no spark

[7d2k5]

new coil , plugs wires, rotor ,cap, points, checked wiring from coil to starter, still no spark- looking for suggestions

[trz1000]

A few thoughts:

Did you have spark before changing everything?
Did you change the condenser as well? If not, change it.
Points clean?
How are you checking spark? I like using a timing light as opposed to grounding the wire. Also, check spark at the coil then at each cylinder.
Wires tight with clean connections?
Make sure the points are making good contact, i.e. closing fully.
Did you pull the distributor?

[7d2k5]

no spark before , have not pulled distributer ? for what reason?

[VanceH]

Very dumb question but it happened to me, have you checked the battery?

[trz1000]

The reason I asked if you pulled the distributor was if you had I was wondering what the drive gear looked like and also to see if you were sure it was meshed with the cam after re-installation.

Can you spin the rotor by hand? You should be able to move it a bit as the mechanical advance stretches but it should not spin freely. Don't force it if you can't move it.

How was the truck running last time you had spark?
What happened, if anything, that resulted in no spark?
Have you checked for 12v at the coil? There is a resistor between the starter and the coil, maybe it broke or the wire has a break.
Are any fuses blown?
And as already mentioned, is the battery up to snuff with good clean cables and such?

I feel your pain, ignition problems can be tedious.

[7d2k5]

thanks for replies, battery is not real strong but was jumping it & had plenty of power to turn over... will check rotor , have not had truck running since i bought it ... it turns over well when i purchased it i really believed it was points... had a spare harness & replaced yellow from starter which merges with yellow to coil & both join red @ firewall but no resistor in there? also which fuses would affect ignition?

[litebulblsc]

Seems like time to upgrade to HEI.

[VanceH]

Ok first i am not a mechanic, so not sure how much i can help, but i will throw things up there anyways, there is a small black box on the drivers side fender?? Not sure what its called, i lost it a while back and had no spark. if it was me i would try using a volt meter from the battery back, might be a broken wire?

[VanceH]

Ok i also forgot to ask what is it your working on, What year?? also do you have any pics of the engine compartment, maybe someone could see something that you are missing??

[trz1000]

I've re-wired my Jimmy with a late model universal harness and don't recall the original fuse layout. However, here is a link to some wiring diagrams that should help.

http://67-72chevytrucks.com/vboard/s...d.php?t=185856

Since you've never had it going you need to start at ground zero. The absolute first step is to see if you have 12v at the coil. If you do, check to see if the coil is firing by attaching a timing light to the coil to distributor cap wire, hold the trigger, and crank the engine. If the timing light doesn't blink then the coil isn't firing. If the coil is firing, then check each cylinder in the same fashion.

If the coil is not firing make sure that all of the wiring in the ignition circuit is correct. Usually it's pretty easy to tell if someone in the last 40 years has done some hacking to the wiring. If something even seems out of whack, make it right. A little re-wiring can go a long way.

If the coil is firing and the distributor is not check it out real good. Wiring, rotor, points, etc. as I described before.

Now, if everything checks and you're getting spark but the motor still isn't firing then you've got another problem. If that's the case you need to check the fuel system first then suspect the ignition system again. Distributor could be 180 out or the timing could be so far off that it won't fire. Lots of other stuff too but we don't need to speculate just yet. Find out what IS working then we can work on what's not working.

I'm not a fan of just throwing parts at a problem but I do agree, since you're going to be doing all of this ignition work it's a good time to upgrade to an HEI. Another option would be pertronix or an aftermarket complete ignition. I run an MSD 6A box and Pro billet distributor on all my rides. Can't say enough good stuff about this setup, but it's an expensive route and quite honestly over kill for most applications. Looks good under the hood though.

[Jtrux]

Hmmmm, let's see. I've been here many times before. For a points system to operate properly they should only have 12 full volts during starting, at all other times the coil should only receive approximately 9 volts. Many people mistakenly run a wire directly from the battery to the coil which will foul the points. I don't recall how the voltage is reduced (i've upgraded to HEI...hint, hint, hint) but it can either a built in resistor in the wire or a ballast resistor maybe bolted to the firewall. My wiring was all hacked up and I had a direct 12 volts hooked up to my coil so in order to correct it I ran a ballast resistor inline to the coil to reduce it and I also ran a wire from the starter solenoid (cannot remember where to hook it, maybe the "S" terminal but not 100 percent) to provide 12 volts during starting because during starting the starter uses lots of juice and if the coil only had 9 volts during starting you have issues getting it to start.

Anyways my recommendation would be to go through and check all the wires and possibly run you're own so you know that they are done correctly and if you still have issues then we'll have to do some more trouble shooting but in the mean time check the wires providing voltage.

[1972 Banana]

Double check your points as well,make sure they are opening and closing! If they are not the field can not build up in the coil and fire! I have seen this more than once due to te screw not being tightened or the points not beeing set with them at their highest point!A quick way to eliminate the rest of the wiring is use a jumper to the wire conector on the coil that has the wire from the starter(+ terminal) The negative goes to the points!Then check again for spark or just try to start it. If timing is to far off with spark it will spit back through the carburator. If it does start and run disconect that jumper,if it dies your problem is in the rest of your wiring! Make sure the truck is in park as this will jump out any neutral start switch! You might also sand your points in case they are burnt.



not trying to insult your intelignce or anything but I have walked away before frustrated as all get out and come back and went OH theres the problem!

Hope this helps

[7d2k5]

thanks working on a 72 original 350 no pics right now , when i first tried to start it , it did backfire thru carb , then noticed dist. was loose & moved it a little at a time ... does jumper wire go from + on coil to ??

[RustyParts]

If you've never had it running and it's spinning over easy, could be timing chain has slipped. I hope not, but good luck.

[71RestoRod]

It's common for the wire going into the distributor to get worn and frayed under the advance mechanism or at the grommet thus grounding out on the distributor housing. Disconnect the wire at both ends and use an ohm meter to check continuity across both ends and then against ground to check for a short.

[D.PASSMORE]

Went through this yesterday, from base knowledge I went through the above actions. No ground to - side of coil. I cleaned the points contacts (w/fine emory cloth) and she fired right up.

[trz1000]

I guess I'll come right out and ask it, are you sure you don't have spark?

If you've moved the distributor then the timing is off. No ifs, ands, or buts about it. Could easily be off so much that it'll never fire. If you for certain don't have spark, fix that first then you need to static time the engine to ~ 10 degrees BTDC. If you have spark and fuel, it should start at 10 BTDC even if the dwell is out of whack. You will have to adjust the dwell angle, timing, and idle once it fires as it most likely won't be drivable at that point. Don't forget to set the point gap as well.

Now, if you're timed right, have fuel, spark, and it still won't start then as previously mentioned you need to start suspecting the timing chain. It's easy to verify but you have to pull the water pump so you can pull the timing cover. It takes a little time but even if you end up having to replace the timing chain and gears it's not too difficult. Like most anything, just go slow and make sure you're doing everything right the first time.

If you don't know how to do some of this stuff no worries, there are lots of folks here with the know how to get you going.

Good luck!

[7d2k5]

ok, still need help , yes i plan to switch to hei but i still feel it is a wiring issue so that needs to be solved first, the black wire that comes off the capacitor behind coil? does this go to + or - & could a bad capacitor stop spark? also there is a larger gauge pink/red wire that wire connects to fuse box & i believe it is marked IGN. not fused this goes to pass side of firewall & is not hooked up it terminates close to a brown w/ white stripe wire mated w/ a green one & they have a slide on clip on the end ( ac wires)?
thanks

[trz1000]

If you're going HEI in the near term just do it now and get this headache behind you. You'll have to do some re-wiring and static time the motor to go HEI so you'll eliminate some of your potential problems by default. Why go through all the trouble to get the points working if you're going to scrap the system anyway?

The electrical system on these motors is not very complicated but nevertheless, wiring diagrams are very helpful, indispensable really. If you don't have them, print out the diagrams I linked to before or go buy a service book (Haynes, Chilton, factory service manual, etc.).

I'm not an HEI guy, I run MSD pro billets so I won't be much help but there are plenty of guys here that have done it. Try a search, I'm sure there are plenty of threads on it.

Don't get discouraged, I can't count how many times I asked myself why I bought this POS while wrenching on my Jimmy in the last few months. Bought it in February and it's been a knockdown drag out ever since. Did body mounts, found I had a bunch of shimming to do. Replaced front cab supports and torsion boxes. Chased down a huge tranny leak (ended up the fluid was weeping out around the dipstick tube). Got tired of sorting through the hacked wiring so redid the whole rig. Welded up new bumpers. New ignition system and carb. Fabbed up a complete exhaust system. Lots and lots of cleaning, floor shifter, seats out of a 68 couger, started to align every body panel and undoing a lot of the PO's handywork.

Still have tons of work to do, couple spots on the floor, sound deadener, carpet, and stereo. Panels need more alignment work. Oh yeah, have to do some work on the windshield frame. That'll probably be one of the few things I'll contract out.

Been looking for one of these for a long time, this one came up for a real good price so I jumped on it. Prematurely as I have a Galaxie project on the rack and a tractor project taking up the rest of my shop. So I did all of this in half of my garage laying on the floor or sitting on the passenger side inner fender. Took a lot of fun out of it, but I had a short time line to get it on the road so did what I had to to get the job done.

But Sunday I finally got the torsion boxes welded in and the top off and I'll tell you what, every headache, busted knuckle, and burn was well worth it. I don't think I've stopped smiling since taking it for the first cruise topless.

So hang in there and keep cracking on it. There is nothing like the satisfaction of solving a big problem that you almost gave up on.

[old man jimmy]

That "capacitor behind the dist." is just for radio static. You don't even need it at all. Mine has been gone for so many years I don't remember even where it hooked to. But the condensor inside the dist. can kill your spark for sure. If you replaced points you should have replaced that also. Matter of fact the condensor can do some really funny things to the way an engine runs.

[litebulblsc]

With HEI, I just ran the single wire to it from the fuse block where it is labeled Ignition. That is it, the HEI is wired in. I think I read that you also need to run the internally regulated alternator, which helps cut down on the amount of under hood wiring.

[roger0080]

I had a bad condenser that caused no spark. Replace condenser and it fired right up.

[underdogkev]

So, I have a simmilar problem with my 72 GMC 350. No spark from coil. Problem seems to be a power issue. I only have 5 volts at the positive post on the coil. Have tried many solutions. None working. I have twelve until the final conection is made. That being the red wire from the neg post on coil to the points. with that wire off I have 12 volts and I now thats too much but when I make that connection it drops to 5 volts. I have changed wire. Same thing. I have done a complete tune on truck. Re timed complete. All new parts except distributor. New rotor, cap, plugs, wires, coil, resistor, points and condenser. Truck ran poorly before tune at higher speeds, so thus the tune up but like I said now I dont have any spark from coil and some strange power loss issue. Kicing myself now but wish I would have gone HEI. Wife wouldnt let me, its "her" truck and wants to keep original.
Any help would be greatly appriceated. Thanks guys!

[7d2k5]

paid $35 for hei fired right up, hei is an original application late 74 on vettes, 75 all