When car sits over night it does not want to.

Tiny
RMCPHERSON
  • MEMBER
  • 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.
Tuesday, October 23rd, 2012 AT 10:52 PM

18 Replies

Tiny
SATURNTECH9
  • MECHANIC
  • 30,869 POSTS
Do you have any codes in the computer?
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Tuesday, October 23rd, 2012 AT 11:04 PM
Tiny
RMCPHERSON
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No DTC codes
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Tuesday, October 23rd, 2012 AT 11:08 PM
Tiny
SATURNTECH9
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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
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  • 10 POSTS
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
  • MECHANIC
  • 30,869 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
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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
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GS 2.0L
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Thursday, October 25th, 2012 AT 4:12 AM
Tiny
SATURNTECH9
  • MECHANIC
  • 30,869 POSTS
Please do the trouble shooting I posted.
Image (Click to make bigger)
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Thursday, October 25th, 2012 AT 4:59 AM
Tiny
RMCPHERSON
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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
Tiny
SATURNTECH9
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The only thing that comes to mind is unpluug all the injectors plugs then pop the injectors up and see if any of the injector nozzle tips are leaking fuel.
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Saturday, October 27th, 2012 AT 2:55 PM
Tiny
RMCPHERSON
  • MEMBER
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Ok, I disconnected the injector rail and removed all the injectors. It was difficult to determine if any of the injectors was leaking they all looked fairly similar (even though two of them were a little darker around the tip end). However, the bottom seals were much harder than the top ones so I replaced all the seals (top and bottom) and reassembled the injectors. I noticed immediately an increase in the idle speed/RPMs of approximately 100 RPMs and an improvement on acceleration. I needed to wait until the next morning to see if it solved the start issue.

The start issue is not completely resolved but the start time has been reduced by at least 75% of what it was previously taking to start the car. But, nevertheless, it still requires some time and a little stepping on the accelerator in order for it to start.
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Thursday, November 1st, 2012 AT 3:36 PM
Tiny
SATURNTECH9
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So is the fuel pressure still bleeding down like it was?
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Thursday, November 1st, 2012 AT 3:55 PM
Tiny
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Idle PSI = 32
Immediately on ignition off it drops to 28 PSI
@ 60 secs = 25 psi
@ 2 min = 24 psi
@ 5 min = 24 psi
@ 10 min = 22 psi
@ 15 min = 20 psi
@ 30 min = 18.75 psi
@ 60 min = 12 psi
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Thursday, November 1st, 2012 AT 5:34 PM
Tiny
SATURNTECH9
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How does that compare to how it was before?
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Thursday, November 1st, 2012 AT 5:39 PM
Tiny
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Before it dropped to 12 PSI after one minute.

Now, it drops to 12 PSI after 60 minutes and is at 25 PSI after one minute.
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Thursday, November 1st, 2012 AT 6:17 PM
Tiny
SATURNTECH9
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A fuel pressure drop could cause a extended start time.
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Thursday, November 1st, 2012 AT 6:49 PM
Tiny
RMCPHERSON
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How can I determine what might be causing the drop in pressure?
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Thursday, November 1st, 2012 AT 7:07 PM

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