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Here’s my problem:
I have a 91 “S” I’m re-building. Top half of the engine has been done by a reliable Alfa mechanic. I had to go in and rebuild the transmission and diff myself (full disclosure: I had the help of a gifted former Porsche mechanic – who was astonished by the “S” throwout bearing). We also rebuilt the cooling system, but that’s another story…
I was left with several problems:
Even worse than usual oil consumption
Intermittent ‘raw gas’ smell
Lousy gas mileage
Intermittent lurching/hesitation on the throttle – especially over 3500PRM in any gear
We replaced the fuel filter and the oil sensor unit and replaced the vent elbow in the trunk (numerous cracks covered over by idiot former owner with electrical tape – sheesh!).
We have checked the plugs – they seem fine, gaps are good no obvious problems
Distributor seems good – no cracking, obvious burns, etc.
The gas mileage seems to have improved a bit since we replaced the cracked vent elbow but the oil consumption remains ridiculous even after we replace the - obviously leaking – oil sensor unit (though the oil pressure gauge now works correctly).
Raw Gas Smell
I had a friend put the car up on a lift and check the fuel lines all the way back and front: he swears there is no evidence of leaks – and the car did have the recall for the fuel spout done.
Another full disclosure: I have a really, really bad sense of smell. My wife refuses to ride in the car because she smells raw gas all the time, still. If I am driving and open the windows, I am pretty much overwhelmed by the raw gas smell…
Suggestions that have already been made:
Check fuel lines where they go through the firewall and turn into rubber hoses. Can’t see that and there is no evidence of a leak and wouldn’t the engine have caught on fire by now?
There must be one or more fuel lines/elbows/gaskets in the rear still cracked and leaking and/or there is a complex on the top of the fuel tank but below the trunk space which can spring leaks and produce this odor.
Oil Consumption
OK, I know that Alfas use oil – perhaps as much as 1qt/500 miles. Fine. I’m going through 1 quart/week. This is ridiculous… I can’t give you mileage since the speedo/odo doesn’t work (and that’s yet another story). But I’m nowhere near putting in 500 miles/week with the car in this condition…
We did a complete oil flush and change (used Castrol High Mileage 20-60 and threw in a bit of zinc for the tappets), new filter, changed oil sender unit, etc. Still goes through oil like it was Kool-Aid. I can handle that, if it comes down to it, I’ll just buy cheap, re-fried oil and change a bit more often.
But…
I can’t help feeling that these are all related somehow, especially since I still have the lurching engine issue to resolve…
It looks like anytime I go up over about 3500RPM in any gear, I start to get stumbling/lurching/racing from the engine. As you can imagine, this nearly always comes at the most inappropriate times: moving in traffic in 1st, trying to negotiate the ‘twisty bits’ on a great local road (2nd/3rd/4th). Pretty much anytime I’m in acceleration mode (trying to get past a ‘drone’). It hasn’t been dangerous… yet, but I can imagine it going badly wrong at just the wrong time…
The plugs seem fine, I don’t see any problem with the fuel rails, the injectors seem OK… but how would I know? We’ve replace the fuel filter, what’s left? Cylinder pressure seems to be good, this isn’t a steady problem… Fuel pressure regulator? Oxygen sensor? Fuel pump? Oh, I’m pretty sure the previous owner installed a Squadra EMU chip (great low end grunt)…
Suggestions are welcome…
 

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If all hoses and lines are intact (you think), check front and rear evap cannistors and tank cover bolts for fuel pump and gas gauge sender. Also check that fuel cap holds pressure when you open it after driving car if not you have a leak in vent system.

As for bucking over 3500 RPM I fought that problem on a GTV6 years ago and it was the computer that was bad. I would plug in another engine computer and see what happens.
 

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There a couple of simple tests to help locate the source of the fumes.

If you turn the hvac system to OFF to close off the incoming air as you are driving around, and then open the front side windows (this creates a suction in the passenger compartment) or pop up the sunroof a little, if then the fumes are still bad or worse after a few miles, then it is likely the source is in the trunk area, the fumes being drawn from the rear into the passenger area.

If you turn on the hvac system and to full blower speed with the windows and sunroof closed tight, if then the fumes are still bad or worse after a few miles, then it is likely the source is from the engine bay, as the intake for the hvac system is in the bay behind the false firewall. A fuel line may be leaking in the bay and fumes getting past the essential bulb seal at the top of the false firewall.

This will give you clues as to where to start searching. One source in the trunk is seepage around the bolts holding the fuel pump and or sender into the tank. All or some of these have a habit of seepage after a few years. Little o-rings and washers (the washer next to the bottom of the head itself) are usually installed under the head of the bolts to help seal them. Do not overtighten, as you can distort/warp the metal flange.

The fuel lines around the engine in these cars get pretty hot, and after a few years they get hard and brittle, cracking or crumbling under the clamps and then start to leak, sometimes quite a bit. With the engine cold, start the engine and watch the fuel line connections in the engine bay for seepage or leaks. There may be leaks which sometimes close up when things get hot as the engine warms up. All 164 owners should by now have replaced all these fuel lines with new fuel injection rated hose and clamps in order to prevent potential fires.
 

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I have a gas smell definitely coming from the trunk area. the gas cap holds no pressure and when i got the car inspected the other day they hooked the cap up to a machine and it was fine. what is a likely source for pressure leakage in fuel system in trunk area? i replaced the fuel pump submersible hose and used the little rubber washers when i reinstalled the fuel pump in tank. any ideas would be appreciated.
 

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I have a gas smell definitely coming from the trunk area. the gas cap holds no pressure and when i got the car inspected the other day they hooked the cap up to a machine and it was fine. what is a likely source for pressure leakage in fuel system in trunk area? i replaced the fuel pump submersible hose and used the little rubber washers when i reinstalled the fuel pump in tank. any ideas would be appreciated.
Crack in one of the two 90 degree molded rubber elbows in vent system on top of tank area, bad check valve on cannistor in trunk or worse case crack in one of the three vent tube elbows on top of the tank beut hidden from view by floor of trunk.
 

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cool. I'm off work today and its sunny and soon to be 70 degrees, so i will check it out.
thanks.
 

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For fuel smell (assuming coming from the trunk), check two o-ring seals shown on image. If they don’t seal 100%, you’ll have a leak that’s not really obvious since evaporates quick. I’d suggest you uncover this area of the trunk, drive it and as soon as you smell the gas – stop and go look around these two seals if even slightly wet. They’re easy and inexpensive to replace.
 

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