Fuel Issues Plus

Napheus · **Joined:** Fri Aug 25, 2006 5:39 pm **Posts:** 57

So I was in Dearborn, Michigan earlier this week and returning on Thursday. While going through Chicago, I left one of the tolls and accelerated hard to get up to speed. I set the cruise while letting the rest of the traffic sort itself out. When I had room to maneuver, I pushed the accelerator, only to find no response; I was at 50 mph and the Liberty would maintain that speed but not accelerate. I had my co-pilot reach under the seat and hook up the computer scanner (I suffer from ORM at times) to check for additional codes.

P0093 Fuel system leak detected – large leak

I pulled over before I got run over. Idled fine, no leaking fuel. Shut it off, re-start, everything running fine. I pumped the primer several times until it firmed up (which took more pumps than normal to firm up) but no tools to bleed off air. Accelerator now worked fine. Drove the rest of the way home with no problems. I obviously have an air leak and the swift acceleration coupled with the long trip was the "final straw" that set the light because this had never happened in 20,000 previous miles.

I have not done the Cat filter mod yet, but I have replaced the fuel filter previously. I don't have any visible leaking fuel on the filter mount or other usual places although I will be climbing under it today and inspecting it. I do suffer from bucking on occasion which I am attributing to air leak(s), and that was occurring even with the factory installed fuel filter.

A couple other notes. I bought a new GPS (Garmin C550 StreetPilot, WONDERFUL UNIT) and this was the first trip. I have the ORM and EHM, I am running 42 PSI in the stock tires, and from Central Wisconsin to Dearborn I ran anywhere from 55 MPH to 80 MPH; ran into traffic jams, congestion and an accident that re-routed traffic when on I-94 in Michigan. For those of you that are hand calculating and basing it off the mileage on the odometer, well, my GPS showed 40 miles more traveled than what the odo was reading (580 GPS vs. 540 on odo when filling up). On the trip over I averaged just under 30 MPG (29.87) in the "rotten" driving conditions for what should have been all interstate "cruise" driving. The lesson is to take the variance of the speedo being off into consideration. That 40 mile difference would equate to a full 2 miles per gallon less in the mpg department! It only took 19.some gallons using a visual stop point in the filler neck and the light was on. My dealer told me they put a fuel tank that was 3 gallons larger than the stock Liberty gas tank but I don't know if I want to find out.

Before this trip I didn't have great (meaning over 30 in all driving conditions like some are getting routinely) but it wasn't low 20's either. Probably about 25-27 MPG average; and I mostly drive interstate to work (26 miles one way of which about 20 is interstate). This is by far the best mileage I have ever had and I would have never guessed it to be that high due to the conditions stated above. I have a trip to Toronto, when I will be alone and able to drive the way I want, that should be an even bigger testament to the ease with which most CRD's can achieve 30 MPG. If I could only find some high cetane fuel...

The other thing about the GPS. It is a great tool. But man, when it "re-routed" us around construction, my passenger and I almost died! That sucker re-routed us through the south side of Chicago! Don't believe everything a GPS tells you. I would have rather have stayed in the slower moving congested traffic then make that drive. Thank goodness it was at about 1PM instead of 1AM!

Bill.Barg · **Posted:** Fri Aug 10, 2007 12:51 pm

Thanks for the fuel mileage summary.

Did you notice that although your odo is wrong, the speedo is wrong in a different amount ( or correct if you have had it calibrated). ?

I have heard the the ODO is read through the ABS wheel rotation and nothe tranny "pinion".

Bill

jeep06 · **Posted:** Fri Aug 10, 2007 1:17 pm

I can testify that mine is in fact off by 3 mph fast. When I am traveling at 60mph on the speedo, I am actually only going 57mph on the GPS. But this would make my actual mileage worse going by the GPS miles traveled than what it shows on the odometer, well if in fact my odometer is off the same way as the speedometer. Guess I will have to take the GPS on a short trip to see if the actual miles are less than reported on the odometer. :shock:

Cowcatcher · **Posted:** Fri Aug 10, 2007 2:10 pm

I just got my GPS Wednesday and check both the ODO and the SPEEDO against it yesterday with my 245/70 16's. The ODO read a tad over 5% under in 10 miles and the SPEEDO was all over the place depending on speed. At a GPS 55 SPEEDO was reading 59 and at 25 it was nearly right on.

Bill.Barg · **Posted:** Fri Aug 10, 2007 4:12 pm

Keep in mind that the GPS spedo can have up to two seconds lag time (notice this when you come to a stop)

Also, the scangauge II is easier to read accurately (compared to the dial spedo), and can display in kM, giving you another +-0.5 mph resolution on the measurement . Put the gps into metric mode also, to do the comparison in real time. Holding the speed steady at 75 mph will give you the best (legal) resolution to your measurement, limited by the scanguage, at about 0.8%. You can also compare the gps and scangauge max speed values, for confirmation.

Bill

Cowcatcher · **Posted:** Fri Aug 10, 2007 4:51 pm

Bill.Barg wrote:

Keep in mind that the GPS spedo can have up to two seconds lag time (notice this when you come to a stop)

Also, the scangauge II is easier to read accurately (compared to the dial spedo), and can display in kM, giving you another +-0.5 mph resolution on the measurement . Put the gps into metric mode also, to do the comparison in real time. Holding the speed steady at 75 mph will give you the best (legal) resolution to your measurement, limited by the scanguage, at about 0.8%. You can also compare the gps and scangauge max speed values, for confirmation.

Bill

Yes Bill but if the data source in the Jeep is also the source of the error (likely since it is drive by wire instead of cable) then the ScanGauge will reflect an error similar to the Speedo or Odo. :oops:

fatweasel · **Posted:** Fri Aug 10, 2007 5:08 pm

Pull the plugs off of the fuel temp sensor and the fuel heater (the 2 plugs on the filter assembly) and then pump the primer. If you have the "classic" leak you will see and here air/fule spitting out through the heater fitting. I find that mine does not spit when the heater wire harness is connected.

Good luck!

Bill.Barg · **Posted:** Fri Aug 10, 2007 6:13 pm

Dave

Yes, the scangauge will read the erroneous speed off the bus. BUT, The scangauge lets you calibrate speed, with the gps taken as the true value. The scangauge allows you to put in positive or negative percentage of error. This calibration effects the way SG measures fuel mileage, for instance. So, after you have calibrated the scangauge, it will show correct speed (and distance) to within (at best) one percent.

Bill

Cowcatcher · **Posted:** Fri Aug 10, 2007 7:29 pm

Bill.Barg wrote:

Dave

Yes, the scangauge will read the erroneous speed off the bus. BUT, The scangauge lets you calibrate speed, with the gps taken as the true value. The scangauge allows you to put in positive or negative percentage of error. This calibration effects the way SG measures fuel mileage, for instance. So, after you have calibrated the scangauge, it will show correct speed (and distance) to within (at best) one percent.

Bill

Cool. I am planning on getting one but I was waiting for their upgrade. Are you getting that part of it to stay on or is it checking out on you like it does on other CRD's?

Bill.Barg · **Posted:** Fri Aug 10, 2007 11:29 pm

Dave,

No, it does not stay on. So, for $170 you get a ODB scanner / code clearer, that occasionally functions as a gauge, but never as a trip computer.

You might want to wait, if the trip functionality (accurate milage calculation) is what you are after.

I will try o send mine in for reprogramming if it is offered

Bill

Napheus · **Joined:** Fri Aug 25, 2006 5:39 pm **Posts:** 57

Bill.Barg wrote:

Thanks for the fuel mileage summary.

Did you notice that although your odo is wrong, the speedo is wrong in a different amount ( or correct if you have had it calibrated). ?

I have heard the the ODO is read through the ABS wheel rotation and nothe tranny "pinion".

Bill

Yes I noticed this as well. Speedometer is off by about 1 MPH when at 25-30 MPH, and gradually gets up to about 4 MPH off when running over 65 MPH.

msilbernagel · **Posted:** Sat Aug 11, 2007 1:18 pm

Which size tire is this happening with?

Mark
-

Napheus wrote:

Bill.Barg wrote:

Thanks for the fuel mileage summary.

Did you notice that although your odo is wrong, the speedo is wrong in a different amount ( or correct if you have had it calibrated). ?

I have heard the the ODO is read through the ABS wheel rotation and nothe tranny "pinion".

Bill

Yes I noticed this as well. Speedometer is off by about 1 MPH when at 25-30 MPH, and gradually gets up to about 4 MPH off when running over 65 MPH.

Cowcatcher · **Posted:** Sat Aug 11, 2007 4:14 pm

msilbernagel wrote:

Which size tire is this happening with?

Mark
-

Pretty much all. :lol:

msilbernagel · **Posted:** Sat Aug 11, 2007 7:11 pm

You're funny...

Cowcatcher wrote:

msilbernagel wrote:

Which size tire is this happening with?

Mark
-

Pretty much all. :lol:

Cowcatcher · **Posted:** Sat Aug 11, 2007 9:29 pm

msilbernagel wrote:

You're funny...

Cowcatcher wrote:

msilbernagel wrote:

Which size tire is this happening with?

Mark
-

Pretty much all. :lol:

Seriously Mr. Mildew!!!!! :roll:

My OD was off about 6.5% with the stock tires at 40 PSI. I went 245/70x16 at about 37 PSI expecting my ODO to go to perhaps 7-8% error and it went to about 5%. What's with that I ask you?

I am positive that there is absolutely no way to calibrate both the speedometer and the odometer on the CRD. I don't see the gassers talking about this too much. Do they not care or is it a CRD issue?

vtdog · **Joined:** Fri Sep 30, 2005 11:27 am **Posts:** 640

When I changed out the OEM tires I went with 245/70 and had the dealer re-set (program) the jeep's little brain for the new tire size. They charged me about $ 15 for the task. I checked both the odo and spedo against my gps unit and found that both were in sync with an error of less than 1% at hiway speeds between 55 and 75mph. I have not checked it at lower speed.

Napheus · **Joined:** Fri Aug 25, 2006 5:39 pm **Posts:** 57

vtdog wrote:

When I changed out the OEM tires I went with 245/70 and had the dealer re-set (program) the jeep's little brain for the new tire size. They charged me about $ 15 for the task. I checked both the odo and spedo against my gps unit and found that both were in sync with an error of less than 1% at hiway speeds between 55 and 75mph. I have not checked it at lower speed.

Isn't it amazing that they can't get the odo and speedo "on" from the factory, yet for a mere $15 can re-calibrate it for a new tire size. If it really is that simple, we should be able to return the vehicle to a dealership and have them re-calibrate for the tires that are currently on the vehicle.

BiodieselJeep.com · **Posted:** Mon Aug 13, 2007 2:40 pm

fatweasel wrote:

Pull the plugs off of the fuel temp sensor and the fuel heater (the 2 plugs on the filter assembly) and then pump the primer. If you have the "classic" leak you will see and here air/fule spitting out through the heater fitting. I find that mine does not spit when the heater wire harness is connected.

Good luck!

fatweasel: your's may not spit fuel when it is plugged in, but it is most certainly sucking in air. Remember the fuel line is under negative presssure and air leaks in easier than liquids. Replace the filter head (or try your luck with Racor or others), but I think this situation is serious. This may also be the case for the original writer. I was very p.o.'d when I saw this:

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