1996 Chevy C1500 silverado 5.7l vortec engine 2wd CRANK NO START ISSUE.

[simperfi84]

Hello,
As the title says I have a crank no start issue on my truck. Brief history, engine is a new gm factory 5.7l engine installed a year ago but has not been ran much untill last few months. Alot of new components on this engine all stock. New distributor, plugs, wires ,sensors, cats, and AC delco mpfi injectors. Truck was running fine good fuel trims. No codes, started up 1 morning and it fired right up and I had walked back inside for a few minutes and when I cam out it had quit running. Tried to restart and would not fire, good crank though, I have confirmed Good spark, good fuel pressure 61psi, new Delphi fuel pump, holds at 55psi for good 10 minutes. I have determined that the issue is most likely a flooded engine, oil smells like gas and the level is more then it should be. Cylinder wash. I pulled off peluim to confirm no.leaks and inspected each injector for open condition and if they were functioning as they should everything seems to be as it should be. My question is this what should my next step be, to determine the problem that caused the flood issue in the first place.I will drain and refill oil this weekend and install new plugs and hopefully get it running and post some live data as well as compression readings and fuel pressure readings.

[dave w]

The injectors are triggered on by the computer sending a ground pulse to the injectors. The injectors are wired with constant 12 volts when the ignition switch is in the On or Start position.

I curious about the injector drivers in the computer? A Noid light test would be helpful information, but connecting a Noid light to the Vortec injector pod requires some out of the box thinking and creative wiring.

dave w

[myburb]

Possible leaky poppet valve on the spider.

[simperfi84]

The injectors are triggered on by the computer sending a ground pulse to the injectors. The injectors are wired with constant 12 volts when the ignition switch is in the On or Start position.

I curious about the injector drivers in the computer? A Noid light test would be helpful information, but connecting a Noid light to the Vortec injector pod requires some out of the box thinking and creative wiring.

dave w
Yes I am aware of that I did check the plug for the injectors assy with a test light. I do have 12v and I was getting a pulse from the other side for each injector. I have never used a noid light but I know they can be a valuable dignostic tool. (Should get a set.). I am curious if I am having a issue with the ECM . It the EGR and MAF sensors are all original or at least I have not replaced them. The ECM pretty sure its original. Truck was a 1 owner and has 320000 miles on it. Engine and tranny about 200 I would have to check my notes. Same on MPFI by the way. Thanks

[simperfi84]

Possible leaky poppet valve on the spider.

This truck has the upgraded MPFI spider injector assy installed. No poppets. I visually inspected each injector as I was having a helper crank engine over. Also performed a leak down test. System held a steady 55 psi for over 10 minutes.

[stew86MCSS396]

Is it throwing any codes? I'd check sensors that can contribute to a rich condition. Frigid coolant temp sensor, high volts on throttle position sensor, high map, etc.

[simperfi84]

No codes. Thanks I will check all the sensors. I back off the truck let my mind and frustration clear a bit overnight. I believe that I am most likely responsible for the flooded engine issue, what with the constant cranking and starting attempts. 1 of the first things I did after a quick check as to spark and fuel status was to change the fuel pump. I also went ahead and change the coil. I just really didn't think of the engine getting flooded or it even being an issue. But it is definitely flooded so I will get that cleared out and see what we have after that. Thanks for your help, I will update asap. Got to prepare for hurricane Dorian today.

[myburb]

Pull the fuel pump relay, the plugs, change oil if cantaminated with fuel and crank it over. should clear everything out

[THEFERMANATOR]

Anytime you have a mysterious crank no start on a corrected firing order distributor cap, I always start by trying another cap. I've lost track of how many times I've seen them with fuel, good pressure, spark, and everything needed to run, but they just wouldn't start. Put another cap on it and they fire right up. It's also common to get fuel washdown from a bad cross firing cap.

[simperfi84]

I am going to get back at it today, pull the plugs, clear the cylinders, change the oil. Then see where I am at, I will let you all know what happens. Working on getting my caffeine level up to recommended levels����☕☕☕☕

[1project2many]

It really seems like pinpointing the system that has a problem should be easy.

When an engine stalls and won't restart my approach as a tech is usually fairly simple. Remove fuel pump fuse, open throttle, crank engine for 15-20 seconds. At 60-90 deg. F temp this will dry the plugs. Then spray a touch of starting fluid into the intake. If the problem is fuel related the engine will start and stall. If the engine doesn't start I check spark.

Checking spark involves placing an ST125 or similar in the coil wire in series. If you get a bunch of regular sparks then we move on to testing at the plugs. I check multiple plugs because I too have seen way too many of the L31 cap/rotors that fail (due to moisture, and there is a partial cure). If plenty of spark but the engine tries to fire at the wrong time I pull the cap, grab the rotor, and give it a good twist. If it turns the distributor is junk and needs replacement. This happens more often than it should.

If spark and fuel are good then I move on to checking sensor values, plug condition, and engine compression. These engines are fairly reliable and usually the first two tests are enough.




I agree that the distributors and caps for these engines are notorious for problems. The pressed steel rotor "plate" will loosen on the distributor shaft and cause misfires.

[vilefly]

After you follow 1project2many's advice, then pull out and inspect the crank sensor in the timing cover for damage from contacting the reluctor. Older engine = more endplay. When the reluctor contacts the crank sensor, it can send an erratic signal that the computer interprets as a higher rpm, and sends out a burst of injector pulses in error as a result. The new aftermarket crank sensors include shims to compensate for old aged, wobbly crankshafts.

The other thing to watch for is the crank sensor harness burning itself on the passenger side exhaust manifold. The yellow wire is the signal from the crank sensor. Maybe yellow-black, I can't remember. Same erratic result or sudden death, there is no in between symptom.

REMEMBER: run all distributor tests first. Check ALL the outputs for each cylinder and coil. A high voltage bite-through on the rotor to the shaft is pretty common, too.

I doubt if the antitheft is stopping you, since you stink of gas, heh.