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Sometimes when I'm driving my fuel gauge will go down really fast and if I put it in park it will go to empty but then if I shut the truck off and turn it back on it goes back to where it's supposed to be do you think it's a bad fuel sending unit? Also can I just change the fuel sending unit and not the pump as RockAuto sells them for $87 it's a 03 blazer ls 4x4
You can change just the sending unit, but there's a few things to think about before you decide that's what you're going to do.
1) Reference the first picture below. If the fuel pump has ever been replaced, there's a chance that the replacement fuel pump uses a different design mechanism for the sending unit (how it's clipped to the pump assembly). So if you order a sending unit designed to replace the one on a factory pump, it may not install onto an aftermarket pump assembly. I see this a lot working in an auto salvage yard; aftermarket fuel pumps (aftermarket parts in general...) that although will serve the same function in the end once installed, they're design might differ slightly, enough to where you can't simply rebuild it or replace small parts on it with good parts from an OEM unit or another aftermarket unit from another brand.
2) To replace either the sending unit OR the fuel pump itself, you have to drop the fuel tank and remove the fuel pump. So let's say you go through all the work, install the new sending unit onto the old pump, how long do you trust the old fuel pump to still be good as you reassemble and reinstall the fuel tank? It's not like changing a headlight or something, dropping the fuel tank can be an involved process, not one you want to be doing over and over again... Or paying someone else to do for that matter...
My personal opinion, deal with the gauge acting wonky and put a little money aside until you're ready to just buy a complete new Delphi fuel pump assembly. Do the work once and be done with it, knowing you have a quality pump and sending unit in it that'll last years to come.
I went through this process on my 04 when I first got it. Had an erratic fuel gauge just as yours. I didn't have to rely on the truck at the time to get me around, so I had to time to mess with it. I dropped the tank and found that on the sending unit there's two small "fingers" that wipe across the contact board. Over the years those "fingers" wore out and were only making contact with the board every once in a while, which is what was making the fuel level gauge work sometimes and not others (see second picture below). Since I KNEW what the assembly looked like, I scrounged the salvage yard and found one that would work that looked like it was in good shape (3rd picture below; old one on the right, replacement on the left). So I installed that sending unit on my old pump, put everything back together, and low and behold it fixed the erratic gauge issue! The next week I started driving the truck every day, and all was well. Until about 2 weeks after that... The truck died on me in town, wouldn't start back up after running into a store. Turns out, the fuel pump went out... So I had to go through all that again and go ahead and change the entire fuel pump anyhow...
Last edited by blazen_red_4x4; Jun 29, 2021 at 10:29 PM.
You can change just the sending unit, but there's a few things to think about before you decide that's what you're going to do.
1) Reference the first picture below. If the fuel pump has ever been replaced, there's a chance that the replacement fuel pump uses a different design mechanism for the sending unit (how it's clipped to the pump assembly). So if you order a sending unit designed to replace the one on a factory pump, it may not install onto an aftermarket pump assembly. I see this a lot working in an auto salvage yard; aftermarket fuel pumps (aftermarket parts in general...) that although will serve the same function in the end once installed, they're design might differ slightly, enough to where you can't simply rebuild it or replace small parts on it with good parts from an OEM unit or another aftermarket unit from another brand.
2) To replace either the sending unit OR the fuel pump itself, you have to drop the fuel tank and remove the fuel pump. So let's say you go through all the work, install the new sending unit onto the old pump, how long do you trust the old fuel pump to still be good as you reassemble and reinstall the fuel tank? It's not like changing a headlight or something, dropping the fuel tank can be an involved process, not one you want to be doing over and over again... Or paying someone else to do for that matter...
My personal opinion, deal with the gauge acting wonky and put a little money aside until you're ready to just buy a complete new Delphi fuel pump assembly. Do the work once and be done with it, knowing you have a quality pump and sending unit in it that'll last years to come.
I went through this process on my 04 when I first got it. Had an erratic fuel gauge just as yours. I didn't have to rely on the truck at the time to get me around, so I had to time to mess with it. I dropped the tank and found that on the sending unit there's two small "fingers" that wipe across the contact board. Over the years those "fingers" wore out and were only making contact with the board every once in a while, which is what was making the fuel level gauge work sometimes and not others (see second picture below). Since I KNEW what the assembly looked like, I scrounged the salvage yard and found one that would work that looked like it was in good shape (3rd picture below; old one on the right, replacement on the left). So I installed that sending unit on my old pump, put everything back together, and low and behold it fixed the erratic gauge issue! The next week I started driving the truck every day, and all was well. Until about 2 weeks after that... The truck died on me in town, wouldn't start back up after running into a store. Turns out, the fuel pump went out... So I had to go through all that again and go ahead and change the entire fuel pump anyhow...
Great advice ! I'll.probably wait to do it all at once. Thanks for the confidence in my issue
You can change just the sending unit, but there's a few things to think about before you decide that's what you're going to do.
1) Reference the first picture below. If the fuel pump has ever been replaced, there's a chance that the replacement fuel pump uses a different design mechanism for the sending unit (how it's clipped to the pump assembly). So if you order a sending unit designed to replace the one on a factory pump, it may not install onto an aftermarket pump assembly. I see this a lot working in an auto salvage yard; aftermarket fuel pumps (aftermarket parts in general...) that although will serve the same function in the end once installed, they're design might differ slightly, enough to where you can't simply rebuild it or replace small parts on it with good parts from an OEM unit or another aftermarket unit from another brand.
2) To replace either the sending unit OR the fuel pump itself, you have to drop the fuel tank and remove the fuel pump. So let's say you go through all the work, install the new sending unit onto the old pump, how long do you trust the old fuel pump to still be good as you reassemble and reinstall the fuel tank? It's not like changing a headlight or something, dropping the fuel tank can be an involved process, not one you want to be doing over and over again... Or paying someone else to do for that matter...
My personal opinion, deal with the gauge acting wonky and put a little money aside until you're ready to just buy a complete new Delphi fuel pump assembly. Do the work once and be done with it, knowing you have a quality pump and sending unit in it that'll last years to come.
I went through this process on my 04 when I first got it. Had an erratic fuel gauge just as yours. I didn't have to rely on the truck at the time to get me around, so I had to time to mess with it. I dropped the tank and found that on the sending unit there's two small "fingers" that wipe across the contact board. Over the years those "fingers" wore out and were only making contact with the board every once in a while, which is what was making the fuel level gauge work sometimes and not others (see second picture below). Since I KNEW what the assembly looked like, I scrounged the salvage yard and found one that would work that looked like it was in good shape (3rd picture below; old one on the right, replacement on the left). So I installed that sending unit on my old pump, put everything back together, and low and behold it fixed the erratic gauge issue! The next week I started driving the truck every day, and all was well. Until about 2 weeks after that... The truck died on me in town, wouldn't start back up after running into a store. Turns out, the fuel pump went out... So I had to go through all that again and go ahead and change the entire fuel pump anyhow...
Would one of these 42$ units be a bad idea? It got a pump/assembly/sending unit for cheaper then what they sell just the sending unit and actual pump for
Personally, I would be hesitant to cheap out on the fuel pump... For the same reason as mentioned before about just replacing the sending unit alone. If the less expensive pump doesn't last long and fails prematurely, you'll be doing it all over again.
When mine went out, I was in a pinch and had to just buy one local, so I didn't have much of a choice as to the brand, just whatever the local parts stores had in stock. I don't recall the brand of the one I ended up with, I got it from Oreilly's Auto Parts, but I didn't get the cheapest one they had, I did at least step up to one with a lifetime warrantee. I think it cost me right around $200. That being said, I now have a junkyard spare sitting in the garage that, if this one ever goes out, I can quickly pop in and keep riding while I warrantee exchange the one I bought with a lifetime replacement But at the same time it's not that big of a deal now for the truck to be down a few days, since I now have 3 vehicles that I can go back and forth between lol, but that wasn't an option for me the first time when the pump suddenly bit the dust...
Personally, I would be hesitant to cheap out on the fuel pump... For the same reason as mentioned before about just replacing the sending unit alone. If the less expensive pump doesn't last long and fails prematurely, you'll be doing it all over again.
When mine went out, I was in a pinch and had to just buy one local, so I didn't have much of a choice as to the brand, just whatever the local parts stores had in stock. I don't recall the brand of the one I ended up with, I got it from Oreilly's Auto Parts, but I didn't get the cheapest one they had, I did at least step up to one with a lifetime warrantee. I think it cost me right around $200. That being said, I now have a junkyard spare sitting in the garage that, if this one ever goes out, I can quickly pop in and keep riding while I warrantee exchange the one I bought with a lifetime replacement But at the same time it's not that big of a deal now for the truck to be down a few days, since I now have 3 vehicles that I can go back and forth between lol, but that wasn't an option for me the first time when the pump suddenly bit the dust...
I totally understand I just don't have the money right now and the fuel gauge is really pissing me off. I'm going to keep the one that I pull out because I know the fuel pump works but the sending unit is finicky. I'm going to change the fuel tank straps and everything so the next time I have to do the job it shouldn't be that big of a deal
I totally understand I just don't have the money right now and the fuel gauge is really pissing me off. I'm going to keep the one that I pull out because I know the fuel pump works but the sending unit is finicky. I'm going to change the fuel tank straps and everything so the next time I have to do the job it shouldn't be that big of a deal
Fuel sending unit going bad ?
But at the same time it's not that big of a deal now for the truck to be down a few days, since I now have 3 vehicles that I can go back and forth between lol, but that wasn't an option for me the first time when the pump suddenly bit the dust...
