Gas in Oil-91Caravan


#1

Have a 91 Caravan SE AWD with only 60K miles. After a serious acceleration to avoid a car, I saw a reduction of oil pressure. Once I checked the oil, I found it heavily diluted with gasoline. Changed oil and in short order (5 minutes running) it was diluted again and no oil pressure. I think this model has electric fuel pump and not mechancial so no diaphram burst of fuel pump. Is there possibly an emission control link back into crankcase? I am stumped about his. Help??


#2

I recall a similar problem that involved a broken cam (SOHC V-6). The engine ran very poorly and the low vacuum caused by the intake valve being hung open had the computer maxing the fuel flow and in the dead cylinder the fuel was forced past the rings.

Also, a short on the low side of the injector circuit will keep it flowing gas at max.


#3

Maybe there’s a broken diaphragm in the fuel pressure regulator. Pull the vacuum line loose and see if there’s gas in the hose. I would think there would be since this seems to occur so quickly.

Hopefully gasoline diluted oil has not done too much damage to engine internals.


#4

This sounds most plausible. Can you tell me how the fuel pressure regulator works? If the diaphragm is broken, would fuel come directly into the crankcase?


#5

The fuel pressure regulator is controlled by engine vacuum. So there’s a vacuum line between the regulator and intake manifold.

When the accelerator is depressed, the intake vacuum drops off. This causes the regulator to allow less gas to return to the fuel tank and more to the injectors. Because when you step on the gas you need more fuel. When the accelerator is released, the intake vacuum increses. This causes the regulator to allow more fuel back to the gas tank and less to the injectors. Because when you let off the gas you need less fuel.

If the regulator diaphram developes a leak, It can send raw fuel into the intake manifold via the vacuum hose. This fuel not only enters the engine while the engine is running, but also when the engine is turned off because of the residual pressure from the fuel pump.

The regulator is mounted on/near one of the fuel rails. It’s a small canister looking device with a single vacuum hose attached. As OK recommended, remove this hose, and if there’s the slightest hint of gas at this connection, the regualtor requires replacement.

Tester