96 K1500 Hard Start condition

Discussion in 'GM Powertrain' started by Brently Harris, Feb 23, 2011.

  1. Brently Harris

    Brently Harris New Member

    Hey guys, this is my first post here. I've been searching for some insight on a problem I've been having and this forum looked well informed so here goes.

    I have a 96 K1500 with the 5.7 Vortec engine. The trucks been sitting for a few days and out of the blue when I tried to start it I'm getting nothing but sputtering. It tries to fire but never actually catches. I've pulled the plugs and I'm getting spark, I've peered into the intake manifold through the throttle body and theres a little bit of pooling so it's getting fuel, plus the plugs were damp when I pulled them out. I checked the DTC's and theres nothing. The interesting part is the fuel pressure. With key on engine off I'm seeing about 62psi which is in range. When I crank it, I'm seeing mid 50s and a lot of flutter on the gauge (I'm not sure if the flutter is normal +or-5psi). The fuel pump makes the normal sound when I hit the key, but every few cycles of key on engine off the pump seems to stop about a second early and the pressure drops all the way to 0 almost instantly. However, when the pump runs its allotted time, the pressure remains at 62. The majority of what I'm hearing is that most likely its the fuel pump check valve. Does this sound correct? The pump is also only 1 year old. Thanks in advance.
     
  2. stephan

    stephan Rockstar 4 Years 5000 Posts

    Welcome to the club Brently. That's most likely why your fp drops like a rock when the pump shuts off, but that's not keeping it from starting. Since your plugs are wet, the fp's working & the fuels getting to the cylinders, so I think you either have a weak spark, or it's just happening at the wrong time.
     
  3. silveradotrailblazer

    silveradotrailblazer Epic Member 5+ Years ROTM Winner 5000 Posts

    Welcome to the club.
     
  4. 2COR517

    2COR517 Epic Member 5+ Years 1000 Posts

    The Vortec manifold is dry. The fuel is actually injected into the intake port of the head. If you have standing fuel in the intake, you have some problems. At the very least, your fuel pressure regulator is gone. Very common problem on these trucks. It's not terribly difficult to change the FPR, you need to pull the upper plenum off the intake. If you have the money, replace the entire spider with the MPFI upgrade. It's more money than time, about $400 and three hours. If you haven't replaced the intake manifold gasket, that's an important item too. It's more time than money, about $50 and six hours. That time includes replacing the spider.

    In addition, the FP wiring on these trucks leaves a little to be desired. Poor connections can cause erratic FP operation. There are two trouble spots. First is at the tank. The original sending unit connector on this vintage is very poor. The connections are simply inadequate, and overheat. The overheating causing the connector to loose spring tension, which further weakens the connection. The failure is also accelerated by a weak pump drawing excess current to supply adequate pressure. And as the voltage supply to the pump drops, the current increases. It creates a viscous cycle of overheating and eventually arcing and total failure. In fact, the majority of FP failures in these trucks is actually due to the poor electrical connection. The other trouble spot is much easier to access. It's the FP relay under the hood. Pull the relay and look for signs of overheating near the load side contacts. There may be darkening/browning of the relay case. Also the base socket may show signs of melting. You can pull one bolt and check the underside of the relay/fuse housing too.
     

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