Following.

Your last photo there, looks like that flipper EOS switch is open. That means no power to the coil’s main winding. It should be adjusted so it is closed at rest position and opens only when the coil pulls in.

Good call on the eos, and when
It is adjusted it should only open at the very last of the flipper travel.

YUP! Great job on the photos too! This made troubleshooting very simple. That EOS switch should be clean and tightly closed until the last bit of the flipper stroke. When it opens, it should open about 1/8 inch.

It looks like there may be wear around the plunger end on the flipper link. If there is it too will contribute (to a smaller degree than the EOS swtich) to a weak or sloppy flipper. Here's a clearer picture of what I'm referring to:
Worn flipper link 1 (resized).jpg
This is a clue that the holes in the flipper link have become elongated and may need replacing.
Worn flipper link 2 (resized).jpg
Elongated holes in the flipper link mean that the plunger has to travel farther before the flipper will start moving. Any wasted movement like this is energy that doesn't get transferred from the plunger through the flipper to the pinball.

/Mark

You could try swapping the two coils to see if the problem moves to the other flipper. That would let you know if there is something wrong with the coil itself.

You just need to rebuild the flipper. It's not the last resort. It's a must for just about any game i do.

Check the resistance of both coils. That will tell you what you need to know there. You have to open the EOS to check the hold winding.

Most assuredly the spring is not causing a weak flipper situation.

I concur with Lee that not only is the EOS open it appears to be missing a contact.

The Pinball Resource has these: http://www.pbresource.com/rebuildkit.html#KT-GFLIP02

Maybe you would like to show us a photo of your "after" work?

Also, did you clean those EOS contacts? A dremel with a wire-brush attachement works well for this.

In Vid's guide, he goes over flipper rebuilds for Williams, but the same rules apply. Also, new style EOS switches have a 3rd "tension" leaf for holding the switch closed tightly when at rest

https://pinside.com/pinball/forum/topic/vids-guide-to-upgradingrebuilding-flippers#post-284658

That EOS needs to be tightly closed until the flipper is at the end of it's stroke (hence, the name), then only open about 1/8".
EOS copy (resized).jpg

Perhaps you can show pics both at rest and full plunge?

Did you do a flipper rebuild or just replacing the spring? Get a flipper rebuild kit from pbresource like EMsKC stated in previous post.

I agree with this. The flipper coil cant get all the power it needs when the EOS switch contacts are pitted like that. It may not be the only problem, but definitely something that needs attention for long term operation.

Replace the coil, could be a broken wire on the high power side.
You can check this by closing the eos that it won't open on the last bit of the stroke.
If it stays weak check the cables on the eos switch and on the coil.