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

[93FatBottom]

I'm planning my smog-legal 2003 5.3 swap into a 79 K5 Blazer, and in California I have to utilize the fuel evap system from the 2003 donor truck. I have everything else lined up, except for a suitable fuel tank. The K5 tank doesn't have the valve in the tank or the evap, so I'm looking for ideas. Do I need to have a custom tank built or can someone give me the part number for the proper valve so I can drill and weld it into my K5 tank? Has anyone come across a solution that does not involve using a misshapen Tahoe/Yukon tank?

[Nitis]

Can you use one from a later model that was efi 87-91?

[solidaxel]

I used the sending unit and fuel pump (new parts) from a 2000 Camaro which fit my 87 fuel tank and it had a port for the evap hose, I just need to hook up the canister.
Will that help?

[dayj1]

Originally Posted by solidaxel

I used the sending unit and fuel pump (new parts) from a 2000 Camaro which fit my 87 fuel tank?

Are you saying that the 2000 pump assembly drops in the '87 tank without mods?

[solidaxel]

That is what I used and it even fixed my broken fuel gauge!
The 87 tank has a well for fuel injection and the 2000+ Camaros have LS engines and the right fuel pump pressure for your engine.
A little plumbing and a 10 micron filter.........only money !

[dayj1]

Originally Posted by solidaxel

That is what I used and it even fixed my broken fuel gauge!
The 87 tank has a well for fuel injection and the 2000+ Camaros have LS engines and the right fuel pump pressure for your engine.
A little plumbing and a 10 micron filter.........only money !

I've always used a Delco EP381 pump on a stock '87 hanger in the '87 tank for square body swaps. I never thought about using a Camaro pump assembly in the '87 tank, but I looked at some pictures after you mentioned it and they look very similar in size. I like it because the Camaro assembly has quick connect fittings instead of the hose barbs on the '87 hanger. Thanks for the tip!

[solidaxel]

Originally Posted by dayj1

I've always used a Delco EP381 pump on a stock '87 hanger in the '87 tank for square body swaps. I never thought about using a Camaro pump assembly in the '87 tank, but I looked at some pictures after you mentioned it and they look very similar in size. I like it because the Camaro assembly has quick connect fittings instead of the hose barbs on the '87 hanger. Thanks for the tip!

Someone on the board told me about this set up, just passing on what worked for me!

[93FatBottom]

Originally Posted by solidaxel

I used the sending unit and fuel pump (new parts) from a 2000 Camaro which fit my 87 fuel tank and it had a port for the evap hose, I just need to hook up the canister.
Will that help?

Thanks a bunch, thats awesome to hear! I'm going to have to speak with a smog ref and discuss this idea further. I have the evap canister, purge valve and solenoid and hoses from the 2003 truck, but couldn't figure out how to connect it to the tank. I was told it had to have a new port installed, but if the fuel sending unit fits the way you say, thats awesome. How about the depth of the fuel sending unit? Does it run dry early? I'm switching to a baffled tank anyways, so if the camaro fuel sending unit is deep enough, I'm thinking that would work out nicely. My 79 doesn't have an in-tank pump, just the mechanical pump mounted on the side of the old 350, so I would have to wire it, what pump are you using and how did you wire it? Does the factory wire harness plug right into the camaro sender?

Pictures would be amazing, if you're in the mood

[solidaxel]

The tank I used is for a 87 short bed truck it has a well for the 2000+ Camaro pump the SENDING UNIT is for a 87 Chevy truck, it has pressure and a return port along with a vent port for the evap hose connection.
I have several thousand miles and there is no starvation on the set up

[93FatBottom]

Originally Posted by solidaxel

The tank I used is for a 87 short bed truck it has a well for the 2000+ Camaro pump the SENDING UNIT is for a 87 Chevy truck, it has pressure and a return port along with a vent port for the evap hose connection.
I have several thousand miles and there is no starvation on the set up

Can you elaborate what part is the well?

[solidaxel]

I used a Dorman new gas tank for a 87 chevy truck that has a "well" in the bottom for the fuel pump to set in to keep it from running low or starving when turning corners when the fuel level is very low
Was that the answer?

[littlevictories]

i added an evap can to my set up. was really pretty easy. now the garage doesn't stink.
you might need to go in and turn the evap codes back on, most base tunes have them turned off.

[solidaxel]

After re reading your post I see that it is a Blazer, did they have a EFi throttle body in 87 for the Blazer?

[chebyshortbox65]

It's not going to be that easy you are going to have to do some tricks here to get it through

[NorCalAnthony]

If the Camaro sending unit isn't a direct fit you should still be able to make things fit like NastyBuzzard did here: http://67-72chevytrucks.com/vboard/s...=627161&page=9

Originally Posted by chebyshortbox65

It's not going to be that easy you are going to have to do some tricks here to get it through

Have you gone through the smog ref for a swap yet? I plan on doing basically the same thing on my '89 K5 soon and would love to hear some of the stuff they specifically looked for/made you go through.

From all of the reading online and over-the-phone conversations with my local smog ref, it doesn't seem like it's going to be that bad. I have a complete wrecked Yukon that I'll be swapping everything over from and as long as I keep all of the cats, O2's, and evap system in place from the newer truck, I shouldn't have any issues. I'll just have to be sure the tuner doesn't disable all of that stuff when they re-flash my ECM.

[BigRed76]

Well for a 2003 the only part of the evap system that is mounted on the fuel tank is the fuel tank pressure sensor. The charcoal canister and vent solenoid are separate, and the purge solenoid is mounted up on the intake manifold. So really you can use any fuel injection capable fuel tank, and just find a way to make the fuel tank pressure sensor read the pressure/vacuum of the tank.

[93FatBottom]

Sorry for the delayed response.

So as it stands, I have EVERYTHING figured out. I have step-by-steps and write ups saved, parts lists and numbers saved, and I did inventory on the donor and the K5 and made a list of things I have to buy. The ONLY thing I haven't figured out yet, is how/where to put the fuel tank pressure sensor. The sensor literally just pops into place in a hole on the top of the fuel sending unit. Now I'm wondering if its really as simple as drilling a hole in the top of the K5 sending unit (my k5 has fuel evap already so I'm not going to replace it)? Should I cut fuel sender from the 2003 and have a shop drill and attach it to my K5 tank? can I just drill a matching diameter hole in the top of my K5 tank, pop the sensor in place and call it done?

Anyone ever done this before? I'd LOVE to hear from you.

Thanks!

[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.

[BR3W CITY]

I just skimmed but in regards to the gauge thing; you can use a resistor to adjust the sweep of the sending unit depending on which exact parts you end up using. I don't have the link handy, but on Stovebolt (and I'm sure here too) there are some threads about using resistors from new to old and old-to-new alike.

FWIW I don't even have a sending unit, I just use the fuel calc in the Scanguage that I run in my dash. Its not exact since it uses injector pulse to "Assume" how much fuel is being used, but its just a way to know when to pull over.

[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?

[BigRed76]

The pressure sensor doesn't have to be mounted directly on the tank. It can be anywhere in the evap line between the tank and the charcoal canister, because the evap line will have the same pressure as the tank.

[93FatBottom]

Originally Posted by BigRed76

The pressure sensor doesn't have to be mounted directly on the tank. It can be anywhere in the evap line between the tank and the charcoal canister, because the evap line will have the same pressure as the tank.

Would you by chance have any examples or ideas of a quick cheap easy way to mount the sensor?