Leaking fuel injector(s)

[dkryan]

I have an 2001 Infiniti I30 with a 3.0L V6 with 85k miles on it. Due to the gas mileage having dropped over the past two years (about 3-4 mpg - city/highway) and due to fuel dilution of over 1.5% (closed cup testing method), I suspect I have one or more fuel injectors leaking at shutdown.

The sparkplugs (NGK platinum - 100K mile plugs) were pulled and inspected at 58k miles and they looked good. New NGKs went back into the holes. The PCV valve was changed with no issues noted.

So what is involved in determining if one or more injectors are leaking? Removal and bench testing? Any guess as to how much? (I know, independent versus dealer as to price). Since it is baseball season, I'll take a ballpark figure.

Thanks.

 

[Quest]

hook up a fuel pressure gauge onto your fuel rail and watch the fuel pressure drops in the matter of hours.

If that is the case, you may either (a) have a fuel rail pressure regulator pressure leak or (b) fuel injector leak.

I would consider running a bottle of PEA first and see if that helps, if not, take the injectors out and consider sending them in for ultrasonic cleaning and benchtesting.

Q.

 

[tom slick]

I've sent injectors out to RC engineering, they clean and flow check/balance them for $24 each. in theory they are better than new when the come back because they've been flow balanced.

 

[Billy_D]

A new injector will cost between $30 to $100 a piece.

 

[Donald]

PEA is a cleaner like Techron or Gumout Regaine. You might also consider getting a injector cleaning where they hook up a canister of cleaner to the fuel rail, disable the fuel pump and run the engine on the fuel injector cleaning stuff for a few minutes.

 

[Chris142]

How about a slow 02 sensor? They are due at about 80K. A few injectors that leak down when it's not running wont cause a 4mpg drop because they just don't hold that much fuel. Plus it would be hard to start.

 

[mechtech2]

You are zeroing in on injectors, but it may be the alcohol infused gas that is now used everywhere.
Really, this could be all sorts of other things.

 

[harry j]

I had the same problem some time age, it turned out to be a faulty fuel pressure regulator and not the fuel injectors.

 

[Rooy]

Originally Posted By: tom slick
I've sent injectors out to RC engineering, they clean and flow check/balance them for $24 each. in theory they are better than new when the come back because they've been flow balanced.


Actually they don't flow "balance" them. All they do is tell you what each injector flows. There is no way to alter the flow. The only way to make a matched set (if you have injectors that are flowing out of tolerance) is to have extra injectors flow tested.

Also, there are other injector cleaning places that are significantly cheaper than $24 per injector, if anyone's thinking of going that route.

 

[Donald]

I have seen some injector cleaning places on EBAY where they send you cleaned injectors and you send yours back as cores. Thus you are not down for days with no injectors.

 

[Gary Allan]

Originally Posted By: Rooy
Originally Posted By: tom slick
I've sent injectors out to RC engineering, they clean and flow check/balance them for $24 each. in theory they are better than new when the come back because they've been flow balanced.


Actually they don't flow "balance" them. All they do is tell you what each injector flows. There is no way to alter the flow. The only way to make a matched set (if you have injectors that are flowing out of tolerance) is to have extra injectors flow tested.

Also, there are other injector cleaning places that are significantly cheaper than $24 per injector, if anyone's thinking of going that route.


They typically have enough of the injectors on hand to match them within 5% of each other. You don't get your injectors back unless they're within some +/- tolerance.

This could still be clogged injectors. I'm unsure how sophisticated the PCM/ECM is, but the O2 typically reads the average air:fuel ..so a clogged injector may be running lean ..broadening the pulse width of all injectors to compensate.

I'd go the in tank cleaner route a few tankfuls before pulling the injectors. At that point, I'd buy a comparable set of injectors off of ebay and then ship them out as cores for a matched set of reconditioned injectors.

 

[dkryan]

harry j:

how did you determine for certain it was a faulty fuel pressure regulator?

mechtech2:

I agree. It could be several things and I really do not want to start "chasing parts" to fix this problem. I could easily end up spending $990 on parts to save $440 in gasoline over the remaining ownership period of this ride.

ALL: If those injectors are dirty, there's gonna be heck to pay at Chevron, LCD, and BG.

I normally treated the fuel with Techron 20-ounce every six months. I also had a BG fuel system cleaning done at the stealership. I then began using FP60, then FP Plus when it was introduced, for every single tank of gasoline over the past three or so years. So those injectors had better be spotless.

One of the two cats (yep, two) had been replaced 20 months ago, along with two of the four 02 sensors. That did not solve the fuel mileage problem, though that was not the reason for the cat and O2 replacement. I had thrown a code indicating a bad cat/O2 sensor.

I'm leaning toward the fuel pressure regulator, though I'm loathe as to how to accurately check it.

 

[andyd]

A fuel pressure test and your nose are all you need to check out the FPR. You can rig a gauge from 10$ worth of hardware store bits. If you pull off the vacuum line to the FPR and you smell gas, or gas trickles out, the diaphram is shot.

 

[Ignatz]

I switched from Techron to adding 3oz. of Marvel mystery oil per 10 gallons of gas. I pre-measure the MMO and put it in my old techron bottles. In the trunk of my MB 190 and wifes Volvo, it looks like we have a "six" pack of techron. My Benz suffered from an ocassional leaky injector and would stumble sometimes. I never replaced an injector and I must say my Benz runs as good as new. I'll turn 200,000 in a day or two. Could'nt be more happy with MMO. Not to ask a dumb question but, Did you change tire size to throw off your mileage?

 

[dkryan]

andyd:

Well, my nose obviously works 'cause I always felt (at least the past two or so years) that the engine was running "fairly rich" at startup due to the gasoline smell. And yes, the garage door was up! I know the engine runs rich at startup but it seemed a little too rich for me.

ignatz:

Nope. I'm running the same OEM size: 215/55/16.

Guys, help me out just a little bit more. If the fuel pressure regulator is leaking, would it leak all of the time or just at startup or shutdown? And I really hate to ask this question but I have to learn at some point: exactly where does the "leaked fuel" go? Into the cylinders?

 

[Jason2007]

I had a fuel pressure regulator leak on the ouside one time puddling gas in the intake manifold. But it could be leaking on the inside and pudlding up on the inside of the fuel rail. best thing to do is hook up a pressure gage to it and monitor idle pressure, pressure at speeds and see how long it holds pressure once the engine is shut off.

 

[PT1]

Originally Posted By: Gary

I'd go the in tank cleaner route a few tankfuls before pulling the injectors.


+1 Try a whole bottle (16oz) of Redline S-1 in a full tank of gas or double a techron dose. Then another tank with regular dose and re-evaluate.

 

[harry j]

Originally Posted By: dkryan
harry j:

how did you determine for certain it was a faulty fuel pressure regulator?

mechtech2:

I agree. It could be several things and I really do not want to start "chasing parts" to fix this problem. I could easily end up spending $990 on parts to save $440 in gasoline over the remaining ownership period of this ride.

ALL: If those injectors are dirty, there's gonna be heck to pay at Chevron, LCD, and BG.

I normally treated the fuel with Techron 20-ounce every six months. I also had a BG fuel system cleaning done at the stealership. I then began using FP60, then FP Plus when it was introduced, for every single tank of gasoline over the past three or so years. So those injectors had better be spotless.

One of the two cats (yep, two) had been replaced 20 months ago, along with two of the four 02 sensors. That did not solve the fuel mileage problem, though that was not the reason for the cat and O2 replacement. I had thrown a code indicating a bad cat/O2 sensor.

I'm leaning toward the fuel pressure regulator, though I'm loathe as to how to accurately check it.




The FPR was the main suspect due to higher than spec fuel pressure.

 

[dkryan]

Update:

I took the car to the dealer today and they performed a fuel pressure leak down test. They said everything read within normal paramenters in terms of the fuel pressure regulator, i.e., the pressure was neither too high nor too low.

They also said there was zero indication of any of the injectors leaking. They ran the car at idle and at speed with some kind of diagnostic tool hooked up to the diagnostic port. They claimed all readings were within spec. They said the only reading that was slightly off was the fact that the engine was running slightly LEANER than normal.

The master tech told me he saw absolutely nothing in his diagnostic testing that would lead him to suggest going after the FP regulator and/or the injectors.

Now, you would think a dealership service department would sell that kind of work ($$$) if they could.

I'll have to post my recent UOA from Terry Dyson on this vehicle with its second run of RLI SHP 10w30 HD oil. After an 8.2k mile run over 15 months (including two winters), the oil had been beaten up. The fuel dilution was somewhere between 1.4% and 1.7% using the closed cup method of testing.

After today's diagnostic work (and a new PCV valve, MAF, and plugs within the last two years), I'm loathe to chase any more guesswork as to the fuel dilute source.

I may kick back to 5k mile OCIs and a Pure One filter and not worry about it, using whatever full syn 10w30 is on sale at WalMart.

Thanks for your prior input which led me to eliminate the FP regulator and injectors today.