5.3 swap in K5, need new fuel tank for 2003 fuel evap system

[NorCalAnthony]

I plan on adapting the newer sending unit to my stock tank (89 K5 w/TBI) for my swap. If you have a brand new tank you can have a shop weld an adapter ring to it or if you're using an old tank you can use some two part epoxy and small hardware to mount the plastic locking ring area of the donor tank to your steel tank (that's what I'm trying first). NastyBuzzard showed us what both of those methods look like in his build thread: http://67-72chevytrucks.com/vboard/s...=627161&page=9

The TBI sending units are already pretty crowded and I don't think you'd be able to find enough open real estate to mount the FPS on it. You may be able to mount it somewhere else on the tank but I'm not sure how far it would stick up or if you'd run in to any clearance issues once you go to mount the tank back up...

[93FatBottom]

Originally Posted by NorCalAnthony

I plan on adapting the newer sending unit to my stock tank (89 K5 w/TBI) for my swap. If you have a brand new tank you can have a shop weld an adapter ring to it or if you're using an old tank you can use some two part epoxy and small hardware to mount the plastic locking ring area of the donor tank to your steel tank (that's what I'm trying first). NastyBuzzard showed us what both of those methods look like in his build thread: http://67-72chevytrucks.com/vboard/s...=627161&page=9

The TBI sending units are already pretty crowded and I don't think you'd be able to find enough open real estate to mount the FPS on it. You may be able to mount it somewhere else on the tank but I'm not sure how far it would stick up or if you'd run in to any clearance issues once you go to mount the tank back up...

Hm... do I have to upgrade the fuel sending unit from a carb'd set up to the TBI sender? I hadn't seen that, or I simply overlooked it... Thanks for the link, I'm gonna do some reading. I DO plan on a brand new tank so I'll probably just take it to a shop and have them fix me up with a hole for the sensor. I thought about adapting the newer sending unit, but ruled that out quickly so I could maintain the stock fuel gauge set up. If I were going to go to custom wiring/gauges/dash, I'd probably try that first, but i'm going for stock... for now

[NorCalAnthony]

Most people that do this swap use a TBI tank and sending unit from an 87 truck/Blazer and then install an AC Delco EP381 fuel pump since it's a direct replacement for the TBI pump and supplies the higher fuel pressure and flow that the LS engines need. Most people also don't have to worry about smog and remove the cats, evap system, etc. and tune all of that stuff out of the PCM.

Since you're trying to do a CA smog legal swap (like me) you'll have to be keep all of that stuff in place and it sounds like you're on the right track so far. You may be able to use the stock sending unit if you can hook up all of the required lines for the newer system but then you'll still need to add the FPS somehow. OR you could just adapt your tank to accept the newer sending unit that already has everything you need in one piece. There are a couple of different ways to do that depending on budget and how pretty you want it to look lol.

Not sure why you think you'd need custom gauges for the newer sending unit though? I've seen a few guys use them before and I think they just added a small resistor to the wiring so that it had the proper resistance for the stock gauge to read properly. I'll see if I can find the thread for how they did it and post up a link.

There may be more ways to get the same stuff done and I hope others will chime in with some other tips or suggestions. I'm just passing along what I've learned so far and plan on doing for my swap in a couple of months.

[93FatBottom]

Originally Posted by NorCalAnthony

Most people that do this swap use a TBI tank and sending unit from an 87 truck/Blazer and then install an AC Delco EP381 fuel pump since it's a direct replacement for the TBI pump and supplies the higher fuel pressure and flow that the LS engines need. Most people also don't have to worry about smog and remove the cats, evap system, etc. and tune all of that stuff out of the PCM.

Since you're trying to do a CA smog legal swap (like me) you'll have to be keep all of that stuff in place and it sounds like you're on the right track so far. You may be able to use the stock sending unit if you can hook up all of the required lines for the newer system but then you'll still need to add the FPS somehow. OR you could just adapt your tank to accept the newer sending unit that already has everything you need in one piece. There are a couple of different ways to do that depending on budget and how pretty you want it to look lol.

Not sure why you think you'd need custom gauges for the newer sending unit though? I've seen a few guys use them before and I think they just added a small resistor to the wiring so that it had the proper resistance for the stock gauge to read properly. I'll see if I can find the thread for how they did it and post up a link.

There may be more ways to get the same stuff done and I hope others will chime in with some other tips or suggestions. I'm just passing along what I've learned so far and plan on doing for my swap in a couple of months.

Excellent info! I had read a thread or two about the wiring, gauges and ohms/resistance being way different between carb/tbi/ls. I had just planned on a fuel pump on the frame, re-using my sending unit (it has a port for the fuel evap) and putting a Baffled TBI tank in (the truck has sat since 2005 with a full tank of gas, or as it is known today, lacquer thinner ) so I was gonna buy a new tank regardless lol. So, if I can make the evap system from the 2003 truck hook up to the evap port on my carb'd sending unit, then all I would need is a hole for the FPS, in theory of course.

MID-POST EDIT:

I did a quick couple of Google searches and it would seem that I have to run the TBI sender. Bummer, but no big deal. I did read that the fuel gauge will work the same as long as its a square body truck. Do you know how people are wiring the in-tank sender to the rest of the truck though? It is just a plug? How would I go about wiring that TBI sender? Back to Google on my next break to see what I can find.

[ls1nova71]

Originally Posted by 93FatBottom

Excellent info! I had read a thread or two about the wiring, gauges and ohms/resistance being way different between carb/tbi/ls. I had just planned on a fuel pump on the frame, re-using my sending unit (it has a port for the fuel evap) and putting a Baffled TBI tank in (the truck has sat since 2005 with a full tank of gas, or as it is known today, lacquer thinner ) so I was gonna buy a new tank regardless lol. So, if I can make the evap system from the 2003 truck hook up to the evap port on my carb'd sending unit, then all I would need is a hole for the FPS, in theory of course.

MID-POST EDIT:

I did a quick couple of Google searches and it would seem that I have to run the TBI sender. Bummer, but no big deal. I did read that the fuel gauge will work the same as long as its a square body truck. Do you know how people are wiring the in-tank sender to the rest of the truck though? It is just a plug? How would I go about wiring that TBI sender? Back to Google on my next break to see what I can find.

To wire up the sender you would just have to adapt your original gas gauge sender wire to the one coming out of the TBI sender, pretty simple. The other two wires will be the power and ground for the fuel pump. As for the pressure sensor, I don't think you can just drill a hole in the sender and pop it in because the sender is steel and too thin for the grommet on the sensor to seal properly. If you have an extra port on the tank somewhere, like a nipple sticking off the side that used to go to another part of the smog system, you should be able to put a hose on it, and put the pressure sensor in the other end, that way you could maybe move the sensor around to a better location? It's just reading pressure and vacuum, so I would think it could do that through a hose?