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Weird fuel pump and fan operation while engine temporarily dead.

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Weird fuel pump and fan operation while engine temporarily dead.

  #1  
Old 05-26-2012, 06:50 PM
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Default Weird fuel pump and fan operation while engine temporarily dead.

This is a problem I've been living with for years and its getting worse on my '94 sable wagon, big 6. When I turn on the ignition, the fuel pump and cooling fan run and the engine spark is dead. I have to leave the ignition on for about a half hour until the fan and pump quit, and then the spark is back and engine starts. Is this a fuel pressure sensor? Or more likely, the ECU since the cooling fan is part of the behavior? This used to take 10 minutes every time, but now more like 20~30. Oh and for the rest of the day the problem is not manifested, but returns the next morning.
 
  #2  
Old 05-29-2012, 12:28 PM
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I would suspect the fuel pump is not pressurizing the fuel line or the fuel pressure regulator may be at fault. In almost all fuel injected engines, the fuel pump should reach normal line pressure in a couple of seconds with the ignition key turned to run or start.

Since lots of devices connected to the engine and the computer use sense and activation systems, a failure of one can cause the computer to keep the engine from starting.

I would connect (if possible) a fuel pressure gauge to the fuel line and with the key on run (engine stopped), look for pressure above 40 lbs or at 40 lbs after the fuel line regulator. If these pressures don't come up in a few seconds, either the regulator or fuel pump screen is restricted with dirt. If there seems to be a low pressure problem, try checking any filters in the fuel line for restrictions (better to replace them to make sure they are not the problem).

Another tip as to the problem - the engine needing to cool down before starting again may be a sign that the fuel line regulator may be the problem when hot. So if possible, measure the fuel pressure after the regulator when the engine is cold and when hot . In either state the pressure should reach 40 lbs (typical) after the regulator and within a few seconds.
 

Last edited by Mr Q; 05-29-2012 at 12:35 PM.
  #3  
Old 05-29-2012, 09:04 PM
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Originally Posted by Mr Q View Post
I would suspect the fuel pump is not pressurizing the fuel line or the fuel pressure regulator may be at fault.
Thanks for the reply. Would anyone have any idea why the cooling fan runs along with the fuel pump, for up to 30 minutes while I wait? When both the fuel pump and cooling fan stop, then the engine will run. What does the cooling fan have to do with this?
 
  #4  
Old 06-01-2012, 11:19 AM
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OK update. Put a fuel pressure gauge on the fuel rail and pressure comes up normal. Fuel pump and cooling fan continue to run abnormally and engine won't start until fuel pump and cooling fan stop, which happens after about 20 minutes. Switched out ECM and problem unchanged.
 
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