97 K1500 wont start sometimes, runs great when it starts

I know, another Vortec that wont start. I have searched and searched but can't seem to figure just what my issue is. So I will post a tale my woes in hopes someone may have some insight.

I have a 97 K1500 ECSB 5.7 with about 230k miles. I bought it 4.5 years ago with 205k on it. Mostly has run great since I've had it but had developed issues now. After sitting for a short while, sometimes 4 hours and sometimes 4 days, it will crank but won't start. Other times it will crank and start hard. Once it starts it runs fine. It runs strong and smooth. It currently is on plow duty as I got a new truck. I don't enjoy shoveling when it won't start.

It has new distributor cap and rotor and I just replaced the coil too. Plugs and wires have about 20k on them and appear to be in great shape.

I have checked fuel pressure and it is at 60psi. When I shut the key off it holds pressure for greater than an hour. I first thought it was leaking down and would flood the truck as it acts like it is flooded when it won't start.

I have a scan tool app Torque Pro and can seem some sensors. Coolant temp sensor seems to be working right, MAP seems to be good.

Part of me says it has to be fuel related but when it runs there is no hesitation to indicate it is starving for fuel. Could the fuel pressure regulator be feeding too much fuel?

I really don't know what to replace or check next. I am not a big fan of just tossing parts in it and hope it works.

Anyone have suggestions as to where to go from here?

Kevin

Pull the #2 plug out (because it's the easiest to get to) ground it to the exhaust manifold and have someone start it, you should have a nice hard to see skinny blue spark... if it's a fat yellow spark then you don't have enough angry pixies making it to the plug so trouble shoot from there. Check for vacuum leaks because a small one will have a more noticeable effect on start up then after its running. Hook a fuel pressure gauge up to it and turn the key to pressurize the system and see how long it takes to bleed down. If it bleeds down fast your spider could be leaking fuel into the manifold and flooding the motor. That's kinda the basic check list I got based on what you've already checked/ replaced

Fuel pressure was at 60psi and was not dropping hardly at all in the hour I kept checking on it. I'll be checking spark again later.

Sent from my Moto Z (2) using Tapatalk

Brandon Schnautz said:

Hook a fuel pressure gauge up to it and turn the key to pressurize the system

Click to expand...

klittle1417 said:

Fuel pressure was at 60psi and was not dropping

Click to expand...

Test the fuel pressure with the engine NOT RUNNING, preferably after it's been parked overnight.

Turn the key "ON", (not START) the pump should run for two seconds. If it does, great. If it doesn't, you know why the truck is hard-starting. The fuel pump relay, relay wiring harness, or ECM is faulty--no "prime" signal to the fuel pump. Pump doesn't run until engine builds oil pressure.

Schurkey said:

Test the fuel pressure with the engine NOT RUNNING, preferably after it's been parked overnight.

Turn the key "ON", (not START) the pump should run for two seconds. If it does, great. If it doesn't, you know why the truck is hard-starting. The fuel pump relay, relay wiring harness, or ECM is faulty--no "prime" signal to the fuel pump. Pump doesn't run until engine builds oil pressure.

Click to expand...

The truck was not running when I hooked up the fuel pressure gauge. Turned the key on, fuel pump runs 2 seconds and have 60psi. Shut key off and let it sit and it holds pressure for the hour or so time span I checked on it.

Sent from my Moto Z (2) using Tapatalk

Let it sit for a while and try to start. If it won't start spray starting fluid in the tube connection on the back of the intake plenum and try to start again. If it fires right up you'll know its fuel related. If not, most likely ignition.

Sent from my SM-G930V using Tapatalk

If it's not even attempting to fire when you start it then it's most likely an ignition issue

Fuel and Spark... start there! Good advice has already been given... You have fuel pressure, now check for fuel "Spray" by using some starting fluid. I didn't have anyone to help me, so I pulled a plug and laid my phone where it would take a video of it while I cranked it.

It just throws me off that it runs perfect after it starts. Have to find something that is affected by a cold cranking condition...

It about 10 degrees out. I went out to the truck today and it started right up with no hesitation. That's what she does. Now if I let it sit until tomorrow it may not start. Doesn't seem to matter whether it's cold and dry or warmer and wet.

I did check the spark quality after driving it 10 miles and parking it. Good blue spark.

Sent from my Moto Z (2) using Tapatalk

I had that problem with my 350 vortec.if you have the crab cap and rotor button.use dealer factory cap.i tried after market set up.that was my problem.pay the price.that solved my problem.recent deal.engine started running rough.throttle body.was dirty.i sprayed it with carb cleaner.and the fixed that problem.