My fuel pump went out receintly in my 2003 cavalier. I had to have it towed off of the highway and brought to a small garage in the middle of the nearest town to get fixed. Now after I picked it up the car as been drinking gas like none other and the the gauge is reading the wrong. I think that the sender unit is messed up because when im on E and i fill up it only fills up 9 gallons and it normally fills up 12. Also after i fill up the gauge used to pop into the Full spot really quickly, not it takes a really slow time to do so. Is there anything that they may have forgotten to do or messed up while they were in there that would be causing this?
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Yes, I have seen it before to. There normally isnt a lot of room there to install the pump and sending unit. Sometimes the float gets accidently bent upon install, that will cause messed up gauge readings.
Go back to the shop and explain the problem to them
- 2004 Cavalier - 124k, owned since new
I'm not sure, but I think on our cars, the pump and sender are one assembly, maybe someone can confirm this.
What I think happened in your case is that the garage swapped in a pump/sender assembly made for an older J. My '98 Cavalier's gauge is not proportional and reacts slowly just like yours does now. My '02 Cavalier's gauge reacts instantly to changes in fuel level and is almost perfectly proportional. I can watch the gauge move as it fills.
Are you basing the gas guzzling off what you pump in vs how far you go or off the fuel gauge?
I'd go back to the garage and demand more detailed information about what they installed and what car it was made for. If they can't supply that info, demand that they install a sender specifically for an 03 Cavalier.
2002 Cavalier 2200 5spd
Yeah im basing the gas guzzling off of what i pump in vs how far i go. Before the car went in id get about 80-100 miles per 1/4 and now im only getting 50. Im goign to contact the garage that did the work tomorrow, i was just wondering if you guys had any advice.
Quote:
Yeah im basing the gas guzzling off of what i pump in vs how far i go. Before the car went in id get about 80-100 miles per 1/4 and now im only getting 50. Im goign to contact the garage that did the work tomorrow, i was just wondering if you guys had any advice.
No, you're basing it off the (now broken) fuel sender. The sender is merely exaggerating the drop in fuel level. In other words, the needle falls faster, but you're still using the same amount of fuel. Try this:
1. Fill up and don't top off.
2. Drive around 150 miles.
3. Fill up at that EXACT SAME PUMP and don't top off.
4. Take how far you've driven divided by how many gallons are on the gas receipt. This is your mpg average.
I strongly doubt the new pump is actually causing a drop in economy, it just seems that way.
2002 Cavalier 2200 5spd
yeah, i dont think the pump is causing a drop, i really think the there is something wrong w/ the sender. Is the sender and the pump one assembly or are they two different ones?
I think it's the same part. The thing that makes me think that it's a part for an older car is the fact that it takes a while to report the correct amount of fuel. My 98 has this behavior while my 02 does not. I think maybe there's a capacitor across the sender line in the older models which smooths out the voltage. Since the newer instrument panels are digital, the cap is no longer necessary as the averaging can be done in software. I'm putting my money on you having a sender made for an older J.
2002 Cavalier 2200 5spd
Think about it...
in 00+ cars the instrument panel is different, it's fully digital.
The gauge and sender are two parts that must be matched for each other, otherwise readings will be non-linear / erratic.
The fuel tank did not change between pre and post 2000 cars which means, all 3rd gen senders will fit all 3rd gen tanks even though they might not be electronically matched for the instrument panel.
2002 Cavalier 2200 5spd
Well then i guess this really sucks. I will call the shop tomorrow and find out what they did, if you are correct and they did put a older J pump in mine then to make things back to normal I would need them to change it back out to one made for an 00 plus. Do you think that this could be the only thing that would cause this to happen?
A bent float doesn't account for the slow reaction time of the gauge. If you had a bent float, the needle would be stuck at F and then fall suddenly once it got shaken loose. The slow reaction of the needle just reeks of a pre 2K sender. Those were hit or miss, pretty much no two cars gave the same readings per X gallons of fuel. There is just nothing else that I can think of that it could possibly be.
Ask the garage for what model years the sender they put in your car is made for. If they say "It's for all Cavaliers" that would be a red flag for me. Yes, it will fit the tank, but I'm pretty sure when GM redesigned the instrument panel system, they modified the sender as well. Maybe it's possible to detach the sender from the pump assembly installed in your car right now. That way you can have the shop install your old sender on the new pump assembly.
2002 Cavalier 2200 5spd
thanks a lot for your help man, im in class right now but will call them later.
