Need help with Vortec 350 recurring hard-start/no-start

[geeeee89]

I bought the truck in Alaska in 2017 with 100k miles on it. No humidity there and always started before I could even let go of the key. Since bringing it back to Mississippi last year if I let it sit for 3 or 4 days it's slow to start. It is very humid here and rains a lot. Sometimes it would take forever to start but finally would, sometimes it wouldn't start at all. This usually only happened if I let it sit for a while. It was my daily driver for the past year and had no issues because I ran it almost everyday.

Fast forward to recently. Bought a beater car in August and had been dailying that and left the Chevy parked. Tried to start it before hurricane Ida hit so I could go fill up gas jugs. Took forever to start but it finally did. 3 days later when the storm is about to hit I try to start it to move it into the car port and it won't start and the starter solenoid goes out.

Order the starter and the truck sits while I wait for it to come in. Got the starter put in last week. Removed the ground and hit them with a flap disk to make sure all connections are clean. Put in the new crank sensor. Put everything back together, try to crank it and nothing. Stumbles a little bit like it wants to start but doesn't. Crank on it for a while with no progress. Smells like gas around the truck. Had a stored code for high voltage at ignition module

The next day I go get a cap and rotor and install that. Checked for clogged screens in the distributor base - no screens at all, just small holes. Put it back together and fires right up. I let it run for 30 mins and killed it. Went to start it on Saturday morning and it wouldn't start. I opened the hood and held the leaf blower at the distributor area for 5 mins and then let it sit in the sun with the hood up all day. Later in the day it was slow to start and stumbled a little but finally got started and ran fine after that.



Recent new parts and stuff I've done:
Battery is a month old
New gear reduction starter last week
Crank sensor last week - based on GM service bulletin outlining a hard-start issue
Checked for clogged screens in distributor - no screens there at all
New cap and rotor 3 times in the last year - points in the cap get severely corroded. Most recent cap and rotor was last week
Ignition module about this time last year
Fuel pump in 2019
Plugs and plug wires in 2017
Lower intake manifold gasket replacement in January.
Put a fuel gauge on it and had 62 psi with key on and truck off. Dropped to 58-60 while cranking. Dropped to 55 after a few hours. Dropped to 35-40 the next afternoon. I think this is normal


Truck info:
97 K1500 with L31 350, no mods done to motor minus a Blackbear PCM tune after re-gearing it in January. 150k miles


I found a lengthy post by @thegawd on another forum outlining some of the issues. I intend to drill out the holes in the distributor base and see how that affects it. Will I benefit from one of the fancy aluminum MSD distributors?

After that though, seems like a new distributor is the next step. I bought a inline spark checker but have to wait for my wife to get back from visiting her folks so I can get her to turn it over while I check for spark.

Any ideas? Seems like moisture buildup in the cap is my issue. The points in the cap I just removed were black. Once it finally gets running it runs perfect with no stumbles, misses, or codes. It's just getting it started that is the problem.

 

[thegawd]

I could not find any vent holes in the dist. base that is on my 97 Burb. apparently it was a manufacturing defect and they installed the faulty base's anyways. Ya I drilled 2 × 1/8" holes where they were supposed to be. this was apx. 8 or 9 years ago. I recently had to replace the cap due to corrosion so those holes did help a lot. I could have cleaned the cap as they were not green but I had a spare cap n rotor with brass contacts so I just installed it instead.

I live almost in the middle of 3 great lakes and we have extreme humidity and this summer we had a lot of rain. after one massive rainfall the truck just wouldnt start. I pulled the dist and the aluminum contacts were covered in that white fuzzy type of corrosion. what a mess.

I have an aluminum billet type dist that I need to install instead but I dont think I have the ability to reprogram the cam/crank correlation and once I do I will swap it out.

The Burb has been sitting a lot more than it has in the passed. that's actually probably why it corroded so badly as it wasnt being driven every day.

 

[thegawd]

heres that 8-9 year old cap n rotor. I cant tell you what brand it is all I can remember was it was whatever the parts store stocked as its premium parts... no idea. those are all aluminum contacts though.

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[stutaeng]

Yes, had this exact same problem on a 4.3 Vortec 99 NBS. I changed pretty much everything you did except the fuel pump (my pressure was lower than yours, but that wasn't the problem.) Truck started right up if it was sunny, but dreaded trying to fire it up in wet/damp/humid conditions. In my case, I was down to either the FPR somehow slowly leaking under those wet conditions and/or distributor (or cap.) I was leaning toward the distributer because I also I turned on a heat gun the top of the engine once and was able to fire up after about 15 minutes. The FPR had a very slow leak, but I did not think that was the problem either. And surprisingly, the OEM spider injectors passed the injector balance test, so it didn't seem logical for me to change the FPR only.

I always seemed to have spark, so my theory was what that the humidity inside the cap somehow caused the spark to jump to the wrong conductor, but I was never able to prove that.

Unfortunately, I gave up on her, since engine had low oil pressure and truck got retired from being my daily driver. I eventually replaced it with a 5.3, but it was frustrating for sure.

I don't know why some trucks have this common problem, but others don't. My 5.7 in my K3500 never has done this, and I have a buddy also with the same truck as mine with the 4.3 and he didn't have this problem either. I was talking to my mechanic and he said one of his trucks with the 5.7 randomly also did this (but his didn't do it when wet) and he just kept going to the junkyard and stealing a distributer for it, LOL.

I know this founds goofy, but do you have a garage you can park it in overnight and see if the problem goes away? I think in the winter that's the only way my truck would start if the weather was damp...parked inside. LOL.

Edit: My truck had 260k miles. Distributer was changed around 180k-ish. I think I started having this humidity problem around 220k-230k IIRC. Towards the end, I had changed the battery to a larger capacity (V8 battery) and I was able to make it start, but after letting her crank like 2-3 minutes straight. Obviously, not ideal and on the brink of melting my starter!

 

[thegawd]

it's the having spark that's stops our logical thinking. at least it sure did mine! i had spark so I did not ever consider there was a problem with any of the ignition parts. to be fair to myself, this was the first time I had any trouble like this and I was relatively new to these trucks in general with only about 4 years experience owning a 94 Burb and then my current 97 Burb. So I really didnt understand all the logic.

One of my best friends came by and asked me if I pulled the distributor. he bet me that it was a mess and firing out of order.

he was right.

the spark will always take the shortest path and so a spark dosent mean it is sparking at the right time.

 

[geeeee89]

heres that 8-9 year old cap n rotor. I cant tell you what brand it is all I can remember was it was whatever the parts store stocked as its premium parts... no idea. those are all aluminum contacts though.

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about what I would expect for one 8 or 9 years old. I was really surprised mine were so black. I'll go ahead and buy a spare cap for when I inevitably need it

Yes, had this exact same problem on a 4.3 Vortec 99 NBS. I changed pretty much everything you did except the fuel pump (my pressure was lower than yours, but that wasn't the problem.) Truck started right up if it was sunny, but dreaded trying to fire it up in wet/damp/humid conditions. In my case, I was down to either the FPR somehow slowly leaking under those wet conditions and/or distributor (or cap.) I was leaning toward the distributer because I also I turned on a heat gun the top of the engine once and was able to fire up after about 15 minutes. The FPR had a very slow leak, but I did not think that was the problem either. And surprisingly, the OEM spider injectors passed the injector balance test, so it didn't seem logical for me to change the FPR only.

I always seemed to have spark, so my theory was what that the humidity inside the cap somehow caused the spark to jump to the wrong conductor, but I was never able to prove that.

Unfortunately, I gave up on her, since engine had low oil pressure and truck got retired from being my daily driver. I eventually replaced it with a 5.3, but it was frustrating for sure.

I don't know why some trucks have this common problem, but others don't. My 5.7 in my K3500 never has done this, and I have a buddy also with the same truck as mine with the 4.3 and he didn't have this problem either. I was talking to my mechanic and he said one of his trucks with the 5.7 randomly also did this (but his didn't do it when wet) and he just kept going to the junkyard and stealing a distributer for it, LOL.

I know this founds goofy, but do you have a garage you can park it in overnight and see if the problem goes away? I think in the winter that's the only way my truck would start if the weather was damp...parked inside. LOL.

Edit: My truck had 260k miles. Distributer was changed around 180k-ish. I think I started having this humidity problem around 220k-230k IIRC. Towards the end, I had changed the battery to a larger capacity (V8 battery) and I was able to make it start, but after letting her crank like 2-3 minutes straight. Obviously, not ideal and on the brink of melting my starter!

I had the FPR on my to-do list until I tested the fuel pressure and got those readings. Am I leaking down too fast? I'm really leaning toward the distributor here but wanted to get some advice before dropping $2-300 on one.

Totally different truck and motor but I had a 78 K20 in Alaska too, 350, carb, HEI distributor. When i first bought It would crank and crank and crank but not start. New distributor cured it. Much simpler truck to work on though

Good idea on the garage. I'll see if the truck fits in there but I suspect it won't.

What's weird is I never once had this problem with it the 3.5 years I lived in Alaska. Drove it every single day there. Tons of wet nasty snow in winter and tons of rainy weather and damp nastiness in summer. Just kept on going with no complaints. I did start having a random misfire while up there that I fixed by setting the cam retard offset - maybe that was the beginning stages of the distributor going out. But the issues I described in my first post didnt start until getting the truck to Mississippi where it's hot, humid, rainy, and muggy for most of the year

 

[stutaeng]

Do you know if your distributor is original? Maybe look for a high quality unit. Don't buy the cap just yet. A new distributor cones with the cap AND camshaft position sensor. Those 2 other items are a good $75 for both...

Same thing with the FPR. A new MPFI injector set comes with a new FPR, so if you are going to go through the hassle, might as well upgrade to the MPFI setup. Unless that's already been done.

 

[thegawd]

I decided to clean it up and see if it was "salvageable" just in case I need one, one day, to get to the parts store or whatever.

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For the most part it cleaned right up. but the center button on the cap dosent seem to want to come clean. its black on mine and seemingly will continue to sand off. hmmm I have no idea what it is made of and maybe thats normal but this contact is no doubt a source of "something" black. rotor cleaned up fairly nice.

So I grabbed a multimeter to test for continuity between the center button contact and the connector and it dosent want to make good contact. it appears to be brass underneath... maybe, more cleaning.

well it's still black but is making an easy connection now.

whatever the center contact is made from is no doubt a source of black residue.

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[HotWheelsBurban]

If you do end up putting a new distributor in, see if you can get one that has the vented cap and that it and the rotor have brass contacts. I think the vented cap has helped a lot on my Burb (99 5.7 L31) because I used to have trouble sometimes on humid or rainy days starting it. Hasn't been a problem since I put the UMP vented cap on. Also, my Burb was going through the cheaper white rotors about every 6 months or so; the Blue Streak rotor ( blue stronger plastic and brass contacts) lasted for 2 years. This truck gets driven every day in Houston, Texas area and we have lots of humidity too!
I'm having a longer crank issue with it lately, but I can prevent that by "priming" the pump by having the key in Run for a few seconds before starting. Battery is 2 years old and connections and cables are good. Vapor canister might be involved too because it does it worse when it's hot. Otherwise it's just if it's been sitting overnight or for several hours. Burb has 201K on original FI parts, so I'm sure replacing all that stuff would help. Hoping to do this over the winter, once I can get something else to drive for a bit. And of course the $$$ for parts....

These rotors are toast when the blade contact in the middle ( the springy thing that the carbon button in the cap touches) is burned through, or the plastic under it is burned. Basically it'll look like someone took a pencil and drew on the depression in the middle of the rotor.

 

[Schurkey]

For the most part it cleaned right up. but the center button on the cap dosent seem to want to come clean. its black on mine and seemingly will continue to sand off. hmmm I have no idea what it is made of ...

...whatever the center contact is made from is no doubt a source of black residue.

The center button is carbon. You'll wear it down to a nub and never hit "metal". Depending on how much you've already removed, that cap is scrap.





Verify that the rubber/plastic hood seal, at the windshield-end of the hood is in place and functional. Otherwise, rainwater can flow down on top of the distributor.

Connect the spark-tester to the distributor end of the coil wire. Point the sparking bit towards the driver's seat. Now you can crank the engine and watch the sparks at the spark-tester as a one-person operation. Same deal with using the spark-tester on plug wires--point the spark tester towards the driver's seat so you can see it from the seat; or from standing at the driver's door, reaching through the window to turn the key.

Wouldn't hurt to put an ohmmeter across the coil wire, and across the plug wires. OEM wires should be less than 4000 ohms per foot of wire. Aftermarket wires may be as low as ~50 ohms per foot--but don't believe the advertising that suggests you get a stronger spark because of the low resistance. It's a lie of omission. They "forget" to tell you that the low-resistance plug wires have high inductance. Resistance, or inductance, can and does kill spark current without disturbing voltage much.

Run the engine in a dark garage, or on a moonless night with the hood open. Look for "glow" around the plug wires. If the plug wires glow like a neon light...you need new plug wires.