She died......
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Joined: May 2011
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She died......
She died on the freeway..
1986 suburban
4x4, 5.7/th400
carburetor
Man oh man....
I was driving down the freeway going 70 mph and all the sudden it died... threw it in neutral and started it again and all it did was let out a huge backfire.... got it towed home at 1 AM....
In the last six months i did a full tune up (cap, rotor, plugs, coil, wires, fuel filter, etc, etc)...
I've been messing with it all day today, but all i can get it to fire briefly, then sputter out, all the while slightly backfiring and coughing out the carburetor...
I am sure fuel is pumping, but need someone to help me confirm the spark, but being that it keeps starting and backfiring, i would assume that the spark is fine....
I noticed today that the muffler blew it top off when it backfired on the freeway! I've never seen that before! That musta been a hard backfire!
I would guess that the timing chain advanced..... what would you guys think???
Any idea fellas????
4x4, 5.7/th400
carburetor
Man oh man....
I was driving down the freeway going 70 mph and all the sudden it died... threw it in neutral and started it again and all it did was let out a huge backfire.... got it towed home at 1 AM....
In the last six months i did a full tune up (cap, rotor, plugs, coil, wires, fuel filter, etc, etc)...
I've been messing with it all day today, but all i can get it to fire briefly, then sputter out, all the while slightly backfiring and coughing out the carburetor...
I am sure fuel is pumping, but need someone to help me confirm the spark, but being that it keeps starting and backfiring, i would assume that the spark is fine....
I noticed today that the muffler blew it top off when it backfired on the freeway! I've never seen that before! That musta been a hard backfire!
I would guess that the timing chain advanced..... what would you guys think???
Any idea fellas????
Administrator
Joined: Apr 2006
Posts: 11,337
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From: KC, MO area
Welcome to the forum.
Before I read the rest of your post, timing chain was the first thing I thought of. But I think if it slipped a couple of teeth, it would retard timing. Which could actually cause ignition as the exhaust valve is opening.
Before I read the rest of your post, timing chain was the first thing I thought of. But I think if it slipped a couple of teeth, it would retard timing. Which could actually cause ignition as the exhaust valve is opening.
Thread Starter
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Joined: May 2011
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all right fellas! I got the timing cover off and set everything to TDC, but the rotor in the damn distributor is pointing at cylinder FIVE, not ONE.
So, the timing chain and gear/sprocket all look solid with little play at all, and no teeth are missing... I am guessing that I should pull the distributor out and check the gear on the end of it....
Well, I guess the first question should be: How much play should there be on the timing chain?
What would you fellas recommend?
So, the timing chain and gear/sprocket all look solid with little play at all, and no teeth are missing... I am guessing that I should pull the distributor out and check the gear on the end of it....
Well, I guess the first question should be: How much play should there be on the timing chain?
What would you fellas recommend?
Last edited by burbinman; May 22, 2011 at 1:43 PM.
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Joined: Apr 2006
Posts: 11,337
Likes: 194
From: KC, MO area
Timing chain should be tite. So you're saying that the punch marks on the crank gear and the cam gear line up? I suspect the chain has jumped several teeth unless you find something wrong w/ the dist. gear.
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Well, i finally found the time to work on the truck again. LOTS of work = NO TIME to play with truck.
So. this is what i found. The timing marks are lined up 12 o'clock (cam) and 12 o'clock (crank). This is a DTC piston #1. Is this right? I heard that this should be 6 and 12 as opposed to 12 and 12.
So. this is what i found. The timing marks are lined up 12 o'clock (cam) and 12 o'clock (crank). This is a DTC piston #1. Is this right? I heard that this should be 6 and 12 as opposed to 12 and 12.
Last edited by burbinman; May 30, 2011 at 12:32 PM.
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Is this normal?
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Joined: Apr 2006
Posts: 11,337
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From: KC, MO area
I thought the cam gear should be at 6:00 and crank gear at 12:00 or IOW pointing at each other.
Bottom line is that when #1 is at TDC, both valves should be closed.
And yes, you need to do a compression check or pull the valve covers to ensure no bent valves.
Bottom line is that when #1 is at TDC, both valves should be closed.
And yes, you need to do a compression check or pull the valve covers to ensure no bent valves.
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Joined: Apr 2008
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From: Austin, Texas
I too believe that they are supposed to point at each other, that is how you know its lined up...
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