78 fuel pump/ oil pressure sensor issues!

Discussion in 'Maintenance/Repair' started by Cache, Nov 16, 2015.

  1. Cache

    Cache Newbie

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    I have a got a 78 chinook newport 20r pickup…. fuel pump stopped working after sitting threw summer without starting…. thought that was the issue so dropped tank, did all that fun stuff… come to find out that it was lack of power to the fuel pump…. so, after a day of chasing that around, i saw a log post in here aout if you unplug the oil pressure sensor you get power to the fuel pump…. it worked, however, does this mean I need a new oil pressure sensor?

    Talked with someone, said these trucks were notorious for them going out… does it sound like this is the prolem…..?

    Anyone have a similar situation? Please Help!:bowdown:
     
  2. first80toyota

    first80toyota Addict

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    There is a fuel pump relay under the dash on the passenger side of the steering column. In my old truck I took that out (went bad, no replacements could be found) and just wired in a switch between the keyed power and wire for fuel pump. Never had any issues, basically just skips the oil sender..
     
  3. jetas

    jetas Grand Toyotaholic

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    Only issue with that is i think the oil pressure sensor acts as a cut off switch for the FP in case of impact or anything like that
     
  4. Perkolator

    Perkolator Toyotaholic

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    I'll look through my internet search history, but I could have sworn I came across an oil pressure sending unit this past weekend, for the RN20 pickup. I want to say it was eBay.
     
  5. Cache

    Cache Newbie

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    yeah, I have 2 of these 78's and the second one came with a ad fuel pump and the previous owner rigged up a similar fix, however, I replaced connectors and fuel pump and and the prolem he was having went away……so, now I am on the first 78' that I got and it is having the same issue, however, it did not just go away….. and i want to figure out what is going wrong with it…. as a last resort I will do a direct link with switch, i like the safety feature of a cut off, if I can't fix it, I will fix it up!

    Thank you for your responses!!!
     
  6. Cache

    Cache Newbie

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    so….is it the oil pressure sensor you think?
     
  7. fred heath

    fred heath Addict

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    Oil pressure sensors are cheap for the 20R.
    Change it out and see what happens.
    I wouldn't recommend bypassing the sensor. It could save your engine in the event of sudden loss of oil pressure.
     
  8. Cache

    Cache Newbie

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    I agree and I have one on the way! thank you all and i will let you all know how it goes!
     
  9. fred heath

    fred heath Addict

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    Does your Chinook have the fake duel rear tires or just singles?
    Lots of problems caused by the fake duels.
     
  10. Cache

    Cache Newbie

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    It has the singles….
     
  11. Cache

    Cache Newbie

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    hello all, Well, I am smarter from all this run around with my fuel pump! Turns out the fuel pump was good… the oil pressure sensor was good… all electrical was good…. what happened was that the oil level in the engine after sitting through the summer had dropped enough in the engine enough for the oil pressure sensor to not get a reading, which in turn cut power to the fuel pump…. so, I did what was mentioned from "Nook" … and disconnect oil pressure sensor, get it started and then, when the oil was all running around in the engine, shut it off and hook up the oil pressure sensor and there you go…. it will then have power again since the sensor can now sense that there is pressure…. there you go, newbie learning some tricks…. I ended up coming full circle, and if I was more mechanically minded, I might have seen this … however, i wasn't, i am now and i want you all to know how much i am gratified and humbled by this learning experience! i hope this helps someone someday!
     
  12. mrhanky

    mrhanky Member

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    I apologize for being "that guy" bringing back an old thread.

    That being said, I believe I am having the same issue and didn't want to start a new post.

    I have no power to my new pump. When I turn the key my fuel pump relay clicks (I have pulled the cover and know that it does close). Problem is, with the key on and relay pulled in no power goes to the pump. If I turn the key on and then force the relay back into the "not pulled in" position, it fires the pump up.

    Is this the oil sender problem y'all have mentioned?

    Mine is a 78 w/ 20r and in tank pump.
     
  13. fred heath

    fred heath Addict

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    On initial start-up the fuel pump will only get power when the ignition is in the "crank" position. This will bypass the oil pressure sender. Once pressure is reached, power is maintained to the fuel pump.
    You can check pump operation by detaching the pigtail from the oil pressure sender. This will allow power to the pump as soon as you switch on the key.
     
    Last edited: Apr 22, 2016
  14. mrhanky

    mrhanky Member

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    Thanks. I traced the wires and figured it out already. It works when the sensor is unplugged.
     
  15. nottoshabi

    nottoshabi Enthusiast

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    Sorry to rehash an old thread like this, my 78 20r hilux is having the same problem. Replaced fuel pump and still wont start. Disconnected the oil pressure sensor that is located on the engine block right next to the oil filter, pump wont come on, disconnected fuel pump relay still nothing. There is sufficient oil in the engine.

    Before installing the tank back in I checked if there was a signal coming to the connections of the pump with the key in the on position, and there was an electrical current going to the pump but it was very dim.
     

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