Ka24det injector sealing issues

[Teitoku]

Okay so i'm currently tuning a Ka-t for a customer of mine, after replacing the ka and I've run into an odd issue on cylinder #1. Mainly that the #1 injector will not seal and keeps creating a vacuum leak.

for some background information the ka is running a stock s13 manifold on a s13 head, with stock: fuel rail (with new risers), fpr and emissions delete. The owner elected to go with some eBay 550cc injectors,

When i put the new motor in i noticed one of the large o-rings that seals the injector to the manifold was torn and ordered a new one from Nissan. This new ring (ring A) will not seal, and is creating a very large vacuum leak. It almost appears that the o-ring isn't big enough in diameter to seal in its seat all the way.

Now i have tried six different rings (2 new from Nissan (ring A), 4 old from another manifold (ring b)) and none of them have worked. but if i move the 3 seals that came with the manifold originally (ring C) i can move the vacuum leak i.e. all of the new seals will not do their job regardless of what injector the are on.


I have noticed in the process of moving all these black rings around that ring c appears to have a more saturated feel and appearance than rings b or a and feels almost swollen. this seems to be creating the perfect seal that neither ring A nor B can create. so I was curious if there was another type of seal i have not been able to find or some process that i have forgotten about to make ring A act like ring C.

We're about two weeks into this issue so any help is appreciated.

[PapaSmurf2k3]

Using a vaseline or petroleum lubricant typically helps seal the rings and expands them/saturates them like you mentioned the other ones feel like.
There's no burrs or anything down in the bores are there?
I wonder if the new injectors o-ring groove diameter is slightly smaller than an OE injector, so it isn't pushing the O-ring outward enough. If you have a set of calipers, that might be something to check.

[Teitoku]

The bores are smooth and Vaseline helped some when i tried it before, but it may just need a more vigorous application to actually saturate them. i have not checked the o-ring groove diameter yet, so i will check that and relay my findings for future reference.

This is an odd issue i haven't encountered in my time of working on schassis (though not much was spent with ka's to be fair).

[PapaSmurf2k3]

Yeah, I tend to stay away from Ebay injectors.

[Teitoku]

11.84 mm on the ebay injector 12.15 on the factory injector, at the o- ring. 9.45mm at the cap on factory and 9.27 mm at the cap on the ebay,
so there appears to be a discrepancy, now i'll have to pull the other three and see if it is an error within the matched set or if the whole set is off.

so for future reference ebay injectors for ka's may be a bit small.

[PapaSmurf2k3]

That's a good bit of difference, and can definitely account for poor sealing.

[Teitoku]

So update on the situation after a few weeks, i picked up an oem Nissan seal and it definitely has a different consistency then the bwd ones as well as having a larger diameter. before i put it in i did some measurements and the diameter came to about 29.7-29.9 mm which was worrying as the seat in the manifold is 30mm if not slightly bigger. upon installing the new seal, the leak disappeared at first but reopened as we began tuning the vehicle. so now were back to square one. i'm beginning to think the manifold has always had some sort of casting issue or possibly has warped. as non of the available seals will actually seal a vacuum.

[PapaSmurf2k3]

Have you replaced the injectors?