Weak spark

[Hog nose]

2000 volvo penta 5.7 gsi pefs. Motor just stopped running after a 45 min run. It started and ran 2 more times and stopped in a few seconds, won't start again. The spark is weak. 2 New coils, rotor, control module. Pulling 12 volts at hei coil with key on and drops to 9 when starting. 12 volts at starter and 9 at the alternator. Batteries are fully charged. It has a holley sniper efi and is getting fuel, even tried starter fluid. Getting weak spark at all plugs, so distributor is turning. In the previous outings it did shut off for no reason but started and ran fine. Dio greased every connection i can find, cleaned grounds as well. Any thoughts would be appreciated

 

[Wave34]

May I ask how you test for weak spark?
With a spark tester or by holding the cable near grounded metal and moving it?
If the later, the danger is having the coil trying to spark, but the cable is too far, and the coil will spark inside itself, and destroy its insulation, and reducing its output. What color is the spark?

Even if the coils are new, measure the ohms of the input and the output. The secondary should be 7500 ohms or more.

Have you checked the ground cable between the engine block and the battery negative?
If you measure 9 volts at the coil, is it in reference to the batterie or the block? 9 volts seems on the lower limit I think, I have more than that on mine. (10 something)

 

[CaptnKingfisher]

Just had this same symptoms on my Silverado, it stalled on me. I could restart it a few times but it would stall at shorter and shorter intervals til finally it refused to start. I found a broken ground connection from the negative terminal of the battery to the engine block. If you've got weak spark on all cylinders I'd start by cleaning and retightening connections and inspecting for damaged wires or terminals. resistance test on your new coil circuits and resistance test the coil to distributer leads.

 

[Hog nose]

May I ask how you test for weak spark?
With a spark tester or by holding the cable near grounded metal and moving it?
If the later, the danger is having the coil trying to spark, but the cable is too far, and the coil will spark inside itself, and destroy its insulation, and reducing its output. What color is the spark?

Even if the coils are new, measure the ohms of the input and the output. The secondary should be 7500 ohms or more.

Have you checked the ground cable between the engine block and the battery negative?
If you measure 9 volts at the coil, is it in reference to the batterie or the block? 9 volts seems on the lower limit I think, I have more than that on mine. (10 something)

I used a spark tester and I've removed both grounds, from the block and batteries, cleaned and dio greased. Is there a way to check the wire running from coil to the cap? That would isolate coil from cap is what I would like to do

 

[Hog nose]

I used a spark tester and I've removed both grounds, from the block and batteries, cleaned and dio greased. Is there a way to check the wire running from coil to the cap? That would isolate coil from cap is what I would like to do

Spark is orange

 

[dypcdiver]

I had a problem on my boat that turned out to be the pickup coil in the distributor Part number 3854001 it had corroded though the varnish on the copper wires, easy to test but a pain to replace as it needs the Distributor removing to replace it.

 

[Wave34]

I used a spark tester and I've removed both grounds, from the block and batteries, cleaned and dio greased. Is there a way to check the wire running from coil to the cap? That would isolate coil from cap is what I would like to do

You could use the spark tester at the HV wire of the coil. If you have weak spark there also, the problem is not the cap or anything downstream.

Usually, a yellow color is a weak spark, blue is a strong spark, orange, well, ok in good condition, may not spark a high compression engine...

Do a voltage drop test while cranking. B+ to starter, and engine block to B-. Even if you cleaned the terminals, there's may be corrosion inside the crimp.