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Cranks good, only starts temporarily when fuel is poured into throttle body

Tiny
PHILLYCHAVEZ
  • MEMBER
  • 2002 CHEVROLET SILVERADO
  • 120,000 MILES
4.3 V6, fuel pump and filter new 2 months ago. Original problem was fuel pump. Buddy bugs introduced during diagnosing problem. Got 2 injectors swapped (cyl.#4 & cyl.#6) but got that corrected. Fuel pressure goes to 10psi on initial ignition on, them drops to 0psi. Pressure goes up to 20psi while cranking then (while still cranking) drops to 0psi. Jumper past fuel pump relay (after swapping with known good relay) and fuel pressure goes to 20psi (cranking or not) and goes to 0psi when removed. Any ideas? SWAGS are welcome.
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Friday, June 22nd, 2012 AT 6:46 PM

7 Replies

Tiny
DOCFIXIT
  • MECHANIC
  • 18,828 POSTS
Fuel pressure needs to be 55-62 psi so right there have problem with pump
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Friday, June 22nd, 2012 AT 7:42 PM
Tiny
PHILLYCHAVEZ
  • MEMBER
  • 5 POSTS
I just removed the fuel filter (no resistance, you can blow right through it) and using a hose and hose clamps hooked up the fuel pressure gauge directly to the fuel line coming from the fuel pump. We jumpered past the relay and the gauge shot up to about 90 psi and blew the hose off the gauge. Fuel pump and filter are out of the equation, both good. What happens after fuel is pumped up to the injector assembly?
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Saturday, June 23rd, 2012 AT 3:46 AM
Tiny
CADIEMAN
  • MECHANIC
  • 3,544 POSTS
Ck. The injecter fuse.
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Saturday, June 23rd, 2012 AT 4:48 AM
Tiny
PHILLYCHAVEZ
  • MEMBER
  • 5 POSTS
Checked every fuse and relay under the fuse box cover - all visibly OK and ohmed out OK. Swapped all identical relays and no change.
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Saturday, June 23rd, 2012 AT 1:55 PM
Tiny
CADIEMAN
  • MECHANIC
  • 3,544 POSTS
U have some pressure so the pump is getting voltage so recheck the pump installion. If correct warrenty or replace the pump.A new part isnt allways a good part.
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Saturday, June 23rd, 2012 AT 5:33 PM
Tiny
PHILLYCHAVEZ
  • MEMBER
  • 5 POSTS
Pulled the fuel line on top where it goes into spider body and got about 90 psi and no bleed down. If there's 20 psi at the Schrader check port then it sounds like pressure relief valve is wide open and bleeding off through the return line. Blew air through the spider body fuel inlet orifice and it came out the return orifice. Bought a new valve and will install tomorrow.
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Sunday, June 24th, 2012 AT 2:12 AM
Tiny
PHILLYCHAVEZ
  • MEMBER
  • 5 POSTS
BAD PRESSURE RELIEF VALVE (which you have to pull all the sensors, brackets, plugs, bolts, nuts, etc. Off the plastic plenum [and the plenum] to get to the injector "spider" to change it). The small "O" ring on it was GONE. A new relief valve and all the hassle of reassembly and it's up and running again. Would I love to meet a GM engineer in a dark alley.
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Monday, June 25th, 2012 AT 3:38 AM

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