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Fuel pressure issues

Tiny
FLEEMANUFACTURED
  • MEMBER
  • 1999 FORD EXPLORER
  • 5.0L
  • V8
  • 2WD
  • AUTOMATIC
  • 155,890 MILES
The fuel pump only kicks on for about 3 seconds when the key is turned on. I have swapped relays and changed fuel pump. The truck won’t start most of the time, although a couple tries were successful but truck ran roughly. Please help thank you in advance.
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Sunday, December 29th, 2019 AT 7:45 PM

7 Replies

Tiny
SCGRANTURISMO
  • MECHANIC
  • 4,897 POSTS
Hello,

If the fuel pump turns on when the vehicle ignition switch is turned to "run" then the fuel pump and the fuel pump circuit is working properly. I would recommend checking your vehicle's Crankshaft Position Sensor[CKP]. Here is a link to a generic guide explaining how to do this below:

https://www.2carpros.com/articles/crankshaft-angle-sensor-replacement

In the diagrams down below I have included the Original Equipment Manufacturer[OEM] part number for your vehicle's CKP for reference and the instructions for the removal and installation of the CKP for your vehicle. Please go through these guides and get back to us with how everything turns out. Happy Holidays.

Thanks,
Alex
2CarPros
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Sunday, December 29th, 2019 AT 9:48 PM
Tiny
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  • MEMBER
  • 4 POSTS
Thank you for your help and direction, I changed the crankshaft position sensor and still not starting, when I spray starting fluid in intake the motor fires for a brief moment, spit and sputters, it must be fuel delivery that is failing, I am led to believe. The fuel pump has been replaced and when the key is turned on it only runs for 2 seconds, I installed a fuel pressure gauge and with each cycle of the the key from Off to on the fuel pressure increases 10 lbs, if cycled 1 time or more the pressure does not increase with the motor turning over, so the fuel pump isn’t turning on after the initial Two seconds. What is responsible for the fuel pump failing or is it something else, thank you for your time and help
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Friday, January 3rd, 2020 AT 3:36 PM
Tiny
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  • MECHANIC
  • 4,897 POSTS
Hello,

There is going to be a problem with the wires that go from the Crankshaft Position Sensor[CKP] to your vehicle's Power train Control Module[PCM] or "computer", the CKP electrical connector, or the PCM itself. Lets check the CKP electrical connector and wires first. In the diagrams down below I have included the engine management wiring diagrams for your vehicle with the two wires to check high lighted for you, as well as guides for finding unwanted resistance using voltage drop, and checking for opens in an automotive electrical circuit as well. You will need to use a Digital Multi-meter to go through these guides, so here is a link explaining how to use, if needed, below:

https://www.2carpros.com/articles/how-to-use-a-voltmeter

Please go through these guides and get back to us with what you are able to find out.

Thanks,
Alex
2CarPros
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Friday, January 3rd, 2020 AT 9:16 PM
Tiny
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  • MEMBER
  • 4 POSTS
When I disconnect the 2 wire plug at the crankshaft position sensor and place my leads on the two wires I get a reading of MV, when I attach ground lead to neg terminal on battery and positive lead to either wire on two wire plug I get a reading of 11.33 volts when I reverse leads posi on battery and ground to either two wires I get 1.69 volts. I think I’m confused.
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Saturday, January 4th, 2020 AT 1:16 AM
Tiny
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  • MECHANIC
  • 4,897 POSTS
Hello again,

Can you check the battery that's in your DMM and or replace it? This would ensure that you are getting an accurate reading. Please do this and double check the voltage readings again and get back to us with what you find out, please. We can take it from there.

Thanks,
Alex
2CarPros
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Saturday, January 4th, 2020 AT 4:54 AM
Tiny
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  • MEMBER
  • 4 POSTS
Okay, I found that it is the PATS system causing my issue. The theft light rapidly flash’s after the key is turned on, and flash is out trouble code 12 when the light quits blinking rapidly after a bout a minute. Which means not receiving information from the transceiver located in the steering column by lock cylinder. When the Pats system Is activated it does exactly what my symptoms have been will turn over but will not fire. Allows fuel pump to keep going for about a second but shuts off before initial priming can be achieved. I’m going to open up the steering column and check my connections. Thank you for your time and direction once again. Is there any knowledge you have on this pads coded key system and maybe bypassing or disabling?
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Monday, January 6th, 2020 AT 6:58 AM
Tiny
SCGRANTURISMO
  • MECHANIC
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Hello again,

I have included in the diagrams down below the information that we have on repair procedures for reprogramming the PATS system. Unfortunately this needs to done by either the dealership or a locksmith, so people can't go running around stealing other people's cars.

Thanks,
Alex
2CarPros
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Monday, January 6th, 2020 AT 12:15 PM

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