Blazer 99 fuel system explanation needed.

Nandy

Commander
Joined
Apr 10, 2004
Messages
2,145
I need a bit indeep explanation of the fuel system for this vehicle. Very interested in the tank and the peripherals around it. I have a chilton book and it is useless. I could not find much in the net either.

Lets start with the fuel pump.
There are 2 electric connectors there. One is for the fuel sender and the pump. The other connector seems to be some sort of sensor. I am guessing pressure sensor or vacuum sensor.

There are 3 hoses connections. One is for the fuel pump and it is to the extreme right. The one in the middle seems to go to some sort of valve. Im guessing it is meant to shut the fuel system if the suv rolls. The one to the left I cant tell what it does.

The tank has 3 hoses connections. One is the fuel filler hose, the other one is the vent hose. Those 2 are side by side on the back part of the tank. To the front of the tank there is a 1/4 fitting connected to a hose. I have no idea what that one is for.

Can anyone fill the voids, what are those hoses and connections and what are they for? I guess Im trying to understand how does the system works to detect the obd 452 and 453 codes.

My guess is that the system puts some pressure in the tank and that sensor measures it to stay the same for x amount of x. Then it puts vacuum to the tank and the sensor measures it to stay the same for x amount of time. If any of these 2 tests fails so many times then the system turns the light MIL light on. If the test past so many times more then the light is clear....

Anyone?
 

Bob_VT

Moderator & Unofficial iBoats Historian
Staff member
Joined
May 19, 2001
Messages
25,841
Re: Blazer 99 fuel system explanation needed.

There are a few GM wrenches here but I will try to help.

That mysterious small line is a return line to the tank since the system is pressurized. In my experiance I have found that a faulty fuel line with a slight air leak is the biggest problem. GM fuel lines are trash and rust throughs along with wear throughs are common.
 

Knot Waiting

Senior Chief Petty Officer
Joined
Jun 23, 2006
Messages
761
Re: Blazer 99 fuel system explanation needed.

I have access to Alldata Pro. If you need any detailed info just PM me and I'll try to email it to ya. It wont let me sent links or copy/past because of the password restriction.
 

PierBridge

Chief Petty Officer
Joined
Sep 3, 2004
Messages
617
Re: Blazer 99 fuel system explanation needed.







 

Nandy

Commander
Joined
Apr 10, 2004
Messages
2,145
Re: Blazer 99 fuel system explanation needed.

Pier, the photos wont show up. can you try again? Please...

Knot, pm your way!
 

Nandy

Commander
Joined
Apr 10, 2004
Messages
2,145
Re: Blazer 99 fuel system explanation needed.

Pier, so if the tank pressure is correct I should have over .3 volts at the sensor. I wonder about that excess vacuum statement. I wonder how does the sensor or unit knows that the vacuum is in excess. Do you have any information about the excess vacuum detection? It shows a 453 every know and then but it goes away.

Knot, do you have a diagram with the pump itself? I cant tell which is the return. I know which is the pump. I am guessing that the return is the hose to the left as the one in the center has like a check valve that operates if the vehicle is upside down. I will think that center hose is what the system uses to apply vacuum to the tank there fore it will be blocked if the vehicle roll over or if somehow I manage to fill that tank to the point where the gas hit that check valve (very unlikely for it to happen).

Both of you have pm, thank you very much!
 

PierBridge

Chief Petty Officer
Joined
Sep 3, 2004
Messages
617
Re: Blazer 99 fuel system explanation needed.





Can you see these? did you end up seeing the orignal pics I posted?
 

Nandy

Commander
Joined
Apr 10, 2004
Messages
2,145
Re: Blazer 99 fuel system explanation needed.

yes, I can see all now. Is that what cause the excess of pressure code? I did have a problem with the cable going back to the pump. Imight have the pump direct. I cant remember. I will check tomorrow.
 
Top