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Frank

Frank 12/6/2019

2007 Chevrolet Impala LT 6 Cyl 3.50L

Engine

Cranks no start fuel pressure builds and slowly drops after

I have an issue I can't seem to find answers to or figure out myself. When I start my car it cranks but will not turn over. I hooked up my fuel pressure gauge to the Schrader valve and it is showing me 59 psi while cranking. When I just use the ignition to check pressure without cranking it shows about 47. In either of these cases, it slowly drops pressure. I'm confused as to why I can't get it to at least start and stall when the gauge is showing 59psi at crank. I have replaced other items also such as purge valve evap canister spark plugs air filter and changed the oil. I can hear the fuel pump kick on, the regulator is attached to the fuel pump on this model. If I'm building pressure to the correct psi, why won't this turn over? Don't want to drop a tank or rip off the plenum unless I'm sure. All videos show diagnostics when cars running, not when the vehicle won't turn plz help!

1 Answer


Jimm

Jimm 12/7/2019

Really the only way to isolate your fuel pressure drop is blocking off the feed line and the return line with a fuel line block off kit. I don't know if you can get one or not, but it's basically a set of hoses with fittings on each end that connect between your fuel rail and your feed and return lines.
They have valves on them so you can open and close them. What you do to check for an injector leak is pressurize your fuel system (key on) with a fuel pressure gauge attached to the service port. Then close both valves on the return and feed block off lines and monitor your gauge.

If the system keeps pressure you know that injectors are ok and the problem may be down stream (fuel pump or fuel pressure regulator).

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