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1989 ford f250 5.8 issues

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  #21  
Old 01-12-2021, 02:24 PM
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Originally Posted by worthingtonRacing
just replaced the oxygen sensor.cold start and idle are alot better but warm start and idle seem worse.
I realty, the O2 sensor has no effect on how the engine performs for the first few minutes after a cold start.
 
  #22  
Old 01-12-2021, 06:47 PM
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ok so after doing the compression test i was looking over the spark plugs.They are all firing but barely plugs are but now covered in black soot.Am i wrong for thinking that maybe the distributor is the the cause of this?less spark same fuel rich condition and miss fire?
 
  #23  
Old 01-13-2021, 05:58 AM
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Distributor is not your problem. You are running too rich. Any codes?Have you checked fuel pressure with a gauge. Is the pressure holding after shutdown which could indicate leaky injectors.Problem is you haven't checked the areas which have already been suggested and you are starting to guess now.
 
  #24  
Old 01-13-2021, 06:56 AM
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Ok i will do a fuel pressure test as soon as i get home from work.
 
  #25  
Old 01-13-2021, 07:02 AM
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There are some things you just need to do so you know if you are doing a worthwhile diagnosis..
You can rent a fuel pressure gauge , verify if the system is operating at the correct fuel pressure level.
You are getting the evidence of excess fuel by the appearance of the excessive carbon on the plugs.This needs to be corrected before moving on to anything else.
The gauge will help determine if ,as suggested earlier, whether you have a possible defective fuel press reg or leaking injectors. You pinch off the return line , engine off, to check for leaking injectors.
Until you do this , get your wallet out and be prepared to part with some hard earned $$$ because as raski stated, guessing isn't good and can get expensive and disappointing.
 
  #26  
Old 01-13-2021, 07:47 AM
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Ok so pinch off the return line.key on or off?
 
  #27  
Old 01-13-2021, 12:55 PM
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Once you connect the fuel pressure gauge to the schrader valve on the fuel rail,turn the key on and allow the pump to pressurize the fuel system. Note the reading ,should be 35-45 psi. Watch the gauge if it drops more than 2 psi in the first 3 minutes , you need to determine the cause.Since we are not suspecting the fuel pressure regulator, pinch off the return line from the regulator to the fuel tank , . If it drops down more than what was specified, could be leaking injector(s).

Whatever is causing the problem is common to all the cyls since all the plugs are showing evidence of over fueling.
Keep in mind , the fuel pressure regulator is what keeps the pressure to spec preventing higher fuel pres than required.
 

Last edited by hanky; 01-13-2021 at 01:04 PM.
  #28  
Old 01-13-2021, 06:00 PM
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ok so just finished the fuel pressure test.Turn the key on gauge went all the way to 100psi then settled at 35psi.i let it sit for about 10 minutes and only lost 1psi.
 
  #29  
Old 01-14-2021, 06:53 AM
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My first question is,,, where did you purchase that fuel pressure regulator ?
It should never allow the pressure to go that high,,, ANYTIME !
It could be malfunctioning, and the way you prove it is to drive the vehicle and observe what the fuel pressure does.
 
  #30  
Old 01-14-2021, 07:02 AM
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This pressure regulator was purchased from oriley auto parts.the first was from advanced auto parts that was bad out of the box.
 


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