Carb problems? Or Ignition?

[orange72350]

My truck died on me the other day for no apparent reason. After some digging, i realized that there was no spark./ replaced the hei module and the rotor. the truck started then. but only when the choke was open. it idled fine. but really wouldnt run really well under load. it would cough and sputter. so, i parked it on the driveway, and 2 days later, ui went out 2 start it. nothing at all. so, tonite, i drug it in the garage, and started reaplcing stuff.'i did the cap and the coil. it started, but agian only on the choke. so, now it runs, but it bakcfires like a mother and rattles and shakes the crap out of the engine. What gives here? something isnt clicking for me, and im sorta new at this? btw, the engine was running fine until it just died. COuld u guys please help me? yer my last hope before getting raped by a dealership. i really appreciate any help i can get. Thanx alot
dale

[beau396]

If I had to guess, and I am, it is timing either ignition or cam timing. How old is your timing chain set? Also check and see how much voltage the HEI is getting from your ignition, if it is really low it will run like that.

[beau396]

Oh and check the firing order of your wires on the cap. Remember that GM numbers there cylinder different from Ford.

[orange72350]

I dont know how old the timing chain set is. the truck is fairly new 2 me. How would i voltage test the hei? run a meter 2 the yellow wire that goes into the coil? Shouldnt a guy have seen timing problems like this coming though? i dunno, but the truck has been great for the last six months, and now bang, it sucks!!

[orange72350]

how does a guy check the firirng order on the cap? i changed out the cap, and just put the wires in the same place as on the old cap. Is that a big no-no? or is the cap numbered as 2 whcih wire goes where?

[dmurphy68]

I had the same problem on my 70 chevelle the timing chan was wore out and it jumped time on me replaced it and set timing and every thing was fine after that

[orange72350]

when yer timing chain wore out, did it just go out over night or slowly over time? im just sorta suprised that all of a sudden something is out of wack, not slowly over time. btw, is changing a timing chain a big deal?

[dmurphy68]

It started acting funny a day or two before but paied no att to it because i put cheep gas and just thought that was my prob. Did you check your firing order? it really sounds like it is out of time but it might not be getting enough spark. As to answer your question about checking the spark there is such a thing as a spark plug tester. It looks like a glass vile. you can pick it up at most higher end parts stores . p. s . the firing order is 1-8-4-3-6-5-7-2 hope this helps
Darren

[O'l Buck]

Normally when a timing chain jumps a cog, it goes all at once, like you described. It will cause it to do all kinds of funny stuff, like fire on an intake or exhaust stroke, or in between. What kind of carb do you have on it? if it's a double pumper holley, you most likely lost your accelerator diaphragm when it backfired. It could also be in the distributor itself, there's a roll pin that holds the drive gear on the shaft, it could have sheared off and is only catching part of the time. If it turns out to be the timing chain, which is very possible, it does take a bit of work to replace it. You have to pull the fan, waterpump, all accessories from in front of the engine, crank pulley and harmonic balancer, timing cover, and finally you get to the timing set. When you replace it, make sure the sprockets line up vertically, because if they are offset at all, it will cause the chain to fail early (and also be noisy). Make sure the timing marks are aligned between the crank sprocket and the cam sprocket.

[c-tenkid]

Yep sounds like jumped time to me to.

Old buck gave you good instructions on replacement.Just make sure you get it lined up properly when reinstalling it.


Also I learned a trick a guy that races stock cars told.If you snipe a little bit of the flange that holds the front of the seal on the timing chain cover.You can reinstall the timing cover without dropping the pan.I also held the seal in the timing cover with a little rtv.I had to lightly tap on it with a mallet.But it went in there.And didn't leak.So I was happy.Even though less than a week later I pulled the pan to replace the gasket anyway.


Isn't that how it works?

[Longhorn Man]

hmmm, with the choke pulled...not to be a smart @ss....but is there a chance that your out of fuel too...maybe a bad fuel pump or messed up carb.
Try opening the choke, and pouring a little gas in the carb. see if it'll start.
If nothing, you're out 15 min of your day.

[orange72350]

Thanx fer all the help guys. I gotta go to school today, but tonite im really going 2 dig into it and get it figured out.