Running rich after pump change

Discussion in 'Tech Discussion' started by Nick87, Aug 11, 2018 at 6:48 AM.

  1. Nick87

    Nick87 Junior Member

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    Hey fellas, I’m new to the asking for help bit, but I need some. I have a 1987 crew cab v30. It’s actually the forest service truck out of dauntes peak, the one that drove through lava.
    I got it running right and got it legal and insured. Drove it for a few months and it started having fuel problems. I have only been using the passenger side tank and the drivers side is disconnected. The pump would cut out as it got warm so I swapped it out and made sure my lines on my sending unit were in there correct orientation. Now the truck would idle fine and before the pump swap. While doing the swap I pulled the tank and cleaned it out. I started the truck after the swap and it couldn’t be richer. Folks, i don’t know if anyone on here as flooded a TBI motor but I have. It ran so rich it had the whole neighborhood smoked out in a matter of minutes. I thought it could be the wrong pump pushing to much pressure, not that, I thought it could be the diaphragm in the tbi that regulates the fuel pressure, rebuilt the tbi and no result. Swapped a few sensors, checked timing, checked injectors, swapped the damn pump again! Nothin. Still runs like shit. I’m thinking gunk or something got into the return line? Or the fuel tank valve is stuck or something. I’ve been racking my brain for a month and a half. Any help or ideas would be so appreciated!

    ~Nick
     
  2. Charlie

    Charlie Full Access Member

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    :welcome:
     
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  3. bucket

    bucket Super Moderator Staff Member

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    What's the spray pattern of both injectors look like?
     
  4. Nick87

    Nick87 Junior Member

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    The pattern is good, solid cones and good misting but pulsing crazy fast. The pulse with is crazy. I checked the o2 and made sure it was working and traced it back to the cpu mad it’s good along with some other sensors

    Also, thanks for having me here. I really appreciate the help
     
  5. 1987 GMC Jimmy

    1987 GMC Jimmy Full Access Member

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    What brand of pump did you use, and would you happen to have the PN anywhere? What was the pressure reading? Was one of the sensors you swapped the CTS? Have you checked spark quality and plug quality to make sure there’s not a weak spark (coil) or worn plugs in the picture? And no codes 13 or 45 if it’s running that rich? Hmm. Unless deductive reasoning can knock this out, I’d be thinking about making a diagnostic cable and downloading the software to interface with the ECM using your laptop or buying a pre-made cable to do the same thing. The former costs about six dollars, and the latter costs sixty. That would also show you injector duty cycle to answer your concerns about pulse.
     
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  6. bucket

    bucket Super Moderator Staff Member

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    Yeah, how about the CTS? If those fail, they can make the engine run extremely rich. They can suddenly fail to, with no warning.
     
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  7. Nick87

    Nick87 Junior Member

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    I did swap the coolant temp sensor and checked my grounds and made new contact on each. It ran the same, full rich. I don’t have the part number of hand but it’s the standard tbi pump. It’s the Delphi one. I had already put in new plugs. It could probably use wires and a coil but it has a new cap and rotor. The issue occurred right after I swapped the pump. I haven’t taken a fuel pressure reading yet. I’m not sure of the best way of going about that.
     
  8. 73c20jim

    73c20jim Supporting Member Supporting Member

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    Sometimes new plugs can be quickly fouled by too much gas.
     
  9. Snoots

    Snoots Supporting Member Supporting Member

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    Fuel Pressure Regulator?
    EGR (sometimes)
    Vacuum leak?
    MAP sensor?

    Mine had a bad Intake Air Temp Sensor. ('88)

    It's really best to get a scanner.
     
  10. 1987 GMC Jimmy

    1987 GMC Jimmy Full Access Member

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    I will say that vacuum leaks are going to hurt you. Especially if you’re leaning the engine out, and then the computer says dump more fuel. The EGR is a very unlikely culprit at idle, but on the road, its potential to hurt you is very prevalent if it’s not working right. @Snoots, the OP did mention replacing the regulator diaphragm, but I’d say the MAP sensor is up there in its potential to mess you up. There is a vacuum test you can do by getting a Mityvac, pumping up the sensor, and checking voltages, but I’ve never done it. I just hook up my laptop to see what all the sensors are saying. Mine is generally very quick about telling me when there’s a problem. If you’re interested in the homemade scanner, Georgeb wrote an excellent post on how to set it up, and it’s a sticky in the TBI section.
     
  11. Nick87

    Nick87 Junior Member

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    I’ll take a look at a few of those things. I checked the Egr and made sure it’s good and it is, I checked a few other things but I’m thinking about just finding a scan tool. That would help
     
  12. Nick87

    Nick87 Junior Member

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    The part number on the pump is fe0115
     
  13. chengny

    chengny Full Access Member

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    Check for leakage through the injectors when off stroke. Simple test, just unplug the injector connectors and crank the motor. Obviously, there should be no fuel spraying/dripping from the injectors.

    Another sensor that the ECM relies upon to calculate required injection duration is the TPS. If the TPS is indicating that the throttle is being opened, the ECM will crank up the fuel/air ratio. The only codes associated with the TPS are 21 (a short in the circuit) and 22 (an open in the circuit). However, if it is just providing screwy outputs no DTC will be thrown.
     

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