1996 Chevy 5.7L HELP...please?

[Cyclejohn]

Hi, my name is John and I need help troubleshooting crank-stop-no start condition on my 1996 Chevy truck with a 5.7L.

I would just ask the questions on a Chevy Truck Forum but I can't remember which one I joined a few years back. Through reading other's writings on the pages of this forum over the years I know there are quite a few gearheads and retired mechanics in this neck of the internet woods who have quite the collective of knowledge on everything auto/truck-wise.

3 days ago I cranked it and went to the grocery store less than 2 miles from my house. Truck started and ran flawless like it has for years. Loaded up the groceries and when I turned the key, engine started right up but immediately was running rough. Like only a few cylinders were firing. I live close enough so I took the chance I could make it home. I did but I had to constantly play with the accel pedal and it never would get over 30mph.

Engine shut down completely just as I coasted into my driveway.

Since that time, when I turn the key to the start position, the engine will start to turnover and hang-up like it hit a wall, try to turn again and hang-up, try to turn again and hang-up. All of this happens within a few seconds and then I release the key. When I release the key, the engine will release 3 chuffs that sound like those 3 compression strokes tried to fire but at the wrong time.

The battery is good (12.6 readout on a meter with only a 1 volt drop while trying to crank). It is only a couple of years old. I pulled it out and took it to the auto parts store and had it load tested. Test said OK. Actually stopped by another auto parts store on the way home and had them double test it since the test are free. Again battery OK.

Just for good measure I cleaned all of the ground wire eyelets and points of ground in the engine bay area.

Every time that I have turned the key to the start position over the last couple of days, with all electrical components plugged in, it does the same thing as said 3 paragraphs above. I replaced the crank position sensor and that didn't change anything. It still acts like timing is off and the compression is stopping the engine from turning anymore.

If I remove the coil wire from the coil, the engine will turn over just as fast and strong as it has since the day it was born. Put coil wire back in, engine hits the wall and keeps hanging up and stopping.

I removed the distributor cap and checked the rotor for slow in the housing bushings, there is none. I tried to turn the rotor both ways with my hand in the longshot that the roll pin on the drive gear had sheared, I couldn't budge it either may. I do realize that the pin still could have sheared and the gear locked onto a different position on the shaft. I will pull the distributor out after I check a few more things.

I am going to pull the plugs out and turn the crank by hand to TDC of the compression stroke on #1 cylinder and check the alignment of the dizzy rotor button. I still have the mark it should line up with on the intake manifold I made when I pulled the distributor out 12-13 years ago.

If that is OK I am going to crawl under and remove the crank position sensor so I can turn the engine by hand and use a screwdriver to see if the crank reluctor wheel has sheared it's key. I have never heard of one shearing but I am grasping at straws here.

When it cranked up running rough at the grocery it did throw the service engine soon light but, because  I disconnected the battery to take it for a load test, it reset itself and my neighbor's OBDII code reader doesn't have the capability of pulling memory stored codes.

I am open to any other suggestions, tips, words of wisdom, etc., for possible culprits  to check for in this endeavour.

Thank You,
John


PS - I'm trying to talk myself out of thinking about the timing chain and sprockets.

[Rams]

What engine?

I doubt it's an electrical issue, sounds like a timing issue.   My guess is, the timing chain or gear is broke.  IMO, it's a mechanical issue, not electrical.   Could be and sounds serious.   Need a lot more information and I'm not the best guy to ask but, here's a bump for you back to the top.  What ever the cause, the engine is locked up based on your description.   Time to get a real mechanic/tech involved.

Rams

[Cyclejohn]

What engine?

Hey Rams,

It's the 5.7L Vortec (I like to call it a 350)

John

[old2soon]

What engine?

Hey Rams,

It's the 5.7L Vortec (I like to call it a 350)

John

          P M mad6gun. Former G M tech for a Lot of years. Just helped out a friend of mine with his Chevy pick em up. RIDE SAFE.

[Skinhead]

What engine?

Hey Rams,

It's the 5.7L Vortec (I like to call it a 350)

John

          P M mad6gun. Former G M tech for a Lot of years. Just helped out a friend of mine with his Chevy pick em up. RIDE SAFE.

I agree with 02S, Call/PM Mark.  How many miles on this engine?  My initial thought is jumped timing chain.  In the future, if you get a CEL, always read the codes before disconnecting the battery, the DTCs are very helpful in diagnosing a problem.

[Patrick]

A compression check will help. As will checking to see of there are any codes. The truck may be either an OBD1 or OBD2 probably dependent on build date.

[Bigwolf]

Take the distributor cap off and throw it away!  Buy 3 new distributor caps and try them one at a time.  Those caps are notorious for crossfiring.  Brand new caps for that are quite often bad too, hence the 3 caps.  If you get one that actually works, take the other 2 back.

Yes, I wasted a lot of time trying to understand why my 98 model year 5.7 with the brand new cap was running crappy and engine code said random misfire.  It was that brand new cap!   There is no way to test the cap unless you have access to a machine that can test it at sparkling high voltage.


Bigwolf

[Binkie]

Since the engine turned over normally when you disconnected the coil wire I don’t believe you have a hard part failure. On vortec engines the cam sensor is in the distributor. I believe what you have is a bad cam sensor. You can check it with a dvom but  they aren’t expensive so I would just replace it. I had one go bad on 99 Tahoe I had and it acted similar to yours. Big wolf is right , those distributor caps are known for just failing and usually causing a crank no start.

[Cyclejohn]

Before I forget,

I wanted to thank the people that have replied and offered up suggestions, so, THANK YOU.

The truck is a 1996, has 254,000 miles, and has the OBDII connection port. 1995 and earlier had the OBDI connection post.

I am going to take the suggestions offered and add them to the list of checks that I am going to do over the next couple of weeks as weather permits.

All of my mechanical work is done on my driveway (no garage). I pick and choose the days when I work on it because it is difficult (at least for this old man) to turn wrenches with insulated gloves on and difficult to turn wrenches when they are so cold they freeze my bare hands. And now I have to wait  a couple of days for the snow to melt and the driveway to dry out so I can slide under the truck.

Again, THANK YOU,

John

[old2soon]

Before I forget,

I wanted to thank the people that have replied and offered up suggestions, so, THANK YOU.

The truck is a 1996, has 254,000 miles, and has the OBDII connection port. 1995 and earlier had the OBDI connection post.

I am going to take the suggestions offered and add them to the list of checks that I am going to do over the next couple of weeks as weather permits.

All of my mechanical work is done on my driveway (no garage). I pick and choose the days when I work on it because it is difficult (at least for this old man) to turn wrenches with insulated gloves on and difficult to turn wrenches when they are so cold they freeze my bare hands. And now I have to wait  a couple of days for the snow to melt and the driveway to dry out so I can slide under the truck.

Again, THANK YOU,

John

          pickin and choosin the RIGHT weather to work in! i absofrikkinlutely GIT IT!  I have a garage but it ain't heated and right now the garage IS Phatt Ghurls cave!  RIDE SAFE.

[Patrick]

OK, couldn't remember if all '96 had a OBD2 connector.

Having to work in the cold, changing the sensor and cap shouldn't take too long [ or much expense] even with stiff fingers.

[Bigwolf]

I forgot to mention the vats!  If you are still using the original key at 250 plus thousand miles, you could be having a vats problem.  There are some kits available to delete the vats.  Pay attention to the dash lights when you try to start the engine.  If the security light stays on, the problem is the vats.  You can sometimes do reset and get it to run until you turn it off again.  You do that by turning the key on without trying to start it, and leave the key turned on for 30 minutes or until the security light goes out. Be sure to set the park brake so that the head lights are not on for that 30 minutes.

If it is the vats, plan to get a kit and delete it ASAP because the symptoms tend to get increasingly worse and eventually not even the reset will get you going.  The vats on those trucks can create  a bunch of spooky problems.  The vats on my 99 Suburban would only act up when the weather was damp……….yes, that one took me a long time and cost a lot of money before I caught on to it.  There once was a time when I preferred GM vehicles………no more!  There is no excuse for such crappy engineering!

[Rams]

Since the engine turned over normally when you disconnected the coil wire I don’t believe you have a hard part failure. On vortec engines the cam sensor is in the distributor. I believe what you have is a bad cam sensor. You can check it with a dvom but  they aren’t expensive so I would just replace it. I had one go bad on 99 Tahoe I had and it acted similar to yours. Big wolf is right , those distributor caps are known for just failing and usually causing a crank no start.

Obviously, I could be wrong but, the quote below makes me believe the problem isn't a sensor but.....

Since that time, when I turn the key to the start position, the engine will start to turnover and hang-up like it hit a wall, try to turn again and hang-up, try to turn again and hang-up. All of this happens within a few seconds and then I release the key. When I release the key, the engine will release 3 chuffs that sound like those 3 compression strokes tried to fire but at the wrong time.


John


PS - I'm trying to talk myself out of thinking about the timing chain and sprockets.

Looking forward to learning what the problem really is.

Rams

[hubcapsc]

There's so many complex thingamabobs on cars now, I'd be lost.

But I am reminded of when my fuel filter finally clogged up all
the way on my not-complex pickup truck...



-Mike

[Cyclejohn]

Just to update:

Truck is fixed. It was the cam position sensor. Now I just need to find somebody or someone that has a scan tool with the capability to read cam retard offset so I can dial that back in. I had to pull the distributor out to remove the old one because both screw heads that retain it just snapped off with little effort from the corrosion going all the way through them.

Again, Thank You to all for your knowledge and suggestions,

John

[Rams]

Interesting, glad you got to the bottom of it.   I'm very happy that I was wrong about the mechanical failure of the timing gears/chain.   Although with the reported mileage, I might suggest that it's time to consider checking them out when weather permits.

Rams