Weak spark after engine change

[HuD 91gt]

I finished rebuilding my engine and am starting to swap it in.

280zx distributor, MSD coil.

The setup ran fine 3 days ago on the L24. Now with the new L28, I have very weak spark. Spark from the coil to the distributor is strong. It is intermittent and weak from the plugs.

 

Will the oil drive spindle being in the wrong position have any effect on the timing of the spark in the rotor? 

We we tried a new MSD coil and no change. The other option could be wires, ignition module, cap, rotor or plugs. Everything is new or less then 2000miles.

i ran the ignition for a while testing oil pressure without the plugs in. Without them being grounded, is it possible I damaged something?

 

 

[Patcon]

16 minutes ago, HuD 91gt said:

i ran the ignition for a while testing oil pressure without the plugs in. Without them being grounded, is it possible I damaged something?

Unfortunately, yes that is possible

[Zed Head]

24 minutes ago, HuD 91gt said:

Spark from the coil to the distributor is strong. It is intermittent and weak from the plugs.

I wrote a whole thing about modules then realized that it's creating strong spark.  If you're seeing two different spark qualities, it kind of implies a cap and/or wire problem.  The spark has to get from the coil wire, through the cap button, down the rotor metal, across the gap to the wire electrode, etc.  Maybe measure resistance along that path.

[Chickenman]

^ ZH is on the right track.

What are you using for plug wires? If strong spark at coil output lead but weak at spark plug end, that could be high resistance plug leads or a distributor cap or rotor issue.

1: Measure the plug lead wires for excessive  resistance with an Ohm meter. You should be using a good spiral core wire. NGK wires are inexpensive, high quality and inexpensive. NE-61 is the number for our cars. MSD, Magnecor and Aurora ( Local production in Langley ) are also  very good. Taylor and Accel are often junk, especially their lower end wires.

Good Tech article on plug wires from Magnecor:

http://www.magnecor.com/magnecor1/truth.htm

2: What brand of new cap and rotor did you get? Some aftermarket brands have a very high resistance in the center button. Check it with an Ohm meter. I've also seen mismatches between aftermarket rotors and dizzy caps resulting in a very large gap between the rotor tip and the dizzy plug terminals. This is really hard to find, but will drive you nuts.  A few local Vancouver guys have run into issues (IE: excessive gap, high resistance center button and loose rotors )  with caps and rotors supplied from some local Automotive suppliers.  Mixing one brand of rotor with another brand of cap can cause issues with excessive gap to the dizzy terminals as well. OEM Nissan cap and rotor are still available from your local dealer if you need them. Factory Nissan caps and rotors are very good quality.

3: Make sure you have the coil polarity correct. Having it reversed will dramatically lower spark output, particularly at the plug.

4: The 280ZX module does not require a ballast resistor. Using the factory ballast resistor will reduce spark out put. Wiring diagrams from Atlantic Z:

http://atlanticz.ca/zclub/techtips/distributor/index.html

 

 

 

 

 

Edited April 17, 2016 by Chickenman

[HuD 91gt]

thanks for the replies everyone. That is good to hear, as I was thinking similar in my head. Spark seems strong at coil wire to distributor. Easily jumps when wire is over and inch from ground.

Unsure of rotor and cap brand but there is one locally available at lordco.  I will pick it up tomorrow. I have NGK wires, but the connections are suspect. These are also in stock. I'll update tomorrow.

[Zed Head]

How did you check spark from the coil?  Just making sure that you were actually running power though the module.  If you tested by tappng a jumper from coil negative to ground with the key On, you were bypassing the ignition module.  If you spun (span?) the engine with the coil wire disconnected then the module was being used.

I had a weak module.  Orange-yellow spark, would start with starter fluid, but not normally.  Killed it by running the engine with two plug wires off.  I've written these words before.  Sqwawk.

[HuD 91gt]

It was tested by disconnected the wire from the distributed and turning the engine.  Blue spark, arc from over an inch. I never tried any further.

[HuD 91gt]

Thanks for the quick replies guys. It's really useful in times of chaos. Sorry for the short replies yesterday. 

 

Im working out at a friends house without internet service (complete boonies) and a single bar of cell service. By the time I had posted this I was scouring wiring diagrams and researching everything on this silly device.  It was also the point in time where I decided to call it quits and had a few wobbly pops.

 

Anyhow, I drove into town early this morning to catch the parts store opening. Taking this time to do a little research at Starbucks and steal their wifi.

I don't know the brand of cap and rotor, but I bought them online and I would put money on the fact they are beck and arnley. I will compare resistance with the old and the new and see if there are differences before installing. 

 

I really hope hope it is one of these items. I suspect the prolonged cranking without being grounded did some damage. To what, I guess we'll find out soon.  Unfortunately if I don't get this figured out this morning, the new engine will sit for about 2 months before I get the chance to try again.  I'll be out of town for work for the next 2 months starting this afternoon.

 

 

fingers crossed

[HuD 91gt]

Just a quick update. Replaced the coil, rotor and plugs and then I had spark. Didn't have luck starting the engine so I swapped in a HEI module (suspecting weak spark) instead of the e12-80 ignition module. No change.

With the help of chickenman over the phone, we realized my timing was way off (way off). He told me to take a look at where the rotor was pointing under the cap.  I never thought of doing this and it caught the error.

The engine fired right up after setting the timing properly.  Thanks everyone.

 

 

 

 

Edited April 18, 2016 by HuD 91gt