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Tacoma 4.0L hard to start when warm

Discussion in '2nd Gen. Tacomas (2005-2015)' started by Fike, Jul 15, 2017.

  1. Aug 5, 2017 at 10:52 AM
    #201
    Fike

    Fike [OP] Well-Known Member

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    After an hour it is down to 10 psi

    Also, I'll add that I tried to use a bore scope down the throttle body, but it was a cheap one, and I couldn't see anything. When I pulled it out, I did have a drop of what appeared to be fuel on the end of the scope.
     
    Last edited: Aug 5, 2017
  2. Aug 5, 2017 at 2:00 PM
    #202
    Fike

    Fike [OP] Well-Known Member

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    I know I've had lots of posts today but I've been trying to update as I go.

    So I just completed the fuel pressure leak down test with the return line pinched off.

    While running, when I pinched off the return line, the fuel pressure jumped from 41 to 52. This means the fuel pressure regulator is bad according to the Haynes manual...

    So I shut it off and pressure was 39 with the return line pinched. After 10 minutes it's was 35, after 30 22, and after 1 hour it dropped to 10.

    So it basically followed the same path as all other tests. The only difference was, on all the other tests after an hour it gave me the hard start condition, but with the return line pinched, it cranked fine after an hour.

    Now I'm leaning towards a bad fpr.
     
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  3. Aug 5, 2017 at 2:08 PM
    #203
    boogie3478

    boogie3478 Tacomaholic & Hollywood

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    Progress! :D
     
  4. Aug 5, 2017 at 2:32 PM
    #204
    12TRDTacoma

    12TRDTacoma Pulley Man ;)

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    Bad FPR. Your first post had me more than convinced it was.

    As for me I have the issue every once in a blue moon. So I think the diaphragm for mine leaks a super miniscule amount but sometimes enough to choke it. I need to replace mine at some point anyways.

    You would have had to do the fuel pump anyways at some point. The OE ones are trash on these later model 2nd gens. The earlier ones it's a toss up. Be glad you did it now rather than later.

    Replace yours and enjoy your 2015.

    You too @boogie3478
     
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  5. Aug 5, 2017 at 2:48 PM
    #205
    koditten

    koditten Well-Known Member

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    When I'm done it will have a custom fabbed winch bumper and hopefully a Softtopper.
    That sounds more like a bad check valve in the pump, but it sounds more like leaky injectors.

    Anyways, the regulator is easier to change than injectors. I'm pulling for it to be the issue.
     
  6. Aug 5, 2017 at 3:04 PM
    #206
    Fike

    Fike [OP] Well-Known Member

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    After seeing the filter sock in the old pump I can only imagine it was about to crap out on me.

    I ordered a new fpr online with a company that says I can return it as long as it is in like new condition. I'm going to be very careful installing it in case it doesn't change anything I can return it and look deeper into injectors.
     
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  7. Aug 5, 2017 at 5:44 PM
    #207
    Fike

    Fike [OP] Well-Known Member

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    So do you know what residual fuel pressure should be? Should it hold pressure indefinitely, it will it always eventually lose all the pressure
     
  8. Aug 5, 2017 at 8:08 PM
    #208
    12TRDTacoma

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    The fuel pump is brand new. If he is pinching the return line and is not seeing 82 PSI or higher that indicates the fuel pressure regulator is not doing it's job correctly.

    The fact that he is dropping pressure relatively quickly on a system with a known good pump indicates that he has a leak somewhere. Seeing that the fuel pressure regulators on these trucks are not good to start and that the fuel injectors do not have a known history of failure rate tells me that's a strike two for the regulator. It is cheaper to change that piece out anyways and highly accessible so he should do it anyways. Those diaphragms on the FPR's leak and have ruptures all the time.

    Keep it. The OE FPR's are not the best anyways and even if it does not resolve your issue think of this as a preventative maintenance.

    One other thing you could attempt to do is pull the line which attaches to the FPR. If it smells like fuel at the vacuum line that would. Indicate it is no longer just applying vacuum to it but it is pulling fuel past a leaking regulator diaphragm.

    It should not hold pressure indefinitely as it does eventually drain back. It is not uncommon to have a good amount of pressure in the system well past a day later though.
     
  9. Aug 12, 2017 at 3:47 PM
    #209
    Fike

    Fike [OP] Well-Known Member

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    Just put on the new fpr, ran the truck up to operating temp. Now I'm letting it sit for an hour or so and I'll go check how it starts
     
  10. Aug 12, 2017 at 4:00 PM
    #210
    koditten

    koditten Well-Known Member

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    When I'm done it will have a custom fabbed winch bumper and hopefully a Softtopper.
  11. Aug 12, 2017 at 4:28 PM
    #211
    Fike

    Fike [OP] Well-Known Member

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    Well, had the long start again... i guess my next course is to check and replace injectors
     
  12. Aug 12, 2017 at 5:30 PM
    #212
    12TRDTacoma

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    If the injectors takes care of it you will have had one of the most unique hard start issues out there on these trucks for sure. I hope this resolves it.
     
  13. Aug 12, 2017 at 5:40 PM
    #213
    Fike

    Fike [OP] Well-Known Member

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    I really don't want to have to take it to a mechanic, but you are right, this has got me stumped...
     
  14. Aug 12, 2017 at 7:18 PM
    #214
    koditten

    koditten Well-Known Member

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    When I'm done it will have a custom fabbed winch bumper and hopefully a Softtopper.
    It's not that unique. Many people have leaky injectors, but just don't know it because they don't let the truck sit for 1 hour.
     
  15. Aug 12, 2017 at 8:13 PM
    #215
    12TRDTacoma

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    Unique to the Tacoma. Do a search and you'll be hard pressed to find many "I have leaky injectors" threads. The fact yours may be leaking is a case I have yet to hear on these. I believe Delphi makes these injectors, but I could be wrong. Usually the stuff is pretty rock solid and reliable. Especially at the mileage you are at.

    Idk about that. A lot of people let their trucks sit for an hour or less in most instances. I know I do. I am actually plagued by constantly failing MAF issues. It's pretty annoying.
     
  16. Aug 13, 2017 at 6:46 AM
    #216
    Fike

    Fike [OP] Well-Known Member

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    Have you been able to test or attempt to diagnose anything on your truck? I'm close to the point of giving up on it...
     
  17. Aug 13, 2017 at 6:50 AM
    #217
    Radarninja

    Radarninja Safety 3rd

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  18. Aug 13, 2017 at 6:55 AM
    #218
    boogie3478

    boogie3478 Tacomaholic & Hollywood

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    Not yet. I'll try the fuel pressure regulator first.
     
  19. Aug 13, 2017 at 7:15 AM
    #219
    Fike

    Fike [OP] Well-Known Member

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    Before you replace the fpr, look around on eBay. There are entire fuel rail systems there with injectors and fpr that are used for cheap. And you can add a warranty to them for 10 bucks. You could replace the entire rail for less than I spent on my fpr. If I would've known that, I would have bought them
     
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  20. Aug 13, 2017 at 7:23 AM
    #220
    Fike

    Fike [OP] Well-Known Member

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    Did you pull you injectors at the same time you replaced your fuel pump?
     
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