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Fuel sending unit Questions
- Thread starter Bent77
- Start date
Believe all the '73-87(91) lock rings are interchangeable. You need to ensure the tank depth is the same however, depending on what you have. The K5's had two different tank depths, senders don't interchange of course.
The only issue with doing this is that you will run into issues with low fuel levels and angles and/or fuel slosh. The factory (and aftermarket) EFI tanks are all baffled one way or another, to ensure fuel delivery even with low-fuel levels.
The only issue with doing this is that you will run into issues with low fuel levels and angles and/or fuel slosh. The factory (and aftermarket) EFI tanks are all baffled one way or another, to ensure fuel delivery even with low-fuel levels.
Good information there.
Had not considered the baffle issue, but I do usually run the tank full off-road
Do the older trucks have 3 lines coming in the sender? My 89 does.
Saddle tanks are either 16gal or 20gal. I believe it's the length that's different between them. If the 16gal tank is also shallower, I'd be tempted to switch to gain some ground clearance. But I think the depth is the same so the senders would be too.
The locking ring looked the same as any GM truck I've messed with. Unfortunately I don't think I could get my hand up there to measure for you.
Saddle tanks are either 16gal or 20gal. I believe it's the length that's different between them. If the 16gal tank is also shallower, I'd be tempted to switch to gain some ground clearance. But I think the depth is the same so the senders would be too.
The locking ring looked the same as any GM truck I've messed with. Unfortunately I don't think I could get my hand up there to measure for you.
I have considered replacing them, but that lead me to new tanks, as all the junk yards puncture them. Once I priced out to replace them both, decided that wasn't cost effective.
Honestly all I need is the return, and I might just modify the factory units I have and run a single frame pump.
Just soliciting responses to help consider all the options
I was looking at gastanks.com and they list 3 line & 2 line sending units for a truck your vintage. And the differences between 16 & 20 gallon tanks is the length.
FWIW, gastanks.com gets $117 for a FI 20 gal saddle tank. Not sure about shipping cost tho.
A buddy of mine did a TBI swap into a 78 pickup. He had enough trouble getting the 78 saddle tank to work, he ended up getting a burb TBI tank and mounting it in the bed below his tool box. I will see if I can find out of he was trying to use a frame or in-tank pump with his saddle tank.
FWIW, gastanks.com gets $117 for a FI 20 gal saddle tank. Not sure about shipping cost tho.
A buddy of mine did a TBI swap into a 78 pickup. He had enough trouble getting the 78 saddle tank to work, he ended up getting a burb TBI tank and mounting it in the bed below his tool box. I will see if I can find out of he was trying to use a frame or in-tank pump with his saddle tank.
look at local junk yards or radiator shops . they sell new tanks the cheapest most of the time.
spectra premium is the best off the shelf brand and lots of times oem supplied.
as said truck tanks short or long only for size difference .
and 87-up got the tray in the bottom for the fuel to puddle for pump .
and don't just make a return drop in from high on efi . give it a way to drop to bottom so you don't get air bubbles in low tank conditions . lots of oem stuff now has return on tube then flexable closed off nipple to open under pressure . this keeps it from backing up when off and also open under return flow and fan out nice and even .
spectra premium is the best off the shelf brand and lots of times oem supplied.
as said truck tanks short or long only for size difference .
and 87-up got the tray in the bottom for the fuel to puddle for pump .
and don't just make a return drop in from high on efi . give it a way to drop to bottom so you don't get air bubbles in low tank conditions . lots of oem stuff now has return on tube then flexable closed off nipple to open under pressure . this keeps it from backing up when off and also open under return flow and fan out nice and even .
Cool, good info, I will go research those for my application.
I did look at junk yards, but they all puncture the tanks here. Not a problem to weld them back up, but for that effort a new tank or good sender makes more sense to this kid
Definitely want to avoid the tank in the bed. That was one of the things from the Bent72 I wanted to change.
I know that the 87s have a driver's side saddle, those might drop in. A friend of mine has one, might need to take over some beer and a tape measure
tank is same left or right .
just the hoses from filler neck and the sender are side specific .
so if you need pass side tank for older truck but efi just get a tank and pass side efi sender unit .
and if doing performance or vortec swap you can get new sender with out tbi low psi pump . then just get a pump for a 96 c3500 crew cab with 5.7 vortec . its a 60 psi pump and clips direct on to older sender unit style we run .
also like I said but just wana clearify info junkyards can get brand new tanks and radiators lots of times cheeper than parts stores.
just the hoses from filler neck and the sender are side specific .
so if you need pass side tank for older truck but efi just get a tank and pass side efi sender unit .
and if doing performance or vortec swap you can get new sender with out tbi low psi pump . then just get a pump for a 96 c3500 crew cab with 5.7 vortec . its a 60 psi pump and clips direct on to older sender unit style we run .
also like I said but just wana clearify info junkyards can get brand new tanks and radiators lots of times cheeper than parts stores.
I am in the middle of replacing both my saddle fuel tanks right now. My truck is TBI, and the spectra fuel tank part numbers are different for carb and TBI equiped trucks (TBI tank PN# GM1C/CARB tank PN# GM1B). The sender units are different part numbers ,of course, because of the return line. I am replacing the tanks, senders, pumps, straps, filler necks, and filler neck hoses on my truck. This cost me about $600. The cheapest place I found saddle tanks is a company called Dave's Discount Auto Parts (ask for Joey). Thier Spectra TBI tank is $101 with shipping and everything.
You are going to have fun with the tank straps, if you have to replace those. The tank straps are riveted in, and I had to take an angle grinder to the seam welds on the brackets, and then use the same angle grinder and a punch to remove the tank strap rivets. I am not going to rivet the starps back on. I am going to use small screws and prevailing nuts to hold the straps in. The I need to drill a few holes in the brackets, in order to hold the bracket together where the factory seam welds use to.
You are going to have fun with the tank straps, if you have to replace those. The tank straps are riveted in, and I had to take an angle grinder to the seam welds on the brackets, and then use the same angle grinder and a punch to remove the tank strap rivets. I am not going to rivet the starps back on. I am going to use small screws and prevailing nuts to hold the straps in. The I need to drill a few holes in the brackets, in order to hold the bracket together where the factory seam welds use to.
On a TBI saddle tank set up the large filler neck hosses are the same left to right. The smaller vent hose I think, but not postive, are the same too. At least I hope so because I bought two of the same filler neck vent hose for my truck, and they appear to be the same from looking at mine.
FWIW the sending units themselves aren't that failure prone, if you are looking to try and save money, you can check wrecking yards. Although the '87-91 trucks aren't real common in any sense, they can sometimes be found.
Plus, any other parts outside of the tanks you need, will also be there.
Plus, any other parts outside of the tanks you need, will also be there.
When tanks get old, they get a lot of crap build up in them. My 25-year old OEM tanks had so much crap in them that when I removed all the old gas from them, and tilted them to one side, I could hear what sounded like 2-pounds of loose gravel and rust inside. There was so much crud built up on the sender, pick up sock, pump, and tank I could not believe my truck ran at all.
Apparently some do. Probably depends on how/where they were used. Didn't used to be unusual to see people driving around with rags for gas caps.
I took two 1967 Firebird tanks out, looked brand new on the inside. Taken apart a fair number of '73-91 truck tanks, can only recall a couple having more than just a tiny bit of debris in them. Took mine out after about 10 years of use, nothing at all in it.
Problem I saw with the '87+ tanks was that if anything was bad, it was the baffle having broken free.
I am hoping I do not have any problem with baffles in my new tanks because the Spectra tanks baffles do not look as good a quality as the factory baffles did. The factory ones are made of a thick plastic, and there was an inner and outer baffle. The spectra tank has a single thin sheet metal baffle (spot welded in) about the size of a cooking pan used to cook brownies or corn bread in. Since GM discontinued availability of the saddle tank 20-years ago, I have no choice but to buy the aftermarket ones. My truck tanks could have been submerged in water.
I only tried taking a saddle tank out once by leaving the tank brackets on the frame,and removing the rivets on the straps--it was a bear!..
--it is no picnic sometimes getting the 4 bolts holding each bracket to the frame,they can round over ,or break off in the weld nuts--but its the "best" way to get the tank out,and put it back in,with the brackets and straps already installed as a unit..worst part is you usually cant use torches or a grinder to assist,because your removing a leaky tank..
--it is no picnic sometimes getting the 4 bolts holding each bracket to the frame,they can round over ,or break off in the weld nuts--but its the "best" way to get the tank out,and put it back in,with the brackets and straps already installed as a unit..worst part is you usually cant use torches or a grinder to assist,because your removing a leaky tank..
Yes, my tank is also a Spectra and as far as I can tell, the "baffle" in it is about the worst thought out piece I've seen used in an otherwise fine product.
I don't run my truck under 1/4 tank if I'm going to be anywhere near offroad because of it, and even then I start to get nervous at around an 1/8 of a tank on steeper highway grades.
I've never had it stall, but the "baffle" has holes in the bottom of it, no idea how or why they thought that design was acceptable. The factory baffle is 100 times better (at least) I assume the cost wasn't worth it to them to replicate in steel, which would probably be pretty tough due to the mass of the fuel as it moved around the tank.
When I took out my tanks
1. Disconected the filler pipe and filler pipe ground strap from the plastic gas door insert.
2. Lifted the truck bed up about 5" (this made for more room to get tools into area)
3. Unpluged the sending unit connector and ground wire.
4. Cut the fuel lines to the tank selector switch (I am putting all new fuel lines into the truck)
5. Unbolted the four screws on each bracket, and let-er drop onto a couple of milk crates I had under them.
I am going to do like you said, and re-install them as a complete unit with all the straps, brackets, filler pipe and hoses bolted together. I am going to tie them down with a tie-down strap to a tranny jack, and lift them into place, in order to re-install them.
Taking a bed off a pickup here or even lifting it some,on an older truck,usually is a painful involved process..
In Nevada,the bed bolts probably look brand new even 30 years later..
Where I live,they whittle away from salt,you'd most likely have to torch them off,because the hex part of the nuts are now rounder than rivets,and the carriage head bolts are likely to strip out the square hole in the bed (unless its a wooden floor like my stepside,which is "gone" completely and covered with sheet metal to keep cargo from dropping out the bottom !)..so I wouldn't use the bed lifting method on my truck..
Due to the fact most tank removals are due to leaks,that negates the ability to torch the bolts off anything...your left with few options,sawsall or air hammer,or cold chisels ,all of which can make sparks too...I got all the stripped bolts out of my tank brackets using Irwin "bolt out extractors" over the rounded heads,and was lucky that only one out of the 8 snapped off in the weld nut on the bracket..
I found it easier to just grind the weld nut with the busted bolt right off the bracket,and weld on a new nut,rather than drill the bolt out and try tapping it...
In Nevada,the bed bolts probably look brand new even 30 years later..
Where I live,they whittle away from salt,you'd most likely have to torch them off,because the hex part of the nuts are now rounder than rivets,and the carriage head bolts are likely to strip out the square hole in the bed (unless its a wooden floor like my stepside,which is "gone" completely and covered with sheet metal to keep cargo from dropping out the bottom !)..so I wouldn't use the bed lifting method on my truck..
Due to the fact most tank removals are due to leaks,that negates the ability to torch the bolts off anything...your left with few options,sawsall or air hammer,or cold chisels ,all of which can make sparks too...I got all the stripped bolts out of my tank brackets using Irwin "bolt out extractors" over the rounded heads,and was lucky that only one out of the 8 snapped off in the weld nut on the bracket..
I found it easier to just grind the weld nut with the busted bolt right off the bracket,and weld on a new nut,rather than drill the bolt out and try tapping it...
