Any GM Techs Here?

stein700sx

stein700sx

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I have a 99 Sub and 98 Chev PU. In the last 3 months on both vehicles the fuel gauge has gone shakey. Both fuel pumps have been changed with GM units at different times have different mileage on them. Even with just the ign on and not running the needle shakes. Any ideas?
 

im not anymore but from what ive heard this is prob with all makes, from new fuel i believe, try running some gm fuel injection cleaner (plus) ive been told that works
 
stein700sx said:
I have a 99 Sub and 98 Chev PU. In the last 3 months on both vehicles the fuel gauge has gone shakey. Both fuel pumps have been changed with GM units at different times have different mileage on them. Even with just the ign on and not running the needle shakes. Any ideas?
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Check to make sure that the ground strap that goes to the tank wasn't forgot to get re-hooked. I did my sister inlaws 98 burban and no issues, and on another thought my brother had his burban done at the dealer and his needle shakes (he's NOT happy) fwiw on his the comp sending unit was replaced and on hers I only replaced the fuel pump.
 
Sxr700Bandit said:
Check to make sure that the ground strap that goes to the tank wasn't forgot to get re-hooked. I did my sister inlaws 98 burban and no issues, and on another thought my brother had his burban done at the dealer and his needle shakes (he's NOT happy) fwiw on his the comp sending unit was replaced and on hers I only replaced the fuel pump.
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I agree bandit, stein, if that was the metal style sending unit, make sure the connections on top and on the underside of the sending unit are not burned. i have seen many cases where the terminals of the underside connectors on the sending unit were burned, giving false indication of a bad pump. i was just looking at the schematic, if the ground strap to the frame was completely disconnected the pump would be in-op. loose connection might result in your symptoms. if you have the plastic style sending unit however, make sure the "feelers" on the level sensor are not broken off. if you have the sending unit back out, you can do a resistance sweep on the level sensor. i'd put my money on a bad connection at the sending unit though.

stein, i have the manuals handy for both your burban and truck. let me know if you need anything.
 
mountain_man said:
Stein, did you replace the whole sending unit including the level sensor?
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I replaced the whole unit. Pump was shot. Really don't like the engineers that came up with the sending unit and pump as a non-serviceable unit. I still have the old ones hiding in a box somewhere.
 
Sxr700Bandit said:
on hers I only replaced the fuel pump.
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How did you just replace the pump? I looked at that option. If I remember correctly you need to break the strainer off and some how remove the fuel line that is heat shrunk on the pump itself. Then you need to find a pump that fits. GM only lists the pump/sending unit together.
 
no1chevyboy said:
im not anymore but from what ive heard this is prob with all makes, from new fuel i believe, try running some gm fuel injection cleaner (plus) ive been told that works
Click to expand...

I was thinking fuel as well. We do fill up at the same gas stations all the time here. They both started doing this about four months apart but the age of the replacements units is about three years apart. The sub has been doing this for about 5 months now and the p/u started about three weeks ago while on a trip south to purchase a sled. :dunno:
I will check on the grounds. Both pumps still working well atleast.
 
We have seen fuel issues too at our dealership, even with the cleaner it may take several fill-ups to correct the issue. did the sending units come with new level sensors?
 
no kidding. can't wait until mine goes... try the fuel injector cleaner. i would use the gm stuff. good luck, let me know if you need info from the service manual.
 
stein700sx said:
How did you just replace the pump? I looked at that option. If I remember correctly you need to break the strainer off and some how remove the fuel line that is heat shrunk on the pump itself. Then you need to find a pump that fits. GM only lists the pump/sending unit together.
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I guess that I would have to see your set up. On the sending unit that I replaced just the pump, to remove the pump there is a plastic type "clicker" clamp that had to be disengaged to be able to remove the pump and the strainer pulls and twists off of the end of the pump via a screwdriver and or channellocks. and after you remove the strainer you push the pump farther up the pipe to make clearance so the pump is able to be removed from the fuel pump bracket. Nothing is staked together or perminantly sealed or non removable on the one that I did... remember this was a '98 (old square body style) burban, maybe their fuel system design changed when they went to the 5.3liter from the 5.7L?? I don't know.
 
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stein/bandit, 96-99 old body style c/k trucks were a mix match of parts you might say, i have seen the metal sending units in the 98's before (what bandit is describing) but more common from 98-99 is the plastic sending unit which is non-serviceable, with the exception of the level sensor, which gm does not include anymore with the new sending units, the level sensors are now purchased seperately.
 
Wow!!! This is really crazy this topic was brought up, because I was heading up north a few weeks ago and my truck started doing the same thing. I have a 99 chevy z71 in the c/k chassis. So I figured it was the sending unit. So I shelled out my $450.00 for the pump/sending unit/level sensor/etc... and the needle is still shaking. Still trying to figure out wtf is going on. Checked the ground and have been running the lucus oil injector cleaner and no change? Wondering if theres a problem in the gauge cluster? Let me know if you guys have any luck. :o|
 
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#05-00-89-078B: GM Fuel System Treatment PLUS, Fuel Sending Unit Corrosion and Fuel System Deposits - (Feb 6, 2008)


Subject: GM Fuel System Treatment PLUS, Fuel Sending Unit Corrosion and Fuel System Deposits


Models: 2008 and Prior GM Passenger Cars and Trucks (including Saturn)

2008 and Prior HUMMER H2, H3

2005-2008 Saab 9-7X




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This bulletin is being revised to add model years. Please discard Corporate Bulletin Number 05-00-89-078A (Section 00 -- General Information).


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Important : The GM Fuel System Treatment PLUS is not recommended for use with diesel fuel. The GM Fuel System Treatment PLUS is specially formulated for use in gasoline and/or E85 fuels.

GM Fuel System Treatment PLUS
GM Fuel System Treatment PLUS, P/N 88861011 (for U.S. ACDelco®, use 88861013) (in Canada, 88861012), is now available for use in gasoline engines.

Added Benefits and Uses
The PLUS portion of GM Fuel System Treatment PLUS is the addition of a filmer additive that, when used regularly, can protect fuel system sending units from the corrosive effects of certain sulfur contaminants found in some of today's gasoline.

Sulfur contamination can disrupt electrical continuity of certain fuel sending units and lead to erratic or false fuel gauge readings. With scheduled usage, GM Fuel System Treatment PLUS protects against the effects of harmful sulfurs in gasoline.

The Four Benefits
Just pour in one bottle of the GM Fuel System Treatment PLUS into the fuel tank when refueling around each oil change interval:

• Cleans -- Sulfur corrosion from fuel gauge sending units.

• Prevents -- Harmful sulfur components from attacking sensitive fuel system electronics.

• Protects -- By coating metallic surfaces of the fuel system.

• Removes -- Engine deposits left from use of poor quality fuels.

Parts Information
Part Number
Description

88861011 (for U.S. ACDelco, use 88861013)

(in Canada, 88861012)
 
this is what GM gave to us, After looking again at wiring diagram for the 98-99 c/k platform realized that i had a d/a attack. the fuel pump utilizes the ground at the frame. the fuel level sensor gets signal voltage from the ECM and sends signal voltage back to the ECM. disconnecting the ground at the frame would disable the pump, but the level sensor would still work.

haha this is what i get for spending too much time on TY between cars. hopefully the above bulletin helps.
 
I had a problem like that in my 99 silverado and I changed out the fuel level sensor. It would jump all over the place. That is where I would start if the pumps are fairly new
 
mountain_man said:
We have seen fuel issues too at our dealership, even with the cleaner it may take several fill-ups to correct the issue. did the sending units come with new level sensors?
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Other mfgs. are using Techron to combat the affects of high levels of elimental sulfur. It can corrode the precious metals used on the sender card and with the action of the contact wiper, create plowed areas that lift the wiper off the resistor pads creating intermittent opens.

I'd try using either (the GM stuff or Techron) and run a tank or two through it before dropping the tank.
 
mine is still doing this. it started doing it on the old pump, then pump failed nasty (had to blow lines out as they where full of impeller parts). put on new pump and sending unit with a new fuel tank. still does it. i am not taking that sucker back off untill the pump blows again (5 years on average, its 3rd pump atm) or i have a good reason to pull the box off.truck is 1998 k1500 with a 5.7l. cost me a coil, cap/rotor, set of taylor wires and e3 spark plugs when it blew too.
 
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