Dead Fuel Gauge 1999 Chevy Blazer

[Nandy]

On Saturday the gas gauge for the Blazer dies. It just went past the E mark as when you turn off the vehicle. I check the fuses and there is a gauge fuse but is for all of the gauges and it tested ok. I could not find any other fuse associated with the gas gauge. The sender is built in the pump which I changed maybe 2 years ago, maybe more. It was over $200 if I recall right so I am not crazy about changing it again. I looked for the old pump as I thought I kept it but I cant find it now. Anyway, the problem could be somewhere else.

Does anyone know which pins I need to short at the pump connector to test away from the sender to see if the needle goes up? I hate to take the gas tank down and the pump out just to be able to trace the cables. The book I bought was a Chilton CD and I have to say that I will never buy one of their cd's again.

 

[puddle jumper]

Re: Dead Fuel Gauge 1999 Chevy Blazer

What you need to do is unplug the sending unit from the top of the tank. If the gage goes to over full the problem is in the tank. If it does not the wire for the fuel sending unit has grounded out somewhere.

 

[Nandy]

Re: Dead Fuel Gauge 1999 Chevy Blazer

Oh, so the more resistance the higher the gauge to the full side... I have no idea why I thought it had to be the other way. I did have a problem with the pump cable going open at one time and I had to run new cable. I will try it tomorrow...

 

[JMRuth72]

Re: Dead Fuel Gauge 1999 Chevy Blazer

Haven't tried tracing this problem before, but if you have a mulitmeter you should be able to find it fairly easily. If you happen to have a potienometer and a couple of small aligator cleps it would help also. Basically that is what a fuel sender is. So questions:

1.) how many contacts (wires) do you have at the disconnect?
2.) what colors are they (if you can tell)?

Atleast one will be ground. The rest will be power. If you have one ground and 2 power wires then it should be only a little interesting. Most FI vehicles that I know of when you turn the key to on (not start) apply power to the fuel pump through a relay. Once it is up to pressure it cuts off ( only on a couple of seconds ). With a helper disconnect the cable and turn the power on and off a couple of times to figure out which wire doesn't have power. Out of 3 wires if only one has no power switch to ohmmeter and leave that pin connected to the meter and hook the other lead to a nut, bolt etc. Note it should get a low to 0 reading, but it has to be a clean bare metal attachment on the frame. If you get a very low say .5 or under then you have a good ground and can move on. If not try to trace out the cable until you find the ground and clean it. Protect all connections with a die-electric grease. Then check you power wires by switching back to voltmeter and cycling the power again. One should stay hot (12Volts or so) the other should in theory go hot for a few seconds and then drop off. The constant hot should be your fuel guage. Remember what I said earlier about most fuel pumps only kick on for a few seconds. If that doesn't help and you can gleem enough information out of the chiltons on the wiring. Try to break the system in half. If you are getting the expected signal at that point then move towards the sender. if not move towards the guage. keep breaking it in half and you will eventually find the problem. I have written better posts before, but it is late and I am tired. Search my posts and if you have questions I will do my best to answer them. I was an AT in the Navy and troubleshot planes for a living and was pretty good at it. I will do what I can to talk you through it. Of course if you were here it would probably be easier to do hands on teaching, but that is always true. Good luck and let us know what you find.

 

[Nandy]

Re: Dead Fuel Gauge 1999 Chevy Blazer

I found the old pump today so I got motivated. Got under the Blazer. Hooked the old pump with the sender all the way up as if it was full tank and in 2 second my gauge went all the way up to full. Hook it back to the pump in the tank and went all the way back to empty. I should have put the old pump all the way to empty to see if the gauge stops at the same spot but it is all academic. I will take that tank down sunday and replace the sender. Hopefully it is just the float, but if not I have the old sender... If I can find a sender for a decent price I would do that better than put an old sender.
Thanks everyone!

 

[puddle jumper]

Re: Dead Fuel Gauge 1999 Chevy Blazer

I would just use the old sending unit. As a rule thay are bullet proof. I bet you find something simple. Like the float stuck in the empty position.

 

[Nandy]

Re: Dead Fuel Gauge 1999 Chevy Blazer

When I was searching for the wiring information I saw a few and they were like $15.00 or so. I would not mind spending that money and get the feeling that it will be less likely for me to have to take this tank down again. It is a major pain to do.

 

[puddle jumper]

Re: Dead Fuel Gauge 1999 Chevy Blazer

Ya for $15 you cant loose. That's one of the problems with most Minnie trucks thay can be hard to work on.

 

[JMRuth72]

Re: Dead Fuel Gauge 1999 Chevy Blazer

Not just true of the minnie trucks anymore. My Ram has several things mounted either in or on the tank. The sender, the pump, the filter and the pressure regulator. The filter and regulator are one assembly and I can only find it through the expensive places like NAPA and the dealer. I think that I will take the over $300 dollars and put it torwards building a custom fuel system that I can actually maintain where the only thing in the tank is the sender. Hope you got your guage figured out. If not just keep posting what you find as you find it and we will try to help you with it. Sometimes hard over the web, but it usually works out good.

 

[Nandy]

Re: Dead Fuel Gauge 1999 Chevy Blazer

Im sorry guys, I forgot to update. I found the sender online for 45 and up online. The $15 price must have been from another part. I still have the old pump that the gauge works so I figure I just swap.
When I took the pump assembly out i found out what the problem was. The arm with the float has come loose. I collected it from the bottom of the tank and put it back where it goes. I heard it click and then try to take it off but it felt secure. I worked on it Sunday and it is still working. Thanks for all of the suggestions and help!

 

[JMRuth72]

Re: Dead Fuel Gauge 1999 Chevy Blazer

Glad that you got it fixed.