I found a long flexible piece of plastic tubing that fits down my dipstick tube. When I get home tonight I am going to try removing the dipstick tube with the plastic tubing still snaked into the sump. I will then clean it and put on the new O-Ring I bought.

I snaked my inspection camera down there and it is a little oily, perhaps it is leaking. That could also account for the fuel trim issues.

Wish me luck, I am nervous at the prospect of removing that tube!

 

I missed that she was that high.

 

Suddenly my fuel trims have gone crazy! I am driving my oldest to a school function and the fuel trims have been so high I have a pending bank 2 lean code. It has been fairly consistent at 5-10 positive for weeks, now craziness!

frustrating...

 

Jeff,

Goddamn Murphy's law! You made the mistake of talking about your fuel trims being high but not as high as mine and Murphy heard you!

 

I am seeing high "reactionary" fuel trims, for lack of a better term. Sometimes when I coast I'll get a crazy -25 or so STFT and sometimes when I coast I get a crazy +25-30 STFT, which I think are wreaking havoc on my LTFT. I did a straight interstate drive home tonight, 30 miles at 75 mph, and the LTFT stayed around +4-5 with minor variation in the STFT, causing the pending lean code to go away. It's the stop and go driving around town that made everything go crazy.

When the car is not under load the STFT doesn't know what the heck to do. The wild up and down readings then freaks out the LTFT. This is my theory anyway. If I let everything stabilize at idle, after about 30 seconds of up and down it will steady out the LTFT at about +7 bank 1 and +10 bank 2, with minor variations in STFT.

I read in another thread that the wild up and down of the STFT when coasting was a sign of a bad MAF, but hey...everybody's got a theory. haha.

I labor to detail all of this in the hopes that someone might see a pattern or remember a similar problem, triggering a memory of what should be addressed. (Ross?, Jim?, lol).

I have tomorrow off, so in addition to attempting to change out the dipstick tube O-Ring and conducting another smoke test, I am open to opinions about other things I could work on. I REALLY wish someone on here was near me so I could try a known good MAF. FCP Euro sells a re-manufactured MAF by Cardone for $126.00. Do you guys think that would be a quality product?

 

I have had bad results with MAF sensors for Land Rovers or Jags from aftermarket suppliers. You (and I) might be to the point of removing the injectors, having them cleaned and flow bench tested, then replacing the injector seals. However, just becasue that fixes mine or yours, it proves nothing to the next guy with these problems.

 

I have been so stressed about this, fearing an all day debacle repair, that I have not tried it even though I've had the O-Ring for about a month. I managed, however, to change the O-Ring in about 15-20 minutes!

The long plastic tube that comes with those $7 siphon pumps you buy at Walmart is designed to snake down the dipstick tube for removing oil. I took that tube and inserted it all the way into the sump, and then removed the dipstick tube. The picture, which is much lower quality than I'd hoped, shows the tube in the foreground after I removed the old O-Ring and cleaned it. The upper part of the picture, very poorly lit, is my hand holding the plastic tube that is snaked down into the hole where the dipstick tube needs to go back.

I tried to memorize exactly what twists and turns were required to remove the tube and duplicate them in reverse after I installed the new O-Ring. The maneuvering took 15 of the 20 minutes, but I was slow and gentle so as not to damage or force anything.

The old O-Ring was not in terrible shape, but it was a little harder and slightly smaller than the new one. I could tell a difference when I pushed the tube back in because it required a little more force and made a "thump" sound when it went into place.

I have no idea if that place was leaking, but for $1.09 the little O-Ring in the Jaguar sealed bag seems like a good preventative maintenance idea. Who knows, maybe on my next drive my fuel trims will be fixed!

Haha, I can't even say that with a straight face. At the very least I have provided directions now for an easy way to replace that O-Ring.

 

Jennifer, I apologize. I realized that I have sort of taken joint custody of this thread without your permission. I hope at least my trouble shooting to solve the same problem has helped you along your path as well. But, if I'm butting in where I am not helping, I have pretty thick skin, just tell me to start my own thread.

I will make one last uninvited update (hey, I already started the post... haha).

After replacing the O-Ring this morning I did another smoke test with inconclusive results. I had trouble getting everything hooked up properly. It seems if I overdose the smoke test pressure a bit (above 2 psi) I get leaks from the area of the part load breather and the brand new full load breather hose, but at normal pressure I didn't get any leaks. I cleaned the MAF really good (worried about mineral oil based smoke soiling element) did a hard re-set and took if for a drive. The trims are closer to what they were before, +7 to +12 LTFT. High speed interstate driving is +5 on both LTFT. Heavy acceleration puts four zeros on the screen, all fuel trims perfect. It still did the occasional crazy up and/or crazy down on STFT, but overall was more stable like it was before.

I decided to test the fuel pressure. I know my recently installed secondary pump is working because when I turned the ignition the gauge went from 0 to around 45 psi in less than a second. Then I started the car and the pressure dropped to about 36 psi. When I unplugged and capped the vacuum line to the regulator the pressure went up to around 45 psi again. I have my suspicions that my gauge reads a couple of PSI lower than reality based on some previous experience, but even so those pressures seem pretty good. If I punch the gas the pressure initially jumps up to about 41 PSI and upon continued high RPM it drops to 32-33 PSI and steadies there until RPMs are allowed to drop.

I am still thinking I just have undiscovered vacuum leaks. The quest goes on.

 

Jeff,

I am not bothered at all by your posting .

 

Jeff:
Your fuel pressure actually seems a little suspicious to me. The gauge pressure - the pressure you read on a gauge is pressure vs atmosphere. The fuel regulator is designed top keep the pressure vs the manifold pressure at a constant. So, if your "continued high RPM" has boost, the pressure should be higher. If you have manifold vacuum under these conditions, the gauge pressure will be lower.

 

The JTIS only lists 44 PSI for disconnected regulator and 38 PSI for connected regulator. Mine came pretty close to both of those. I just bumped the throttle as an impulse to see what would happen. Getting the gauge connected to an XJR was no small feat, so I played around a little getting readings since I went to all of that trouble.

I'm sorry Ross, but i didn't really understand what you were saying about how the fuel pressures should respond when revved a little. I never revved it high enough to engage the second fuel pump; I don't think the rev limiter would even allow that. In fact I probably never got above 1,500 RPM. I guess that's not really "high RPM", but it seemed like a lot when I was testing.

Edit: What I "think" you are indicating is that my manifold should boost (be under positive pressure) and therefore the regulator would allow the fuel supply to follow suit. It appears however that when I raise the RPM my manifold is experiencing vacuum, which is causing the regulator to LOWER fuel pressure. Is that what you are saying? Would the presence of a load on the engine make a difference, since that was not the case during the test. I AM trying to understand, lol.

 

Could one of you take a picture of the schrader valve location so that Jennifer will know where to connect the pressure gauge?

 

Well it's difficult to get a clear picture because the part-load breather hose, supercharger coolant lines and some electrical connections are occluding the view.

The first picture is the "location", basically just behind the part-load breather connection to the valve/cam cover. The second picture is looking underneath and just past the part-load breather connection and you can just make out part of the blue dust cap that's threaded onto the schrader (sp?) valve connection.

I had to remove the part-load breather connection and then loosen the two nuts holding the metal bracket onto the valve/cam cover. After I loosened them, I lifted that little tray up and slid it away from the fuel connection. Moving that tray, and the electrical connectors on it, allowed enough room for me to snake the test hose down through the coolant lines and get a straight on angle.

I hope that helps.

 

That looks to be just where it is on my XK8, on which it's hard enough to connect, but the XJR should be many times more difficult.

 

Sorry I was not more clear! Your Edit is right; The fuel pressure should remain constant RELATIVE TO MANIFOLD PRESSURE. So, as the manifold goes negative relative to atmosphere, the fuel pressure (mearured vs atmosphere) should lower.

BTW, the second pump kicking in should not change the pressure at all. It keeps the flow up so the rail pressure stays at the regulated pressure.

Also, your pressures seem right compared to my experience for no load. I thought you meant when you goosed the throttle under load!

 

Update: I have driven a couple hundred miles since I did anything to the car. Within the first 30 miles after I replaced the dipstick tube o-ring, cleaned up the MAF and did a hard reset, the fuel trims showed a remarkable improvement.

Under any load at all, even just highway cruising, the long term trims never go above +4 or +5. Much of the time, especially if I am accelerating, they are right around zero (0)! The STFT don't swing wildly anymore. They fluctuate + or - about 5 as compared to the LTFT. When doing extended coasting the trims still go a bit positive, +6 bank 1 and +10 bank 2. They are the same at idle as they are when doing extended coasting.

They are certainly not perfect, but there is NO risk of a lean code with fuel trims like that. I feel like the dipstick tube o-ring may have been leaking. It would explain the improvement because it's the only thing I really changed. I have cleaned the MAF before without improvement.

 

I think that under extended coasting, the STFT, will go positive as the injectors cut off during coasting.