1meanGTA

you guys are going to love this. i was driving to a dr appt yesterday, when all of the sudden the check engine light comes on, and about 2 seconds later the car dies. i pull it into some ladies driveway, try to start it and it just cranks. could smell gas, so im pretty sure it isnt a fuel problem. i tried to check the codes and all it gives me is 12. i tried starting it quite a bit, and for the most part it just cranks but 2 or 3 times it sounded like it wanted to start, sounded like it normally does starting for maybe a second, then died. well the 3rd time it did that, it backfired, and blew my flowmaster 80 series muffler apart! one just gaping rip in it and a smaller hole maybe an inch around. now i've never had any sort of trouble with the engine backfiring, or ignition trouble before. i checked most of the wires, and none of them showed any spark. i believe my motor runs about 9.8:1 compression based on what the previous owner told me, anyone heard of a motor just blowing the muffler while being cranked? how do i go about diagnosing the ignition and pinpointing the problem? thanks a lot,
Shaun

Token

odds are your timing is off. I *just* made a post about timing.

https://www.thirdgen.org/techbb2/sho...hreadid=285988

1meanGTA

how would my timing being off make the car just die like that after running fine?

86z/92rs

How many miles on your engine? Try taking your valve cover off and visually inspect the components on the heads. Turn motor over and see if valve train is working correctly.

84 Restore

You prolly jumped a timing chain. It will make it go out of time and then you put gas out the exhaust and an imtermitten spark and bang. You might want to check the valve train like token said when these thing back fire like that they can do damgae to a valve. If you have a lot of miles on the motor the timing chain spoket is plastic and wears out and you can jump a tooth or two.

Brazen

Do as these other members said, and check that valvetrain for operation.... if something looks amiss or you have a loose pushrod, etc., you "may" have wiped a lobe on the cam, or possibly have a collapsed hydralic lifter. This will cause severe backfire (seemingly out of nowhere).
If it backfires out the carb/plenum, it's an intake lobe, backfires out the exhaust (as in your case?) it's an exhaust lobe. Hopefully this isn't the case though... best of luck.
Jim

Lo-tec

Do a search to find out how to diagnose a no spark condition and start from there. Don't pull a valve cover or anything else.

No spark=gas pumping out exhaust while cranking=BOOM.

Fix the ignition problem and you should be fine.

1meanGTA

the car has about 80k on it. except for the block and intake, the rest of the motor has about 13 or 15k on it. i'll get a picture of the muffler after i get the thing running again, and get it taken off of there, its pretty funny. how can i go about checking the coil? i checked the short plug wire that connects the coil to the distributor, and there was no spark there, should i remove the coil and take it into autozone? does there not being spark there rule out everything in the distributor? im thinking its the coil, or the ecm, but i know squat about ignition systems, so im just taking my best guess.

1meanGTA

also, there must have been a spark to blow my muffler, would that point to it being the timing? or can a bad coil/ecm or whatever still give a spark every now and again?

Brazen

I believe you use a digital multimeter and check the resistance (ohms) of the primary side to test a coil. I just had an ignition module go out at 80 mph and it just stopped running... this was on a 91 w/remote coil/small distributor.
Jim

92MaroRS

pull the cap off of the dist. see if rotor turns when you crank the engine. ive had the gear shear the pin holding it on.

1meanGTA

ok, i pulled the ignition module and coil out of the car, going to autozone later to have them checked. underneath the distributor cap i notice a buildup, looks sort of like dirt, on the pickups for each cylinder. is this normal? looks like it is right where the rotor comes around.

Damon

Put a new cap and rotor on it. My first car was a 69 Pontiac Catalina and it had a hairline crack in the rotor. Sometimes the motor would just "shut off" for no particular reason. I'd crank and crank it and then finally- BOOM! Another muffler bites the dust.

New cap and rotor are cheap insurance. Having cracks and shorts in caps/rotors these days is a lot more rare than it used to be in "the old days", but it can still happen.

Do what you can to clean up that dusty dirty crud that build up all over the pickup. They call get like that so it's what I'd call "normal" but that doesn't mean you should just leave it there since you've already come this far.

1meanGTA

autozone said the ignition module was alright, but couldnt tell me for sure about the coil. said the specs for a stock 87 coil on the second primary would be 6 and mine tested 5.37. they said the 1st and 3rd were normal though, does anyone know whats normal for an msd coil? i dont really want to replace more than i have to, the whole ignition system is msd, its pretty nice and i dont want to just spend a bunch of cash, my insurance is almost due.

im thinking the coil is alright though, so i want to check out the rotor.

pull the cap off of the dist. see if rotor turns when you crank the engine. ive had the gear shear the pin holding it on.

i'll have to retime it after this though right? i've never timed a motor before and would have to buy a timing light, but im a fast learner and want to maintain the car myself as much as i can. any suggestions on timing lights? i saw a craftsman professional at sears for 70 bucks that looked pretty nice, do you need a good one, or will any one do? thanks,
Shaun

92MaroRS

pulling the cap off will have no effect on timing, if that gear did shear the pin then there is no way around it the dist. will have to be pulled an repaired and will need to be timed anyway. but if its not broken and the rotor does spin the motor doesnt need to be retimed

1meanGTA

i checked the short wire from the coil to the distributor with a wire tester light, and it wasnt showing any spark. had the coil tested and im pretty sure its good. where do i look next, the ecm? ordering a gm service manual today, so i dont have to keep bothering you guys with all this basic stuff. lookin forward to hearing that nasty blown open muffler idle

92MaroRS

that means either the distributor or computer isnt sending the signal to the coil to fire. as i said before pull the cap off and turn the engine over and see if rotor moves.

notmuch

You should check the input wires to the coil and see if you have power there. If not keep checking backwards until you find power on that circuit and then you will find where you are losing it.

Don't waste your hard earned money just throwing parts at the car, that will only fix it by luck. Trace the problem down and fix it at the source.

Your muffler is what we call around here a "key bomb". We take our winter beaters, rev em up, shut em off, pump the gas, and hit the key and watch people duck for cover. Laugh for hours when your not blowing up a car you care about.

Good luck, work at it systematically and you will find it. Don't try to skip steps or you may skip the problem.

Jeff

Brazen

Heh... that brings back 20 year old memories! [BOOM!]

Jim

1meanGTA

ok i pulled the cap, turned it over and the rotor kind of jittered, maybe half an inch, but didnt turn. so i'm thinking 92maro was right and it sheared a pin. so i guess now i have to pull the distributor right? can a performance shop fix this for me, or do i have to send it back to msd? also, what should i use to clean all that crud off the pickups, alcohol? thanks again, you guys are loads of help

1meanGTA

ok i pulled the cap, turned it over and the rotor kind of jittered, maybe half an inch, but didnt turn. so i'm thinking 92maro was right and it sheared a pin. so i guess now i have to pull the distributor right? can a performance shop fix this for me, or do i have to send it back to msd? also, what should i use to clean all that crud off the pickups, alcohol? thanks again, you guys are loads of help

now i've got the distributor out, but im not sure what im looking for to diagnose a "sheared pin." from what i can tell, it looks pretty solid, i was expecting to see something broken or obviously out of place, but it looks alright to me.

Lo-tec

Hold the gear at the bottom and the rotor at the top and see if they will spin independently. Also, do the teeth look chewed up on the distributor gear? If not look down at the cam gear in the engine and see if it is chewed up. How long did you crank the motor? Just bump it once or let it crank for a couple of seconds?

1meanGTA

i guess i didnt look hard enough, the gear teeth are chewed all to hell, about half of them on one side are just about gone. i probably spent at least 30 seconds trying to turn it over, on a few different tries. i couldnt get a good look at my cam, is it likely it looks just as bad?

Lo-tec

You'll need crawl on top of the engine with a flashlight to get a good look at the gear on the cam. Sounds like the wrong gear on the distributor. What kind of cam? (stock or aftermarket)

I would call MSD and see if they can help in getting the correct distributor gear.

1meanGTA

its a zz4 cam, i was looking straight down, and i could see through the oil but didnt see any gears. summitracing has msd gears, bronze for 45 and 60, and iron ones for about 25-30. is it worth it to go with bronze or does it matter? could a wrong gear have worked alright for 13-15k miles? then all of the sudden go out?

Lo-tec

DON'T GO BRONZE. GM uses a "melonized" gear for it's factory roller cams . This should be what you need. I would check with MSD (have part # of distributor handy) and ask them what comes on your distributor. I would bet it is for a regular flat tappet cam. See if the GM gear will fit on your distributor and get one (unless they sell the equivalent).


And change you oil filter...all that crap is in it (hopefully)!

1meanGTA

by the way, how do i shrink pictures down so i can post some smoky burnout pics?

Lo-tec

Resize them (600x800) etc.

1meanGTA

could someone recommend a freeware program to do that for me, or resize a couple for me please?