Fuel guage problem

I have a 99 chevy silverado 1/2 ton with 50,000 miles, I am have trouble with my fuel guage dropping off to empty and my low fuel light coming on. If While driving I can shake the wheel and it comes back to where its supposed to be. This will happen over and over again, it doesn't ever stop. It seems like a wiring issue but where do I start. Anyone have any suggestions.

I have a 99 chevy silverado 1/2 ton with 50,000 miles, I am have trouble with my fuel guage dropping off to empty and my low fuel light coming on. If While driving I can shake the wheel and it comes back to where its supposed to be. This will happen over and over again, it doesn't ever stop. It seems like a wiring issue but where do I start. Anyone have any suggestions.

Welcome to the forums :smokin: I hope you can be patient in getting your answer here. People are usually quick to help out, but being the holidays I guess were all busy. There are some very good GM efficionados here (GM gurus) and I am sure one will chime in soon. I am a new GM owner, but I have had your problem in other makes and models. I hear the float and sending unit on these trucks go weird sometime. You may have to loook into a replacement. Try cleaning the ground at the tank and all connections with a contact cleaner solvent.
Good Luck!!

It's a very big possibility it's sulphur contaminated the sending unit. Try some strong doses of Techron.

It's a very big possibility it's sulphur contaminated the sending unit. Try some strong doses of Techron.
Mine did something simmilar to it put a new sending unit in and it stoped. That is what is most likely wrong with yours.

Mine did something simmilar to it put a new sending unit in and it stoped. That is what is most likely wrong with yours.
This seems to be common on GM vehicles i had a 99 camaro and it would stay on full while driving and empty while the car was sitting in idle. Now my 99 silverado has started to flucuate while i drive, mainly around startup it tends to show lower than there really is. This is after i had to replace the fuel pump, before it was doing it much worse.

You have two ways to go.
Tank sending unit or dash gauge.
If it quits sitting still tap or give the dash a few whacks.
A good eng capable sanner will sometimes test the gauges.
If it quits sitting still ground the wire going to the tank unit or hook a test light to it and see if dash gauge kicks in.
Any problems on the odometer lighting up or going out?
MT

I have a 99 chevy silverado 1/2 ton with 50,000 miles, I am have trouble with my fuel guage dropping off to empty and my low fuel light coming on. If While driving I can shake the wheel and it comes back to where its supposed to be. This will happen over and over again, it doesn't ever stop. It seems like a wiring issue but where do I start. Anyone have any suggestions.

My son has a 2000 Silverado, the fuel gage is also screwed up, on his, if you put the truck in neutral the gage comes back up and shows the correct level, but isn't damped well but at least you know about how much gas you have, it's pump is fine, shooting out 50 psi, so we're living with it as is, the cost for after market is about $300 plus labor to install, so we're just putting up with the problem for now, I understand this is a notorious problem on this model and late 90's and 00 models.

Dhspring
You also may have a dash problem with the fuel gauge.
Fuel pecs for 4.3 5.0 and 5.7 are 60/66 lbs pressure
Fuel specs for 4.8 5.3 6.0 and 7.4 are 55/62
Any less and you have a fuel prssure problem.
MT

Sounds like the old Silverado sending unit problem like most everyone has or had. I have it and I don't want to enrich the dealers pocket by $400+ to replace it and I don't have a place to do it myself. I just fill up when the trip-o-meter hits 300 miles (350 on a freeway road trip)and then reset it again.

Dhspring
You also may have a dash problem with the fuel gauge.
Fuel pecs for 4.3 5.0 and 5.7 are 60/66 lbs pressure
Fuel specs for 4.8 5.3 6.0 and 7.4 are 55/62
Any less and you have a fuel prssure problem.
MT

That's interesting because I posted earlier that my son's truck is having problems on start-up, it doesn't want to run well unless you give it some gas at startup, it acts like it's not getting enough gas, when I checked the pressure it's right at 50 psi, which I thought was plenty, I didn't check the book specs. So maybe this is our problem, low fuel pressure? Could very well be.

Secondly, as I described the fuel gage working properly when putting in neutral, you think this could be a problem in the dash? What is the solution? To me it seems to be in the steering column since we have to move the shift lever to make the gage work.

Thanks

On the gas gauge it could go either way tank unit or dash. Working when you put it in neutral rings a bell on dash.
I repaired one that had a lose solder joint.
It would knock out fuel gauge and odometer light and maybe gear selector indicater. That stuff is all computer controlled in the dash modules.
Try tapping on the dask when it quits.
Your fuel pressure is low. That will caues hard start more when cold. You are luckey it is starting.
Tips on checking fuel pressure.
The specs are for 4.3 5.0 and 5.7 engines if other eng use the specs I posted in upper post.
Hard to start cold.
Check cold start fuel pressure.
Check engine running fuel pressure.
Check engine running on the road fuel pressure.
Then shut it off and watch for fast leak down.
Pinch off at rubber part or block off return line and check full pressure.
Later V6 and V8 4.3 5.0 and 5.7 gm engines should have 60-66 fuel pressure.
other V8 55/62 but check year and book for specs.
Cold start should be 64-65 lbs of pressure.
If you do not have full fuel pressure on a cold start the injectors will not squirt fuel.
Do not leave home without it.
Engine running should be 60-66 lbs pressure depending on engine load.
Full pressure with return pinched off should be 75-85 or more.
And if it has a fast leak down after shut off you have a leak.
Post back fuel pressure readings.
Let us know how it goes.
MT

On the gas gauge it could go either way tank unit or dash. Working when you put it in neutral rings a bell on dash.
I repaired one that had a lose solder joint.
It would knock out fuel gauge and odometer light and maybe gear selector indicater. That stuff is all computer controlled in the dash modules.
Try tapping on the dask when it quits.
Your fuel pressure is low. That will caues hard start more when cold. You are luckey it is starting.
Tips on checking fuel pressure.
The specs are for 4.3 5.0 and 5.7 engines if other eng use the specs I posted in upper post.
Hard to start cold.
Check cold start fuel pressure.
Check engine running fuel pressure.
Check engine running on the road fuel pressure.
Then shut it off and watch for fast leak down.
Pinch off at rubber part or block off return line and check full pressure.
Later V6 and V8 4.3 5.0 and 5.7 gm engines should have 60-66 fuel pressure.
other V8 55/62 but check year and book for specs.
Cold start should be 64-65 lbs of pressure.
If you do not have full fuel pressure on a cold start the injectors will not squirt fuel.
Do not leave home without it.
Engine running should be 60-66 lbs pressure depending on engine load.
Full pressure with return pinched off should be 75-85 or more.
And if it has a fast leak down after shut off you have a leak.
Post back fuel pressure readings.
Let us know how it goes.
MT


Thanks very much, sounds like a bad fuel pump could likely be the problem and may fix both problems at once. I don't guess changing the pump is too awful bad, the worse part is dropping the tank as usual.

Usually the fuel pum is the problem but run the fuel pressure test to make sure.
And yes it could solve gas gauge problem to.
To replace the fuel pump it is either drop the tank or remove the truck bed.
Some go one way and some go the other.
Good luck and let us know how it goes.
MT

Usually the fuel pum is the problem but run the fuel pressure test to make sure.
And yes it could solve gas gauge problem to.
To replace the fuel pump it is either drop the tank or remove the truck bed.
Some go one way and some go the other.
Good luck and let us know how it goes.
MT

Will do, thanks very much for all your help

DH

Will do, thanks very much for all your help

DH

I checked the fuel pressure tonight, it's 48 psig at start-up and 44-45 during fast idle and drops to about 42 at shut off with no further leakoff. It sure looks like a fuel pump since it should be 55-62 psi. I don't guess it could be the fuel pressure regulator, I checked my Haynes book and they say if pressure is low to check restrictions in the line, fuel filter etc and if all clear, replace the fuel pump. I don't guess the fuel press. regulator can fail and restrict fuel pressure, it fails and lets pressure elevate above the normal 65 psi max, correct? I think I'll check the fuel filter and if that's good, it's probably the pump.

A fuel pressure regulater bad or a internal leak can cause low fuel pressure.
You can pinch off or plug the return fuel line and then check pressure or the best test is to check the fuel pump pressure direct at fuel filter.
The fuel pump should be putting out 20-30 lbs or more pressure than the running pressure that is regulated by the fuel pump regulater.
MT

I replaced the fuel pump on the old Chevy and wah-la, that was the problem, fixed the start/idle problem and also that dammed fuel gauge that has never worked since we owned the truck. So we're good to go.

One thing, we dropped the tank to replace the pump and there are 2 hoses going into the fuel tank, an internal which is where the fuel actually travels into the tank. It has a one-time hose clamp put on that is extremely tight and hard to get back on. There is the outer hose about 2-3 in. in diameter. I did not get the internal hose back where it goes, so I just plumbed up the outer hose and called it good to go. Does anyone know about the inner hose, and do I need to put it back on?

Thanks

A fuel pressure regulater bad or a internal leak can cause low fuel pressure.
You can pinch off or plug the return fuel line and then check pressure or the best test is to check the fuel pump pressure direct at fuel filter.
The fuel pump should be putting out 20-30 lbs or more pressure than the running pressure that is regulated by the fuel pump regulater.
MT

I got her fixed, it was the fuel pump so that was a helluva job but we got it done. DO you know about the 2 hoses going into the tank. There's a small 1-2" dia hose plumbed to a nipple at the neck of the fill receptacle, then an outer ~3" dia that goes over the receptacle neck and onto the tank. I could not get the inner hose back on, it had one of those one-time clamps on it and it's too close to put a standard clamp on so I left it off, plumbed up the outer hose and called it good. Hope this doesn't cause any problems. Any advice is appreciated.

Thanks

dhspring

It is more for venting the air out when you fill up the tank.
If it refills up good. No problem. If it gives you problems on fill up you may have to work on the small inside hose.
And yes I know they are a pain to get back in there.
And thanks for letting us all know how it went.
Good luck MT