Odd fuel/starting issue

[TheAutumnWind]

This only happened once, but I want to see if anyone has run into anything like this.

Wife tells me the fuel gauge "bounced" back and forth from full to empty, and the truck died after she tried to start it. She attempted to start again and it died again. On the Third attempt she blipped the throttle, it fired fine, and ran fine.

No SES light, no codes.

More than half of a tank of gas.

I drove it today and no problems. Maybe she didn't hold the key in the start position long enough? I'm hoping for this.

Otherwise fuel pump or clogged filter maybe? Any ideas or input would be great. Thanks TYF!

 

[OR VietVet]

Need to get a fuel pressure reading asap and keep in mind the sending unit for the fuel gauge is attached to the fuel pump. There is a shrader valve attachment at the fuel injection rail that you can attach the gauge to.

 

[TheAutumnWind]

Need to get a fuel pressure reading asap and keep in mind the sending unit for the fuel gauge is attached to the fuel pump. There is a shrader valve attachment at the fuel injection rail that you can attach the gauge to.

Thanks raiderron! I'll have to go buy a pressure tester. Looks like Harbor Freight has one that works fine for $20 with some teflon tape.

The Autumn Wind is a pirate
Blustering in from sea,
With a rollocking song, he sweeps along,
Swaggering boisterously.

His face is weather beaten.
He wears a hooded sash,
With a silver hat about his head,
And a bristling black mustache.

He growls as he storms the country,
A villain big and bold.
And the trees all shake and quiver and quake,
As he robs them of their gold.

The Autumn Wind is a Raider,
Pillaging just for fun.
He'll knock you 'round and upside down,
And laugh when he's conquered and won.

 

[OR VietVet]

Hopefully the hose on the gauge will be long enough for you to tape it to the windshield and you can watch it while driving and monitor the pressure in real time driving. You can get extension hoses for that purpose if needed. That is the best because all you can do with the hood up is monitor the pressure at start up, at idle, at acceleration and after you shut the engine off you can see if the pressure bleeds off. It shouldn't. May drop 4-5 psi but no more.

 

[TheAutumnWind]

Hopefully the hose on the gauge will be long enough for you to tape it to the windshield and you can watch it while driving and monitor the pressure in real time driving. You can get extension hoses for that purpose if needed. That is the best because all you can do with the hood up is monitor the pressure at start up, at idle, at acceleration and after you shut the engine off you can see if the pressure bleeds off. It shouldn't. May drop 4-5 psi but no more.

Hopefully there is enough hose, looks like I should be able to snake it up between the hood and cowl.
http://www.harborfreight.com/fuel-injection-pump-tester-92699.html

 

[OR VietVet]

Yea that looks like it is doable. Put the engine thru it's paces while driving. All sorts of driving. That looks like a decent kit for just $20.

Stop at a parts store and check for any stored codes or history codes. Make sure to get detailed code numbers and report back.

 

[TheAutumnWind]

Yea that looks like it is doable. Put the engine thru it's paces while driving. All sorts of driving. That looks like a decent kit for just $20.

Stop at a parts store and check for any stored codes or history codes. Make sure to get detailed code numbers and report back.

I can pull codes with Torque Pro and a bluetooth elm327 module. Nothing there.

That was the first thing I did.

 

[OR VietVet]

Ok, well get back with us when you get some pressure readings. By the way how old is the fuel filter? I have seen where old filters make the pump work to hard to push fuel through and then damage the pump.

 

[SLCHOE]

Fuel pressure would not affect the fuel gauge. The fuel gauge is reading from a float indicated potentiometer much like the float in a toilet tank.

Sounds like a bad stepper motor to me. Let's say you have a full tank and go to crank the engine. The gauge goes from empty to full because you have powered on the ECM/Cluster in the process. Even if the engine was to die from lack of fuel, the gauge would still read the same because the key would have still been in the "ON" position.

Fluctuation indicates a stepper motor these trucks are known for IMHO.

 

[OR VietVet]

I agree about the stepper motor but that will not keep the engine from running or starting. The fact that the potentiometer better known as the sending unit is attached at the hip to the fuel pump in the tank leads me to believe that the whole assembly is bad and not just a stepper motor in the cluster. Yes, they are known for stepper motor problems but not for the stepper motor keeping it from running or starting.

 

[SLCHOE]

I agree about the stepper motor but that will not keep the engine from running or starting. The fact that the potentiometer better known as the sending unit is attached at the hip to the fuel pump in the tank leads me to believe that the whole assembly is bad and not just a stepper motor in the cluster. Yes, they are known for stepper motor problems but not for the stepper motor keeping it from running or starting.

You may be correct since they use the same conector/wiring pigtail but I was thinking of two separate issues here. First an erratic gauge and secondly and coincidentally a driveability/starting issue. I could be wrong.

 

[HUMBL57]

From your scenario my opinion is a loose electrical connection at the top of the fuel tank. Was it raining or anything that day? Might want to check the pins of the pigtail plugging into the sending unit.

 

[TheAutumnWind]

Thanks for all of the replies. I have not had the chance to get the fuel pressure tester. I drove the nali Friday and Saturday with no problems.

I don't know when the fuel filter was last replaced, probably not recently.

Will likely replace that asap. Hopefully I'll have time to work on the thing tomorrow.

 

[SLCHOE]

Here's a cheap easy diagnosis for you.

Grab a nice cold beer.

Sit in the driver's seat and cylce the key on/off/on/off over and over letting the gauges do their normal thing. Look for erratic behavior.

The pre 04 GMT800s had tons of cluster issues, Your Nali is included. Key on... key off /repeat. Also, the needles should sweep up/down smoothly. Any jerky motion indicates a failing stepper motor.

 

[TheAutumnWind]

Here's a cheap easy diagnosis for you.

Grab a nice cold beer.

Sit in the driver's seat and cylce the key on/off/on/off over and over letting the gauges do their normal thing. Look for erratic behavior.

The pre 04 GMT800s had tons of cluster issues, Your Nali is included. Key on... key off /repeat. Also, the needles should sweep up/down smoothly. Any jerky motion indicates a failing stepper motor.

I'm all for any diagnosis that starts with step 1: grab cold beer
[emoji41]