98 Chevy k3500 5.7 fuel issue?

Discussion in 'General Chevy & GM Tech Questions' started by jarends, Aug 25, 2013.

  1. jarends

    jarends New Member

    Hi Everyone,

    My dad has a 98 k3500 with the 5.7L engine. He bought a newer dually and this one has been sitting around because it needs a few repairs. I am no mechanic by any means, but like to try to fix stuff myself if I can. Anyway, he was having issues with it starting and running rough when pulling. It seems to start fine when its cold, but after it has been driven and you go to start it, then it doesn't always start. A friend told him it is probably some fuel sensor and if it doesn't start, pour some gas in the top of the engine (not sure where, cause I don't think this has a carb, its fuel injected right?). So, when he was still using this truck, he would carry a small gas can with him, and if it didn't start he would pour a small amount of gas somewhere under the hood (I never asked or watched to see how he did this) and then it would start right up. Can someone tell me what this issue could be? I would like to get this truck running so I can use it :happy:

    Thanks for any help!
  2. MAD JAX

    MAD JAX Member


    Yep, I'm shouting...You sound very inexperienced for both your discription of "fix-stuff myself if I can" AND inability to properly identify certain components, not the least-of-which is the Ignition Coil and Distributor located immediatly behind the Throttle Body ~ where GAS FUMES can immediatly migrate to then cause an explosion of FIRE that can burn Your face off of Your skull faster than you can imagine!

    Sh*t happens ~ and that's one-way it MAY : ?

    BE SAFE: Have someone that's knowledeable WITH the proper tools and equipment check the Fuel Pressure and Delivery Volume "COLD", then run the engine to Operating Temp and re-check what's going-on ~ IF the system is leaking-down it may cause a "Vapor Lock", which is simply Fuel boiling in the Fuel Lines, as "Residual Pressure" in the Fuel Line remaining constant AFTER shut-down is what prevents this from happening...

    You may simply have a clogged fuel filter, Pump Sock, or weak/intermittantly performing Fuel Pump... : ?

    P.S. I'm seeing a LOT of Fuel System Contamination problems with vehicles that have SAT for any period of time lately, and that's due to the High Alcohol content of "Todays Gasoline" -- which is HIGHELY "Hydroscopic" -- becomming so saturated with "Atmospheric Moisture" that the "Water" falls out of suspension within the "Fuel" to THEN "pool" on the floor of the Tank as goblules of "TANK-FUNK" ~ and everything that "Fuel" is then pumped TO up-stream goes-to-hell from there for IT becomming contaminated as-such...including Fuel Pressure Regulators and Fuel Injectors, etc. : (
  3. edsmagichands

    edsmagichands Member 2 Years 100 Posts

    I have to agree, pouring fuel into the throttle body IS DANGEROUS!! with your description. i think the fuel pump is the first thing to check.i'm going to repeat some of the previous advice here, with a fuel pressure gauge check pressure & volume cold koeo (key on engine off)then turn key off, wait 30 secs then koeo till pressure builds max. turn key off pressure should hold. if not you have a leak somewhere. if injectors or regulator leaking it could cause a hot engine to "flood" repeat test when warm & immeadiatly at the time of a no start. look for a reduction in pressure &or volume when no start occurs. vortec engines need about 60 psi to open the injectors. a very common problem is the fuel pump is an electric motor that runs constantly when engine is running. worn motors get hot & do not produce the pressure & or volume needed to start the car, let them cool down and they work again. it takes more fuel to start than to keep running. that is why priming w/gas might work. vapor lock not likely, clogged filter or sock would probably cause problems cold also. of course there are other possible causes.
  4. MAD JAX

    MAD JAX Member

    Check fuel pressure specification!!!

    EXCELLENT POINT(s) there:

    I got bit-bad when I MIS-diagnosed a 4.3 Vortec who's fuel pressure was just a little under-spec ~ maybe 5 psi. : ? ~ for having a customer replace what I thought was bad Central Injection Unit...that came WITH A NEW 'n PRETTY "Spyder Assembly" and "Poppet Injectors".

    Those Vortec-Injection System "Poppet Injectors" (located at the end of the "Spyder" assembly) apparently DON'T "POP" if it's more than a butt-hair UNDER "Specification"...THEN replacing the Fuel Pump fixed the vehicle, and refunding nearly $500 bucks kept the Customer "happy" : ?
    Last edited: Aug 31, 2013
  5. edsmagichands

    edsmagichands Member 2 Years 100 Posts

    I'm lucky to have not been bit. fixed some that other techs were " throwing parts at" though. i believe the specs for 5.7 is 60 to 66psi, i like to see a minimum of 62psi. you might be able to tell if the poppets are opening by cranking for 15 secs a few times when it doesn't start. make sure to let starter rest between cranks, don't want to burn it up! then pull a plug should be wet. even so if fuel pressure is not above 60psi it may not be enough. also i can tell you how to get a quick check of flow & pressure with a meter, but that's another discussion.

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