BMW Z3 Wacky Gas Gauge

One of the most consistent failures in the BMW Z3 is the gas gauge. I’ve heard different excuses as to why the gas gauge fails, but rather than pretend to be an engineer or parts inspector let me just share with you some observations I have made regarding my wacky gas gauge.

Let me start by saying I never had a problem during my first year of ownership. But others were having problems during that time so I heard a lot of speculation regarding what caused the failure and I got to see what BMW’s fix was for those under warranty. I can almost pin-point the exact time mine started acting up. I was refueling and for some reason, when the gas pumped stopped I squeezed the pump trigger one more time. I don’t know why I did it, I had been warned not to yet for some reason I did it.

It was long afterwards I saw the gas gauge do its first flip-flop dance between empty and full. The error was initially intermittent, but over time it has become very consistent. Now mine always (and I do mean always) does its dance between empty and full right after I refuel. This will continue until I travel roughly 30 miles, I’ve never noticed the problem beyond the first 30 miles of a tank. Couple months ago I decided to try an experiment, instead of refilling until the pump clicks off I started buying my gas in $10 increments (never filling the tank all the way). The gas gauge never did its dance during the 4 or 5 tanks that I did the $10 thing. So at least in my case, these observations seem to back up the theory that the failure is related to the sending unit. I’ve learned to live with it, but learn from my experiences and resist the urge to squeeze that gas pump trigger again once it clicks off.

I have made the decision to live with it rather than have it fixed because I am not comfortable with the “fix”. To get to the sending unit BMW has to cut the carpet behind the passenger seat. Then they have to hook a hose and drain the gas tank (hopefully without leaving your interior smelling like gasoline). If you look behind the right hand seat you can see a seam in the carpet, this is where they will make the cut. Once the sending unit is replaced the carpet is glued back down. Sounds simple enough but I have seen more than one Z3 after this fix where the carpet flap has come unglued and ends up looking like a bad toupee. It also appears the new sending units are not necessarily any more reliable than the original ones.

I’ve owned my M roadster over four years now and my refueling habits are fairly consistent. I’ll usually refuel before the low fuel light comes on, if I push it and the low fuel light comes on then pull off at the next available gas station. I use my trip odometer to measure distance on a tankful, and on average it usually says around 240 miles since my last refueling and it will take around 12 gallons to fill the tank back up.

One day after work I pushed it a too far, the engine sputtered then quit. I zig-zagged a little and got another second or two of runtime before it quit for good. Luckily I was going downhill at the time so I managed to coast into the gas station and right up to the pump. I got lucky, and this provided me with an opportunity. I now know it takes 13.3 gallons to fill a completely empty tank. I started taking notes after that and refilling at different points on my gas gauge. It takes 8.9 gallons to fill a tank that my gauge indicates is half empty. 12.3 gallons to fill a tank right after the low fuel light comes on. I will continue to take measurements at various points on my fuel gauge and update this page.

One last final note: Remember that my fuel gauge has problems so my measurements may not be typical of most Z3s.

Install VDO Oil Pressure Gauge in BMW Z3 M Coupe or M Roadster

The BMW M coupe comes with a warning light for oil pressure, as well as an oil temperature gauge in the center console. I’d like to know if my oil pressure drops below normal without waiting for the oil warning light to come on at 7 PSI, so I decided to install a VDO oil pressure gauge. This project involves interior trim removal and modification, wiring, and replacement of the oil sender (this last one requires you to drain the oil, so you might as well schedule this project when it’s time for an oil/filter change). As usual, Ron Stygar was a big help on this project. Thanks, Ron! His original post in the bimmer.org archives is here.

Parts Selection

The oil pressure gauge that almost matches the existing coupe gauges is a VDO Vision gauge. I say “almost” because standard Vision gauges come in all black, but the gauges in the coupe’s center console are chrome ringed. If you don’t care about the chrome you can buy a Vision gauge anywhere, but to match the existing gauges I went to Jon Maddux at LeatherZ (www.leatherz.com). Jon sells the 0-80 PSI oil pressure gauge ($79.00) that you need for the coupe, and supplies various colored bulb covers. The orange cover makes the gauge light a very close color match to the existing gauges. For this job you’ll also replace the stock sender with a VDO dual sender with angled mounting adapter that provides both the warning light and pressure reading, and Jon offers these too ($67.00). You’ll be running four wires for the electrical connections – one for power, one for dimming power, one for ground, and one for the sender. I purchased four 10-foot lengths of stranded wire in various colors and this was more than enough length. You need #14 wire for the sender wire to give the circuit the correct impedance; the other wires can be smaller gauge. You’ll also need four crimp-on female wire connectors to make the connections to the gauge and two crimp-on O connectors for the sender connections.

Some coupe owners choose to put their oil pressure gauges in the center console, replacing the analog clock. I didn’t want to give up the clock so opted to put the gauge on the A-pillar. The gauge mounts to the A-pillar, or more accurately to the A-pillar trim cover, in a plastic housing called a “pod”. I bought a single gauge A-pillar pod from egauges (www.egauges.com), part # 240-347 ($31.13). They also sell a dual pod in case you want to add a second gauge such as outside temperature.

Getting Started

NOTE: all directions (forward/rear, left/right) are in reference to the driver’s seated position.

Place the pod on the A pillar trim cover and slide it up or down until you get it approximately where you want it. Mark the location of the pod on the trim cover, then remove the cover by wedging your fingertips between it and the windshield and pulling it away from the windshield. The trim cover is held onto the A-pillar with two snap-in connectors. Once the connectors pop loose, slide the bottom edge of the trim cover out from the crevice formed by the A-pillar and the dash.

Cut a hole (I used a Dremel tool with a carbide abrasive tip) in the A pillar trim cover corresponding to the opening in back of the pod.

This hole is used to route wires and to give you access to the back of the gauge for changing the bulb. If your gauge ended up right over one of the trim cover’s snap-in connectors, you may have to adjust the pod position slightly.

Insert the gauge into the pod, orient it so that it will be straight as viewed from the driver’s position, and secure it by screwing the gauge nut onto the back.

To mount the pod to the trim cover, I drilled pilot holes and used the supplied plastic ribbed pins (screws).

Wiring

For power, dimming power, and ground wires, you need a sufficient length of wire to run from the gauge to the footwell area. For the sender wire, you need enough wire to run from the gauge to the footwell area, through the firewall, and on to the front of the engine compartment. Leave plenty of extra length on the wires at this point. Terminate one end of the wires with the crimp-on female wire connectors and, using the instructions with the gauge, mount each wire to the proper connector on the back of the gauge. Tape the wires to the back of the A pillar trim cover to keep them in place. Note which color wire you used for each connection.

Disconnect the battery before proceeding!

You’ll need to remove the lower dash panel just above the pedals, loosen or remove the upper dash panel under the steering wheel, and remove the driver’s kick panel with dead pedal.

Run the wires from the back of the gauge through the crack at the bottom of the A-pillar.

They will come out at the left bottom of the dash.

Re-install the trim cover/pod assembly onto the A-pillar.

Editors Note: The silver metal part with the messy looking ends is an interesting safety feature. Somewhat like a pillow, it’s a soft/thin metal with foam filling. Designed to protect your knees in an accident.

Leave some wire slack under the upper dash panel in case you need to remove the trim cover at some later date. Continue routing the wires down into the footwell area. Locate a violet/any color wire for power, and a gray/red wire for dimming power, from the existing wires in the footwell. You will probably have to release wire bundles by cutting wire ties in order to locate the colors you need. The dimming power wire allows you to control the lighting level of your new gauge by twisting the headlight button, the same way you adjust the other instrumentation.

Cut off any excess on your power and dimming power wires and splice them into the selected wires. I soldered the splices and coated them with some Star Brite liquid electrical tape. Connect the ground wire to the grounding nut, forward of the kick panel speaker. (Ground wires are solid brown in the coupe.)

Resecure all wires with wire ties. You can do a power and dimming test at this point by reconnecting the battery; just don’t forget to disconnect it again!

OK, three wires down and one to go! Take the lid off the fuse box (left rear of engine compartment) then unscrew the four #10 torx screws that hold the fuse box onto the wiring box below it. The right rear screw is somewhat obscured by the hood release cable. Just push the cable out of the way enough to loosen the screw. Disconnect the two black wire junction pods, the large red wire, and the green connector that are fastened to the right side of the fuse box and lift up that side of the box.

This will give you sufficient access to wiring box so you can see and grab the sender wire as you feed it through. You’ll see where the main wiring bundle comes through the firewall and into the wiring box. You can try to get your sender wire through the same hole but it’s already pretty well jammed with wires, so I just drilled a small hole nearby and ran the sender wire through it. Drill another hole in the right side of the wiring box; the sender wire exits the wiring box through this hole. Put a dab of silicon sealer on the hole to keep nasties out of your wiring box, and then reassemble the fuse box.

Route the sender wire along the back of the engine compartment, underneath the intake manifold, and to the oil filter, attaching it to the existing wire looms with wire ties.

Sender Replacement

Now it’s time to drain your oil and remove the old filter insert. Remove the air intake box to allow room to reach the oil sender. Unscrew the old sender from just below the oil filter and cut the wire attached to it, leaving as much length as possible. Terminate it, and the new sender wire, with O-connectors.

Mount the new sender to the angle adapter. Hand-tighten the sender to the adapter until snug but don’t over-tighten. The sender has tapered threads that do not require excessive torque to achieve a good seal. Align the sender so that the connector posts on the top are perpendicular to the engine-mounting hole on the adapter. Install the adapter/sender assembly in place of the old sender. Caution – improper installation of the oil adapter can damage your engine and cause oil leaks. Tighten the adapter bolt to 35-40 NM.

Connect the old (alarm) wire and the new (pressure) wire to the correct posts as marked on the top of the sender.

Finishing Up

Replace your filter insert and oil, reconnect your battery, start your car, and check out your new gauge. Under normal operation you’ll see a range of around 15 PSI at idle to 58 PSI. Assuming everything works, replace your interior panels, and you’re done!

Digital Temperature Gauge

In my old 1.9 Z3, I had the on-board computer which told all sorts of interesting things such as estimated range, average speed, and outside temperature. Call me strange, but with my new M roadster I miss that. I miss the 400 mile trips during winter in the dead of night with the top down, watching the temperature fall to below freezing, with the reassurance that yes, I was out of my mind.

On the Euro-spec M roadsters, they get an outside temperature gauge. According to rumor, it doesn’t work that well. Besides, to add that to my US-spec M roadster would cost more than $200, which I don’t have. I finally found a digital temperature gauge that met most of my needs, RadioShack part number 63-1023. They offer 2 different temperature gauges for cars, this is the better one (and more expensive, about $20).

The good things about this gauge are that it displays both the inside and outside temperature at the same time, it records the highest and lowest temperature, and it has a nice electro-luminescent backlight. On the down side, the LCD is hard to see from some angles, the backlight only stays on for 3 seconds when the button is pressed, and it uses batteries instead of car power. But altogether, it’s the best one I’ve seen anywhere.

The first thing I did was add a black sticker to the front that covers up the “RadioShack” name. It’s a small thing, but call me anal-retentive. Next, I went out and bought a radar detector windshield mount. I decided the best place for me to put the gauge was above the rear-view mirror, on the driver’s side. I had to be careful about the angle I placed the gauge at, since from some angles it’s hard to see. Once I had the angle figured out, I had to cut the detector mount down to the right size.

Next, it’s time to do something destructive. Cut the lead for the external probe halfway between the display unit and the probe itself. You will need to attach some extra wire to make things work. The place I placed the probe was up in the front bumper, behind where the front license plate goes. I took the black mounting bracket that comes with the gauge, removed the rubber piece, and superglued the mounting bracket in place. Next, I connected some more wire to the probe piece and ran them into the passenger compartment.

In the cockpit on the passenger side, underneath the glove compartment there is a piece of plastic held in place by 3 plastic screws. Remove this piece of plastic by turning the screws a half turn and removing them, then the plastic piece slides out. You should be able to see a rubber grommet by the speaker grill.

On the inside of the engine compartment you should be able to see the other side of it. Run the wires for the temperature probe through this hole, you should be able to push the rubber grommet aside enough to get the wires through. I then attached one side of a plastic 2-lead connector to the wires I ran through the hole. Don’t forget to use lots of nylon wire wraps to hold things in place in the engine compartment.

You can see (kind of) how I ran the wires along the passenger side of the engine compartment. Now it’s time to remove the plastic covering the inside of the pillars. To remove the side coverings, simply “pop” them off. I would recommend using a screwdriver with the tip covered by a towel (to prevent marring the surface) and wedge it in the top, then pull down. These should come off with a nice “pop”. You need to do both sides. Next, you need to remove the top frame covering. The clear plastic around the dome light gets scratched very easily, so please be careful (it’s white plastic under the paint, so it really shows when it’s marked up. The clear plastic pops off, try prying from the drivers side – that side is supposed to come off first. Then remove the light bulb assembly, it also pops out. Once again, be careful not to mark up the paint. Next, remove both visors, you will need a torx screwdriver. Then remove the one remaining torx screw that holds the top piece in place, it’s behind where the light assembly was. Last, just pull up to remove the covering.

Now it’s time to start placing things where they go. Use some superglue to attach the gauge to the radar mount, and be sure to let it dry thoroughly. Place it on the windshield in the proper location, and run the wires where they would need to go (you will have to attach more wire, the gauge only comes with 10 feet of wire and much more than that is needed. You will be running it along the top of the pillar and down the sides, next to the glove compartment. Once down there, attach the other end of the nylon 2-lead connector.

Now, just plug the connector in, replace the plastic piece below the glove compartment and put the molding back in place along the pillar and you are all set! Not quite as good as a factory installation but it does the job.

Discuss this article and other Convenience upgrades in the

///MZ3.Net discussion forum.

BMW Volt Meter

BMW Part Number: 62-13-2-695-215
Maker: VDO
Cost: $0 for US M roadster owners

After waiting a long time, BMW finally delivers something to fill in the blank gauge location on the dash.

Thanks to persistent questioning and a fantastic dealership it is my understanding that you are looking at one of, if not the first, dealer installed volt meter gauge in the US.

Behind the dash an unused wiring harness was waiting for the simple volt meter to be plugged in. The BMW technician that installed it (Larry Nissen of Moritz BMW) tells me it was quite easy to install, getting behind the dash to find the wiring harness was the only time consuming part of the task.

I’m not claiming to really understand what is happening to make a volt meter read high or low. To me it’s most important feature is the fact that it fills the once blank plate in the dash. However now that I’ve watched the needle move around for a couple weeks I’ve noticed where it usually resides. If I turn the key far enough to engage the electrical system but not far enough to start the engine the gauge usually reads just right of straight up (about 12.5 volts). Once I start the car the needle usually swings way right and climbs to 14 volts. After the car has been running awhile I notice the gauge slowly sneaking back towards 13 volts. So now that I notice a regular pattern, if I ever see the gauge breaking from this pattern I’ll probably freak out and over-react (which might be the goal of a volt meter). But like I said before To me it’s most important feature is the fact that it fills the once blank plate in the dash.

M roadster owners should be receiving this volt meter via USPS Priority Mail. Along with the volt meter (part number 62-13-2-695-215) is a letter from BMW apologizing for the inconvenience. The letter states that you can schedule an appointment with your local BMW center to have the volt meter installed free of charge. However they also attach installation instructions (which don’t look that difficult) so you could install it yourself if you want to.

Aluminum Gauges

Pros: Dramatic change in the dash appearance for not much money
Cons: Semi-hard to install, light color dials and white needles make reading the dials more difficult
Cost: $179

Available Colors: White, Yellow, Parchment, Aluminum*

Replaces: Speedometer, Tachometer, Fuel Gauge, Temperature Gauge

Sold By:

NR Automobile Accessories

www.nrauto.com

(800) 225-3498

Backlighting

During the day, the gauge face will have the specified color (white, aluminum, yellow, etc.) with black numerals. At night, the gauge face will be black and the numerals reverse to be the color of the face during the day. For example, when a white face gauge inverts at night, the face becomes black and the numbers become white.

Needles

If faces are front lit, needles can be colored with a very light coat of spray paint or magic marker. Backlit gauge faces will require needles to be painted with a translucent or clear paint. However, because needles are 3 dimensional, you should not have problem seeing them against the face.

Cluster Removal

Removal will require some mechanical aptitude. You can refer to a shop repair manual for your car to determine the best method. The clear cover usually attaches to the cluster with clips which can be depressed with a flat bladed screw driver. Removal of the needles and faces can be done at this time.

Recalibration

This is accomplished by using tool provided to remove needles and then replacing in the same position after new face is installed as per instructions provided.

Installation

Can be done with a little mechanical inclination. If you are comfortable working with your hands and have a certain amount of patience, installation is relatively simple. We provide basic installation instructions and a tool to help you remove the gauge needles; however, you need to know how to take your cluster out of the dash. Most of our customers do their own installations but we recommend professional installation if you are not comfortable doing this kind of work. Mechanics, speedometer shops and stereo shops also do installation of these gauge faces.

Chrome Rings in the Instrument Pod

Pros: Looks really good
Cons: Cost
Cost: $200

This is definitely not a do-it-yourself project. Your local BMW parts department can take your VIN number and order you a replacement dash pod for around $200 (yes, you will need to get an entirely new dash pod). The BMW dealership can then swap the dash pods for you for roughly two hours of labor. This is something you might be able to do yourself, but I highly recommend you let a dealership do the swap for several reasons.

1. Well documented that the dash pod was switched (in case there is any odometer questions later on).

2. Lots of electronics in this dash pod. The dealership will probably set off a few sensors (mine did) and resetting the sensors is something you can’t do at home. So you would probably end up back at the dealer anyway.

I got lucky; my original dash pod had a scratched fog light indicator lens in it. I was going to get a new dash pod under warranty. The service advisor was kind enough to order the chrome ringed dash pod upon my request (no extra charge). So consider this if you ever have warranty work done on your dash.