WHEN CAR SITS OVER NIGHT IT DOES NOT WANT TO ...

  • Tiny
  • RMcPherson
  • 1998 Mercury Mystique
  • 196,000 miles

When car sits over night it does not want to start in morning. I have to pump the accelerator pedal continuously and it takes between 1-2 minutes before it begins to start. Once it starts it runs very good with no missing and will start throughout the day. Fuel pump pressure tests ok, pressure regulator new, CKP new, TPS new, IAC new, Relay ok, new fuel filter, injectors all clicking (no other test on them yet), Coil pack ok, spark plugs and wires ok. Fuel pressure does drop quickly when car is shut off.

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Tuesday, October 23rd, 2012 AT 10:52 PM

18 Replies

  • Tiny
  • saturntech9
  • Expert
  • 29,356 posts

Do you have any codes in the computer?

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Tuesday, October 23rd, 2012 AT 11:04 PM
  • Tiny
  • RMcPherson
  • Member

No DTC codes

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Tuesday, October 23rd, 2012 AT 11:08 PM
  • Tiny
  • saturntech9
  • Expert
  • 29,356 posts

That fuel pressure drop could cause the the fuel lines to bleed down all the fuel and cause excessive cranking and start time. Try this in the morning before starting it. Turn the key to the run position wait about 3 four seconds then turn it off then repeat do that about 5 times then start the car. Does it start better?

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Wednesday, October 24th, 2012 AT 4:18 AM
  • Tiny
  • RMcPherson
  • Member

I cycled the ignition switch 6 times allowing the fuel pump to pressurize each time then tried to start the car but it had no appreciable affect on accelerating the engine start time. As I press and depress the accelerator pedal I do get some backfire through the air intake at sporadic times.

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Wednesday, October 24th, 2012 AT 2:24 PM
  • Tiny
  • saturntech9
  • Expert
  • 29,356 posts

Do you have a scan tool that can read live engine data?The next thing I would be looking at was coolant temp sensor reading when your starting it cold?You could have a bad coolant temp sensor.

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Wednesday, October 24th, 2012 AT 4:17 PM
  • Tiny
  • RMcPherson
  • Member

I have an CAN OBD2/EOBD scan tool but not one that will read live engine data that I am aware of. However, I had previously purchased a coolant temp sensor but had not installed it but went ahead and installed it. However, it did not make any difference regarding the cold start problem.

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Wednesday, October 24th, 2012 AT 10:13 PM
  • Tiny
  • saturntech9
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Just because you a new sensor doesnt mean its reading correct thats why I asked to read the coolant on the scan tool. Which engine do you have?

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Thursday, October 25th, 2012 AT 2:29 AM
  • Tiny
  • RMcPherson
  • Member

GS 2.0L

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Thursday, October 25th, 2012 AT 4:12 AM
  • Tiny
  • saturntech9
  • Expert
  • 29,356 posts

Please do the trouble shooting I posted.

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Thursday, October 25th, 2012 AT 4:59 AM
  • Tiny
  • RMcPherson
  • Member

Regarding the trouble shooting tests:
1. Everything checks out ok.

2. Fuel Pressure at idle = 32PSI; @ 2500 RPM = 32PSI (Spec is 27.5 to 33.5 w/Vaccum connected) (There is about a 6 PSI rise when I step on the accelerator quickly.)

3. Engine off cycle 4 times fuel pump pressure = 38 - 40 PSI;
Fuel Pressure drop with engine off after 1 minute = 12 PSI.
Recommends checking the Pressure Regulator and Fuel Injectors for leakage. The Pressure Regulator is new and there is no leakage from it. I do not know how to test the Fuel Injectors for leakage?

Thank You

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Friday, October 26th, 2012 AT 1:56 AM

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