Gas gauge and not starting

My 2000 Montana, died on my wife a couple of weeks ago. It would just keep grinding. Similiar to other messages I have seen. Although, it died while driving. Towed to a repair shop and it started. No problem, except after about 2-3 min, the gas gauge goes clear to empty and the light goes on. Any suggestions would be great. Thanks.

you have a fuel module going bad. The pump got hot and failed ( do you run on empty a lot? ). Once the pump cooled down, the van started. It's only a matter of time until it fails altogether.

I have a 2000 montana with 101000 mile and I have also had many of the same issues as posted, intake gasket (75,000) and a/c compressor @ around the same time although on the whole I have been happy with it, (hard not to be since i am so far averaging 1 big ticket repair a year, small price since it has been very reliable in the 2 years i have owned, big improvement over last 2 vehicles i owed prior ) anyway i am now having a problem with my gas gauge. started with periodically ready full or empty, incorrectly. gradually got worse until i ran out a gas 1 day (i normally don't let it get below 1/4 tank) since then it has not worked at all. it sometimes reads what i think is acurate after putting gas in, but i almost always fill. I have read that this could be the fuel sending unit and have heard this is a big ticket repair. We are curious if there are any other possibility's that could fix problem. Does anyone know if this could be something that cleaning the fuel injection system or something along those lines. it has also been suggested to me that throwing high grade gas and some additive in the gas tank might solve. I just had shocks and tires and am in proccess of putting tire rods on and am researching whether there is a cheaper fix.
Sorry this is so long, but any help/suggestions anyone might have is appreciated (this forum was right on about the intake gaskets when mine started leaking!)

There can be several problems, and any one of them can cause the same end result, a non-functioning fuel gauge. The float in the tank is attached to a variable resistor called a potentiometer. As the fuel tank empties, the resistance falls. 97 vans had a range of 1 ohm at empty to 88 ohms full, 98 and later (at least through 2001) ranged between 40-250 ohms. Over time, the carbon wipers on the potentiometer have a tendency to either wear out or corrode. High sulfer content in fuel once was a contributing factor although I don't know if that is the case. GM redesiged the wipers in later model years do to many people's guages failing to work.

If the resistance indicates an open connection, then the gauge will peg full on start up then slowly drop down to empty. When mine was doing it, it would take anywhere between 10 seconds to 2-3 minutes to read empty. The more recent the vehicle had been ran, the quicker it droped (or so my thinking was).

The good part is that the fuel sending gauge is easy to test without removing anything from the van. Their is a connector on the underside of the vehicle just behind the drivers seat. There is a 4-wire and 8-wire connector. You want to unplug the 8-wire connector. There should be a purple and a black/white (my shop manual says black/orange in a few places and black/white in other spots...on mine it was black/white) wire IIRC. It was either the 1st and 4th wire or 2nd and 4th wire in the same row. These wires lead to the fuel level sending unit. Take measurements with the tank empty and full. If you get resistance values near where they should be (it's a linear scale), then your sending unit is fine. If you get the same resistance, no resistance, or the resistance is outside the limits above, then the sender is shot.

If the sender reads ok, then you probably have a broken wire in the system. It's a fairly straight shot between the connector identified above and the PCM although there are several connectors inbetween. The easiest connector to to test would be the driver's side firewall passthrough connector. It's just above where your left foot rests. It's a large black connector held in place with a silver screw.

The wire colors should be the same. The numbering of the pins is screwey. If you look at the plug with the "key" in the middle on the bottom, the rows are labled A-G starting at the top. The columns are numbered 1-5 for the left side and 10-6 on the right side, so always count from the outside edge of the connector in. The black/white wire should be D7 and the purple wire C8. Check the resistance here as well. If you don't get anything here but you did above, you have a broken wire. This is where I found my broken wire a few months ago. It had slipped out of the bundle some how and got pinched/severed. I put in a butt splice and I had a guage. My sending unit was going out though as well.

You should be able to find a fuel pump/sending unit after market for under $280. Dealership price for the pair was around 330 IIRC. Each component is available seperately, but I would recommend replacing them as a pair, especially with 100K+ miles. The take drops out easily with just the 3 straps.

If you need more help, just post a message or send me a PM. If you need any other connector locations or pinouts, just ask as well.

My wife drives a 2000. The fuel guage has not worked in 2 years. The last oil change at the dealer - they put an additive in the tank for a Hundred Bucks. the guage was fine for a week or two but went right back to what you're describing here. Is GM doing anything about this or are we all on our own????? They must be having similar trouble with other cars aren't they?

...Is GM doing anything about this or are we all on our own????? They must be having similar trouble with other cars aren't they?

Well, the short answer is that in 2002 through 2004 GM and Shell Oil acknowledged that high concentrations of sulfur based compounds in gasoline (transported through the same pipelines used for other petroleum products) was the root cause of erosion of the metal contact in the sending unit. The GM sending units are the most susceptible for some reason; - but not all manufacturers.

The sulfur compound destroys the contacts and has been known to cause the unit to arc and burn up too. No record of any explosions that I know of. If the tank were full when it burned up it would not cause any problems as only gas vapor itself will burn or explode at the right concentration. (I'm told that you can drop a match into a container of gasoline that is not moving; - thus not very many vapors - and it will go out! I don't recommend trying this though)


Here's an article from 'The Car Connection':

URL:http://www.thecarconnection.com/Industry/Daily_Edition/Daily_Edition_Jun_1_2004.S173.A7193.html

" Holiday Weekend Debacle Will Cost Shell

Just before the holiday weekend, Shell Oil had to stop selling gasoline at more than 500 stations in Florida and Louisiana due to unusually high levels of sulfur that could cause fuel gauges to stop working. The bad fuel was sold throughout Florida in stations branded as either Shell or Texaco, and also in the New Orleans area. About 40 Chevron stations in the New Orleans area were also affected.

The problem fuel, supplied from a refinery in Norco, Louisiana, contained unusually high sulfur levels-high enough to foul the delicate silver circuits of fuel-level switches, either rendering them temporarily inoperable or completely ruining them. Shell said that the sulfur levels should not cause any engine damage. High sulfur levels are also known to affect some emissions equipment, though Shell did not release any information about the possibility of damage from such short-term use.

Prior to the news breaking on Friday, Shell had already received 825 claims of fuel gauge problems likely due to the bad fuel and many more inquiries. The gauge issues could prove a significant financial liability for Shell, as gas gauge issues normally cost several hundred dollars to fix-much higher for some vehicles. Station owners also will have deal with the loss of income from one of the year's biggest driving weekends.

Despite the supply issues for Shell, there did not seem to be any shortage and gasoline was still selling at low prices in the region compared to the rest of the country. The average for the New Orleans area on Friday was $1.94 per gallon. By the end of the weekend, Shell had managed to bring gasoline service back to most of the stations in the affected regions. Premium fuel was reportedly unaffected by the problem, and was being offered for the price of low-grade in some locations so they could do business.

Customers who believe they have a problem with their vehicles due to the bad fuel should call Shell at 866-562-6690 or 877-825-2467, or Chevron at 800-362-8900. -Bengt Halvorson"

GM Canada sent out $20 Petro Canada gas cards and a free oil change to most owners last fall as a 'goodwill gesture' to anyone who hadn't already had the sending unit destroyed and replaced free of charge by GM. Most folks picked up bad fuel from Shell or Petro Canada that killed the unit.

We had this problem in 2002 after (stupidly!) filling up with Shell before going on the ferry to Victoria from Vancouver, BC. The van sat for three days in Victoria while we walked and sightsee'd and then we drove back to the ferry and the mainland.

The gauge didn't work for over 600 miles. I used about 2 or 3 liters of good quality fuel injector cleaner over the next 1,000 miles and the gauge slowly started working again. Of course, it hasn't been accurate since. It takes about 32 liters before the gauge registers a 1/4 of a tank used (tank holds 92 liters when full) and when it reads 1/4 remaining there is only about 10 liters in the tank.

I rely more on the overhead DIC to tell me how much fuel has been used (plus the tripometer). Easier yet on the pocket, it is better to fill the top half of the tank than the bottom half, I think!

Hope this sheds some light on the problem.

Well, the short answer is that in 2002 through 2004 GM and Shell Oil acknowledged that high concentrations of sulfur based compounds in gasoline (transported through the same pipelines used for other petroleum products) was the root cause of erosion of the metal contact in the sending unit. The GM sending units are the most susceptible for some reason; - but not all manufacturers.

The sulfur compound destroys the contacts and has been known to cause the unit to arc and burn up too. No record of any explosions that I know of. If the tank were full when it burned up it would not cause any problems as only gas vapor itself will burn or explode at the right concentration. (I'm told that you can drop a match into a container of gasoline that is not moving; - thus not very many vapors - and it will go out! I don't recommend trying this though)


Here's an article from 'The Car Connection':


URL:http://www.thecarconnection.com/Industry/Daily_Edition/Daily_Edition_Jun_1_2004.S173.A7193.html

" Holiday Weekend Debacle Will Cost Shell

Just before the holiday weekend, Shell Oil had to stop selling gasoline at more than 500 stations in Florida and Louisiana due to unusually high levels of sulfur that could cause fuel gauges to stop working. The bad fuel was sold throughout Florida in stations branded as either Shell or Texaco, and also in the New Orleans area. About 40 Chevron stations in the New Orleans area were also affected.

The problem fuel, supplied from a refinery in Norco, Louisiana, contained unusually high sulfur levels-high enough to foul the delicate silver circuits of fuel-level switches, either rendering them temporarily inoperable or completely ruining them. Shell said that the sulfur levels should not cause any engine damage. High sulfur levels are also known to affect some emissions equipment, though Shell did not release any information about the possibility of damage from such short-term use.

Prior to the news breaking on Friday, Shell had already received 825 claims of fuel gauge problems likely due to the bad fuel and many more inquiries. The gauge issues could prove a significant financial liability for Shell, as gas gauge issues normally cost several hundred dollars to fix-much higher for some vehicles. Station owners also will have deal with the loss of income from one of the year's biggest driving weekends.

Despite the supply issues for Shell, there did not seem to be any shortage and gasoline was still selling at low prices in the region compared to the rest of the country. The average for the New Orleans area on Friday was $1.94 per gallon. By the end of the weekend, Shell had managed to bring gasoline service back to most of the stations in the affected regions. Premium fuel was reportedly unaffected by the problem, and was being offered for the price of low-grade in some locations so they could do business.

Customers who believe they have a problem with their vehicles due to the bad fuel should call Shell at 866-562-6690 or 877-825-2467, or Chevron at 800-362-8900. -Bengt Halvorson"

GM Canada sent out $20 Petro Canada gas cards and a free oil change to most owners last fall as a 'goodwill gesture' to anyone who hadn't already had the sending unit destroyed and replaced free of charge by GM. Most folks picked up bad fuel from Shell or Petro Canada that killed the unit.

We had this problem in 2002 after (stupidly!) filling up with Shell before going on the ferry to Victoria from Vancouver, BC. The van sat for three days in Victoria while we walked and sightsee'd and then we drove back to the ferry and the mainland.

The gauge didn't work for over 600 miles. I used about 2 or 3 liters of good quality fuel injector cleaner over the next 1,000 miles and the gauge slowly started working again. Of course, it hasn't been accurate since. It takes about 32 liters before the gauge registers a 1/4 of a tank used (tank holds 92 liters when full) and when it reads 1/4 remaining there is only about 10 liters in the tank.

I rely more on the overhead DIC to tell me how much fuel has been used (plus the tripometer). Easier yet on the pocket, it is better to fill the top half of the tank than the bottom half, I think!

Hope this sheds some light on the problem.
Hi there I was wondering about some advice..I read your replys and you seem very knowledgeable about the guaging/connectors systems, take a look at this if you dont mind
On my 99 Venture I started to notice that my fuel guage started to act up last week, it will climb to full or empty. as soon as it does this the van starts acting up, downshifting/upshifting ect. the engine light will come on as well.,. With all the info on the forum you guys gave me I decided to look into the sending unit.. Last night after the tank was off I looked at the sending unit and it looked brand new, it tested fine reading 39 ohms empty and around 200 full..same as the new ones out of the box.I decided to put it back togeather saving the money and the van worked fine...for a day. Back to square one, I have cleaned all connections on almost sensors and now am stuck.. I can't seem to believe the new sending unit will fix my problems..someone else said a ground may be the problem and the fuel guage is the first thing that gets affected. I know lots of stories about the sending unit failing but it doesn't affect the rest of the vehicle. I
did have the codes read last week and there were a pile stored. does this sound like just one component? or other electrical problems....
where to next. perhaps I should just put the new sending unit on take the 200$ chance and see what happens,. I can't see it fixing anything though as the guage reads proper until it fails and then immediatly following that the van starts working bad.
Sorry for the long post but any advice would help
Andy

Andy,

You appear to have a raft of issues, but may not.

I don't have a firm answer for you, but I think there a quite a few knowledgeable folks on here who may.

Let's see if they pick up on this, scratch their heads and come up with some probable causes.

Grounding of the pump/sender or elsewhere in a main harness or sub harness does sound like a root cause though.

What about a bulkhead connector that passes through the firewall? An old hot rodder's nemesis.


Unlikely so many different components would fail at once.