it and qualifies my beliefs.

 

[70bigblockdodge]

If it's a big block car the weep/vent hole above the diaphragm will leak gasoline before it travels into engine oil, but anything is possible. I don't think your too rich (by looks of plugs). The start ups probably causing the issue oil temps, not water, need to be above 150°f to gas off the non oil contaminates.

 

[mike daugharty]

Hey all,

Soo.. I am still a newbie and therefore have no idea if this should be normal but it is better to be safe right..

Last summer i got the car with fresh oil and a new filter. I drove it around 2000 miles and, with my country being relatively small, the car usually gets out and runs about 1-2 hrs with a 1 or 2 short stops. I recently noticed a gas smell on the oil dipstick. I rebuild the carb last summer aswell, however, I must admit that I think it is still running a bit rich. In addition to that, I started the car and let it warm up a few times during winter. I wonder if this would be enough to make the oil smell slightly gassy (its noticable). I plan to change the oil this week but I held off because I might aswell put a new fuel pump on it when I am at it. Should I just get a new fuel pump for cheap insurance or check the pressure and keep rolling with it. (I plan to take the carb of and go through/retune it aswell.)

Best,
fuel pump would be my thought
Thom

 

[mike daugharty]

fuel pump is my bet

 

[383man]

All mechanical fuel pumps have a 1/8" hole in the side of the housing and that hole is there to release fuel to the outside rather the pump fuel into the engine in the case of a diaphragm failure. If your diaphragm failed and is pumping gas into the engine oil, you should see a higher level on your dip stick when you read it.

Actually that hole is to vent the top side of the pump diaphram. If not and the top was sealed it would cause some pressure and vacuum to build on the topside of the diaphram. Course if the diaphram sprung a small leak much of the fuel can go out the hole but the diaphram may push more fuel right into the crankcase then out the small hole if its pumping enough to keep the eng running. I would think the bigger opening at the pump arm to the crankcase would put more fuel that way then out the hole which is much smaller. Ron

 

[383man]

I also dont run a choke on my hotrods. But I like and always use Holley Double Pumper carbs which are easier to start in colder winter weather with no choke since it has 2 accel pumps. I live in Md where the winter can average from about in the 20's F to in the 40's or 50's on real sunny days. Sometimes a bit colder but not often. I always run my 63 about once a month for a good 1/2 hr until fully warmed up which is what you want. As long as the eng warms up and runs to opp temp for a while I have never had a problem. Car is not to hard to start with no choke having a double pumper. I also run a PCV system as I feel its always good to run a PCV system on a mostly street driven car as mine. I race it sometimes at the track but only once or twice a year at most. I agree that you always want to run the car long enough to fully warm the eng up as I feel a good 1/2 hr at the least. I have never had any problems of fuel in my oil when running my engine like that without driving the car. Running a PCV always helps pull moister out of the crankcase also since its pulling some vacuum in the crankcase. If you can drive it thats great but I usually cant get my hotrod out to easy in the winter with cars in the driveway and as I said with running a PCV setup and making sure I get the eng to opp temp and run a bit more after that I never have any problems. This eng in the car now has been in my car since 2011 and it never uses any oil and I have never had to add any oil to the eng. Its been 100% perfect and all I do is change the oil and filter once or twice a year depending on how much I drive it and clean the plugs and adjust the valves once a year. In 11 years the most I have done is pull valve covers to adjust valves as its been perfect in every other way. So I know my way has not ever hurt it any. Many have certain ways they do things and not all are the same but that dont mean any are bad. Of course some can be if the person does not understand what they are doing. But like I told my son when he took auto shop since I have been a tech all my life I told him dont try to tell your teacher his way is wrong if he does some job different that I then I taught you as many times some techs do jobs a bit different but that dont mean either way is wrong as some just like doing it one way and some may prefer another way. Always listen and then decide if you think one way may be wrong but make darn sure as many times both ways are fine. Ron

 

[Sixpactogo]

Actually that hole is to vent the top side of the pump diaphram. If not and the top was sealed it would cause some pressure and vacuum to build on the topside of the diaphram. Course if the diaphram sprung a small leak much of the fuel can go out the hole but the diaphram may push more fuel right into the crankcase then out the small hole if its pumping enough to keep the eng running. I would think the bigger opening at the pump arm to the crankcase would put more fuel that way then out the hole which is much smaller. Ron

I may have mis-spoken when I said all mechanical fuel pumps have the 1/8" vent hole. I checked a couple of Fuel pumps I have on hand. Both are AC branded. The small block pump has two 1/8" weep holes in the upper housing and the big block pump has a rectangular hole but the only purpose of those holes is to allow fuel to escape if and when the diaphragm develops a leak. These holes serve two purposes. They are located below the opening to the lever leading to the engine to help insure no fuel enters the engine oil also they act to alert someone that the pump is failing before a complete failure. Not all fuel pumps are created equal and maybe some brands don't even have this feature but Carter and AC do for sure. Here is a pic of what they look like.

 

[Geoff 2]

I think your pump is leaking fuel into the engine, probably a leak in the diaphragm.
Your spark plugs are burning too cleanly for a rich condition caused by the carb to cause a fuel smell from the crankcase. To get that amount of smell would need a significant amount of fuel to be getting into the engine, such as being pumped in..

 

[1STMP]

Never, ever start a car and let it "warm up". The engine never gets warm enough to burn off condensation. It also runs on the choke which adds to the over rich problem and washes down the cylinders, which puts more fuel in the crankcase that doesn't burn off. If you are going start it, drive it. And not just around the block. It also burns condensation from the exhaust. If you can't do that its better to let it sit. Fog the cylinders for the winter layover.

 

[1STMP]

Yes, I hit the big red X. I hate them as to the
degree of disagreement.
As long as the engine is allowed to reach
'normal' operating temps, even when
stationary, it will burn off any contaminants
present.
There are literally 1000's of 440's in the field
performing pump duties. They're not any
more susceptible to fuel/oil contamination
than your garage princess as long as they're
brought up to normal operating temps.