New engine, little to no spark! - Team Camaro Tech
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post #1 of 16 (permalink) Old Aug 19th, 14, 05:26 PM Thread Starter
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Chris
 
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New engine, little to no spark!

The 302 is ready to fire-up for the first time. EVERY part from oil pan to carb is new. It has original style plugs,wires,cap,rotor,points distributor,and coil. All the parts came from HeartBeatCity. The problem is seemingly very weak spark at the plugs. Once in a while you get a nice blue spark while cranking, but mostly it's very small or not at all. This what I've checked so far;

* Brand new fully charged battery
* 7 volts to coil in "run"
*11 volts to coil during "crank"
*Timing set at 6* BTDC
*Points gap set at 19 thou

I tried the new coil on my truck and it started my truck fine, but my truck gets constant 12V to the coil. So, I put the coil back in the car and ran a 12V jumper wire from the battery, still no good. If I put a spark plug directly into the coil wire, I get decent spark! I'm not sure if it could be a bad condensor in the distributor that could cause this, so I've ordered a Pertronix module to replace the points and condenser.

I just want to spend extra money when it could be something simple that I have missed.

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post #2 of 16 (permalink) Old Aug 19th, 14, 07:09 PM
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Re: New engine, little to no spark!

what wires do you have to the coil? Sounds like you are missing the resistance wire one. If I remember right it supplies the constant 12 volt power for start.


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post #3 of 16 (permalink) Old Aug 19th, 14, 07:20 PM Thread Starter
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Re: New engine, little to no spark!

I have a new wiring harness. There are two wires going to the positive side of the coil, a white with brown stripe (resistance wire) coming from the firewall, and a yellow one coming from the starter solenoid. On the negative side there is a black wire from the distributor, and a brown one (tach signal) coming from the firewall.

I dug an old condenser out a working distributor that I'll try tomorrow. Any other suggestions would be great.


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post #4 of 16 (permalink) Old Aug 19th, 14, 07:46 PM
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Re: New engine, little to no spark!

Quote:
Originally Posted by Z28BUILD View Post
I have a new wiring harness. There are two wires going to the positive side of the coil, a white with brown stripe (resistance wire) coming from the firewall, and a yellow one coming from the starter solenoid. On the negative side there is a black wire from the distributor, and a brown one (tach signal) coming from the firewall.

I dug an old condenser out a working distributor that I'll try tomorrow. Any other suggestions would be great.

any oil or anything on the points contact surface? Condenser grounded?

You hot wired it so that rules out wiring.

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post #5 of 16 (permalink) Old Aug 20th, 14, 08:22 AM Thread Starter
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Re: New engine, little to no spark!

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Originally Posted by Vega$69 View Post
any oil or anything on the points contact surface? Condenser grounded?

You hot wired it so that rules out wiring.
I cleaned the points and get a nice blue spark at the points. Is the condenser supposed to be grounded to the distributor body, or isolated from it?

1969 Z28 RS (building)
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post #6 of 16 (permalink) Old Aug 20th, 14, 09:06 AM
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Re: New engine, little to no spark!

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Originally Posted by Z28BUILD View Post
I cleaned the points and get a nice blue spark at the points. Is the condenser supposed to be grounded to the distributor body, or isolated from it?
The wire connects to the points terminal and the body is grounded.

Jerry G.

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post #7 of 16 (permalink) Old Aug 20th, 14, 09:21 AM
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Re: New engine, little to no spark!

7V to the coil in run? Isn't that low?
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post #8 of 16 (permalink) Old Aug 20th, 14, 09:42 AM Thread Starter
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Re: New engine, little to no spark!

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Originally Posted by alanrw View Post
7V to the coil in run? Isn't that low?
I checked on-line and supposedly the coil is only supposed to get 7-9V while running to prevent the coil from "burning up". That's why there is a resistive wire feeding power to the coil. A second wire does feed 12V to the coil during cranking to start the engine. There is a warning right on the coil that says "To be used with resistive wire"


ANYWAYS!!!! I changed the new condenser for 30 year old one, and the engine fired right up!!!!

I ran it for 20 minutes at 2000RPM to break in the cam. It got a little warm near the end, about 210*. I'll let it cool down for a while and go back out and set the idle and air screws.


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post #9 of 16 (permalink) Old Aug 20th, 14, 11:24 AM Thread Starter
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Re: New engine, little to no spark!

Ok, trying to tune it up now. I have less than 5" of vacuum at idle, something is wrong.
Adjusting the idle air screws did nothing.
Taking the vacuum hose off the distributor while running didn't change the vacuum reading?!
I re-torqued the intake manifold bolts (30lbs) and the carb bolts (12lbs)
I removed the vacuum hose for the power brakes and plugged the fitting.
Timing is still set at 6* BTDC.
It has backfired twice through the carb when I snapped the throttle open.
The headers are ceramic coated, but I noticed the header tubes for #6 and #8 are discoloured. The other 6 tubes haven't changed colour.
I also noticed that the vacuum reading would increase with RPM. I thought vacuum should decrease as the trottle blades opened?
I'm going to try using a propane bottle around the intake manifold to see if I can find a leak.
Any other suggestions would be great. I don't want to run it too much (and risk hurting it) till I figure this out.

1969 Z28 RS (building)
DZ302
M21
12-bolt, 3.73

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post #10 of 16 (permalink) Old Aug 20th, 14, 11:35 AM
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Re: New engine, little to no spark!

I would check your rocker arms. You may have them too tight, not allowing the valves to fully seat. Do you have hydraulic or solid lifters?
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post #11 of 16 (permalink) Old Aug 20th, 14, 01:25 PM Thread Starter
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Re: New engine, little to no spark!

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Originally Posted by gwbutch View Post
I would check your rocker arms. You may have them too tight, not allowing the valves to fully seat. Do you have hydraulic or solid lifters?
I have the 30-30 solid lifter cam. I used the method found on this site to set the valves. I thought the rocker seemed too loose (sloppy)when I set them, so I took a video and went to the machine shop to show their engine builder. He said they were fine? I did some more reading on this site and I've bumped up the timing to 14* and set the idle at 1000 RPM. They engine sounds better, hasn't backfired through the carb, but still only 5" of vacuum. At least now when I snap the throttle open, I get a momentary decrease in vacuum followed by an increase up to about 10" as I snap the throttle closed. Keep the suggestions coming.

1969 Z28 RS (building)
DZ302
M21
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post #12 of 16 (permalink) Old Aug 20th, 14, 05:37 PM
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Re: New engine, little to no spark!

When setting the rocker arms of a solid lifter, they need to be set with a certain lash (gap between the rocker arm and valve). The lash is dependent on the cam. It may be different for intake or for exhaust. There is also a difference in setting the lash with a cold engine and a hot engine. The lash that is listed with the cam is usually when the engine is hot.

Do not set the rocker arms of a solid lifter the same as a hydraulic lifter!
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post #13 of 16 (permalink) Old Aug 20th, 14, 06:32 PM Thread Starter
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Re: New engine, little to no spark!

Quote:
Originally Posted by gwbutch View Post
When setting the rocker arms of a solid lifter, they need to be set with a certain lash (gap between the rocker arm and valve). The lash is dependent on the cam. It may be different for intake or for exhaust. There is also a difference in setting the lash with a cold engine and a hot engine. The lash that is listed with the cam is usually when the engine is hot.

Do not set the rocker arms of a solid lifter the same as a hydraulic lifter!

I set the valve lash at "30 thou" with the engine cold. I thought that was how the 302 cam got it's nickname (30-30 cam?)

The engine starts and runs fine, just very little vacuum. I hooked up my vacuum gauge to my truck to make sure there wasn't a problem with the gauge. The gauge seems to be working fine too. Tomorrow I'm going to do a compression check. That should tell me if the valves are sealing or not. My theory is that f the valves aren't sealing properly, the engine won't build much compression? What should I expect for compression from this new, stock 302?

1969 Z28 RS (building)
DZ302
M21
12-bolt, 3.73

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post #14 of 16 (permalink) Old Aug 21st, 14, 03:49 PM Thread Starter
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Re: New engine, little to no spark!

Now that the spark issue is resolved, I think I should start a little to no vacuum thread to try and get some more respnses.

1969 Z28 RS (building)
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M21
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post #15 of 16 (permalink) Old Aug 21st, 14, 08:38 PM
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Re: New engine, little to no spark!

Depends on the cam used.


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