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Fuel Pump amperage

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6 years 2 months ago #18178 by Harrison3267
Good Evening ladies and gentlemen.
Sooo heres what I got. 2006 Ford F-250 5.4L with a P0191 code only.
Customer Complaint lacks power on up hill pull.
Checked fuel pressure with scan tool and fuel pressure dropped to 6 psi on a high throttle run and I wish I had gotten a picture of that.
But what I do have is pictures of the amp wave forms of the fuel pump start up and the fuel pump running.
What I dont know is how good these look. I see some issues but am I seeing things?
So for those in the know and are use to looking at these wave forms and calling pumps any advice?
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6 years 2 months ago #18198 by juergen.scholl
Replied by juergen.scholl on topic Fuel Pump amperage
Your code refers to a circuit problem within the fuel pressure sensor circuit. Verify the true pressure with a gauge. FPS sensor readings when working correctly will be higher than gauge readings. This is because the gauge references to atmospheric presssure while the sensor to absolute pressure.

The pump current wave forms looks fine, a bit on the high side. ...... might be a resttriction like bad filter, but not very likely.

What do the O2 show on WOT acceleration?

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6 years 2 months ago #18212 by Chad
Replied by Chad on topic Fuel Pump amperage
+1 for what juergen.scholl said.

"Knowledge is a weapon. Arm yourself, well, before going to do battle."
"Understanding a question is half an answer."

I have learned more by being wrong, than I have by being right. :-)

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6 years 2 months ago #18213 by GeekDIYMechanic
Replied by GeekDIYMechanic on topic Fuel Pump amperage
Great input from juergen.scholl.

The O2 and fuel trims can tell you a great deal about fuel delivery as well. How do they look at idle, 2400, and at a snap throttle?

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6 years 2 months ago - 6 years 2 months ago #18226 by bruce.oliver
Replied by bruce.oliver on topic Fuel Pump amperage
P0191 isn't necessarily a circuit code. Code set criteria says this code will set when the difference between commanded pressure and pressure reported by the pressure sensor is greater than 20psi for more than 8 seconds.

This is a PWM pump controlled by the fuel pump driver module. Tap into the power and ground at the pump, between the pump and driver module. At idle your DVOM should show 7-8 volts. And as the demand for more fuel increases the voltage will rise on the volt meter. Put a fuel pressure gauge in line to verify the pressure sensor is working. The gauge and scantool will be different unless you unplug the vacuum hose from the sensor, then the readings will be roughly be the same. Last one I did the voltage on my meter was almost battery voltage at idle so the fuel pressure had no where to go but down under a load. It needed a pump
Last edit: 6 years 2 months ago by bruce.oliver.
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6 years 2 months ago #18229 by juergen.scholl
Replied by juergen.scholl on topic Fuel Pump amperage
Bruce is right on this one!

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6 years 2 months ago #18236 by Chad
Replied by Chad on topic Fuel Pump amperage

bruce.oliver wrote: This is a PWM pump controlled by the fuel pump driver module. Tap into the power and ground at the pump, between the pump and driver module. At idle your DVOM should show 7-8 volts. And as the demand for more fuel increases the voltage will rise on the volt meter.


Does this have anything to do with the, slightly, higher amp draw? I have often wondered what the effects of a PWM pump would be on the current waveform. I have not taken the time to play. And, have not had a NEED to, yet.

"Knowledge is a weapon. Arm yourself, well, before going to do battle."
"Understanding a question is half an answer."

I have learned more by being wrong, than I have by being right. :-)

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6 years 2 months ago #18248 by bruce.oliver
Replied by bruce.oliver on topic Fuel Pump amperage
I can't explain the current draw being a little high. I will have to try to get some known goods on some if I have time. Might try to get a waveform off my wife's explorer this weekend

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