5.7 Starting Issue

[Slime]

Well, it's back again... Exact same issues as before. After reading through past threads, I do believe it's been damp out when this has happened. I'm going to see what I can find today, but last night it started and ran fine. I know it;s a fuel issue as the last time it wouldn't start there was no fuel in the line. When it did start, and I had a gauge on it it was near the threshold on PSI. VERY aggravating..

 

[HotWheelsBurban]

Have you checked the battery cables and connections? My Burb has done things similar to your truck's problem when damp or cold. Also check the distributor cap and rotor for cracks, carbon tracking and excessive wear on the contacts. A cap and rotor with brass contacts will help a lot with damp starting problems. The battery cables on these trucks are prone to unseen corrosion under the insulation. If you have access to a battery shop or welding service shop, they can make new cables for you. Less than a quarter turn loose on my ground cable terminal at the battery makes my truck do all sorts of crazy stuff. Also how old are the ignition module and coil? They do go bad, and not always all at once. Good luck!

 

[Schurkey]

Problems when "damp" make me think ignition, not fuel. But that's not guaranteed.

Put a fuel pressure gauge on that thing. Install it "for real", with the gauge mounted where you can see it from the driver's seat. Leave it there until it fails to start. Either you have proper fuel pressure even when it won't start, or you don't.

I'd also be testing for spark. Get a proper spark-tester, calibrated for HEI. If the truck won't start, pop a plug wire at the plug end, connect and ground the spark tester where you can see it from the driver's seat. Crank the engine. Again, either you have spark...or you don't.

No spark AND no fuel? Start looking at the crankshaft sensor and it's wiring. Which, frankly, is best done with a scan tool. If the engine is cranking but not starting, and the scan tool isn't showing RPM...the sensors aren't telling the computer to provide fuel and spark.

 

[Slime]

Problems when "damp" make me think ignition, not fuel. But that's not guaranteed.

Put a fuel pressure gauge on that thing. Install it "for real", with the gauge mounted where you can see it from the driver's seat. Leave it there until it fails to start. Either you have proper fuel pressure even when it won't start, or you don't.

I'd also be testing for spark. Get a proper spark-tester, calibrated for HEI. If the truck won't start, pop a plug wire at the plug end, connect and ground the spark tester where you can see it from the driver's seat. Crank the engine. Again, either you have spark...or you don't.

No spark AND no fuel? Start looking at the crankshaft sensor and it's wiring. Which, frankly, is best done with a scan tool. If the engine is cranking but not starting, and the scan tool isn't showing RPM...the sensors aren't telling the computer to provide fuel and spark.

Leaving everything else aside, shouldn't the fuel system pressurize when the key is turned on? I mean, as long as the pump sees enough voltage it should pump correct? I just cleaned , tightened and dielectric greased the battery terminals. Fires right up, as it did last night and this morning before I checked the battery. I wish I could get fuel pressure reading on my scan gauge. I guess that's on newer systems.

 

[stutaeng]

Leaving everything else aside, shouldn't the fuel system pressurize when the key is turned on? I mean, as long as the pump sees enough voltage it should pump correct? I just cleaned , tightened and dielectric greased the battery terminals. Fires right up, as it did last night and this morning before I checked the battery. I wish I could get fuel pressure reading on my scan gauge. I guess that's on newer systems.

Yes, you should have fuel pressure with key ON before cranking.

I battled the same crank-no-start on my 4.3 for like 2 years at around 220k miles. Always on wet or damp conditions in the morning. Even if I got to work and it rained, never had the issue leaving work.

My fuel pressure was always around 58 psi. Distributor had been changed around 175k. New coil, spark plugs, ICM. Crank and cam sensor all were good. Numerous cap and rotors.

Just retired that truck because of low oil pressure on engine at 255k. But got frustrated that I could not figure it out.

My fuel injectors were the original, but I did an injector balance test and they surprisingly tested ok.

I suspected the rotor cross-fires inside the cap when moisture gets in there. There something about some screen vents...a TSB I think. My replacement distributor did not have those. If I put a heat gun pointed in the cap for about 15-20 minutes I could get it to start.

Last few months I got a replacement battery under warranty and went with a larger class. Previously I would crank until the smaller battery died. But with larger battery I could crank for about 2-4 minutes straight and finally it would start. My theory is that cranking this long would also cause the moisture to evaporate. Obviously, that's on brink of frying the starter, especially when it rains or is damp for 3 or 4 conservative days around here.

It was that or fuel pressure regulator leaking down overnight. I did have a small leak on mine towards the end, but when I started having the no start issue it was okay.

Not sure why it happens. But on the 4.3 it's a VERY common problem on certain engines. My friend has a 4.3 with almost 400k and doesn't have that problem.

And I also have a 5.7 Vortec on another one of my trucks that starts just fine, even when damp/wet. Coinsidently, I changed the injectors on that engine because one was faulty and discovered the cap had a small crack. Was too scared to change it because of this problem on my 4.3, so I put it back on, LOL. It did look like the original!

 

[Slime]

Yes, you should have fuel pressure with key ON before cranking.

I battled the same crank-no-start on my 4.3 for like 2 years. Always on wet or damp conditions in the morning. Even if I got to work and it rained, never had the issue leaving work.

My fuel pressure was always around 58 psi. Distributor had been changed around 175k. New coil, spark plugs, ICM. Crank and cam sensor all were good. Numerous cap and rotor s.

Just retired that truck because of low oil pressure on engine at 255k. But got frustrated that I could not figure it out.

My fuel injectors were the original, but I did an injector balance test and they surprisingly tested ok.

I suspected the rotor cross-fires inside the cap when moisture gets in there. There something about some screen vents...a TSB I think. The replacement distributor did not have those. If I put a heat gun pointed in the cap for about 15-20 minutes I could get it to start.

Last few months I got a replacement battery under warranty and went with a larger class. Previously I would crank until the smaller battery died. But with larger battery I could crank for about 2-4 minutes straight and finally it would start. My theory is that cranking this long would also cause the moisture to evaporate. Obviously, that's on brink of frying the starter, especially when it rains or is damp for 3 or 4 conservative days around here.

It was that or fuel pressure regulator leaking down overnight. I did have a small leak on mine towards the end, but when I started having the no start issue it was okay.

Not sure why it happens. But on the 4.3 it's a VERY common problem on certain engines. My friend has a 4.3 with almost 400k and doesn't have that problem.

And I also have a 5.7 Vortec on another one of my trucks that starts just fine, even when damp/wet. Coinsidently, I changed the injectors on that engine because one was faulty and discovered the cap had a small crack. Was too scared to change it because of this problem on my 4.3, so I put it back on, LOL. It did look like the original!

So, how do you do a balance test on a 96 Vortex injection system? Do I need something along the lines of a SnapOn MT290? I know I need to check the fuel pressure too, but I know that the last time this happened when it wouldn't start there was no fuel coming into the system. I checked by opening the test plug for a gauge. When it did start, it had fuel pressure I think of around the lower end of the scale. Being unemployed I don't really want to buy more tools at this point. I'm actually waiting on a CFM Technology fuel pressure gauge and the adapter for my 4.3 TBI. It's the same setup for the 5.7, but they are on back order until at least next week. One thing that did happen when this started is the EGR code it kept giving me has now gone away.

 

[stutaeng]

So, how do you do a balance test on a 96 Vortex injection system? Do I need something along the lines of a SnapOn MT290? I know I need to check the fuel pressure too, but I know that the last time this happened when it wouldn't start there was no fuel coming into the system. I checked by opening the test plug for a gauge. When it did start, it had fuel pressure I think of around the lower end of the scale. Being unemployed I don't really want to buy more tools at this point. I'm actually waiting on a CFM Technology fuel pressure gauge and the adapter for my 4.3 TBI. It's the same setup for the 5.7, but they are on back order until at least next week. One thing that did happen when this started is the EGR code it kept giving me has now gone away.

Here's the cheapest way to do it. OTC also has something similar, but around $100. The guy on YT channel called Ratchets and Wrenches shows you how to use the cheapie one.

The more advanced diagnostic scanner tools also do it. In any case you need the fuel pressure guage.

I would try the trick with blow dryer or heat gun on the distributor cap when it won't start. If you get it to start after that, then injectors may be okay and issue is ignition.

Edit: forgot the link:
https://www.amazon.com/Automotive-F...ocphy=9026913&hvtargid=pla-915232771563&psc=1

 

[HotWheelsBurban]

Yep I forgot about the crankshaft position sensor. If that's no good, it can't tell the computer to allow spark and fuel pump activation. And it's something else that doesn't go out all at once.
Had the CPS go bad on my Burb a couple years ago. No crank, no start. Nada. Replaced it, got cranking, but still no fire up and start. Replaced the rotor. Fired right up!
I was also beginning to have passlock issues intermittently, but your truck is old enough to not have passlock. Lucky you! It's a pita when your truck thinks you're trying to steal it.....
I have also heard about the humidity problem with some vortec distributors. Fortunately not experienced it personally, but I know my cap and rotor are good. When I got this Burb, it had been having carbon tracking in the cap. Eventually broke the nose off the starter and ruined the flywheel, since it was firing 2 cylinders at once. Not a good idea while starting (or really anytime).

 

[sbump]

I am having a similar problem except that mine will start but die immediately. Sometimes it will fire right up and be fine. I did find
that if i give it gas/throttle immediately at start will will run and not die. Once the truck is running it seems fine and will drive. The start and die issue will happen when engine is cold or warm already. I am leaning towards a sensor issue like throttle position maybe but welcome any input/ help. Truck is 98 5.7.

 

[stutaeng]

I am having a similar problem except that mine will start but die immediately. Sometimes it will fire right up and be fine. I did find
that if i give it gas/throttle immediately at start will will run and not die. Once the truck is running it seems fine and will drive. The start and die issue will happen when engine is cold or warm already. I am leaning towards a sensor issue like throttle position maybe but welcome any input/ help. Truck is 98 5.7.

It could be LOTS of different things. Probably not same problem as OP if it starts and dies and does it warm also. Maybe create a new thread and you may get more input?