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Running On Empty

Created June 2, 2006, at 9:46 am by Anonymous

At my last fill up, I mistakenly grabbed the 93 octane nozzle and dumped 12.5 gallons in my tank. At first, I tried to pump the fuel out when I got home, but could not get a hose to the fuel level. Additives such as ethanol are use to increase octane which screw up the oxygen sensors in the FEH.. This has cause me loses of as much as 15 % in FE. My only alternative was to take the hit and burn the tank off through the engine.

Today, I started my commute with 40 miles past 0 MILES TO EMPTY and put a can of regular gas in the back to prepare to run out of gas.

From those posting on running out of gas awhile back, I expected the engine to shut down and a warning light to come on telling me to come to a safe stop. This did not happen, the LOW FUEL message did not change. Also, we were told that you were restricted to something like 22mph in EV to get to a station. This was not true today.

Here is what happen when I ran out of fuel:

I got on I-95 and was accelerating, but traffic started to slow from 50mph. I went EV at 40mph with only 20% SoC in the battery. Traffic started to pick back up from 30mph, so I hit the gas to go ICE ON and accelerate with traffic. The ICE would not come on, but I accelerated the fastest I have ever done before to 41mph. At first, I thought the ICE was running and the tach stopped working. I was afraid to exceed 41mph in EV, so I back off to 40mph and drove to the nearest exit (about 3/4 mile) and an additional .2 miles to a parking lot. I turned the key off, and tried to restart. Nothing, the FEH acted like I had it in “D” or something. Tried it a few more times, and it started, but idled like it was running out of gas so I turned the key off right away.

I was amazed that the FEH continued down I-95 at 41 mph on a drained battery. This means I dropped the low side of the battery to a level I’ve never been to. What happen after I added gas to the tank and started the FEH was very interesting. to say the least. As I started to back out of my space, an older person was having a hard time getting his car out of his space, so I had to sit there for a few minutes. All of a sudden, the ICE started to tach up like it does with over regen while I was waiting (stopped) for this man to get out of my way. Strange, but all I could think of, was too much charge from the small generator was overheating the battery which may have been at it’s limit from the 41mph EV run. As I got going, the battery level did not show on the Nav energy screen yet, so I tried a fake shift to boost it up. No regen was possible for two miles and the battery level started showing about 25% SoC.. The battery continued to be very sensitive for about 5 miles.

Anonymous

5 years ago

GaryG,

I read your story a while back and had a thought about it today. If the FEH uses the gas guage signal to determine that it needs to run EV only, it may be very easy to add an EV mode only switch. All you would need to do is set the fuel level sensor signal to something that looks like an empty tank. Based on your experience, the FEH could be interesting to drive in that mode. This would have to be done with some restraint since you would not want to over heat the battery to take it to a low charge state. I don't know how much of the battery protection works in the "No Gas" mode but it sounds like you may have had some battery over heating. I would mainly like to have the EV mode switch when I need to move the FEH in and out of the garage or other short distances. As you know, starting the ICE for only a minute or two is not good for it and really hurts fuel economy.

Anonymous

5 years ago

I do not think the FEH uses the gas gauge signal to determine that it needs to run EV only. My guess is the computer (PCM) senses fuel pressure loss from the fuel pump driver module (FPDM), and signals a limited operating strategy (LOS) with the ICE off. When I tried to restart the FEH after parking, nothing happen when I turn the key at first. My guess was fuel was being pumped, but the pressure was not there for the FPDM to signal the PCM to start the ICE. A few more tries and it did start, but ran like it was running out of gas. The PCM controls the variable speed fuel pump and would control shut down of the fuel pump through the FPDM.. After I added fuel to the tank, it started and ran fine. If my guess is right, it is the PCM that controls a shutdown that signals a limp home mode the to the vehicle computers (Traction Battery and transmission control modules).

In other words, the system in the FEH is so complex, I recommend you don’t even think about a modification like that.

Sorry, GaryG

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