Door popping onto secondary over bumps

[Hezath]

Hi guys, my '75 911S Targa had an awful feeling passenger door latch mechanism for a while.

Recently I shimmed the door hinge up so the panel lined up better on the car, lubricated the heck out of the latch, and replaced the broken (cast aluminium) door handle lever with a billet aftermarket job.

Now the door latch action is incredibly easy... devoid of much pre-load or friction, the door just falls open from a light touch on the lever. In many ways, it's hugely improved over how it was before. But on a road with small bumps (not speed bumps... more like cat eyes or a generally uneven surface) the door will "pop" open to the secondary position, where it starts rattling about. Fortunately, it shows no inclination to go further than the secondary position, so it's not currently anything more than highly irritating.

The part of the latch that engages with the striker looks normal:


I had this problem and asked a self-appointed expert at an event who said that my cracked nylon inserts in the striker plates were the problem.

The logic of replacing the nylon inserts in the striker plate to fix a latch that doesn't seem to be staying engaged with the pawl didn't make much sense to me. I bought new inserts for the striker plates and installed these anyway, and it made zero difference:



If anyone has encountered this before, what is my next step?

Do the pawls wear out and need welding up & re-shaping? I've heard someone say that but I have not seen any reference photos of this.

If I do this, does the Targa/Cab door glass have to be removed to get the window rail out? The rail is very much in the way of getting the latch out.

[EC900]

I haven’t ever experienced that problem but I’d look at the linkage and make sure the handle, the rods all have the small nylon bushings intact. As well as space block on the main rod that lead from interior handle to latch. Then make sure nothing is binding or interfering or maybe the turnbuckle adjustment is off, perhaps twisted too tight or too tight.

[PeteKz]

The nylon bumpers are not responsible for the door coming unlatched. When I had this problem, it was wear in the latch mechanism. I had a spare, so I just replaced it.

However, it's odd that this is happening on the passenger side, because that typically gets much less use and wear than the driver's side. SO, make sure that the latch is not restrained from latching completely by the release rods, etc.

[Hezath]

Thanks for the advice, gents.

EC900, could you please clarify which turn-buckle adjustment you are referring to?
It's a good point given the door feels already half unlatched that maybe a preload in some opening mechanism is playing a part.

PeteKz, a voice of reason! I was desperate for any suggestions at the time although it certainly didn't make great sense then, and less sense now.

Yes, fair enough re: the passenger vs. driver's side thing, but a) perhaps the driver's side has been replaced previously or b) the passenger side was very dry and functioning poorly, so maybe some accellerated wear was occurring.

[EC900]

@Hezath - here’s an example of what I refer to as “turnbuckle” adjuster, the first photo of the main rod (circled red) inside handle to door latch, in the second photo are these little screw adjusters act like “turnbuckles” are at various rod points to fine tune the latch mechanism.
The red circled item is an important spacer and guide for the main rod.
The door should have some spring effect when opened, your being so sensitive likely has to do with adjusting the rods.



There are 6 bushings for each door that attach to various bracket, if they are broken off or missing it makes it difficult to open a door, bypassing the $2 bushings with an adjustment perhaps is the issue to compensate for sloppiness at one time under prior ownership.

Worth noting is the amount of “spring-open” your door has, if any of the door surrounding rubber seal is out of place, sliding off, obstructed, etc. that could add tension on the door that maybe causing it to spring-open” more so than driver side. Are all the door gaps level? Any resistance in shutting the door ?

You’ll need to inspect the entire operating with door card removed, adjusting can be tricky if anything doesn’t look right. So checking if any are bottomed or topped out would be are start. Check that springs are original and not swapped out replacements and l hooked onto the proper position.
It may be good to remove both door cards so you can get an idea of what’s what and starting point for how everything it working on driver side in comparison to passenger side door.
Let us know what you find. Good luck.