TheSamba.com :: View topic - Curious, fuel pumps leaking into crankcase...

Tue Jun 25, 2019 7:42 pm

Does anyone know any history of mechanical fuel pumps failing and filling crankcases full of fuel? I was talking to someone that said he's seen it about 5 times... I for one have never heard of this happening...

Tue Jun 25, 2019 7:44 pm

Sure it wasn't the carb?

Tue Jun 25, 2019 8:45 pm

when the pump diaphragm tears, or is holed, fuel will leak into the lower part of the pump, then drain into the crank case. many mechanically pump engines besides VWs can have this happen. This is much better than having the fuel spill outside, where ignition sources maybe.

the diaphragm leak can be small enough that the Bug still runs, yet fuel gets in the crank case.

A faulty carb can also flood the crank case. I bought a Bug in my youth, $110. A 58 model, towed it home, as it would not start. crank case had a couple gallons of gas and oil mix in the crank case. failed carb float was the cause, and being parked facing uphill. the valve train was extremely clean from that soak in fuel, nice shinny metal under the valve covers!

Bug On!

Tue Jun 25, 2019 9:23 pm

Have seen this a few times. It's worse now with ethanol fuels which dry out all the rubber parts.

The inside of the case and rotating assembly also get really clean. The gas gets rid of most of the deposits and crud inside the engine.

brad

Tue Jun 25, 2019 10:00 pm

But your bearings aren't real happy with this mixture :shock: :shock:

Tue Jun 25, 2019 10:28 pm

I've yet to see anyone on these forums actually prove that fuel in the crankcase came from their fuel pump. The pumps that VW/Pierburg
used were constructed so that any fuel leaking past the diaphragm would run out the vent hole below the diaphragm onto the engine case.
Only if there were a major flood of fuel into the pump lower chamber, would any of it get into the crankcase, but at the same time the engine
would be drenched with fuel. Perhaps there are some aftermarket fuel pumps, contructed differently, where such a thing could happen, but
I've never seen any demonstration of it. Having gassy oil in the fuel pump base does not mean it came from the pump, because an engine
with excessive blow-by and crankcase pressure will push oil up into fuel pump base and out past the lever shaft ends. I've had a significant
quantity of grease pushed out of the pump lower chamber just from having the stock breather hose kinked.

I say it's a myth.

Wed Jun 26, 2019 12:41 am

Hm? I had fuel in my case, and I installed a new Brosol fuel pump, and after installing it, I haven’t had any fuel in my case since.

This was about four years ago.

Tim

Wed Jun 26, 2019 3:54 am

FWIW...

Wed Jun 26, 2019 3:58 am

More often than not it's likely other things - bad float, car on a slope for long and a tank full enough that gravity gets gas into the case - thru the needle valve or pump i don't know. But I have had the bad pump happen w/my '72 Super on at least one occasion. After troubleshooting other items, it finally came to down to this - replaced fuel pump, problem solved.

Wed Jun 26, 2019 5:26 am

In the last 5 years I have seen this at least a half dozen or more times. Once with my wifes 61 and with several customer cars. The most recent was a 67 that had the case so full of gas that there was bearing damage requiring a complete rebuild. The customer continuing trying to start the car even as gas was being blown out the tailpipes. He didnt notice it until he looked at the car the next morning.

I have had this happen way more than stuck needle valves or anything like that.

Wed Jun 26, 2019 6:12 am

Ok, great information! My son had a friend recently having this problem...he installed a new fuel pump...the problem started... I will try to find out where he got the fuel pump and see if I can isolate type of fuel pump...

Wed Jun 26, 2019 6:49 am

Tim Donahoe wrote: Hm? I had fuel in my case, and I installed a new Brosol fuel pump, and after installing it, I haven’t had any fuel in my case since.
Tim

dart451 wrote: My son had a friend recently having this problem...he installed a new fuel pump...the problem started...

This is more than enough proof for me.

Like removing an AC clutch shim on my 1998 Frontier fixed my AC clutch intermittent slipping last week - enough "proof" for me !!!

Wed Jun 26, 2019 10:37 am

the first rule is that there's an exception to every rule....back in the day with original pumps if they went bad you knew it cause they leaked out the weep hole...now 50 years later with aftermarket stuff getting progressively worse (and not having weep holes)and ethanol gas eating diaphrams the problem could occur more often than it used to....but i swear tons of perfectly good pumps have been thrown away to try to cure a gas in the oil situation...but heck they were easier to change than an intake manifold and cheaper than a carb on the first step of troubleshooting the problem....fuel pressure readings have been all over the place on the aftermarket stuff so its more likely they have been overpowering the needle and seat than leaking out the bottom

Wed Jun 26, 2019 12:17 pm

Just found out that this was NOT a new fuel pump! Jeesh! It was on the vw when he got it... So much for getting accurate information...

Wed Jun 26, 2019 12:33 pm

Well, I know I saw it back when I was a mechanic 20+ years ago. Dead giveaway was the high mark on the dipstick plus surprisingly clean looking valve cover and cylinder head when you'd go to do a valve adjust.

Wed Jun 26, 2019 12:33 pm

volksworld wrote: the first rule is that there's an exception to every rule....back in the day with original pumps if they went bad you knew it cause they leaked out the weep hole...now 50 years later with aftermarket stuff getting progressively worse (and not having weep holes)and ethanol gas eating diaphrams the problem could occur more often than it used to....but i swear tons of perfectly good pumps have been thrown away to try to cure a gas in the oil situation...but heck they were easier to change than an intake manifold and cheaper than a carb on the first step of troubleshooting the problem....fuel pressure readings have been all over the place on the aftermarket stuff so its more likely they have been overpowering the needle and seat than leaking out the bottom

Sounds like the the tons of thrown away pumps were victims of extremely poor diagnostics . Hardly cheap when they were thrown out while being perfectly good.

High pressure from replacement pumps overcoming the float valve, flooding the carb are a case of extremely poor mechanics, not taking the effort to measure and adjust as needed the pressure by the simple addition of gaskets under the pump.

Poorly done repairs do not negate the fact that leaky pumps can drain into the crank case.

Bug On! With Proper Repair!

Wed Jun 26, 2019 1:03 pm

This all started when my son installed an electric fuel pump on my 72 vw. He was/is convinced that mechanical fuel pumps fail and electric fuel pumps are better. I changed my electric pump because the noise it made was annoying...especially whenever I had to turn on the key to test something electrical! I also didn't like the fact that if I were in a wreck and unable to turn off the ignition, my fuel pump would continue to pump gas which is not a good thing if a fuel line gets ruptured... I just thought I would get a consensus on how many people had experienced the problem of mechanical pumps leaking into the crankcase...

Wed Jun 26, 2019 2:13 pm

dart451 wrote: This all started when my son installed an electric fuel pump on my 72 vw. He was/is convinced that mechanical fuel pumps fail and electric fuel pumps are better. I changed my electric pump because the noise it made was annoying...especially whenever I had to turn on the key to test something electrical! I also didn't like the fact that if I were in a wreck and unable to turn off the ignition, my fuel pump would continue to pump gas which is not a good thing if a fuel line gets ruptured... I just thought I would get a consensus on how many people had experienced the problem of mechanical pumps leaking into the crankcase...

In well over a quarter million miles of my 61 Bug, over 58 years, I had a couple pumps die, none leaked into the crankcase that I am aware of, although some fuel may have gotten in, they simply lost pressure or flow. Over all they are extremely reliable. there is no need to down grade to an electric pump unless you have a highly modified hotrod motor that requires more flow, and yes, the electric pump can be a real hazard in a crash unless impact switch, rev counter or other such device is used to auto shut it off.

Bug On!

Fri Jun 28, 2019 5:44 pm

As I mentioned, I had seen it quite a few times...But I have a shop. Out of the five VWs that we personally have on the road, only 1 has an electric fuel pump....Its a pancake engine and already had an electric. Didn't want to dick with it. So that tells you that I prefer mechanical. HOWEVER, any fuel pump installation should be followed IMMEDIATELY with a fuel pressure test.

Sun Jun 30, 2019 10:28 am

Happened twice to me. I always check the oil level before cranking the car first time. Both times the oil level was higher on the dipstick and the dipstick smelled of gas. And, both times I unbolted the fuel pump and lifted it up and the fuel pump flange between the pump and crankcase was full of fuel. In my case, it was the fuel pump.....period. I installed an electric fuel pump along with a Revolution Electronics fuel pump safety controller. It primes the system for three seconds when first turned on and will kill power to the pump in the case the motor stops running, like in case of an accident. http://www.revolutionelectronics.com/Fuel_Pump.html
Very nice bit of kit.