5.3 vortec swap emissions tidbits (1 Viewer)

orangefj45

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i'm constantly trying to find new ways to make things easier to service and install as part of my conversion work. it's a constant evolution and every swap i do seems to be a little different than the last.
right now i'm working on a couple that need to pass CA emissions inspection so all the oem smog stuff has to be there and working. part of the system is the oem fuel tank sending unit. it's usually part of the fuel pump assy / cartridge. the cartridge contains the sending unit, fuel pump, fuel lines, evap line ( some models ) and the tank pressure sensor.
one solution that does work out well is to modify the tank with one of the vetteworks adapters and sink an entire "cartridge" in them. the problem with the fj6x series taks is that they are very shallow. there's only about 6.75" of debth to the tank in the one and only suitable location. most of the gm cartridges range from 9 to 12" in height. i looked at quite a few and it should be possible to modify one and make it work.
for this application i did'nt need the fuel pump or tank pressure sensor since they'd already been installed ( alternative solutions; frame mounted airtex pump and pressure sensor on one of the evap pipes on the tank ). so i tried to come up with ideas on how to get just the gm fuel level sensor in the tank.

option one: use the vetteworks adapter and sink part of the cartrigde in the tank after some mods to make it fit. this would require a vetteworks adapter, a complete or partial fuel cartridge, cutting a 3.75" hole in the top of the tank and then welding the ring on. might be tough to get a good seal and welding tanks that have already had fuel in them can be somewhat dangerous. ( a chunck of dry ice and a little water will produce enough CO2 to displace all the O2 in the tank and make it safe to weld/cut. straight CO2 will do the same thing for ya but dry ice is cheap and easy to get. i just hate putting water in a good tank although it's not that hard to dry the tank properly when the job is done.

option two: find some other sending unit from a steel tank and graft the late model gm sender onto it. i thought about doing it this way so i could weld an entire sending unit retainer ring to the top of the tank after cutting a 2-2.5" hole in it. would make for a better seal than the vetteworks unit ( imho ) and could be installed in more than one location. in a perfect world, i would try to find a sending unit that had two wires coming out of it and no fuel lines going thru the top of it. i looked at fj60 sending units and mounting rings but there's only one wire coming thru and this option would still require some cutting and welding. see option one.....

option three: graft the gm sening unit onto the stock fj60 sender and make them both work in the same location. hmmm, this might just work. would require no cutting, no welding and as long as i could mount the gm sender in such a way that i could pass the entire assembly thru the oem opening it outta work somehow.

so i decided to pursue this option.

here's a pic of both sending units side by side.
dsu1.jpg
 

orangefj45

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let me back track a little before we get too much further.....

the ohm readings for both senders are very different so the toyota unit can not be wired into the gm harness. also, the gm unit uses a curve, the toyota counterpart is linear setup. gm unit uses 5V incoming voltage going thru a reostat, the toyota unit uses a hot signal and a ground. so without being a complete electronics-supergenius it would be fairly difficult to get either unit to work with the other manufacturers requirements........

so if you're trying to run an oem gauge and a CA smog legal vortec, then you gotta run both units. :frown:

alright, back to option three:

both these senders have some mechanical differences. one of them is that the gm unit uses 90 degrees of sweep, the toyota unit uses less; about 80 degs. i was more concerned about the toyota unit working perfect so the fuel level would show true on the gauge. the gm unit would only be used for the evap portion of it's intended use so as long as i got close, it would work. the programming for the gm ecu dictates that the evap system will only run if there's more than 20% and less than 80% fuel capacity in the tank.
also, the vulcrum ( pivot ) for the toyota sender is very high in the unit. it would be next to impossible to locate the gm unit in such a way that the pivots ended up in the same place. this meant i might have to run both floats. hmm, might be tough to get both of them and both senders in there.

i did a simple mock up by zip-tying both senders together and quickly realized that getting both floats and senders in there would be challenging to say the least. so one of the floats had to go. since i wanted the toyota sender to be as accurate as possible, i decided to keep the factory float. the gm unit got the axe. at first i wanted to weld the two arms together, but the geometry would have never worked and the sender would hav bound up. so i had to make a "sliding gate" type of connection. after some measuring and bending, i got it to work on the first try.:)

another pic.
dsu2.jpg
 

orangefj45

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the next step was to mount the gm sender to the toyota unit securely. this was not easy because the sender itself was quite a bit too large for the opening in the tank where it had to pass thru. so i started to chop away what i thought i could live without, some of that is evident in the pic above.
next i had to make a little steel tab that the gm sender would slide onto. used some 16 gauge sheet metal and had one whiped up in no time. at this point, i had a way to locate the gm sender on the toyota unit. to retain it i drilled a small hole thru the gm sender and drilled and tapped a 2-56 hole in the new tab. this way the gm sender would slide on and then the tiny bolt would hold it in place.
this pic shows the bolt if you look closely. it's just above the bottom purple wire where it attaches to the reostat. small black allen bolt.
dsu4.jpg
 

orangefj45

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sorry about the crappy iphone pics, forgot the digi at home on the charger.:rolleyes:

next i had to deal with passing two extra wires thru the top of the toyota sending unit. i decided to drill two holes and pass the wires thru individually. this way i could use a gromet on each and get a good seal. the tanks for a vortec are pressurized so a good seal is a must. well, if you have to deal with CA emissions anyways. :eek:
i opted to go with some oem style gromets from a weatherpac connector. the wire size was perfect. to make sure i got a good seal, i trimmed two of the three ribs off the gromets and drilled the holes .010 under to make sure the gromets had no play at all.
next i installed the trimmed gromets and passed the wire thru with a dab of high grade silicone to seal them up as good as possible.

almost done!
dsu5.jpg
 

orangefj45

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at this point i had already tried passing the entire assy thru the factory opening and it looked like it was going to work with a little more trimming. a little here, a little there.

moment of truth was near at this point. and this is where one of the best parts of this option came thru: no need to remove the tank! did'nt even have to drain it!!! just pull the access cover, remove the stock sending unit and install the modded unit ( i started with a spare just in case this was'nt gonna work:cool:)
this worked out better than expected. right before installing the new sender we soldered some longer wires to the two signal wires. a little shrink tube and they were ready to go. last but not least i opted to run a grund wire as well. the oem gm connector has four wires; fuel pump hot, ground, fuel level sender 5V signal and fuel level fuel sender ground ( to the computer ). the fuel pump hot was cut and capped. the ground and signal wires were hooked up and done. here's a pic right before the cover was bolted back on.
dsu6.jpg
 

orangefj45

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last step was to do a quick check with the fluke meter and then i went for a drive. ran it for about twenty minutes and it seemed to work as desired. no hick-ups, no check engine light, no codes.

so far so good. i need to put a few more miles on this rig and then it'll be ready to go home.

i'll snap a pic of the 60 tomorrow.

hope this might help some of the others who have done or are thinking about doing a smaog legal vortec swap. obviously there are other components required to make the conversion legal, this post just illustrates one aspect of the system.

hth

georg @ valley hybrids
 
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Damn, Georg, this is WAAAYYY better than our original plan! I look forward to my next trip up there so we can finish up my junk. Do you have a sending unit for me, or do I need to bring one?

GREAT work!
 

orangefj45

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This is great! Thanks for taking the time to write this up.

thanks, thought it was worth posting.


So Georg...got any tricks for mounting an electric pump in a 60 tank suitable for a TBI motor?
there is a write-up in the 60 forum. one of the guys used the vetteworks adapter ring and dropped a gm cartridge in the tank; had to modify the mounting location of the pump. pretty good write-up. i can find the link if you can't Don.
although if you're doing a TBI, then just run a 62 tank and pump. it's a bolt-in.....


Damn, Georg, this is WAAAYYY better than our original plan! I look forward to my next trip up there so we can finish up my junk. Do you have a sending unit for me, or do I need to bring one?

GREAT work!
thanks john. i don't have another useable sender right now but from the research i've done. all the later gm cars and trucks used the same resistance values for the sender. so there's a ton of them out there.

hth

georg @ valley hybrids
 

ntsqd

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My only concern is that over time gasoline loosens & partly dissolves silicone sealant. At least it has done that to those that I've seen used when people tried to make carb base gaskets & similar with it. I would look into one of the "Form-A-Gasket" products. SOP I think the non-hardening version would be the right choice, but I'm not certain. Hylomar might be another option. Gasoline certainly has no effect on it at all.
 

orangefj45

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good point and something i was/am a little concerned about. i used a tiny mount and i don't think it's even needed for this application since the gromets fit really snug. time will tell but so far, so good.

georg
 
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For those of us not required to meet CA emissions requirements but still want to keep the pump in tank, what is the best route? Upgraded pump on stock hanger?


~Bob
 

orangefj45

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Great write up George !!!

Let us know how it all pans out.....
thanks bud, i appreciate it. i've put about 40 miles on the cruiser with the dual senders and so far, so good. runs great, no codes, no check engine light,......going to the ref later this week. and then it's finally going home.

georg
 

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