Auto Mechanics needed

[SonicVanguard]

Hey everyone.

I have a young man from a local University doing a work/study at my studio this fall. He's a great kid, but he's having car troubles and it's causing him to be late or miss work. Being that it's a work/study program, that's not good.

He drives a 1994 GMC S-15 Jimmy with a 4.3l vortec. The problem is that he smells gas when he starts the vehicle and you can easily smell it when you're around the vehicle as well. It's the smell of gas that has him scared to drive the Jimmy - it runs fine, but the smell really makes him nervous.

There's no signs of any gas leak - we placed a large piece of cardboard under the vehicle while it sat in our parking lot all day today - not a hint of anything leaking. The engine itself is very clean and you can't smell any gas fumes around the engine at all. The smell is stongest at the rear of the vehicle - but I've looked underneath and see nothing out of the ordinary around the fuel cell or fuel lines. One thing we do notice is that when he starts it up, he gets a decent cloud of smoke coming from under the vehicle and out the exhaust. So I'm thinking he's getting gas in his exhaust somehow.

Here's the real kicker - since this is a work/study, he doesn't make much at this job - his wages are determined by the University. And he just doesn't make enough to take the vehicle to a mechanic (good or otherwise). Now I'm no mechanic, but a good friend of mine is and he's visiting from out-of-town this weekend. Unfortunatly, I can't get a hold of him until he arrives Friday evening. So...if I can get some idea of what might be wrong with Ted's Jimmy, I think that would help up get a jump on fixing it without much fuss on Saturday (since my friend doesn't have much free time this weekend).

Any help or ideas would be greatly apprecaited.

TIA.

Dave.

[lil Jimmie]

bad injector/s ( leaking fuel into the cylinder/s when not running and loading up the cylinder/s)

lazy or bad O2 sensor

purge canister

[Pete Rock]

Originally Posted by SonicVanguard Hey everyone. I have a young man from a local University doing a work/study at my studio this fall. He's a great kid, but he's having car troubles and it's causing him to be late or miss work. Being that it's a work/study program, that's not good. He drives a 1994 GMC S-15 Jimmy with a 4.3l vortec. The problem is that he smells gas when he starts the vehicle and you can easily smell it when you're around the vehicle as well. It's the smell of gas that has him scared to drive the Jimmy - it runs fine, but the smell really makes him nervous. There's no signs of any gas leak - we placed a large piece of cardboard under the vehicle while it sat in our parking lot all day today - not a hint of anything leaking. The engine itself is very clean and you can't smell any gas fumes around the engine at all. The smell is stongest at the rear of the vehicle - but I've looked underneath and see nothing out of the ordinary around the fuel cell or fuel lines. One thing we do notice is that when he starts it up, he gets a decent cloud of smoke coming from under the vehicle and out the exhaust. So I'm thinking he's getting gas in his exhaust somehow. Here's the real kicker - since this is a work/study, he doesn't make much at this job - his wages are determined by the University. And he just doesn't make enough to take the vehicle to a mechanic (good or otherwise). Now I'm no mechanic, but a good friend of mine is and he's visiting from out-of-town this weekend. Unfortunatly, I can't get a hold of him until he arrives Friday evening. So...if I can get some idea of what might be wrong with Ted's Jimmy, I think that would help up get a jump on fixing it without much fuss on Saturday (since my friend doesn't have much free time this weekend). Any help or ideas would be greatly apprecaited. TIA. Dave.

Those things are known for the injectors leaking and its not a cheep fix, it usually is accompanied with a rough or abnormal idle. Open the hood and see if the smell of gas gets stronger and if it is then its eaither the injectors or the fuel lines leaking. If you cant visibly see a fuel leak but smell it in the motor than its more than likely the internal injectors under the upper plentum.

[Markoman01027]

Any possibility that it could be an exhaust leak?

[Pete Rock]

Originally Posted by Markoman01027 Any possibility that it could be an exhaust leak?

Exhaust can be mistaken for a gas leak but if it has a strong smell of gas its highly unlikely.

[SonicVanguard]

Originally Posted by Pete Rock Those things are known for the injectors leaking and its not a cheep fix, it usually is accompanied with a rough or abnormal idle. Open the hood and see if the smell of gas gets stronger and if it is then its eaither the injectors or the fuel lines leaking. If you cant visibly see a fuel leak but smell it in the motor than its more than likely the internal injectors under the upper plentum.

There is no smell of gas under the hood at all - running or not. The smell of gas is at the rear of the vehicle.

Dave.

[SonicVanguard]

Originally Posted by lil Jimmie bad injector/s ( leaking fuel into the cylinder/s when not running and loading up the cylinder/s) lazy or bad O2 sensor purge canister

Bad injectors I'm assuming would be costly? But related to Pete Rock's post, there is no indication of gas odor under the hood.

O2 sensor - is that fairly easy to replace or should I leave that for my buddy to look at?

And I have no clue what or how to purge the canister.

But thank you for the suggestions.

Dave.

[Pete Rock]

Originally Posted by SonicVanguard Bad injectors I'm assuming would be costly? But related to Pete Rock's post, there is no indication of gas odor under the hood. O2 sensor - is that fairly easy to replace or should I leave that for my buddy to look at? And I have no clue what or how to purge the canister. But thank you for the suggestions. Dave.

Now your talking spanish here. I thought we were troubleshooting a gas leak now we are replaciing O2 sensors. Technically i would fix the gas leak first.
Ok since you have told me there is no gas smell under the hood then the only things left are the lines running to the tank, fuel filter, and the tank itself. You will just have to keep sniffing while the truck is running till you find the leak its common sense and a fuel leak shouldnt be to hard to find if its external. Has the fuel filter been replaced lately or the fuel pump?

[rjfvillarosa]

You say that the smell is at the back of the Jimmy, ok I don't know much about Jimmy's being as I come from the UK but, I have had this problem before on a saloon car. Fuel injection requires quite a high pressure, depending on the system design it can require a vented or nonvented filler cap, check the filler cap which is at the rear of the Jimmy where the smell is, try removing it after the engine has been running for about five mins if there is a strong sucking of air into the tank on removal then the vent is blocked. this can lead to venting problems for the excess petrol return system associated with fuel injection and this will cause it to smell, if the inline fuel filter is blocked then the high pressure will cause blow back into the tank when the motor is switched off and again lead to a strong smell of fuel around the rear of the Jimmy. I have actually replaced more than one "imploded" fuel tank caused by blocked filters or vents. Due to the high pressures involved and obviously the high volatile nature of petrol please be carefull

[glc]

Park it on cardboard - so there is cardboard under the entire vehicle. After sitting in your lot for a while, start it up and let it run for several minutes, drive it off the cardboard, then look on the cardboard for drips. This should prove or disprove external leaks.

Is the gas cap the right one for the vehicle, is it on tight and not damaged? Today's fuel tanks vent through the charcoal canister, not the gas cap. The fuel pump is electric, and inside the fuel tank - and I think the fuel pressure regulator returns excess fuel back to the tank.

Hold your hand close to the exhaust when it's smoking on startup - and see if any liquid condenses on your hand, and smell it - try to determine if it's raw gas, condensation, or burning oil. If it's raw gas, the cold start circuit is probably too rich (stuck air bypass valve - or a leaking cold start injector as already mentioned?). If the smell goes away when it reaches normal operating temperature, this is very possibly the case. Does it idle real rough on cold startup, and does it smooth out when you apply light throttle to kick it up to 2000 RPM or so?

[Pete Rock]

Originally Posted by rjfvillarosa You say that the smell is at the back of the Jimmy, ok I don't know much about Jimmy's being as I come from the UK but, I have had this problem before on a saloon car. Fuel injection requires quite a high pressure, depending on the system design it can require a vented or nonvented filler cap, check the filler cap which is at the rear of the Jimmy where the smell is, try removing it after the engine has been running for about five mins if there is a strong sucking of air into the tank on removal then the vent is blocked. this can lead to venting problems for the excess petrol return system associated with fuel injection and this will cause it to smell, if the inline fuel filter is blocked then the high pressure will cause blow back into the tank when the motor is switched off and again lead to a strong smell of fuel around the rear of the Jimmy. I have actually replaced more than one "imploded" fuel tank caused by blocked filters or vents. Due to the high pressures involved and obviously the high volatile nature of petrol please be carefull

SO youre basically saying that a clogged fuel filter can cause the tank to implode? ***? How will it build any kind of pressure if the vehicle isnt getting any fuel past the filter?

[Spartan]

If the O2 sensor is bad go ahead and replace it. A bad O2 can keep the computer in open loop causing it to run rich. If it running to rich it could be passing unburnt fuel through the exhaust system and as glc said it may condense on your hand. He would also notice his fuel mileage getting worse.

rjfvillarosa is correct that modern fuel injected cars run high psi pumps, up to 47 psi if I remember right. A visual inspection under the car from the tank to the engine is a good idea. The fuel filter on those (if memory serves) is on the driver side mounted to the frame of the truck.

Sometimes there can be a buildup of liquid gas in the charcoal canister and you can drain it off but I don't know how to do it on this model without getting a book for it. glc nailed the return question also, it should go back into the tank unless there is blockage somewhere in the line.

If all else fails....light a match and track down the flames......(just kidding of course).

-Spartan

[Hi Ho]

O2 sensor - is that fairly easy to replace or should I leave that for my buddy to look at?

The O2 sensor should be simple to replace. It is on the exhaust manifold and as long as it's easy to get too it's not too dificult. HERE are instructions on testing and replacing it in that particular vehicle. That website is a great resource for just about any vehicle. If the O2 sensor is bad it should also improve gas milage. I recently replaced the O2 sensor in my 90 Civic which was not working for 10 years and my milage went from around 40 to about 47 MPG in mixed conditions.

[SonicVanguard]

Did the carboard thing - no leaks.

Drove it myself - noticed a little gas odor as I drove. Parked and while the Jimmy was running checked under the hood - no smell. Ran the A/C-vent - no smell. Went to the rear of the vehicle - definite odor of gas. Didn't notice anything coming from the exhaust, but after shutting it down definite smell coming from the exhaust.

So...I guess I get to figure out that O2 sensor. I won't be able to get to it until this weekend when my buddy is at a conference. But at least he won't have to radically change his schedule to accomodate this problem. And if this works, Ted owes many of you a big thanks. As do I, THANK YOU to everyone who contributed to this. I only hope it's only the O2 sensor. If it's not - I'll be back.

Dave.

[rjfvillarosa]

Sorry slip of the pen meant just to say blocked vent pipe, trying to do too many things at once.

[Spartan]

O2 is one of the easiest things to do. Just unplug the connector and slap a wrench on it. If you think you will ever need to take it out again use some anti seize compound (Autozone will often give you a single application packet). I got my fingers crossed for you.....

-Spartan

[flanzig1]

I have the same sort of problem with my Blazer after I fill up with gas. I believe rjfvillarosa is on the right track with the blocked return line. Call a Chevy dealer to see if there has been a technical bulliten issued on the gas smell problem.

[Pounder]

ck the top of the tank where the lines come out and return, I'll bet one is cracked

[fudtone]

Try a factory gas cap or leaving it a bit loose. I'm guessing its not venting and the seal on top of the tank is letting fumes out because the pressure is trapped at the cap.

[doctorgonzo]

Has he noticed any significant drops in his fuel mileage?

[SonicVanguard]

Originally Posted by doctorgonzo Has he noticed any significant drops in his fuel mileage?

Yes he has.

And and as I've noted previously, there are no signs of leaks - I've looked underneath and I've twice had a large piece of cardboard under the Jimmy and there are no leaks.

Dave.

[i486]

head gaskets? valve covers? fuel line? fuel pump? corroded gas tank? i