97 Sierra 2500 5.7 no start all the usual parts replaced - HELP

[old rusty]

Hi everybody, This one has myself and a few car friends stumped I'll try to make a long story short and get to the current issue. I have a 97 GMC Sierra 2500, 5.7, rusty Ohio plow truck with only 127,000 on it,this was a great running truck until a couple months ago,here's the story. Died at work this summer ended up being a no fuel issue after all the common troubleshooting,replacing fuel pump etc. problem ended up being a dicey wire in the harness located after dropping the tank,soldered in 18" of new wire,dielectric grease,heat shrink,reassemble gas tank, done truck fires up but with a bad miss, I figure since it sat outside in the weather for several weeks it may just need driven,bad miss hard starting,runs terrible more or less intermittent, so I put on new cap and rotor which doesn't solve the problem which is getting worse every time I start the truck so I put in a cam sensor same issues this time the truck dies on a test drive no start sounds like it is out of time bad real bad,next move new crank sensor,the old one actually came apart and I had to get it out in three pieces, OK all should be good found my problem or so I thought,same no start,cranking like the timing is advanced way too much. I'm at a loss here everyone tells me there is no way it could be a timing chain with only 127,000, I have a wrecked parts truck with a 5.7 Vortec with 286,000 that is the best running vehicle I own. Any suggestions would be greatly appreciated.

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[351FUN]

>cranking like the timing is advanced way too much.

Have you verified timing? And is it throwing any codes?

 

[old rusty]

>cranking like the timing is advanced way too much.

Have you verified timing? And is it throwing any codes?

No codes, from what I've read there is no "timing" adjustment on 96-99 it is controlled via the ECM ? My understanding is moving the distributor changes the cam/crank correlation not timing like I am used to. To check the cam/crank correlation a scanner is needed ? I'm clueless at this point. Thanks

 

[Schurkey]

Your story indicates that you've replaced some parts based on guesswork. You've done zero actual diagnosis. You're correct about the "timing" however. Turning the distributor changes the cam sensor signal synchronization to the crank sensor signal, it also changes the alignment of the rotor to the distributor cap terminals. This MUST be correct for maximum cap/rotor life.

Do you have an RPM signal at cranking? Do you have spark? Are the plugs fouled? Spark plug wires dead? EGR valve stuck open?

Connect a scan tool, look at the data stream. Look at the cylinder-by-cylinder misfire counter. Any "problem children"? How far off is the cam sensor alignment--cam retard, or whatever your scan tool calls it. TPS, coolant temp sensors working properly?

Verify fuel pressure. Does the fuel pump prime when you turn the key? Did you replace the filter sock and fuel filter also?

Have you updated the "spider" injector system to the newer electronic injectors? I'm told that can make a major difference.

 

[old rusty]

My diagnosis or lack of was based on the symptoms the truck was having, hard starting with a bad miss which got worse until it died at the end of my street. I replaced the easiest items prone to fail from what I've read or been advised. This all started with the fuel pump issue which turned out to be a bad wire,maybe? The truck started and ran after I worked on that but with the intermittent miss. At this point I have no clue if I'm chasing the same issue from the first tow home which was no fuel when I replaced the fuel pump and discovered the bad (?) wire. The distributor has never been moved,cap,rotor and plugs are new I'm sure it needs plug wires but was waiting to get the truck running before doing them. My scanner is limited to a parts store code reader that shows no codes,no check engine light ever came on. Of course I'm over just throwing parts at this and hoping for the best. I don't think the fuel spider,TPS or temp sensor you mentioned would cause a flat out dead no start ? Thanks for the reply I appreciate it.

 

[jvthundercat]

Well first things first. Put a fuel gauge on the port in front of the intake manifold. It could have been the fuel pressure regulator to begin with. If not enough pressure, you need to test to figure out what is bad. Test is in the book. A mis-fire when it hits bad enough, will through a code for that.

 

[351FUN]

Connect a scan tool, look at the data stream. Look at the cylinder-by-cylinder misfire counter. Any "problem children"? How far off is the cam sensor alignment--cam retard, or whatever your scan tool calls it. TPS, coolant temp sensors working properly?

Is there a scan tool you'd recommend for a '92? I'm having no luck finding anything other than code readers for obd1

 

[df2x4]

Is there a scan tool you'd recommend for a '92? I'm having no luck finding anything other than code readers for obd1

The $250-$350 GM Tech 2 clones will work with any GM vehicles from 1991-2013.

 

[Schurkey]

My $350 used-from-eBay Snap-On Solus Pros work well. Beware that the 8.2 software won't do automatic ABS bleeding on my '97. 14.2 does, and I'm told that 10.x does. I don't know when that function was added to the software, but it would be after 8.2 and before whatever version of 10.x.

Except for the ABS bleeding of my '97--which your '92 doesn't need, a Snap-On MT/MTG 2500 will also work just fine, as long as you've got '92+ software.

There's plenty of others that will work with OBD-1; OTC Genysis, Pegysis; and a horde of Chinese consumer-grade tools (be careful!) There's connector cables that plug into a laptop, and laptop software. But I have zero experience with anything but the Snap-On tools I mentioned except that
I used the OTC Monitor 2000 and Monitor 4000 a few times, about forty years ago. Those tools are practically prehistoric.

One of these days, I'm gonna take photos of a scan tool connected to various vehicles, showing what info and features are available.

 

[old rusty]

Well first things first. Put a fuel gauge on the port in front of the intake manifold. It could have been the fuel pressure regulator to begin with. If not enough pressure, you need to test to figure out what is bad. Test is in the book. A mis-fire when it hits bad enough, will through a code for that.

When the truck died on me at work a couple months ago it just shut off like turning the key off,just cranked normal no start. After I had it towed home the first thing I did hoping to get lucky was swap the fuel pump relay from my great running but hit in the front parts truck,no luck so I installed a new fuel pump common problem with these trucks again no luck so my buddy stops by and says yank on the wire harness near the gas tank I'm looking at him like he's lost his mind,sure enough he starts tugging on the wires while I cranked the truck over, within seconds it's running, a couple days later I drive it to work and it doesn't start when I'm ready to head home,so I yank on the wire harness and it fires up and runs fine the 10 minute drive to the house that's how we decided to drop the tank and find a bad wire, the missing and hard starting came after the first fix. Thanks I'll keep checking but I really need to get ahold of someone with a scanner since I'm running blind here.