1992 Chevrolet S-10 Fuel pressure in tank

REZA3AUTO

MEMBER
1992 CHEVROLET S-10
250,000 MILES

Checking the vacum hoses, realized the hose from canister to fuel tank is cut off and seems the guys had no idea where to hide it and just left it there on the left fender.

Result, high fuel pressure creates in tank while engine is running esp in hot weather which can damage fuel system esp the injector. It can proved by opening the filler cap and you can hear sound of the pressure coming out of the tank.

But when I tried to find the pressure return line on the tank, just found out that there's a hose from tank seemingly the pressure relief hose that again went to the filler neck and there wasn't any idle hose to connect to canister.

My Q : Is connecting the hose comming from canister to that hose comming from filler neck a good idea to prevent creation of high pressure in tank? Or is there another way or sth missing from that point?
Thanks.

3 Replies

CARADIODOC

MECHANIC
33,757 POSTS

Would have to see what you're describing, but pressure buildup in the tank is normal and not harmful. It just proves you don't have any leaks. There is a fuel pressure regulator to control how much fuel pressure is at the injectors. You aren't going to hurt them.

There should be a vacuum hose routing diagram under the hood that shows the charcoal canister and its hoses. It sounds like someone plugged the hoses that you found disconnected. All you need to reduce that pressure buildup in the tank is the hose from the top of the tank to that canister. Of course the hose from the canister to the engine can't also be blocked or plugged.

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Sunday, July 28th, 2013 AT 3:29 PM

REZA3AUTO

MEMBER
11 POSTS

First of all, I made a mistake by using " fuel pressure ", what I mean, is the pressure vapor building up in the tank.

I've not seen or heard anything like that feeesing sound when opening the filler cap of any car!
And when I found the canister hose short cutoff, thought that's could be the reason because the tank has no route to breathe. As I know the gasoline can produce vapor even it's not moving or shaking. Shouldn't that vapor be evacuated from the tank?

You said " The hose from top of the tank to the canister " . Ok

My problem is that hose. The canister has its hose to tank, but it's short cutoff.
So I'm trying to use a long enough hose from canister to connect to the tank. I've searched the top of the tank by hand because of hard accessibility and I couldn't find the right place to connect that hose.

So I've looked for a company diagram at the Autozone's repair guides but unfortunately it doesn't show anything about this and still looking for this kind of diagram that can show the correct lines.

After all, the only and final way, is to remove the tank and see what's going on there.
Thanks.

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Tuesday, July 30th, 2013 AT 4:15 PM

CARADIODOC

MECHANIC
33,757 POSTS

If you're using AllData, those diagrams are usually copied right out of the manufacturer's service manuals but sometimes they don't include everything. With fuel supply systems there can be variations depending on which country the vehicle was sold in, federal vs. California emissions, and things like that. You might have to look in the GM manual. The Chrysler dealer I worked for years ago had service advisers who would find an older manual and photocopy a few pages for people with the dealership owner's blessings. Some dealers don't keep manuals that are 20 years old, and those that do may need some time to dig them out, but it's worth asking. Our local GMC dealer, Ford dealer, and an import dealer would also do that for people and we often borrowed manuals back and forth. Only the Chevy dealer in our city is a huge crook and he doesn't cooperate with anyone.

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Tuesday, July 30th, 2013 AT 8:47 PM