I've had a string of issues with my '89 240 that may or may not be connected, I'll start with current symptoms first and work backwards.

The car is currently very difficult to start and will not idle, needs the gas pedal pushed to keep running. It also backfires infrequently. My wife drove it about 40 miles and went through a half a tank of gas! My wife said that if she downshifted (stick) and put the pedal to the floor then it would go, basically operate normal. She said that it lacked a lot of power on the hills.

The exhaust smells rich and the underhood smells of raw gas but I cannot find the source.

Previously the car was running rich (I could smell it in the exhaust) but nowhere near half a tank per 40 miles.

I recently replaced the fuel pressure regulator as I was having a misfire/hesitation issue that the new FPR almost completely resolved but there was still a slight hesitation.

I also have a hard time filling the gas tank, it seems the vent is clogged.

The area between the head and crankcase is wet all the way around which made me think I had a blown head gasket but I cannot find any other evidence; no oil in the coolant, no coolant in the oil, not losing any coolant, no bubbles in the coolant, no pressurized coolant hose.

Are these all related somehow?

When my wife pulled into the garage after the 40 mile trip the underhood smelled of burning/melting wax, I have no idea what that might be. I have never smelled this type of smell on a car before.

The vacuum side of my FPR reeked of gas (the one I just replaced!).

So here's what I've done; replaced AMM with known good sensor- no change, disconnected cold start injector- no change, swapped FPR- no change, checked timing belt (recently replaced) no slack, crank position sensor was recently replaced as was the fuel pump and filter. Plugs/wires/cap/rotor are all relatively new and in good condition.

And there's no codes! Not one single code, how is that possible?

Return line clogged to the tank backing up into the FPR and forcing a rich condition??? I have not yet tried disconnecting it.

I don't think a bad oxygen sensor can cause the engine to suck down half a tank in 40 miles but I'll be getting a new one anyhow (I'm trying to make this a reliable vehicle).

Any ideas what I should try?

Thanks!