Fuel Pressure?
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Laughing Gas
Joined: Apr 2006
Posts: 1,121
Likes: 266
From: Middle Georgia
Fuel Pressure?
Finished installing a fuel pressure gauge today. Truck isn't able to run at the moment due to having no oil in it, but I did key on the ignition and check function.
For reference, the sender is located in the post filter port so it should be showing the fuel pressure that the injectors see.
While fuel pump is running to prime it has the normal 55 psi that it should have. As soon as the fuel pump stops priming the fuel pressure drops off to zero and does it fast.
Is this normal operation, or should I be retaining the pressure after the pump kicks off?
If I should be retaining fuel pressure, any suggestions as to what could be causing it to drop?
I have not noticed see any external leaks. Not saying that there isn't one, just that I haven't spotted it yet if there is. I've also seen no signs of cross contamination with the other fluids.
For reference, the sender is located in the post filter port so it should be showing the fuel pressure that the injectors see.
While fuel pump is running to prime it has the normal 55 psi that it should have. As soon as the fuel pump stops priming the fuel pressure drops off to zero and does it fast.
Is this normal operation, or should I be retaining the pressure after the pump kicks off?
If I should be retaining fuel pressure, any suggestions as to what could be causing it to drop?
I have not noticed see any external leaks. Not saying that there isn't one, just that I haven't spotted it yet if there is. I've also seen no signs of cross contamination with the other fluids.
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Laughing Gas
Joined: Apr 2006
Posts: 1,121
Likes: 266
From: Middle Georgia
So I'll take that to mean that this is proper operation. Will check on idle and operational pressures once I have the truck back up and running.
Seems strange that it would be designed such that it drops off like that. If you let the glow plugs run for an extended warmup, the pump will be off and fuel pressure dropped before you are trying to crank the engine. Unless of course the FP comes back on when cranking. No oil in engine so I didn't try turning the key to crank to see what happened.
Maybe FP isn't that important when starting a diesel considering the way that the injectors work?
FWIW I did not install a fuel pressure gauge because I thought I had an issue with it. I was installing a 3 - in - 1 gauge for boost and EGT, and decided that fuel pressure would be a good option for the third gauge.
Seems strange that it would be designed such that it drops off like that. If you let the glow plugs run for an extended warmup, the pump will be off and fuel pressure dropped before you are trying to crank the engine. Unless of course the FP comes back on when cranking. No oil in engine so I didn't try turning the key to crank to see what happened.
Maybe FP isn't that important when starting a diesel considering the way that the injectors work?
FWIW I did not install a fuel pressure gauge because I thought I had an issue with it. I was installing a 3 - in - 1 gauge for boost and EGT, and decided that fuel pressure would be a good option for the third gauge.
Lead Driver
Joined: Jun 2004
Posts: 6,309
Likes: 577
From: Amarillo, TEXAS!
The fuel pump will run for about 20 seconds at key on, then it times out. However, as soon as the PCM sees RPM from the CMP sensor, the pump is commanded on again and will run continuously while RPM is seen.
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papadelogan
1999 - 2003 7.3L Power Stroke Diesel
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