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[SOLVED] 4.0 SOHC is long cranking when hot

Discussion in 'Stock 1995 - 2001 Explorers' started by slisman, March 10, 2019.

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  1. slisman

    slisman Member

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    Hello,
    I've noticed a warm start issue with my 4.0 SOHC 2000' (returnless fuel system). It starts perfect every morning (if temperature drops under 0 degree too). It also starts just fine after all day at work (8 hours). It only has issues starting when warm (after 15 minutes or more - up to 2 hours from engine off). It is cranking for an extended period of time (5+ seconds) or needs to hold gas pedal down. No trouble codes, proper fuel pressure, truck runs smoothly and has power.

    I have no idea why it only have hard starts with long cranking when the engine is warm. It fueI pressure couldnt be held by fuel pressure regulator - issue will be present on every idle I think.

    I am sure that:
    -fuel pump is good (tried 2 ones before this post)
    -fuel lines intank are new
    -fuel line to basket is not leaking (I've changed it)
    -new fuel pump relay
    -IAC valve is new (OEM)
    -fuel and air filter are new
    -sparkplugs/cables are new

    Any ideas how to diagnose it - maybe via forscan or voltometer? It seems to be electric related issue. Do you think that resetting PCM and proper adjusments can make the difference?

    I would appreciate any thoughts or suggestions to diagnose this issue.:thumbsup:
     
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  3. koda2000

    koda2000 Explorer Addict

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    Coolant temp sensor?
     
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  4. XLTrunner

    XLTrunner Active Member

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    Agreed...sounds symptomatic of a bad ECT sensor.
     
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  5. slisman

    slisman Member

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    Thanks guys, I will check it today :)
     
  6. donalds

    donalds Elite Explorer

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    Coolant temp sensor :)
     
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  7. slisman

    slisman Member

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    Sensor ordered, 2 days and I will know if it is a fix :)
     
  8. slisman

    slisman Member

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    I've checked today ECT sensor readings via forscan - I think that you are right :)
    First idle after cold night (-1 Celsius degree - winter) sensor showed +33 Celsius degrees (impossible!). Next reading (after gaining work temperature) showed +87 Celsius degrees.

    So definitely this sensor is broken, right?
     
  9. koda2000

    koda2000 Explorer Addict

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    I assume when you say "after gaining work temp" you mean engine at normal operating temperature? 87C is around 189F, so that doesn't sound like it's too far off when warm (depending on which t-stat you have). What does it read after sitting for 30 mins and 1hr/2hrs? I would think the coolant temp would drop quite a bit after the engine sits for 30 mins (and certainly after hours). If the ECT believes the engine is stone cold after 30 mins the PCM will add too much fuel trying to start it, making for a long crank.

    An ECT is a fairly inexpensive part, as you've bought a new one I'd throw it in and see what happens.
     
  10. slisman

    slisman Member

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    After your ECT diagnosis I've checked only idle after night and temperature at arrival to work (same idle) :p

    I will check readings after 30mins/2hours now - I am going back home.

    Indeed - this sensor is cheap so it is worth trying.
     
  11. koda2000

    koda2000 Explorer Addict

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    Well, best of luck and please let us know how it works out. Actually on a cold start it should idle a bit higher until the engine temp starts to come up (maybe 3-5 mins depending on the coolant temp) so maybe that's an indication that indeed the ECT sensor is the issue.
     
  12. slisman

    slisman Member

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    Sure I will :)

    I've checked ECT sensor readings 2hours after shut down - temperature is about 60 celcius degrees and in this case problem with long cranking is present.
     
  13. koda2000

    koda2000 Explorer Addict

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    60C is 140F, that's still reading pretty hot after 2 hours. No?
     
  14. slisman

    slisman Member

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    Yes, indeed. Looks like all readings are increased about 30 degrees (celsius). I don't know if that can be cause of long cranking, but definitely sensor is not working properly :)
     
  15. slisman

    slisman Member

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    New sensor already mounted! :) Had to take off upper manifold, without it sensor was unreachable.

    Now ECT sensor reading seems to be correct - it show 7 celsius deegres which is exactly the same as temperature outside! :)
    No test drive yet - I will report it tomorrow after work. Thanks for help and I hope "case closed"!

    54362937_949437758780224_6593383525074862080_n.jpg
     
  16. slisman

    slisman Member

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    Sorry for one post after another. But I have little update - sensor shows correct readings, but when hot engine is still cranking long. Pedal to metal helps and engine starts.

    Can resetting PCM (fuel trims etc.) after earlier fuel pump replacement and ECT replacement help somehow?
     
  17. EB4X

    EB4X Active Member

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    This symptom sometimes indicative of a starter in beginning stages of failure......long cranks when hot....
     
  18. slisman

    slisman Member

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    You mean starter motor on the tranny? It produces weird noise recently (moaning) but it's spinning Good. Can be reason of this issue?
     
  19. koda2000

    koda2000 Explorer Addict

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    As opening the TB helps (BTW if you hold the gas pedal all the way to the floor when trying to start it turns off the fuel injectors) it sounds like the engine is flooded. The ECT sensor could have been the cause of this (especially with the ECT temp reading you witnessed), but also a leaky fuel injector(s) might be the cause. When you turn the engine off pressure remains in the fuel line for quite a while, maybe 30 mins or more. If you have a fuel injector(s) that's not sealing it will leak fuel into the engine and when you try to start it when still warm/hot it will be hard to start. Opening the TB and turning off the fuel supply while cranking will help under this situation.

    You might try removing the fuel pump relay with the engine running (with the engine at full operating temp) and letting the engine use all the fuel in the fuel line. That way there would be no residual pressurized fuel available to leak through any fuel injectors. After letting the engine sit for an hour replace the FP relay and try to start it to see if it makes a difference.
    Note: Before attempting to restart, turn the ignition key from OFF to ON a couple of times to prime the system.

    I honestly don't see how your starter motor could be your problem if it's spinning normally.
     
    Last edited: March 16, 2019
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  20. EB4X

    EB4X Active Member

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    I've read that when inner components of starter/and or solenoid are near failure point that the existing heat soak condition makes them fail in that state before they finally give up ghost completely..
    Or is it possible your engine compartment is experiencing an additional heat soak condition brought on by missing heat shield near starter /minor exhaust leak near starter (not familiar with sohc layout) or additional resistance (heat factor) from less than perfectly clean battery / starter connections...

    "... This absorbed heat adds resistance to the electrical conductors inside the starter. The additional resistance results in the starter requiring more amperage than it normally does when cool. Once under-hood heat warms the battery, cables, and starter, a “tipping point” is reached concerning the overall amount of resistance a starter can accept (and still function properly)"

    Does it crank slightly slower during 'hot starts' ? ....if so this would be red flag for this possibility.....
     
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  21. slisman

    slisman Member

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    Thanks guys for new ideas for diagnosing!

    1) @koda2000 I was thinking about leaking injectors, thanks for this trace and way to check bit. But unfortunately - it does not help -> after taking off fuel pump's relay and using all fuel in system next idle (after 1 hour or more) is the same...long cranking, pedal to metal helps to start at once.

    2) @EB4X starter motor crank with normal speed I think. Maybe I will replace it for a try with another used starter motor (why not). But I have no idea if that can be a reason :)

    I've checked at forscan also PID cmp (camshaft position sensor status) and it's ok.
    My new observation - intake smells fuel a little.
     






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