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Gary, Chevy Technician
Category: Chevy
Satisfied Customers: 17023
Experience:  15 years GM master tech
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I have a 1993 Chevy 3500 extended cab 6.5 turbo diesel truck.

Customer Question

I have a 1993 Chevy 3500 extended cab 6.5 turbo diesel truck. I am having a fuel problem.
The tank is clean the fuel pick up in the tank was changed out @ six mounths ago. It has a
new lift pump and a new filter. The lift pump seems to be coming on but not as often as it should. When I open the water seporator drain valve to purge the fuel filter housing. The fluid will not come out of the hose and the engine will go air bound. Also now the filter housing will not stay full of fuel. The level starts to drop in the filter housing and eventually the engine starts to get air bound. The engine cranks real good and when the filter is topped off it starts ouick and idles great. The mechanical fuel injection pump was rebuilt @ 50,000.0
miles ago when the engine was replaced with a new one. The truck runs and handles great
just need to get this fuel problem solved. Would appricate any suggestions on the problem.
The oil pressure sensor also has been changed out @ 6 months ago.
Submitted: 7 years ago.
Category: Chevy
Expert:  Gary replied 7 years ago.
so if you open the bleeder on the top front of the engine(brass petcock) and crank it fuel will come out?then close the petcock and it should start up and run.will it do that?
Customer: replied 7 years ago.

I have not tried opening the brass Filter drain valve and cranking the engine. When I open the needle valve to purge the filter housing the engine gets air bound. If the engine went air bound I just fill it from the top of the filter housing by removing the air bleeder cap completely and fill it with a bottle with a nozzle on it as not to run my starter down so much. It seems as though the lift pump is not comming on as it should. What component sends a signal to the lift pump to pressure up the fuel system. there is a water in fuel sensor in the bottom of the fuel filter housing. Is there a fuel pressure sensor in line anywhere.

Expert:  Gary replied 7 years ago.
the computer
try to bleed the air from the brass petcock that is how you remove air from the fuel system.then see if it runs
Customer: replied 7 years ago.

What does the computer pick up the fuel pressure signal from in fuel system to see the correct pressure.

Expert:  Gary replied 7 years ago.
the lift pump lifts the fuel up to the fuel filter and to the injection pump once the air is bled out threw the front brass petcock there is supposed to be fuel in that line.if you bleed it threw the brass petcock and get the air all out and it still will bleed down the fuel in that line then there more than likely is a problem where that line is getting air in it and it can not hold the fuel in that line.kinda like if you try to drink a drink threw a straw that has a hole halfway down the straw your gonna suck some air and when its off the fuel that is supposed to be kept in that fuel line will be empty.try bleeding it threw the brass petcock and see if it will run.then if that line and fuel filter line are still getting filled with air we are going to have to trace back that fuel line from the injection pump all the way back to the fuel tank and find the leak
Gary and 3 other Chevy Specialists are ready to help you
Customer: replied 7 years ago.

Your answer is making alot of sense to me and I guess I will have to back check my lines to see where it could possibly be sucking air from between the filter and the fuel tank suction pickup. To me the problem seems to be in that area. I am out of town now and cannot work on my truck at the moment. When I get back in town I will check the system. Thank you for your information I will get back to you when I check for and find the air leak. Tim




Expert:  Gary replied 7 years ago.
ok let me know