HAY GUYS! help me locate gas odor/leak.

[Dan RareGP]

cross posted for added TGP knowledgebase :shock:

 

hey guys, long time no talk. Hopeing that someone could share some of their experiences with me regarding a fuel odor that I get inside and outside the vehicle. Let me describe the symptoms. The car is a 1990 Turbo Grand Prix in which I replaced the fuelpump in the winter. I just replaced the fuel filter, and did it in the winter as well.

 

1. Odor is present when accelerator is at moderate opening and boost is reaching the orange or positive preassure.

2. Odor is present after a quick burst to WOT

3. Odor seems to be coming from the middle of the car and possibly behind the fuel tank. Detected while the car is off and parked. Odor is from under the car.

4. The odor has decreased or ceased when I have tightend the hoseclamps around the filler neck and vent tube hoses on the gas tank.(im having a hard time streatching the vent tube over the metal tank neck all the way to its base.)

5. There is a slight and very slight gas scent in the upper intercooler pipe at the throttlebody when removed.

6. There is no rich or gas odor at the exhaust pipes, nor any smell of a fouled cat converter.

 

Here are my theories as to what is wrong with the car:

1. The vent hose is tough to get all the way to the base of the tank, the hoseclamp is on tight, but yet high preassures in the tank is allowing vapor to excape around it. But its pretty tight as it is, maybe preassure is higher than i think and vapors are easier to excape than I think.

2. One of the quickrelease connecters for the fuel feed or return is loose and allowing gas to excape at wide throttle openings.

3. The locking cam assembly may have rusted or is loose. I checked it well before reinstalling the tank and all seemed fine however.

4. The fuel preassure regulator is failing. Im not sure how to tell, and the fuel smell is not under the hood of the car when its parked and running with the hood up, however when I am on the highway there is a strong odor of fuel in the cabin. Going 70mph on the highway, I doubt fumes are creeping from the tank and into the open sunroof/windows, but air vortexes and other aerodynamic anomolies could account for this, but im no expert on aerodynamice.

5. The fuel injector O-rings are leaking, same theory applies to the FPR.

6. One of the rubber fuel lines has rotted or the metal cracked, most likely at the point the lines turn upward to enter the engine bay.

7. Top of the tank is rotted

8. Tank was damaged(pinched) or the sheetmetal welds that form the top and bottom became seperated when I jacked the tank back onto the car.

 

Things to consider while diagnosing:

1. the fuel odor seemed to go away temporarilly each time I got the vent-hose clamp on tighter.

2. The tank retaining straps were bent a little bit, and the bolts to hold them up were crossthreaded at the rear-pass and the front-driver positions, but the tank appears to be at its highest point and therefore secure and no scratch marks to proove its moving at all.

3. I managed to slightly twist the metal tubing on the return line of the fuel-sender assembly, its twisted about 1/6 of a turn and appeared to flow air well, as well as be able to accept a wire the same diamter as the interior diameter of the fuel-return line.

4. I also managed to overlap the female end of the quickrelease connecter of the fuel sender unit DIRECTLY onto the male end of the threaded nut that goes into it. The fem end flared slightly, but the connections were still tight and had their respective rubber O-rings installed.

5. When I suck hard on the first vacume line from the left on the TB, there is a slight gas vapor taste, not liquid gas, but a slight raw vapor.

6. My fuel filter I just removed was "bent" slightly at the entrance end of it. Im assuming this may have happend as I hastily replaced the tank and the lines were slightly pinched or misguided causing bad placement of the line and the filter to bend to the accomidate the lack of slack in the fuel line.

 

Ive got new O-rings and a upper intake gasket set here ready to go if I need to do the FPR. But im hopeing that its something else, but also hopeing that its not the tank or sender as that tank is a real bitch to take down, and an even bigger bitch to get back into place. Im limited on funds so im trying not to do the FPR unless I have to, otherwise id love to take the upper intake off and have at it.

 

P.S. Im getting about 18-18.4 mpg driving slow on the highway and around town.

 

Anyways, thanks for your concerns and hopefull replies.

Dan

90 TGP red/tan coupe.

Jeff M TG160 chip, 160deg T-stat, unmuffled 2 1/4" exhaust, open element filter on turbo.