1997 Silerado ....5.7 vortec . Wont start when cold

**qpe05** · 09-04-2007, 11:05 AM

I dont know where to look for this problem and was hoping for some direction . This truck wont start when its cold . You can spray fuel into the throttle body and it will start and run , but you need to keep spraying fuel into the TB until the engine warms up . When its up to operating temp , the engine will run fine without being primed . There are no DTC's set from the pcm .

Any help would be greatly appreciated .

**Steve** · 09-04-2007, 11:53 AM

How many miles on your engine? Does it come close to starting and just can't quite pull it together to fire up?

**GaryL** · 09-04-2007, 11:55 AM

Sounds like it might be the fuel pump relay gone bad. When you turn the key on, do you hear the fuel pump run for a couple of seconds? If not, try switching that relay with a similar one from the truck and see if it works and whatever you switched the relay from doesn't. If that is the case, replace the bad relay.

**qpe05** · 09-04-2007, 01:43 PM

The fuel pump is new and working correctly . Relay is good too . This truck has 180,000 miles . The staring problem is ONLY when the engine is cold . IT will start fine if the engine is already hot .

**MrShorty** · 09-04-2007, 02:26 PM

If it will start on starting fluid through the intake, then that almost has to be some problem with fuel delivery.

Fuel pump might be new, but how have you verified that it is working correctly? The only surefire way I know of for testing fuel delivery is to put a fuel pressure gauge on it. What is the fuel pressure when it won't start?

If it's below 50 psi, then something is wrong with fuel delivery (maybe not the pump itself, but something is wrong).

If the pressure is up near 60 psi where it should be and it won't start, then something is likely wrong with the poppet valves. I know GM had issues with the poppet valve on the early Vortec motors, even redesigned the spider. I don't know the specifics, because I haven't had to deal with it, yet. If you determine that the problem is in the injectors, be sure to research this out, so you get the upgraded spider.

**Toymyster** · 09-04-2007, 09:13 PM

Have you checked/ changed your coolant temp. sensor?? Sometimes they die, but since it doesn't work when cold, it will not register with the OBD system!! That's the first thing I would check off of top of my head!! Another question, when was the last time you changed your fuel filter?? Also check your fuel pressure, the pump may be good, but how about the regulator??

**Chevy1997** · 09-05-2007, 04:19 PM

In my truck ( a silverado 5.7 1997) i cleaned idle valve (don´t remember the name) but with that mileage you must to have a problem with that. This valve it´s essential at cold because it control the idle speed. You must to clean it, i think it is not necessary chenge it.

good luck

**Chevy1997** · 09-05-2007, 04:22 PM

the valve it´s IAC.

Some engines control the idle at cold because it need a more fuel in the manifold, then when you have a problems with IAC the mix between air an fuel it´s annormal-