1993 GMC Van EVAP problems 93 GMC G-2500 van

Tiny
ABE_ROBINSON
  • MEMBER
  • 1993 GMC VAN
  • V8
  • 2WD
  • AUTOMATIC
  • 86,000 MILES
I have a 93 GMC G-2500 conversion van. I don't drive it everyday, as fuel is expensive, but I do use it for family trips, and for pulling heavy things like my 1993 Chrysler Town n Country to Pull-a-Part. (I did use a tow dolly). The problem I have had with it since I purchased it in 2005, is that there seems to be a whole lot of fuel vapor in the gas tank when I remove the gas cap. If the tank is fairly full, when I remove the gas cap a lot of fuel vapor escapes, but if I remove the cap when it is almost empty there is an enormous amount of vapor in the tank, so much so that the tank makes a popping sound when the vapor is rushing out, I gues the tank is changing back to it's regular size and shape. I thought perhaps an exhaust leak was warming the gas tank, and replaced all the exhaust from the cat back, but there is no change at all. The old exhaust was rusty and had holes, so it made sense, but it has not helped. I also have replaced the gas cap. So I really am looking for some direction as to why the fuel vapor is building up in the tank. If someone replies to my question, please have a pretty good understanding of GMC vans and the fuel vapor recovery system. Thanks.
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Saturday, September 26th, 2009 AT 9:12 PM

3 Replies

Tiny
MATHIASO
  • MEMBER
The computer should set a code for emission control system faillure. have it scan,
pressure build up in tank could cause tank explosion.

is this a 1993 (VIN N) 7.4L; with AIR ?
if yes, check below.
if no ,let me know


http://www.2carpros.com/forum/automotive_pictures/46384_Canister_1.jpg



Check the hoses to and from the canister. check the tank presure valve.
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Sunday, September 27th, 2009 AT 9:34 AM
Tiny
MATHIASO
  • MEMBER
93 GMC G2500 conversion van
The van has a 350 V8. Vin code K.
thank you for providing me this information


http://www.2carpros.com/forum/automotive_pictures/46384_new_evp_1.jpg



the hoses from and to the canister are same except this one ,it is not air.
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Monday, September 28th, 2009 AT 5:00 PM
Tiny
ABE_ROBINSON
  • MEMBER
I don't use the van much, and have not had much time to work on it. But with the weather being nice and cool now (i live in Georgia), I have been doing a bunch of maintenance on the van, replaced the driver's power window motor, and some other things. I found that the hose from the canister was disconnected at the throttle body, it was unplugged and just laying there, out of sight, under the air cleaner. Hooked it back up, so we will see how it does now. I would figure if the hose is off the throttle body that the fuel vaoprs would just evaporate out of the end of the hose, but I guess it needs vacuum to really suck out all the fuel vapor from the canister and I guess the gas tank. I am hoping maybe this will also help me get more than the 9.9 MPG to 11 MPG city driving that I was getting. I get 17 on the highway right now.
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Tuesday, December 8th, 2009 AT 11:44 PM

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