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

[HotWheelsBurban]

The hard/ long start issue when warm is getting worse. The plugs, cap and rotor were replaced in April,UMP cap and Blue Streak rotor,and AC plugs. I also replaced the coil wire since it's easy to get to, once I'm on top of the engine.
My question is: could this be caused by a weak coil or module? Both are probably original (99 Burb C1500, 5.7 Vortec, 203K). I thought maybe it might have something to do with the vapor canister, because it was acting up worse when hot or humid. But once it starts, this thing runs really well, so I'm kinda mystified....and sometimes it starts just fine!
I have the rest of the set of plug wires,to put on next weekend ( working the first swap meet of the fall this weekend). I'm sure that would help. Is it possible the crankshaft position sensor is going bad? It's about 3 years old.
That's the frustrating thing about this,is its randomness. I was also thinking about the fuel pressure regulator too, but it runs great when you have to get your foot in the throttle.
Hopefully the fuel injection upgrade is in the future,first of the year or so. Gotta have$$$ for parts and something else to drive. And my employer just got bought out and has cut everyone's hours by half ....

 

[Schurkey]

The hard/ long start issue when warm is getting worse.

Good. Eventually it won't start at all, and then it'll be relatively easy to find.

Downside is that between now and then...it's a real pain in the tuckus.

My question is: could this be caused by a weak coil or module? Both are probably original (99 Burb C1500, 5.7 Vortec, 203K).

Put a spark-tester calibrated for HEI on the plug end of eadh plug wire, one at a time, each in turn. Leave the others connected, or ground them. Don't leave them "open".

Crank the engine, see if the spark is getting to the plugs.

If the coil reliably fires the spark tester, (and passes ohmmeter tests) there's nothing wrong with the coil.

Modules have lots of circuitry inside, just 'cause they make a spark doesn't mean everything is working like it's supposed to. You could try a new QUALITY module and see what happens...but don't throw the old one out unless you're sure it's bad. As these vehicles age, modules are going to get harder and harder to find.

Is it possible the crankshaft position sensor is going bad? It's about 3 years old.

Unlikely, but possible.

Hopefully the fuel injection upgrade is in the future,first of the year or so. Gotta have$$$ for parts and something else to drive.

I don't have any experience with the poppet injectors. I keep hearing that when they fail, hard-starting is among the symptoms.

Refresh my memory--what is your fuel pressure at prime and when cranking?

 

[HotWheelsBurban]

Good. Eventually it won't start at all, and then it'll be relatively easy to find.

Downside is that between now and then...it's a real pain in the tuckus.


Put a spark-tester calibrated for HEI on the plug end of eadh plug wire, one at a time, each in turn. Leave the others connected, or ground them. Don't leave them "open".

Crank the engine, see if the spark is getting to the plugs.

If the coil reliably fires the spark tester, (and passes ohmmeter tests) there's nothing wrong with the coil.

Modules have lots of circuitry inside, just 'cause they make a spark doesn't mean everything is working like it's supposed to. You could try a new QUALITY module and see what happens...but don't throw the old one out unless you're sure it's bad. As these vehicles age, modules are going to get harder and harder to find.


Unlikely, but possible.


I don't have any experience with the poppet injectors. I keep hearing that when they fail, hard-starting is among the symptoms.

Refresh my memory--what is your fuel pressure at prime and when cranking?

I haven't checked it. But the truck runs great 99percent of the time.

 

[HotWheelsBurban]

I haven't checked it. But the truck runs great 99percent of the time.

Something else that people have mentioned: the battery. I have always used the biggest battery I can get, more CCA than is spec'd. Houston heat and humidity kill batteries, we learned this quickly in the parts business. The one in the truck is 2 1/2 years old, and most of the time, a battery lasts 3 years on the Gulf Coast. The starter is around 5 years old, and battery cables are almost 2 years old. I check the connections periodically,if we start having starting issues or the voltmeter reacts slowly after high load like starting or having all the lights on. And I keep them clean.

 

[454cid]

I haven't checked it. But the truck runs great 99percent of the time.

When My truck was hard starting it was the fuel pump.... I thought it was injectors for quite a long time. Eventually the fuel pump gave up, and I thought I was fixing a separate issue. After I installed the new fuel pump, I had no more hard starting.... until the starter started going, but it sounds like you have that end covered, already.

 

[HotWheelsBurban]

Mmmm, I'm hoping it's not that! On a Burb you have to drop the tank to change it....