Injector o-rings (running issues with a gen 1 legacy)

[subeman90]

This writeup is written by our member Snowman..please direct any questions to him.

 

orig: post: http://www.ultimatesubaru.org/forum/showthread.php?t=71573

 

I think I may have finally figured out what was wrong with Sophia, my 92 Legacy. So, basically all winter, my fuel economy has sucked. Most of the time it has varied between 19 and 15 mpg running around town or on the highway, which is not what this car should be getting even in the winter. During the last six months, virtually everything that could possibly affect fuel economy has been changed: spark plugs, air filter, oxygen sensor, PCV valve, fuel filter, reset the ECM, and cleaned the MAF (the only thing I left alone was the plug wires, since they appear to be about a year old). None of those things made any difference. At that point, I even started checking around to see if I was leaking fuel out on the ground, which I wasn't. In addition to the fuel economy issues, about 2 out of 5 cold starts would take longer than normal, requiring about three seconds of cranking before the engine would fire. Finally, I realized that these two things might be connected, but what would cause such an issue? I then remembered that a previous EJ22 had developed an external fuel leak from one of the injector o-rings at 150,000 miles, after I had driven through some really cold weather. If the o-ring that seals the fuel passage externally could leak, then why couldn't the one on the bottom that seals the fuel passage from the intake manifold also leak, causing poor fuel economy and flooding the cylinders causing hard starting? Yesterday, I decided to pull the injectors and have a look. Lo and behold, all four bottom o-rings had a bunch of tiny cracks on the inner surface, which looked like enough to leak some fuel. A trip to Schmucks and $7 later, I had new o-rings on my injectors. The starting problem has not reappeared, and I took a short trip down to Girdwood to check out my fuel economy, which came out to be 24 mpg. Of course, that's only one trip, so I can't scientifically prove that any difference was made, but going from 16 to 24 mpg would probably indicate some difference.

 

So, if your fuel economy sucks and you don't know why, pull your injectors out and look at the o-rings.

 

Part 2:

 

I spent a week trying to track down the o-rings by application when I had the external leak last year on my other car, with no luck. None of the parts stores even list them, and the dealer had to special order them but ended up getting the wrong ones. Finally, I just checked around in the o-ring assortment at one of the stores and found some that matched up. The smaller one can be exactly matched, but for the larger one, the closest you can get is one that is just a hair smaller on the inside diameter. It works just fine though...I ran it for several months with no problems. I'll check and see if I can find out the exact dimensions and post them in the USRM for reference.

 

Another thing to mention is that I was concerned about using "standard" o-rings for fuel system stuff. As part of my search last year, I went to a major rubber products distributor and asked about it. They checked in their books and assured me that regular butyl-rubber o-rings are just fine for gasoline and that's probably what the stock ones are made of. The only difference between the butyl-rubber o-rings and the highest grade ones that they manufacture is the ability to withstand extreme high temperatures, but the range they are talking about is way higher than you would ever see in that application anyway.

 

So yes, to answer your question, they are available at any parts store. You just have to take your injector and the old o-rings with you in order to find the right ones. They are also cheap that way. I think I paid less than $10 for enough to do all my injectors and some spares.