Weird Timing problem

[North Coast Hotrod]

I have a 1989 chevy TBI 350. A couple of weeks ago I had to replaced the module in the dist, because of backfiring thru the exhaust (checked timing and all was fine). After I replaced the module the truck ran great. I pulled my 3200 lb boat around for a few days with no problems. I parked the truck. The next time I went to start it, It backfired thru the TBI. The timing seems way off. I pulled the # 1 plug and cranked the engine to get TDC on the compression stroke. When I pulled the cap, the rotor looks like it is pointing to about 2 oclock, when number #1 position is at about 5 oclock. Does this sound like timing chain and gears? Could they go just shutting the truck off like that? The engine has about 90,000 miles on it.

Thanks
Paul

[gremlin96]

sounds like your ready for a timing chain and cam. the cam will have a flat spot on it.

[fuzzypuppy]

I had to replace my chain due to wear at 120k, it was runningf strange and I tried to time it only to find I could not because the timing was jumping around so bad, after I pulled the cover I found the chain so sloppy I was suprised it ran at all, cam was ok but I installed a new mild cam just because it was already tore down a cam is pretty cheap and the new cam helps mpg and performance.

[Rs051802]

When you timed the truck did you disco the timing advance. It should be on the passenger firewall. A brown and white wire I believe running into a harness. You have to disco that wire first, which will remove your advance. Then time it to zero, shut off your ignition, and replug that wire. While the wire is unplugged you will register a code. That is the only way to time these trucks exactly. The ignition needs to be off when you disco the wire. Start it, time it, kill it, reconnect. When you reconnect the computer will advance appropriately.

[fuzzypuppy]

Yes the chain can jump a tooth on a shut off, that is often when chains go, at startup or shut down

[Blue Bowtie]

At only 90K miles, the chain and sprockets should be fine, unless you're using something like Quaker/Pennzoil and not changing it every 1,500 miles.

After 1987 (beginning of roller blocks), SBCs stopped using the nylon toothed cam sprockets in all applications, IIRC. The cast cam sprockets are usually good for a couple hundred thousand, and chain stretch with a stock cam should be minimal IF lubrication is adequate.

I'd bypass the ESC and verify the wire position/firing order. If the chain is truly stretched, you can check that with the distributor cap off. Observe the rotor while you rotate the crank forward and backward. There should be no more than a couple degrees crank motion before the distributor starts to turn with it.

Avoid "street roller" chains or any non-true roller double row timing sets, or you'll be right back at the chain in 30,000 miles. You'd be far better off with an inverted link chain and steel/iron sprockets.

[fuzzypuppy]

I bought my truck used and at 120k the chain was gone, I replaced it with a true double roller.
I did not notice the 90k in the post, but it still could happen. easy check though too.
Did you pull the dist to change the ign module? if so dist off a tooth?
Bad ign module,