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Truck hard to start

Post in 'DIY and General non-hearth advice' started by burnt03, Dec 17, 2012.

  1. burnt03

    burnt03 Burning Hunk

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    Lent my 1996 Nissan pickup to a friend a few weeks ago. He brought it back, it sat for about a week (just below freezing temps), went out and tried to start it.... just kept cranking... and cranking....

    Checked for spark, looks good. Pulled the line off after the fuel filter, getting fuel. Could hear the fuel pump cycle on when I turned the key to ON (not actually turning the truck over...).

    Eventually, it started (after trying the things above, tried cranking it and could hear it kick a bit so kept on it a bit longer and it eventually fired up). Until it gets a little warmer, sort of hesitates and stutters while I'm driving.

    Now if I let it sit for more than a couple days, run into the same problem. I tried running some Seafoam through to take any water out of the fuel, then refilled the tank. Still no dice.

    Any ideas? Fuel pump getting weak? Cold start injector?

    Thanks!

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  2. Hogwildz

    Hogwildz Minister of Fire

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    Electric pump? I had one go bad, then the next year the inline filter was not completely clogged, but enough to let the truck start then run out of fuel on anything but idle.
    Is the choke operating properly also?
  3. burnt03

    burnt03 Burning Hunk

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    Was sort of thinking pump too but thought it might be more intermittent, maybe it would fire up perfectly sometimes, other times no. But so far it'll fire up eventually.... as long as I crank it long enough

    As for choke, it's fuel injected so I don't think it has one?
  4. MasterMech

    MasterMech Guest

    Put a fuel pressure gauge on it and see what you get when you turn the key on, while cranking, and what happens when you shut it down. Most engines have a schrader valve on the fuel rail for easy hook-up. The problems you describe could be multiple causes but if the pump, lines and filter all check out, it's possiblea fuel injector is stuck open or leaking, or the fuel pressure regulator has gone south on you. Report back with the pressure test and I bet we can tell you which one it is.
  5. burnt03

    burnt03 Burning Hunk

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    I'll see if I can get er done this weekend and I'll reply with what I get. Thanks for the tips
  6. raybonz

    raybonz Minister of Fire

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    Open hood and look under hood at night with someone cranking and look for arcing to ground. Could be spark plug/coil wires or a cracked spark plug discharging to ground.. Keep an eye on all the components from the distributor down to the plugs while running with no flash lights on..

    Ray
  7. semipro

    semipro Minister of Fire

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    Along the same lines as what Ray said, I'd check inside the distributor cap for moisture. WD40 can be sprayed inside to remove it. A cracked cap or one with shorts (carbon tracking) might also be a culprit. Usually though with cap problems you get some misfiring or backfiring.
  8. burnt03

    burnt03 Burning Hunk

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    Been starting good the last few days but haven't been letting it sit for long.

    Did a pressure test today, around 36psi with vacuum, 46psi without (right in line with what's spec'd in the Haynes manual).

    I've left it for around 2 hours, looks like it's dropped to about 28psi. If it drops to zero overnight, guess that's a faulty foot valve in the pump?
  9. festerw

    festerw Member

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    Easy way to test the check valve on the fuel pump is to turn the key to "on" twice before trying to start it.

    That should give you good pressure to start.
  10. pen

    pen There are some who call me...mod. Staff Member

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    Or a leaky injector, or a bad fuel pressure regulator dripping fuel back into the intake, etc. Low pressure by morning means it's bleeding off somewhere.

    When it finally does start, do you notice any black smoke? If so, that would lead me to believe a leak in the engine bay area leaving fuel pooling in the intake and/or possibly causing a flooded like condition you are fighting in addition to a low pressure issue that would cause hard starts.

    pen
  11. nate379

    nate379 Guest

    It's fairly normal to loose pressure after a day or two. When you turn the key to "on" the fuel pump kicks on and builds the correct pressure.

    How do the plugs look? If you hold the throttle down a bit will it fire up?
  12. burnt03

    burnt03 Burning Hunk

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    I didn't pull all the plugs when I checked, just the one to see if they were firing. The one I pulled was a little drier than I would have expected with the cranking I was doing. The throttle doesn't seem to help until it actually starts to fire/stutter a bit.

    Pressure had dropped to 5-10psi this morning. Cycled the key to on, pump kicked on right away, pressure up to 45 for a few seconds, clicked off and then back down to 36psi.
  13. burnt03

    burnt03 Burning Hunk

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    How can I tell whether it's the pump, injector or regulator?
  14. MasterMech

    MasterMech Guest

    How the pressure behaves.

    If it pumps up when the key is cycled on, but bleeds off relatively quickly as soon as the pump shuts off, then most likely injector leaking/open.
    If it pumps up partially/very little, then most likely regulator. Pinch the return line closed and re-test.
    If there is no change in the pressure (after pinching the return line) or it doesn't pump up at all, then probably the pump.

    If it pumps up, holds pressure while cranking, you could have dirty/clogged injectors.
  15. burnt03

    burnt03 Burning Hunk

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    Thanks Master. Going to leave the gauge on and park the truck outside for a few days and try to re-create the problem again (been firing good the last few days since I've been running it more lately. So, it's been pumping it quickly when key is cycled on (up to 45psi instant, holds for a few seconds, clicks and drops to 35psi). Holds, but dropped to about 10psi overnight.
  16. MasterMech

    MasterMech Guest

    Could have just gotten a case of bad gas. ;)

    Run her down and fill 'er up at a trusted station and see what happens. I'd pick up some injector cleaner and run that through it too.

    You're overnight psi drop sounds pretty normal, ok so long as it pumps back up to spec (45 psi?) with the pump running.
  17. burnt03

    burnt03 Burning Hunk

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    Checked this morning, dropped down to zero over 24 hours. Going to fire it up to back it out of the garage and leave it (as noted a post or two back) and see what I come up with.

    This started with a 1/4 tank of gas. Poured in a can of Seafoam, ran it to the station and filled up with fresh, so it rules that out (unless I got two bad tanks, definitely possible....)

    One thing I forgot to mention is that after a hard start, once it gets running it runs like a bag of sh*t for about a block before it gets back to normal (hesitating, etc).
  18. MasterMech

    MasterMech Guest

    Are you sure the ignition system is 100%?
  19. burnt03

    burnt03 Burning Hunk

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    I'm not sure. If the fuel pressure is fine the next time I experience the hard start, I guess that should be the next step; replacing ignition parts (plugs, wires, dist. cap, rotor)
  20. burnt03

    burnt03 Burning Hunk

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    Alrighty, left the truck outside for the past 8 days, always just below freezing.

    Tried to start it today, got the hard start (not as bad as it has been but definitely not normal) but had fuel pressure the whole time. As soon as I cycled the key to ON, it jumped up immediately to 45 or so and kept "relatively" steady as I cranked it.

    Once it started running, sort of tough to keep it going. OK at idle but couldn't really feather the gas or it would want to die. Either idle or stomp on it to get it rev. Also, got some darker smoke coming out of the tailpipe.... unburnt fuel?
  21. MasterMech

    MasterMech Guest

    Black smoke = Too rich. Hmm. Does Nissan have a MAP (Manifold Absolute Pressure) sensor? Sometimes it's called a barometric pressure sensor. That can cause the computer to deliver too much fuel, especially on a cold start-up, until it realizes what's going on and adjusts. But that will usually set a trouble code and a MIL (Service Engine Soon) light. Do you have a mechanic's stethoscope? (they're cheap if you don't) Use the aluminum wire probe to listen to each injector, it should be clicking regularly. Could have one sticking.

    Other things that affect cold-start fuel delivery:

    Coolant Temperature Sensor
    Intake Air Temp Sensor

    I'm assuming you've already checked the vacuum lines for leaks. That would most likely show up as part throttle hesitation at all temperatures however, not just cold.

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