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Guest Message by DevFuse

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the suby-sense strikes again! (check your injector O-rings)

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9 replies to this topic

#1 Snowman


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Posted 18 February 2007 - 05:12 PM

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.

#2 Olnick


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Posted 18 February 2007 - 05:40 PM

Good info, Snowman. Sure hope it really has improved your mpg's. Do you drive Sophia everyday?

Be sure to let us know down the road how the mileage holds up.

#3 porcupine73


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Posted 18 February 2007 - 06:14 PM

Good advice Snowman! I had a similar issue after R&R'ing the injectors. A dead easy way to check for leaks is to use the invaluable mechanic's stethescope around each injector with engine running. I could hear small leaks easily that I could not at all hear with the naked ear.

Another way to find the leak would probably be the trusty smoke machine. I've heard great things about them but they're $$$ though it should be possible to build one.

#4 ampsucker


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Posted 19 February 2007 - 02:14 PM

sorry to be clueless about this, but i'm having a hard time understanding how the fuel can leak around the injector into the cylinder head? i thought the o-rings sealed the fuel rail line onto the injector, then the injector pulsed the fuel into the manifold. if the injector is working correctly, how can fuel leak past it into the manifold?

#5 Snowman


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Posted 19 February 2007 - 02:44 PM

The fuel rail attaches to the intake manifold, then the injectors sit in the fuel rail (in this style of mounting...there are other types). So, if fuel gets past that bottom o-ring, it goes in the intake manifold.

#6 rweddy


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Posted 19 February 2007 - 03:01 PM

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

Can you get these rings at the local part store?

#7 Snowman


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Posted 19 February 2007 - 08:28 PM

Can you get these rings at the local part store?

Actually, I forgot to mention that part of it:cool: . 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.

#8 subeman90



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Posted 20 February 2007 - 09:13 PM

care if I put this in the USRM or for that matter cut and paste it into a new thread over there and I could put it in... if that is ok with you... :headbang:

#9 Snowman


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Posted 20 February 2007 - 10:06 PM

care if I put this in the USRM or for that matter cut and paste it into a new thread over there and I could put it in... if that is ok with you... :headbang:

I was actually thinking about making a writeup on this with pictures and part numbers and stuff, but I probably won't get around to that for a while, so go for it if you want.

#10 Reveeen


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Posted 20 November 2007 - 11:31 AM


What about "over fueling"?

I have none of the symptoms of an injector leak (hard starting), but suspect I am over fueling, though my highway gas mileage isn't bad.

What I am seeing:
black tail pipe (though no black smoke)
awfully thin oil at oil change time

The cold start function appears to be working fine, in fact I wish it would hold on a bit longer, because it's off before the engine is warm.

Any, all thoughts are appreciated

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