P0193 and flaky fuel gauge

[01yellerCobra]

I searched and only found people with the code. A couple months ago the gas gauge would randomly show empty and the warning for 0 miles to empty would come up in the message center. Even when there was at least half a tank of gas. So then last Friday the P0193 (Fuel Rail Pressure Sensor Circuit High Input) code pops. At this point the gas gauge was fine. And she had put in about a half tank of gas. I checked the FRPS and didn't smell gas in the vacuum line. I pulled the connecter and reseated it, then cleared the code. Today she filled up and as soon as she started the car the code popped again. But now every few seconds the gas gauge drops to empty and the warning chime sounds. Then it's read full and start over.

While I'm hoping it's something with the FRPS, I'm guessing I won't be that lucky. I'm assuming the sending unit is bad. But do you think I have two different issues here? One in the tank and one on the rail?

 

[JeremyH]

Since your throwing the code I would replace the frps, then inspect the float in the tank. Last is stepper motor.


I have seen a similar problem when the sender wiring grounds to the pump body etc, but if its a stock setup that highly unlikely.

 

[01yellerCobra]

It's 100% stock fuel system. I was beginning to wonder if the float had sunk. I just went out and let it idle for a few minutes. The gauge didn't act up. Guess I'll order the FRPS.

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[07 Boss]

Though not quite the same scenerio, I had an issue with it reading full and then at half a tank it wuld dip to zero and i actually ran out once knowing that there was gas in her. My crossover tube got messed up and wouldn't transfer the gas over to the pump side.

 

[01yellerCobra]

Though not quite the same scenerio, I had an issue with it reading full and then at half a tank it wuld dip to zero and i actually ran out once knowing that there was gas in her. My crossover tube got messed up and wouldn't transfer the gas over to the pump side.

Were you still stock or had you messed with the pump?

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[07 Boss]

Were you still stock or had you messed with the pump?

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I had a GT500 pump in there, but the crossover tube is the same. In your situation it fluctuates. I don't think it is the float that sank because then it wouldn't come back up later. I don't think it would randomly fluctuate. There is a little box that the float arm attaches to and inside there there is a potentiometer type circuit. This could very well be just worn out. I had to replace one on my wife's fuel pump once (hyundai) but they're all pretty much the same thing.

 

[JeremyH]

The thing is the level sender is independent of the frps sensor code. So may have multiple issues.

 

[01yellerCobra]

The thing is the level sender is independent of the frps sensor code. So may have multiple issues.

That's what I'm assuming, but wanted to make sure I wasn't missing something. Like how a bad alternator throws a cam sensor code.

 

[06monera96]

sending unit on the pump side is going bad.
Usually caused by sulfur build up on the plates.
You guys have this thing called Techtron or Chevroom fuel system cleaner.
Drop a bottle in there and give it a few days (y)

 

[01yellerCobra]

She's been filling up at Chevron lately. I replaced the FRPS last night. Naturally it hasn't done either issue since I posted this thread.

 

[01yellerCobra]

Figured I'd go ahead and follow up. Swapping out the FRPS cured the P0193 code. And then Saturday I finally got around to installed the sending unit I had ordered. She said it was so bad the gauge would drop every couple of minutes. We swapped it out and drove the car around for a bit. Everything seems to be good. I pulled apart the stock sending unit and I could see the wear groove in the resistor part of the sensor.

 

[JeremyH]

Figured I'd go ahead and follow up. Swapping out the FRPS cured the P0193 code. And then Saturday I finally got around to installed the sending unit I had ordered. She said it was so bad the gauge would drop every couple of minutes. We swapped it out and drove the car around for a bit. Everything seems to be good. I pulled apart the stock sending unit and I could see the wear groove in the resistor part of the sensor.

 

[01yellerCobra]

Looks like I spoke too soon. On the way to the gym we stopped and filled up. About a mile from the gas station it started dropping again. When I swapped out the sending unit there was only a half tank of gas. Is there a sensor on the passenger side tank as well?

 

[01yellerCobra]

Just to keep things up to date....

I was able to do some research today. The perks of having internet at work. And there is a second sending unit on the passenger side. I know most of you are nodding your heads and thinking "no shit sherlock", but I'm still learning here. Anyway, I found a complete pump and sending unit on ebay so I went ahead and ordered it.

And for those wondering I did try the Techron, but it didn't work.

 

[JeremyH]

Passenger side reads full to half, driver side reads half to empty. The passenger side empties first. When you have a real half tank of gas passenger side will be completely empty and driver side will be full.

 

[01yellerCobra]

Passenger side reads full to half, driver side reads half to empty. The passenger side empties first. When you have a real half tank of gas passenger side will be completely empty and driver side will be full.

Which would explain why it was fine for 3 days since when we replaced the sending unit there was only half a tank.

Something else I'm wondering is for the last couple weeks she's had problems filling up past half tank. I was thinking it was the usual issue with the nozzle and told her to try turning it. She said she did and nothing worked. I'm wondering if she had a half tank left, but the sending unit wasn't registering. I do know it took 13 gallons last night. The new sending unit should be here next week.

 

[JeremyH]

I have seen the circuit boards on the cards get dirty or cracked and then cause a momentary low reading aka, drop to empty of drop to tell you zero miles etc. Happened to me once as well while back.

 

[01yellerCobra]

So I'm about to set the car on fire. It's still randomly going to zero even with the new sensor. It's only between full and half tank though. I really don't want to start tracing wires. I'm also wondering if it's something with the stepper motor. I'd rather deal with that than tracing wires.

 

[01yellerCobra]

So it looks like this probably was also the SJB. She filled it up last week, it did it's thing twice, and hasn't dropped since. At least the sending units are new now.

 

[Dino Dino Bambino]

So it looks like this probably was also the SJB.

Check if the passenger side carpet is wet. If so, your cowl drain plugs may be blocked with water sloshing around inside the cowl and seeping through the cabin air filter.