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HELP!!!!

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Captain Dave

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72 K5, 350/350. I was cruising down the interstate at 65mph. Heard a very loud backfire. Immediately lost power and engine stopped. I coasted to the side of the road. A visual inspection revealed an exploded muffler but I could not find anyother visual damage. Lights work ok, motor won't turn over, starter won't even engage. What the Hell happened??
 
Captain Dave said:
72 K5, 350/350. I was cruising down the interstate at 65mph. Heard a very loud backfire. Immediately lost power and engine stopped. I coasted to the side of the road. A visual inspection revealed an exploded muffler but I could not find anyother visual damage. Lights work ok, motor won't turn over, starter won't even engage. What the Hell happened??
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Sounds like the timing chain may have broke
 
When you say starter won't engage, do you mean it just freespins without hitting the ring gear or that the starter won't spin the engine?
 
Justin V said:
When you say starter won't engage, do you mean it just freespins without hitting the ring gear or that the starter won't spin the engine?
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When you turn the key, nothing happens. No click, free spin or anything.
 
Could be something in the electrical system came loose. Caused the ignition to quit, fill the exhaust with fuel, then re-lit and ignited the fuel and blew the muffler.
 
Can you turn the engine by hand?

The muffler explosion indicates loss of ignition/power. The now not firing engine would still be drawing in fuel and air and exhausting the unburned mix until the heat of the muffler ignites it...

It sounds like an electrical failure to me.
 
tRustyK5 said:
Can you turn the engine by hand?

The muffler explosion indicates loss of ignition/power. The now not firing engine would still be drawing in fuel and air and exhausting the unburned mix until the heat of the muffler ignites it...

It sounds like an electrical failure to me.
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tRustyK5
here's my plan of attack:
1. See if I can turn the motor over by hand.
2. If so, pull the valve cover vent cap and see if the valve train is moving. if it is,
that will eliminate the timing chain issue.
3. trouble shoot the ignition circuit. the fact that the ignition is completely dead, that's probably where my problem should be.

do you and the others that have offered help agree??

Capt Dave
 
Broken timing chain can do all the above , and the distributor will not spin. So no spark

When turning the engine over (if it does) keep in mind if the valves are moving, they may no longer be in time with the crank
 
I've never seen a timing chain break (yet!)--just jump time,its not uncommon on older GM small blocks that had a nylon coated cam gear instead of steel..

I've seen only a few small blocks bend valves when they jumped time,and the engines were revving pretty high when the chain jumped,and the damage was limited to bent push rods or a broken rocker arm....usually they don't touch..

Just taking off the distributor cap and watching to see if the rotor moves ,if you can turn the engine by hand,will tell you if the chain is still on both sprockets--but possibly not be "timed" if it did jump..

You'll have to put it to #1 compression stroke at TDC on the harmonic balancer and see if the rotor is pointing at #1 on the cap..

You may be able to jump the starter solenoid and see if it'll crank then,but I'd try turning it by hand a few revolutions first in case something is bound up inside the engine to avoid doing further damage..
 
On mine there were 2 small glass fuses in the front harness, running on the radiator support, that blew and I had no ignition power.
 
The crank will rotate by hand and the distributor moves with it. Does this mean I am definitely chasing an electrical gremlin? I don't see any additional fuses in the power lead to the fuse box. the purple lead from the ignition to the starter seems intact. The underhood wiring is such a mess, I'm not sure where to start. your ideas are welcomed. thx
 
Captain Dave said:
The crank will rotate by hand and the distributor moves with it. Does this mean I am definitely chasing an electrical gremlin? I don't see any additional fuses in the power lead to the fuse box. the purple lead from the ignition to the starter seems intact. The underhood wiring is such a mess, I'm not sure where to start. your ideas are welcomed. thx
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If you have an aameter, there are two inline fuses in the wiring for it. They are between the alternator and the fuse block. I think they were encased with rubber sleeves on the wires.
 
^ Yes,those fuse holders look much like the plugs back at the rear bumper for the licence plate lamps..
My 72 K5 had both those fuses blown,corroded,and it only stopped the amp meter from working though..not sure what else that circuit may power however..

Just because a test lamp lights on both sides of a fusible link doesn't mean it's any good--it may be so corroded or half burnt it can still light up a bulb,but try and pass any heavier load thru it and it may not allow it to pass thru..

I would try jumping the solenoid now that you know the engine is not seized up..if it spins over then,you'll have to trace the wiring back to the junction block on the firewall and see where the fault lies..
 
Good news! I found the two fuses in the rubber holders. unfortunately, I broke both of them trying to get the rubber holders apart. Replaced both fuses. with the distributor off and coil wire disconnected, i had my wife bump the ignition key. I was trying to see if there was power to the purple wire that goes to the starte IMG_1822.JPG r. Suprise to me, when she bumped the key the starter tried to engage. I put the distributor back together, cleared the decks and cranked the motor for real. It started right up and sounded great. I think i dodged a bullet. Is there anything else i should check? Can i chalk this up to 50 year old fuses and holders?

thanks to all of you that posted. Your involvement certainly expedited the repair to my truck
 
Looks beautiful!

Yup, just old fuses/holders/wires. Probably not the last time you'll run into a wire issues, but overall it's not hard to deal with.
 
Captain Dave said:
Good news! I found the two fuses in the rubber holders. unfortunately, I broke both of them trying to get the rubber holders apart. Replaced both fuses. with the distributor off and coil wire disconnected, i had my wife bump the ignition key. I was trying to see if there was power to the purple wire that goes to the starte View attachment 271809 r. Suprise to me, when she bumped the key the starter tried to engage. I put the distributor back together, cleared the decks and cranked the motor for real. It started right up and sounded great. I think i dodged a bullet. Is there anything else i should check? Can i chalk this up to 50 year old fuses and holders?

thanks to all of you that posted. Your involvement certainly expedited the repair to my truck
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Nice looking Blazer! :thumb:
 
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