Not Getting Full Tank Capacity on refueling

[midijeep]

Hi,
I have a 2001 cavalier with a 6.2 tank capacity. I went to fuel at Torso gas station on redwood road and N. Temple. The tank was completely empty but I could only get 2.9 gallons in the tank. The pump stopped at 2.9 gallons and wouldn't move anymore. Any ideas on the problem?

Thanks

[Lakewood90712]

Re: Not Getting Full Tank Capacity on refueling

Welcome to the real world. Nothing is wrong with your cavi.

A vehicle with multi tanks can have a bad tank check valve , but AFAIK , you have a single tank.

6.2 is with a slow fill from 0 psig in the tank at 84 degres and a little over 3600 psi at the pump.

A real world fast fill on a summer day maybe 80% of rated capacity if starting completely empty, less if not completely empty. The amount of fuel dispenced will depend on temperature, actual pressure, how empty was the tank, and how accurate the dispencer is.

Time for cngmike or Tom from tulsa gas tech to chime in.

[Devo]

Re: Not Getting Full Tank Capacity on refueling

Probably just low pressure at the pump (maybe a big vehicle came through before you). I've filled at that station a few times and didn't always get full pressure.

[freedml]

Re: Not Getting Full Tank Capacity on refueling

Was the needle inside the car reading Empty on CNG when you started (or switched to gasoline) and Full on CNG when you finished?

[CNG MOTORS]

Re: Not Getting Full Tank Capacity on refueling

I assume this is a factory CNG cav. If so I read no mention of an aux tank. So it you actually have trunk space as little as it is you only have one tank and it's 5 gge at 3600 psi not 6.2. I don't think they make 1.2 gge tanks even.

So assuming you have just the stock 5 gge tank, I agree with the others low station pressure is to blame. Unless you already had fuel in the tank and you have another issue with the CNG system could be another reason

[CNG Utah]

Re: Not Getting Full Tank Capacity on refueling

Just so you know. There is a gauge on the side of the pumps. Look at it before filling and you'll get a good idea of the pressure at the pump. You can also watch it raise and stop while you're filling. You'll notice that you very rarely see a reading of 3600 psi in Utah, although it does happen occasionally.

On a side note, we sometimes get over 5 gge in Cavaliers and on one occasion got just over 7gge although that might have been a fluke of the temperature and an extra pressurized pump.

This document shows the CNG capacity of a 2001 Cavalier as 6.2 gge.

[midijeep]

Re: Not Getting Full Tank Capacity on refueling

Was the needle inside the car reading Empty on CNG when you started (or switched to gasoline) and Full on CNG when you finished?

Switched over to gasoline

[midijeep]

Re: Not Getting Full Tank Capacity on refueling

I assume this is a factory CNG cav. If so I read no mention of an aux tank. So it you actually have trunk space as little as it is you only have one tank and it's 5 gge at 3600 psi not 6.2. I don't think they make 1.2 gge tanks even.

So assuming you have just the stock 5 gge tank, I agree with the others low station pressure is to blame. Unless you already had fuel in the tank and you have another issue with the CNG system could be another reason

Its a 6.2 @3600 psi, manual and on the tank itself says so.

[midijeep]

Re: Not Getting Full Tank Capacity on refueling

I have fueled several times now and looked at the gauge on the fuel pumps. The more the pressure on the fule pump the more I got in the tank. I am going to try Questar tomorrow. I hear they have more pressure at their fuel pumps.

[freedml]

Re: Not Getting Full Tank Capacity on refueling

Maybe it's switching with a lot of CNG left in the tank.

[CNG MOTORS]

Re: Not Getting Full Tank Capacity on refueling

I have sold huindreds of cavaliers and filled up just as many and never have I gotten anywhere near 6 gallons from empty. Curious about you 6 gallon cavalier guys. The cav gets roughly 30 mpg at 6.2 gallons are you getting a 186 mile range on NG?. At 5 gallons i get 135-150 miles on cavs. Empty it and fill back up and I still get only 5 gge.

So I am wondering several things. Are the pumps you are filling from inaccurate or are they over-preassurizing you? 4000+ psi?

BTW. Honda says 8 gge also but I only get 6 gge's into it. 2005 and older, duno about 06 and newer

[freedml]

Re: Not Getting Full Tank Capacity on refueling

Don't think I've ever gotten more than 4.5 from a fast fill, but I only fast fill on vacation.

[krnorth]

Re: Not Getting Full Tank Capacity on refueling

I have an 00' Cavalier, and a 99' Cavalier. We were told from MANY numerous sources even from GM that the Cavalier comes with a 6GGE tank. I could further do some research on this.

However, the 00' which I drive around I am able to completely run it out of CNG and I am able to fill up anywhere from 5GGE up to 6GGE, the most I have ever let the tank accept is 6.008GGE. This was at Springville pumps in Utah. They usually have around 3600PSI. I have also filled at stations which register 3000 PSI and have filled up with 5.8GGE before. But I would certainly wonder the accuracy of these PSI gages....

[Highmarker]

Re: Not Getting Full Tank Capacity on refueling

Let me put this to bed.

The Cavalier does state the tank is a 6.2 GGE tank. However that is the tank capacity if the tank were completely empty and then filled with CNG to 3600 psi at 70°F. When a Cavalier switches over from CNG to gasoline, there is approx. 300 - 400 psi still in the tank. When you fill your Cavalier, temperature effects natural gas more than you think. You will get more CNG in your tank in the winter than in the summer (assuming pressure is the same). The most I have ever gotten was 6.002 GGEs in October of 2007. My average fill up (assuming pressure is the same) is about 5.1 - 5.2 GGEs. In the summer, I am lucky to get 4.8 GGEs.

[CNG MOTORS]

Re: Not Getting Full Tank Capacity on refueling

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