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Hard starting after replacing Everything

Rjlee

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Rjlee Enthusiast

Rjlee

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New to the forum here... Need help! No start, hard start WHEN HOT on my 2009 Silverado 1500 5.3 flex fuel, Vin 0. In the rear I have replaced FSCM (gmflash), fuel pump, fuel rail sensor, charcoal cannister, vapor purge valve, and gas cap. In the front I have replaced plugs gapped .04, injectors, coils, wires, tps, maf, map, crank sensor, cam shaft sensor, oil pressure sensor, coolant sensor, purge valve solenoid next to fuel rail, starter, alternator, battery, neg & pos wires. Was slowly replacing these parts when the hard crank began after the fuel pump was replaced. I had the mechanic replace it again just in case the check valve or something was bad but there was no change. Also this is my second set of injectors since it began. I am at a loss. Vacuum leak? Circuit problem? Anything you guys can throw my way is much appreciated.. Just in case it matters.. I had all lifters replaced because of #4 breaking about two weeks before the prob started.

sefiroxx Enthusiast

sefiroxx

Posted
Posted

Change the fuel pressure regulator?
Long crank before catching?

Try turning the key to run for 5-10 seconds before cranking and see if it catches faster. If yes, then fuel pressure problem.

Rjlee Enthusiast

Rjlee

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Thx for replying.. Yes, I've been doing this off an on since it began and it doesn't make any difference whether I'm giving the pump time to prime or not when it's hot. Put a pressure guage on it just last week and upon cranking it immediately goes to 60 psi, even while hard starting. After turning motor off the pressure goes to 35-38 psi in about 30 min but shoots straight back to 60 psi when cranked again.  I'm really wondering about it being a spark problem. I still have the original  oem coil packs I replaced with the new ones. I think I will put them back on tomorrow. I originally replaced them to upgrade only along with new plugs, wires, and injectors just before the hard start began.

sefiroxx Enthusiast

sefiroxx

Posted
Posted

Ok, so fuel is less likely a problem (and spark). So focus on air.

Try cleaning throttle body and MAF. Use a scanner to check tps is operating and operating smoothly.

May need to replace idle air control motor.

Tiana_Nunemaker Enthusiast

Tiana_Nunemaker

Posted
Posted

Did you inject the fuel at wrong time? I think you should recheck the fuel lines, fuel injectors and spark plugs. Fouled plugs could also be a reason of hard start. If you still unable to fix it then better to contact with any auto expert or can call mechanic. 

Rjlee Enthusiast

Rjlee

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Took to mechanic last week. Replaced fuel pump again with OEM this time due to pressure not popping straight to 60psi when turning to start. Now still has hard crank after spending big money on Delphi pump module. Also rough idle is still present with surging whether at idle, driving slow, or fast. Was coasting down hill today at 35 mph and rpms were surging back and forth between 1400 & 1600 without my foot on the peddle. Computer scan showed lean on both banks.. Any other direction to check out since it's obviously not the fp module...?

CamGTP Senior Enthusiast

CamGTP

Posted
Posted

Other than smoke testing for any trace of a vacuum leak or exhaust leak, that's about all I got without seeing the truck in person.

 

I'd also be looking at what the computer thinks the alcohol content of the fuel is. The virtual flex fuel "sensor" often gets screwy and reports something stupid like 50% alcohol content when you're running pump gas that is only 10%. That will throw everything out of whack.

Rjlee Enthusiast

Rjlee

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Thanks for your input. The mechanic last week did a smoke test and says no leaks were found. Interesting enough, the codes last week showed lean on both banks and every now and then a MAF code will come up but the MAF is new as well as the air filter. New throttle body as well. Does anyone know if this vehicle has a flex fuel sensor? 

Ianf Enthusiast

Ianf

Posted
Posted

No flex fuel sensor. It is calculated based on MAF and O2 readings. I would be looking at the wiring for the MAF and Throtle Body before going any further. What codes are showing? What happens to the LTFTs is more critical than the STFTs and as well the ethanol %.

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