Petrol where oil should be

[58A - 71E]

.....Advice required....

Background
Took car for long drive 2 weeks ago - ran fine once going but was a bit of a pig to start (coughing not idling quite right) - assumed fuel going off as not been run for several weeks before that. Filled tank to top with fresh fuel and put in garage. Petcock not turned off.

Garage smelling of fuel for last 2 weeks
Come to crank it this morning smell worse and engine v reluctant to turn (almost seemed fluid locked) even though battery on trickle via ctek, eventually turns - just. Notice fuel gauge only reading 2/3rds - odd

Look under car BIG puddle of fuel (2-3litres)
Under cranking it is pis*ing out of right side but not sure where

Go get fire extinguisher and hose pipe - flush fuel out from under car and let pulse return to normal levels.

Turn petcock off.

Check fuel lines - all ok

Take right carb off, all seems well

Take right rocker cover off at least 3 litres of unleaded/oil mix pours out

Undo sump plug and its absolutely full of petrol

So what could have caused this?

Is it possible has leaked from pump into 3rd piece of case?

Really struggling on this one

[Barwaut]

Nice puzzle...

Car was standing still for two weeks, full tank.

I think it's not possible to get that amount of fuel in to the engine through the carburetors.
They are higher than your tank, so I don't think a leak over there (carbs) could have floated the engine.

Seems like the only possibility is indeed the fuel pump. Low enough to get some gravity pressure from a full tank.
Just take the fuel pump out, check the membrane, I guess it must be torn or something like that...

Keep us posted!! Good luck.

[roy mawbey]

James,

You were sensible to drain the oil/ fuel mix. As you probably are running Zenith 32NDIX carbs I would first of all check the "float valve" this is the screw in needle valve that controls the fuel going into the bowl of the carb. As the float rises with fuel a lever moves the ball to allow it to "seat" to stop incoming fuel rising above the float and then going straight down to the crankcase.

If you remove the float valve situated in the cover directly where the incoming fuel comes in you can screw it out to remove.When one failed on a "C" I owned I could press on the ball and blow in the hole and air would escape because the seat was worn. I also had a few litres of petrol in the oil and the dipstick level was way up.

I would say the problem started on your last run. It was probably not in the garage unless you were up a hill maybe. Gravity does play a part but I would check both float valves first of all.

I have heard you can hydraulically lock pistons in the barrels if too much liquid is in the crankcase. Spark plugs out should that ever be the case.

I am no expert, but the same thing happened to me and new float valves solved tghe problem for me.

Roy

[DustyM]

I suspect that the diaphram in the fuel pump has split and is letting fuel into the crankcase.

[Mick]

Agree diaphram in pump suspect.

[Barwaut]

I don't think this happened on the last run, like Roy says.

You can not have driven the car with something like three liters of fuel in the rockercover and some more in the sump...

[58A - 71E]

Agreed it lends itself more to fuel pump than carbs, but I only rebuilt the pump last year as part of the resto of the car with a genuine OEM parts kit so it will be annoying and unexpected if it is that

old membrane



and with new



pump out tomorrow I reckon

[roy mawbey]

James,

Just be aware, the lower chamber of the fuel pump has a bleed hole to allow petrol that has accumulated under the diaphram to escape. As the pump is isolated somewhat from the engine with only the pump actuating rod in contact with the distributor cam it would result I sort of think with a pool of petrol on the garage floor not inside the rocker box on one side of the engine and in the sump.
The diaphram only moves 0.5mm so it it was new find it hard to believe its cracked. If you did not set the pressure correctly with the stroke movement of the rod a pressure that is to high will overide the needle valve in the carb float valve so that the carb will overflow and pass petrol straight down to dilute the oil.

If it seems fuel is all collecting one side then the float valve might just be
not seating on the conical area because of wear or the fuel pressure is not allowing it to seat.

I only make these remarks because if you see the diaphram is okay you have to look elsewhere and that pump rod set up with the correct number of gaskets is important to get the correct pressure.

Hope its just an easy fix for you!!

Cheers

Roy

[john fletcher]

Hi James,
I think you will find that the tank is actually higher than the carbs and so my thought is that the float valve in the RH carb has stuck open or just not seating properly. Over 2 weeks the the "head" of petrol between your full tank and the RH carb has allowed sufficient petrol through to fill the engine! It will have easily leaked up the valve stems into the rocker cover and past the piston rings into the sump. The faulty float valve will have accounted for the initial rough running but filling the tank to the brim has highlighted the problem rather dramatically.

John

[Graham]

Ive seen this happen a few times and its always been the Carb needle valves,as others have said,its just run into the bores and filled the motor up,we had a car in that must have had a 50/50 petrol/oilmix in the crankcase,how it ran I do not know,god help all the internal rubby bits!

[vwretrosteve]

My old rhd A used to leak fuel if parked for any length on the slightest gradient. Although it did dilute the oil to a degree it mainly emerged from various points on the carbs themselves - (which may just mean internally they were pretty sound)

Hopefully you get to the bottom of it by looking at your carbs , rather than it being a burnt valve .

[58A - 71E]

Right, took the pump out at the weekend and stripped down - all like new and no splits in the diaphragm. So happy to rule that out.

So I guess its the carb/carbs then from what folks have posted - thanks - again, the annoying thing is they are freshly rebuilt Zenith 32 NDIX but I guess its another one of those things More investigations this weekend!

[Dakota]

Hi
in the past I have had pump diaphragm's leaking around the rivet with no obvious fault on the diaphragm itself, was the base of the pump packed with grease as it should be and if so was this washed out? The fuel can get past the needle valves and into the motor that way but I would have suspected it to try hydraulicking on start up, and maybe some fuel coming out the carb in question around its spindle, I know the needle valves can be an issue as I have had to reuse the originals in the past and PRS sell kits with a top quality item, and via Ebay you can get a very comprehensive kit intended for a 404 Unimog for reasonable money, lastly was the pump pressure tested when it was installed and were the float heights checked in situ.

[roy mawbey]

James,

There has been an interesting thread on the registry site concerning leaking "fuel valves" in the Zenith carbs. This problem of fuel overflowing in the carbs and sending fuel ( often litres ) into the sump seems to be well known in the States also.

One of the clever guys over there was recently given a fuel valve that leaked for examination. The body of the valve is brass. At the operational end of the needle valve which is captivated in the body there is a steel ball that when the "pad" of the float touches this and pushes on it (as fuel enters the bowl) it moves the needle valve with a coned end to seal and stop fuel entry.

He removed the captivated needle valve for examination to see the wear values which caused it to leak. The photos shows wear rings on the cone end of the needle valve and also wear on the float pad from the ball.
He removed the wear on the pad as he thought it could tend to push the valve as I understand with pressure on one side.

I was surprised a little to see the needle he extracted was made of brass, I mentioned to the forum I thought it was steel. Back came the reply the original ones were steel and its seems some the later repro?? ones are brass.

Mention has been made that these valves even when quite new can fail and you should always buy the best ones available.
Maybe PRS, KK, Roger Bray et all could advise their comments on this?

Are the best ones produced with steel needle valves?

As I once had the problem I quite often take my dip stick out give it a sniff
just to see if smells of fuel, people watching might think a little strange but it seems to me the only easy to tell if the problems starting.

How are your carbs now James??

Roy

[barryb]

Hi

Would this happen if the fuel was turned off at the tank every time the car was parked?

Barry