patricklav

iTrader: (7)

Hey guys,
Here's my latest dilemma. After I finally nailed down my timing and got the right jetting. I have another issue.
The car was starting and running pretty good each time I started it this week, however yesterday it wouldn't start. It was turning over fine and had good fuel pressure but no spark. Timing gun didn't light up as it was turning so I pulled number one plug and turned it over and it didn't spark either. I checked for voltage at the wire going into the distributor and got 11.88 volts.

this had had happened a few weeks ago causing me to swap out two distributors and eventually buy a brand new one.

I'm confused, I have voltage and all new distributor, cap and rotor but power isn't getting to the plugs.

Any ideas on what I can try here?

Car is a recently rebuilt, carbureted 350 with TBI wiring.

thanks

antares57

iTrader: (8)

Have you had the ignition control module checked or replaced. Mine was cranking but no spark. Autozone checks them for free. Good luck.

vetteoz

iTrader: (13)

Checked the coil
Plenty of online diagnostics available

http://www.speedyjim.net/htm/spark.htm
http://www.clarks-garage.com/shop-manual/ign-04.htm
http://www.aa1car.com/library/no_spark.htm

Means little this days with el cheapo parts made off shore

patricklav

iTrader: (7)

Interesting, the first time I tested the spark at the plug it was not touching anything metal and it didn't spark or light the timing light. Afterward I put the spark plug on grounded metal and it did spark and the timing light lit up. Looks like somehow my engine block isn't grounded properly because the plug will fire when laying on grounded metal but not inside the block. Im going to check my ground wire to see what the problem is.

I currently have a ground wire from the negative battery terminal to the frame, and another wire to the block by the starter. I have had starter problems I n the past so maybe the ground wire isn't seated properly.

patricklav

iTrader: (7)

I ran another ground wire from the battery to the engine block and still no spark. I tested the ground on the block with multimeter and it checks out fine. I also checked the coil and get 12 volts inside the cap. For some reason im not getting a ground on the heads it appears. I even tried running a ground wire from the battery to the head and still nothing when it turns over.
Im not seeing any loose wires touching anything on the engine so im baffled.

Anyone got any ideas? After a lengthy restoration this is the last thing holding me up.

Ransford2987

I've added the positive and negative batter cable diagrams from my 90 Camaro manual, which should be the same. Maybe that will help? I've read your post here and I'm not sure how you're losing spark. Check the resistance to ground with the each head. They should be the same as the block, but you never know. Or you could try and jumper the battery to the head with some jumper cables just to see if you get a spark, but that's a little dangerous I guess.

vetteoz

iTrader: (13)

The plug body has to be touching a battery ground somewhere ;if the plug doesn't have a path to ground it will do nothing as you found out

Not uncommon.
Your spark may be "strong" enough for you to visibly see on the outside but too "weak" to fire when covered in fuel under pressure inside the cylinder

patricklav

iTrader: (7)

That makes sense. What would cause a weak spark? Too large a gap? In have them gapped at .55 right now. I checked the entire distributor , cap and rotor and everthing is getting voltage and grounded properly so it could be a weak spark like you suggested. I have vortec heads and the plugs came gapped at .65 out the box. I lowered the gap to .55 but now I'm wondering of the HEI can support that gap.

Ransford2987

Check the label on the hood, as I think it's .035" (I looked it up after: http://www.iroczone.com/2009/10/1990...pecifications/). You can also check the resistance to the plugs if you're worried about that, but one or two spark plugs with a higher resistance wouldn't cause a no start.

InfernalVortex

iTrader: (4)

.055 seems high. I think I normally gap around .040. I'd tighten the gap a little to see if it helps although I doubt that's the root of the problem.

vetteoz

iTrader: (13)

Plugs are not gapped from the factory.
One spark plug number may fit many different makes and engines , all with different requirements
You have to gap them to the listed spec to suit your particular application.

Arizona IROC

iTrader: (4)

A friend of mine had a similar problem but all I had to do is take off the cap and unhook all the wires feeding the distributor and coil, blow them off with the air hose and hook them back up.
Look around for any obvious corrosion, shorts or carbon and make sure there are no pinched wires.
I never did find out what the problem was because it started right up when I was done and hasn't failed since.