Johnz02Z06

I have had my 2002 Z for 2 years and always fill it up at the same place. I noticed before the last fill up I was at 1/4 tank going to work (4 miles). When I got off work and started the car I got the reserve fuel warning and it was on E. So I drove 2 miles to the gas station and filled it up and went on my way. Today after work I was driving home and the car cut out coming off a light. I looked and the gage was a tiny below 1/4 tank. I went another mile and the car quit! I pulled over and waited about 1 min. and started again then died. I then turned the key and could hear the fuel pump so I know I was out of gas. The DIC said I had 42 miles of range. I put 2 gallons in it and then drove to the gas station and could only get 12 gallons in...

2 questions

1) What can I do to make the gage read accurate?
2) Why couldn't I get more gas into the tank?

tlove32

Fuel gauge issues are a common problem with C5's. Pour some techron in the tank, or run Chevron gas. It seems to cure these fuel gauge issues

LoneStarFRC

If you are in fact running out of gas (and from what you describe, you are), it is not a fuel gauge causing this. It is the right side fuel pump not transferring fuel to the left tank.

Personally I would replace the right tank pump/sender assembly.

HTH

wrmiles

Agree with both the previous posts. The gauge issue and the running out of gas issue (with only taking 12 gallons) can be caused by separate things, the sender and RH tank jet pump respectively.

One thing to add. When the transfer is not working, the PCM will sense the improper fuel levels in the tanks and after a certain amount of driving (about 150-200 miles) from a full tank, drive the gauge to zero as a warning. Does yours do this?

I have experienced this problem and replaced the RH sender and jet pump, which comes as an assembly. Other people have reported success in cleaning out the internal passages in the jet pump. The motive flow nozzle is very small so it doesn't take much to plug it.

LoneStarFRC

Yep. The fact that he has actually run out of fuel yet the tank(s) would only take 10-12 gals (~) is a clue. A big one. Often ignored by many who focus solely on the gauge issue alone, which is designed to read low/zero in this instance.

RonSSNova

So, how much gas should the car take when the tank says 1/4 of a tank left?

I just don't trust gas gauges....been burned too many times before.

Ron

Johnz02Z06

Thanks for all of your help. My Z is my daily driver with 79,000 miles. I will put some techron in the tank first and then run it down to 1/4 tank again and then fill it with Chevron and see if there is a change.

LoneStarFRC

Capacity is about 19 gals (~) so you can compute your own amount from that. Capacity varies a slight amount depending on year model. Some OMs may say one thing yet another year model says another. My '99 OM says 19.3. Everyone should learn what their capacity is, in order to have a better handle on if something is "wrong".

Point being, if your gauge reads "1/4" and it takes say, 14 gals to fill a 19 gal tank, you know you had approx 5 gals remaining. That's just an example, but you get the idea. Fuel gauges are very seldom linear, no matter what kind of car it's in, with one reason being the designers designed a little bit of a "fail-safe" so-to-speak, so even if it indicates "zero" (under normal circumstances), you probably have yet another gal or so of fuel, maybe two. Logic being, it's better to start warning you a little early i.e. "RESERVE FUEL" or "LOW FUEL", than have you actually run out.

The OP, and others (including myself) have experienced erratic readings such as gauge going to zero with a warning - CHECK GAUGES or RESERVE FUEL - and wondered why since they just filled up 50 miles back, or 70 miles, etc and there's no way you can be "out" of, or very low on, fuel, in that short a time so obviously something is wrong. In that short a distance, it probably is the sensor, but on the other hand, if you've driven say 150 - 180 miles (~) and all of a sudden not only does your gauge go to zero but your engine dies due to being "out of gas", it is likely your right tank pump/sending unit assembly that's failed and your left tank is empty. It's the one that supplies the engine. The big clue here being it only takes approx 9 to 10 (or 11, etc) to "fill" back up and it won't take any more, yet the gauge said "zero" beforehand. In that scenario, you likely would have been getting multiple warnings, as the sytem is designed to monitor the sensors in both tanks and continuously compare the two. If the pcm sees a constantly lowering left reading but no lowering (or very little) right reading, it will start screaming at you beforehand.

Each car owner should be aware of about how many miles they've actually traveled on their individual car by the time they reach "1/2" tank so if they're at (or close to) 1/2 a tank and start getting "empty" warnings, don't take a chance. Stop and get gas and see how many gallons it took. I would encourage each person to reset their trip odometer each time they fuel up and become familiar with their own car.

HTH

LoneStarFRC

Be careful. You may want to check it at 1/2 instead of 1/4 because if you actually DO have a right tank pump problem, you may never get to an actual "1/4 tank" and may run out of gas again if you empty out the left tank again. Of course you will have been getting warnings before then (gauge driving to zero) but still. Remember, each tank holds half the total fuel on board but it's only the left tank that supplies fuel to the engine directly.
Keep a close eye on things.

Johnz02Z06

Thanks for your help LoneStar

LoneStarFRC

I just didn't want you to inadvertantly run out of gas again. That kind of thing never happens when it's convenient. BTDT.

RonSSNova

I thank you as well.
I need to fill it, drive it to 1/4 and refill and see where it is.
I believe all is well with mine, it's just that I try to keep it at half or so for drag racing. Don't want to haul all thet extra gas down the track you know.

LoneStarFRC

Hey, I hear ya Ron. Every pound counts when you be racing.

Highpower500

I had the exact same problem. I always had to keep track of my miles and mileage to make sure I didn't run out of gas. I tried at least 1/2 dozen bottles of Techron without success. I was never able to drive more than 240 miles without running out of gas and then I could only put about 11 or 12 gallons in the tank. I finally had the passenger side siphon pump assembly replaced a couple of weeks ago. Over the weekend, I hit over 300 miles on one tank and then was able to put in about 15 gallons. According to my calculations, I probably had about 3 or 4 gallons left in the tanks.

LoneStarFRC

Think of "RESERVE FUEL" as a "first" warning - which it actually is - and, "LOW FUEL" as a "final" warning. I forget the actual amount of remaining fuel, in gallons, that triggers each warning right now. I would have to dig it up in my OM or FSM.

Suffice to say, you can easily check your "remaining miles" in your DIC assuming (very important) your fuel system is operating normally. You can easily see the differences in the remaining miles to "empty" between the two by checking the DIC. Doing this routinely will give you a better informed feel for what your dealing with when you see them.

Important to note here that everyone should become familiar with their car and the use of the DIC display to routinely check on various things. Routine monitoring of the various items will reveal trends or what could be precursors to potential problems. IOW, don't just sit back and wait for something to occur (unusual temps, voltages, oil pressures, tire pressures, etc) and only THEN check it. Don't be paranoid, but don't expect the car to be your nanny either.

The three main areas of focus for me, especially on a road trip, are: Temps, Fuel and Tire Pressures. Besides it give me something to do while driving during those long boring stretches of highway.

Highpower500

Sounds good, thanks!

wrmiles

My experience with RESERVE FUEL and LOW FUEL:

RESERVE FUEL= 3 gallons left

LOW FUEL=2 gallons left

LoneStarFRC

That's in the ballpark for me too. Good to be aware of the numbers on your particular vehicle, as they may be slightly different on someone else's.

I am also an advocate of frequently checking the actual mpg, as opposed to the DIC mpg and becoming very aware of the differences. There will be some. It varies from car to car. The upshot being the ability to be able (or not) to believe the miles remaining when running low, especially you're out on the highway on a trip. I think it's just too easy to believe the DIC all the time and then possibly wind up on the side of the road out of gas.

Johnz02Z06

To add to my post... I turned a corner yesterday and the engine died. Luckly it was the corner to my streeet. I have 3/4 tank of gas and no code or light before hand. When I restarted it the DIC showed "reduced engine power". I left it shut off for 20 minn and came back to see what would happen. I started it and all was good. Took it to my local shop and ran codes and P1415 was the only code. I read through some of the post for this code and it seems this mostly happened to "boosted or cars with H/C mods"

dustysix

can anyone give me a description of how the siphon jet pump works? took mine out expecting to see an ELECTRIC jet pump and realized that the jet pump works by siphoning the fuel from the right tank but that is activated by the electric pump in the left tank!So how is it turned off and on? probably by the pcm seeing sending unit differences? But since the left pump is constantly supplying fuel to the engine how does it start the siphon action? and by the way is the motive flow nozzle the small hole in the front of the face of the shiny round device i saw when i pulled out the right pump and sender?