No Start.

[96_k1500]

So about a year ago I swapped the wore out 5.0 vortec to a 5.7 vortec crate motor from summit, it came as a long block but I reused my engine accessories such as alternator, ps pump, ac compressors and the intake although I replaced the spider assembly, my problem is about once or twice a month if I let my truck sit for more than 48 hours it won’t want to start, it seems to just be getting to much fuel??.. usually I can crank on it for a minute and it will start but after for sitting for 3 days it will low not start at all. The spark plugs are getting fouled out instantly. I’ve replaced the fuel pump, fuel filter, fuel pressure regulator. Spark plugs, distributor cap and the ignition coil! I don’t know what else it could be! It’s getting both spark and fuel!!

Any help would be greatly appreciated!

 

[east302]

One possibility is the coolant temperature sensor (by the thermostat) which reports the temp to the computer. A scanner would be able to see what value it is reporting, an odd-ball reading not being good. It should match close to ambient when cold and go up to around the thermostat setpoint when warmed up.

A workaround is to hold the gas down while cranking, that puts it in “clear flood” mode and temporarily stops injector flow.

 

[96_k1500]

I have replaced the temperature coolant sensor already, and just tried the foot to floor trick and it did not start, it has proper fuel pressure but the smell of gas is heavy upon cranking over even with the foot not to the floor

 

[east302]

What was the fuel pressure when you tested it? Spec is 60-66 psi, key on engine off. It should hold for a bit when you turn it off. If it drops quickly, that would indicate a leak - pump, regulator, lines or injector(s).

Assuming that none of the fuel lines are leaking, determining pump vs injector vs regulator involves valving off the supply and return lines. Install a ball valve in place of the filter, pressurize and close the valve. If pressure holds, the issue is upstream of the valve (in the pump).

If it drops, add a valve on the return line and pressurize. If it drops, it’s an injector leaking. If it holds then it’s the regulator...though whether it was the regulator or an injector probably wouldn’t matter since you’d likely warranty return the whole MPFI assembly.