Seeping Injectors after Shutdown

[seang]

(Wall of text required, bloodshot eyes optional.)

I was having this issue with my oil getting really dark after about 2000 miles; then it happened after 1500, then 1000, and then 700 miles. This took a few years of gradually getting worse to get to where I was not going to just let it go anymore. I thought that I might have a nasty blow-by problem, or a stuck oil ring or something; so I did 1500 mile oil changes with 800 mile filter intervals, and seafoamed my crankcase, which worked okay, but something was still not right. Then I noticed that my oil smelled like gas. It was not a comletely raw gas smell like when you are at the gas station; but more subtle, yet still distinguishable. My oil rings are fine, it turns out that I have leaking injectors.

Every time you shut down your engine, there is residual pressure that your injectors are supposed to just hold there until the ECU fires them off the next time you start up. That is alot to ask from them. If the injectors are leaking, they can leak past open intake valves and down through the rings into the crankcase, which also washes the lubrication off the cylinders.

So, new injectors are $120 a piece and I'm broke, so that is definitely NOT happening right now; but I have found a nice band-aid for the problem: I cut the fuel pump with the ignition still on and right after I cut it I press the gas pedal until the pressure runs out, then I crank it over for a few seconds with wide open throttle to get the remainder. At first people were telling me that my starter was going to go out in a week, but I have been doing this for months (on what I suspect to be the original starter with 146,000 miles) and it has been good. And a starter is not expensive like new injectors, so why sacrifice my engine internals and expensive oil for an external part that can be replaced in a matter of an hour? Anyways, I have 3300 miles on my current oil, and while it is nearing time for a change, I got MUCH more out of it than just ignoring the problem and spinning a rod bearing (and then blaming the rotten Japanese engineers for my f*** up). Also, my starter is on the intake side away from the hot exhaust; and I hear that heat kills starters, so I have that on my side.

All in all, the engine runs great. No lean cylinders, no rich cylinders, plugs look normal. It runs good because there isn't enough time in between firing pulses for the seepage to amount to anything significant, at least not today. So I just wanted to let you know that in case you might be having issues. Nissan wasn't in good financial shape in 97, so maybe they went with cheap injectors; or maybe it is realistic to expect them to go out eventually. Either way, I might have the injectors inspected someday; but for now im running with it.

[Q451990]

I would consider the possibility that one of the lower o-rings is leaking, rather than your injectors themselves. The '97 uses side feed injectors (as does the 1st generation Frontier and a ton of other Nissan products) and having the injectors themselves leak down is pretty rare. The injectors are isolated in the fuel rail by two o-rings, with the pressurized fuel flooding the areas around the injectors. The lower o-rings keep the fuel from seeping (or gushing depending on the size of the leak) around the lower end of the injector, while a leaking upper o-ring will allow fuel to spray out of the top of the rail.

I seem to remember that the fuel rail on my '97 would have been relatively easy to remove - just based on looking at it. That's compared to my Q45 that required removing the entire pleum.

If I were you I would pull the fuel rail and then pressurize it to see if you can isolate the source of your leak-down issue. You might get lucky and find that it's a $5 o-ring instead of a pricy injector. Another option is to send your entire rail to Deatschwerks (http://www.deatschwerks.com) and they can clean them and replace the seals for you... they are an excellent company and the cost isn't that bad.

Good luck!

Heath

[seang]

Thank you for taking the time to write that out. I have never taken apart side-feed injectors, and wasn't aware of those o-rings. I think I have an okay idea, now, from your description; and I am going to get around to checking things out.