Fuel Pressure Test 1998 5.7

[arrowshooters]

I tested my fuel pressure today and was wondering is this is correct. Keep in mind this is a new engine with the upgraded injectors. Fuel Pump is an 8 month old Delphi.

 

Initial turn on gauge goes to 62 psi then when the pump shuts off the needle goes to 60 psi and holds.

 

When the engine is running the needle "vibrates" between 52 PSI and 62 psi.

 

Wheni I shut of the engine the needle goes back up to 62 psi while the pump is still running then settles down at 52 psi.

 

Are these number correct?

[rodram]

-- are you having any problems with the engine, like difficult starting.. or engine missing ?

 

-- by upgraded injectors... which ones do you mean? did you install the MFI conversion? or just replace the SCPI (original style) injectors?

 

-- the spec range for the fuel pressure for the Vortec engines with the original SCPI injectors is 61 to 66 psi.... and this is absolutely critical at all stages of starting and running... dropping to 52 psi while trying to start likely indicates the start of fuel pump failure.... and likely causes difficult starts.. like needing to crank the engine more than 2 times to get it going.... then 10 times, then 20 times, then you get so frustrated you just get a new fuel pump.....

 

-- I am not sure of fuel pressure required for the MFI conversion system, I know that it has it's own replacement fuel pressure regulator in the spider, and I think it runs on lower fuel pressures than the SCPI.

[arrowshooters]

-- are you having any problems with the engine, like difficult starting.. or engine missing ?

 

-- by upgraded injectors... which ones do you mean? did you install the MFI conversion? or just replace the SCPI (original style) injectors?

 

-- the spec range for the fuel pressure for the Vortec engines with the original SCPI injectors is 61 to 66 psi.... and this is absolutely critical at all stages of starting and running... dropping to 52 psi while trying to start likely indicates the start of fuel pump failure.... and likely causes difficult starts.. like needing to crank the engine more than 2 times to get it going.... then 10 times, then 20 times, then you get so frustrated you just get a new fuel pump.....

 

-- I am not sure of fuel pressure required for the MFI conversion system, I know that it has it's own replacement fuel pressure regulator in the spider, and I think it runs on lower fuel pressures than the SCPI.

 

Yes it is the MFI injector conversion. No problems with engine at all, start's and runs like a champ. The engine is running while the needle is vibrating. What has me checking is I am getting codes P0420 and P0430 for the Cats when I come to a stop after the engine has been up to tmep for awhile. I can also hear the fuel "rushing" back through the return line to the tank which I do not recall hearing before the new motor. I want to eliminate all possible causes, like temporary rich condition, before I pop for new cats.

[arrowshooters]

Bump

[rodram]

... sorry , now we've gone to the limit of my understanding of these things...

... don't know anything about the cats, as fortunately I have not had any problem with mine..

 

.. but if you are wondering about temporary rich fuel conditions... check your coolant temperature sensor... it is on the front of the block right beside the thermostat... this is one of the main sensors that sends info to the PCM (powertrain control module) to set the fuel mix..

 

.. you can check it quickly with an ohm-meter... just pull the connector off and measure across the two pins on the top of the sensor ... check to see if the connector looks clean and in good condition... also check for condition of the wires and the connector looking for cracks or poor ground

 

.. don't worry about the exact resistance, but when engine is cold the resistance is high and when hot the resistance should be low...... like at 32degrees F the resistance should be about 9000 ohms; at 68F it should be about 3500 ohms; and at 212F it should be about 200 ohms.....

 

.. so if your engine is sitting cold and you find no or very little resistance across the sensor, then get a replacement coolant temperature sensor .... it is a cheap part and very easy to replace... even for a guy like me.

[VRSCA1]

I tested my fuel pressure today and was wondering is this is correct. Keep in mind this is a new engine with the upgraded injectors. Fuel Pump is an 8 month old Delphi.

 

Initial turn on gauge goes to 62 psi then when the pump shuts off the needle goes to 60 psi and holds.

 

When the engine is running the needle "vibrates" between 52 PSI and 62 psi.

 

Wheni I shut of the engine the needle goes back up to 62 psi while the pump is still running then settles down at 52 psi.

 

Are these number correct?

 

Sounds good to me!

P0420 & P0430 common needs cats if you have no other driveability issues or exhaust leaks.

[arrowshooters]

Thanks, I guess cats is where I am heading.