Hi Guys,
I'm having a problem that I could use some expertise in guiding to a solution. The 5.3 non-flex fuel engine starts hard. Usually takes two cranks to get it running. I did some fuel pressure tests - I'm losing fuel pressure, there's a leak somewhere. Here's the data
Key On Engine Off: ~53-55 psi
After 5 minutes the pressure drops to 32 psi
After 15 minutes it drops to 22 psi
Next, started the engine. Fuel Pressure idling: 46 psi
shut the engine off. within 3 minutes its down to 36 psi
within 10 minutes of shutting off the truck, down to 20 psi
So, I'm losing pressure somewhere. I've done a visual inspection of the lines, fuel pressure regulator, fuel filter, and injectors, and cannot find any leaking fuel. Here's the parts that have been replaced already:
Fuel Pump (AC Delco MU1615)
Fuel Injectors (AC Delco 17113553)
Driver Side Fuel Rail (GM 17113696)
Fuel Pressure Regulator (ACDELCO 2173299)
Fuel Rail O-ring Kit (GM 17113552)
I'm thinking it is unlikely the fuel pressure regulator is at fault. It is brand new, and there's no fuel in the vacuum line. I'm thinking either the injectors or the Fuel Pump, and leaning towards the pump. The fuel trims don't suggest a leaky injector. The trims are less than 5%, and closely matched between both banks. So I think its the pump. But I'm open to further tests to perform. Unfortunately there's no easy way to test the fuel pressure at places other than at the fuel rails. I'm ordering a set of hose pinch off pliers to pinch off the return line, that should rule out the fuel pressure regulator.
Next weekend I'm pulling the manifold and will test the injectors for leaks.
I'm wondering though- brand new fuel pump, why is it loosing pressure? Its ridiculous, a brand new Delco part leaking? Are there any alternative fuel pump assemblies that would guarantee I never have to redo this job?
Thanks for any words of wisdom
I'm having a problem that I could use some expertise in guiding to a solution. The 5.3 non-flex fuel engine starts hard. Usually takes two cranks to get it running. I did some fuel pressure tests - I'm losing fuel pressure, there's a leak somewhere. Here's the data
Key On Engine Off: ~53-55 psi
After 5 minutes the pressure drops to 32 psi
After 15 minutes it drops to 22 psi
Next, started the engine. Fuel Pressure idling: 46 psi
shut the engine off. within 3 minutes its down to 36 psi
within 10 minutes of shutting off the truck, down to 20 psi
So, I'm losing pressure somewhere. I've done a visual inspection of the lines, fuel pressure regulator, fuel filter, and injectors, and cannot find any leaking fuel. Here's the parts that have been replaced already:
Fuel Pump (AC Delco MU1615)
Fuel Injectors (AC Delco 17113553)
Driver Side Fuel Rail (GM 17113696)
Fuel Pressure Regulator (ACDELCO 2173299)
Fuel Rail O-ring Kit (GM 17113552)
I'm thinking it is unlikely the fuel pressure regulator is at fault. It is brand new, and there's no fuel in the vacuum line. I'm thinking either the injectors or the Fuel Pump, and leaning towards the pump. The fuel trims don't suggest a leaky injector. The trims are less than 5%, and closely matched between both banks. So I think its the pump. But I'm open to further tests to perform. Unfortunately there's no easy way to test the fuel pressure at places other than at the fuel rails. I'm ordering a set of hose pinch off pliers to pinch off the return line, that should rule out the fuel pressure regulator.
Next weekend I'm pulling the manifold and will test the injectors for leaks.
I'm wondering though- brand new fuel pump, why is it loosing pressure? Its ridiculous, a brand new Delco part leaking? Are there any alternative fuel pump assemblies that would guarantee I never have to redo this job?
Thanks for any words of wisdom