Tbi swap build thread

[rfmaster]

Originally Posted by 68 TT

I can burn my own chips. I will give it a try with the 7427 PCM and see where it goes from there.

I would love to run RBob's EBL but I am using a 4L60E so it would have to be a piggy back system unless he has developed a PCM version of the EBL.

Yes, early C3 ECM will not control later E tranies.
I got couple of these later 7427 PCM's siting on shelf waiting for their turn. P4 PCM's suppose to have better idle logic and enhanced adaptation algorithms. Time permitting I may put together 7427 PCM on the engine stand and see how it plays with 383 (will need separate harness since I hate moving pins around. I grabbed $0D definition for TP-rt and ZIF socket for G2 board from Moates. You simply get spoiled with EBL flash.

//RF

[68 TT]

Originally Posted by rfmaster

Yes, early C3 ECM will not control later E tranies.
I got couple of these later 7427 PCM's siting on shelf waiting for their turn. P4 PCM's suppose to have better idle logic and enhanced adaptation algorithms. Time permitting I may put together 7427 PCM on the engine stand and see how it plays with 383 (will need separate harness since I hate moving pins around. I grabbed $0D definition for TP-rt and ZIF socket for G2 board from Moates. You simply get spoiled with EBL flash.

//RF

I have a new G1 & ZIF left over from a TPI project. Just happens to fit the TPI 730 ECM as well as the 7427 TBI PCM in the 94-95 trucks according to Moates so I can dust it off for this conversion.

I thought about using a piggyback EBL to get the thing dialed in then transferring the learned VE data and such into the $0D BIN file manually with TP-RT.

I love being able to tweek the trans characteristics and feel with the computer. I just need to figure out the sport mode feature that was in my 95 LT1 car and get it into $0D some how.

[kcblazer75]

One more thank you!

The TBI conversion is complete and the truck is back on the road.

Runs beautifully! It even idles smooth at a 70 degree angle!

Cant wait to get this thing out on the trail!

You guys are the best. Thanks for the help!

Keith

[rfmaster]

Originally Posted by kcblazer75

One more thank you!

The TBI conversion is complete and the truck is back on the road.

Runs beautifully! It even idles smooth at a 70 degree angle!

Cant wait to get this thing out on the trail!

You guys are the best. Thanks for the help!

Keith

Enjoy the ride and tread lightly! Sometimes I kinda wish that I had K truck, but at the time my rig was available for a good price.

/?RF

[kcblazer75]

Now that I have confirmed that it is running good, stock, I am thinking about installing a surge tank because my stock tank does not have baffles.

Can you help me consider the physics of this and make sure I am making the correct assumptions?

See the attached diagram of my design.

The in-tank pump is a stock pump from the donor vehicle.
The 2nd pump is a Carter P5001 (per RF's recommendation)

Quesitons:

Because the in-tank FP is under no pressure, and pumps at full rate, can I assume that it will always pump faster than the 2nd FP?

Worded another way; is there any chance the 2nd FP will pump gas faster than the in-tank FP, thus emptying the surge tank?

Is there any chance that the surge tank could build up pressure, thus causing back pressure to the TB return line? Consider this; the in-tank FP volume + the TB return volume = more volume than the surge tank return line can handle.

Do you see somthing that I have missed in my design? Seems pretty simple, but I have a bad habit of not considering all the factors!

Thanks for your expert opinion!

Keith

on 8/29 i updated the picture to show the 1/2" return line from surge tank.

[rfmaster]

Keith

There are couple of details that you must consider.

1) What is in tank FP maximum flow with minimum back pressure? Even if it it is a stock in tank TBI pump it is probably capable of delivering 40 to 50 GPH! That's a lot of fuel being pushed through the system. With 5/16" return line back to tank surge tank will be pressurized. You can easily check that by attaching fuel pressure gauge to the outlet port for the external (new inline) pump.

2) Ideally you want to have low pressure lift pump inside you gas tank. This pump should be able to deliver about 4 to 6 PSI (20 GPH) which is sufficient to do the job - keeping enough fuel in surge tank without creating too much back pressure for the TBI return line.

3) One way to achieve a low back pressure is go with a larger return line from surge tank to main tank e.g. change over 5/16 to 1/2" line, but this may not possible since most gas tank feed through return ports are sized for 5/16 fuel line". Alternatively, you can modify fuel pick up assembly by installing a larger feed through for return line. You can try 5/16" first to see if your fuel pressure remains steady and same as before - TB FP regulators do not work well with excess back pressure!

4) With 1qt (~ 1liter ) capacity surge tank will always be full with excess fuel returned back into main tank. Under normal operating conditions TBI FP regulator bypasses (returns) most of the supplied fuel back. I had an instance when my lift pump got disconnected and I was able to drive for about 2 miles before I lost pressure and engine stalled.

//RF

[kcblazer75]

Thats great advice RF. I knew there was something wrong with my design, but I hadn't put my finger on it yet. Something just didn't seem right.

Ill step back and think about the options I have.

I'm considering not even putting on the surge tank. Maybe not worth the trouble.

The Blazer tanks are not long and skinny like the pickup tanks. They are about 30" on each side, square, and 12" tall.

I would have to be really low on gas to have a problem.


Anyone else out there with a Blazer...Have you had any problems with fuel sloshing with an in tank fuel pump and no baffles?

Thanks!

Keith

[manimal]

Originally Posted by rfmaster

You need to verify POST functionality - ignition key from off into run position, but do not attempt to crank engine over. You should see SES light go from solid on blink off back to on. Meanwhile fuel pump must come on for about 2 seconds and shut off. If the pump does not come during this check the likely culprit is a bad fuel pump relay, wiring between ECM (Pin A1 dark green/white) and Fuel pump relay coil circuit, or possibly blown driver transistor that provides + 12V to energize FP coil. The black/white wire in the FP relay socket must be grounded. Otherwise coil will never be energized.

When you pour a little bit of gas into TB engine fires and oil pressure switch NO contacts close once oil pressure is in excess of 6 PSI thus providing power to the fuel pump.

Check and see if there +12 volts supplied by ECM to FP relay coil circuit when engine is running (the aforementioned A1 dark green-wht wire) .

//RF

Do you measure this at the ECM or the relay? Can you unplug the relay and check? I am have a problem with my wife's 89 Suburban. Before the 'current' problem, when you turn the key to run,you'd hear a "CLICK" after about 2sec.(I assumed this was the fuel pump priming the system)....now for the current problem:
The truck has a hard time starting......when it does start,it will run then shut off like the key was turned off. I have replaced the fuel pump,and filter.(monday morning). Now when you turn the key to run, you can hear the fuel pump running for 20 seconds(I have the fuel module),but no longer hear the aforementioned "CLICK" after 2-3 seconds. I have swapped around relays to no avail. I also replaced the oil pressure switch this morning...again to no avail. What am I missing? I also have had the coil and ignition module tested at Autozone-both tested good....could this be a pick up coil? or am I looking at an ECM problem? Thank You for any help you can give.
-Lance

[rfmaster]

Originally Posted by kcblazer75

Thats great advice RF. I knew there was something wrong with my design, but I hadn't put my finger on it yet. Something just didn't seem right.

Ill step back and think about the options I have.

I'm considering not even putting on the surge tank. Maybe not worth the trouble.

The Blazer tanks are not long and skinny like the pickup tanks. They are about 30" on each side, square, and 12" tall.

I would have to be really low on gas to have a problem.


Anyone else out there with a Blazer...Have you had any problems with fuel sloshing with an in tank fuel pump and no baffles?

Thanks!

Keith

The problem with fuel sloshing in square bodies is pronounced when there is less than 1/4 tank full. I do not have first hand experience with 30G blazer tanks.
Over the last couple of years I did a lot of research on surge tanks and fuel delivery systems. In one application Ford used lift pump to draw fuel from the tank into a large size fuel filter (which acted as surge tank) before being fed into high pressure FP. Volkswagen used a plastic surge tank - fuel filter part #533 201 511 A on some of their early 80 cars. I bought one of them in hopes of using in my system, but the fuel line size used by Volkswagen was too small (and metric to boot).
In retrospect finding a replacement EFI tank (with built-in baffles) is easiest and least expensive route one can take. Follow up question - is it possible to adapt a 1990 burban gas tank (GM14C Tank Dimensions: 28 3/4" x 28 1/8" x 12 3/4" in your 75 blazer? It looks like 75 blazer also used 31G tank (GM14A; 31 Gallon; Tank Dimensions: 28 3/4" x 28 1/8" x 12 3/4"). Filler neck size might be different.

//RF

[68 TT]

Originally Posted by kcblazer75

Thats great advice RF. I knew there was something wrong with my design, but I hadn't put my finger on it yet. Something just didn't seem right.

Ill step back and think about the options I have.

I'm considering not even putting on the surge tank. Maybe not worth the trouble.

The Blazer tanks are not long and skinny like the pickup tanks. They are about 30" on each side, square, and 12" tall.

I would have to be really low on gas to have a problem.


Anyone else out there with a Blazer...Have you had any problems with fuel sloshing with an in tank fuel pump and no baffles?

Thanks!

Keith

I will be dealing with the same issue eventually as my 67 K10 conversion will be using a Blazer fuel tank just like yours.

I will probably be buying a new TBI Blazer fuel tank with the proper baffles eventually but want to give it a try with the carbureted tank I have now to save some money as my budget is very small.

I may try to build a tank baffle system out of perforated metal that can be installed through the sending unit hole and riveted together. A nice sized center ring around the pickup sock with the return line fed into it should do the trick. A leg heading to each corner of the tank should keep it in place.

[68 TT]

Originally Posted by rfmaster

In retrospect finding a replacement EFI tank (with built-in baffles) is easiest and least expensive route one can take. Follow up question - is it possible to adapt a 1990 burban gas tank (GM14C Tank Dimensions: 28 3/4" x 28 1/8" x 12 3/4" in your 75 blazer? It looks like 75 blazer also used 31G tank (GM14A; 31 Gallon; Tank Dimensions: 28 3/4" x 28 1/8" x 12 3/4"). Filler neck size might be different.

//RF

The GM14C tank also fits the 87 to 91 Blazer so it should bolt right in.

The only problem I have found is that the older Blazers used a smaller fuel filler neck diameter than the newer tanks and the vent hose diameter is different.

I am just going to modify the filler neck and vent tube connection to match the newer tank sizes or pick up a used one from a TBI Blazer that is correct already.

[rfmaster]

Originally Posted by manimal

Do you measure this at the ECM or the relay? Can you unplug the relay and check? I am have a problem with my wife's 89 Suburban. Before the 'current' problem, when you turn the key to run,you'd hear a "CLICK" after about 2sec.(I assumed this was the fuel pump priming the system)....now for the current problem:
The truck has a hard time starting......when it does start,it will run then shut off like the key was turned off. I have replaced the fuel pump,and filter.(monday morning). Now when you turn the key to run, you can hear the fuel pump running for 20 seconds(I have the fuel module),but no longer hear the aforementioned "CLICK" after 2-3 seconds. I have swapped around relays to no avail. I also replaced the oil pressure switch this morning...again to no avail. What am I missing? I also have had the coil and ignition module tested at Autozone-both tested good....could this be a pick up coil? or am I looking at an ECM problem? Thank You for any help you can give.
-Lance

Lance
Do you have a DVM??? You'll need it to perform this check.

Background
Since you have a fuel module it provides 20 sec of timed +12V power to fuel pump once it sees fuel pump relay energized. This rules out FP relay and ECM control circuits. You can unplug fuel module (optional on some 5.7 and 7.4L engines) and observe only 2 sec fuel pump operation during POST vs. 20 sec with fuel module.

Possible problem
You may have a bad or flaky reluctor coil in your distributor. Reluctor coil generates zero crossing (saw tooth) pulses and supplies them ignition control module (ICM - P/N contacts). ICM converts these pulses into square wave pulses and sends on to the ECM - distributor reference pulse (DRP). If ECM does not see DRP it will not fire injectors and engine will stall.

Question:
Do you get spark after engine shuts off by itself???

Checking reluctor coil
Disconnect reluctor coil connector from ICM. Measure coil resistance across connector contacts. It should not be 0 Ohms with typical range being about 300 to 1200 Ohms. If you are reading very high resistance - you have an open coil. Engine heat may cause coil windings to open once engine comes up in temperature. Wiggling connector may also cause intermittent connection.


//RF

[manimal]

Thank You rfmaster
Ok here are my findings...
I checked the resistance of the pick up coil=887 ohms
I unplugged the fuel module and cant hear the pump....??? Should it start with the fuel module disconnected? Because it does not.

[rfmaster]

Originally Posted by manimal

Thank You rfmaster
Ok here are my findings...
I checked the resistance of the pick up coil=887 ohms
I unplugged the fuel module and cant hear the pump....??? Should it start with the fuel module disconnected? Because it does not.

OK - the following checks should isolate fault.
1) Disconnect fuel pump relay from its socket. Locate two pins inside FP socket that correspond to dark green/white - ECM A1 (Fuel pump relay +12V enable) and black/white (ground) (16 or 14 AWG wire). Set DVM to measure DC voltage between those two socket pins. Disconnect oil pressure switch connector (IRC should have three wires Orange / Gray and Brown or orange red/black). You may get SES fault code 51. Just disconnect neg battery to clear for 30 seconds.

Turn ignition key into run position - DVM should read +12 volts for two seconds and then turn -off and read 0 to 0.6 Vdc. If you got +12 volt during POST then attempt cranking - you should see 12 volts as ECM powers up FP relay during cranking!

At the output side of the FP relay there is (some harnesses omitted) an inline fuse link - it sits between fuel module and FP relay. One side you should see Pink/black wire and other side you should have Tan/white -10 or 12 AWG size wires. Wire colors changed depending on OE harness contractor that assembled harness! Try to find it since if it has been overloaded it will be flaky with temperature!

I may have one of them in my collection - just do not have photo handy.

Do you get spark during no start condition???? - VERY IMPORTANT

//RF

[manimal]

Thanks rfmaster, I just drove it down the street(about 2 miles) and back without any problems. I will do these checks in the morning and post the results. Thank You for the help, it's VERY much appreciated. BTW I am not sure about the spark on shut off. The next time it happens, I will check that. Thank you again and I am sorry for the thread hijack.

[kcblazer75]

Originally Posted by rfmaster

The problem with fuel sloshing in square bodies is pronounced when there is less than 1/4 tank full. I do not have first hand experience with 30G blazer tanks.
Over the last couple of years I did a lot of research on surge tanks and fuel delivery systems. In one application Ford used lift pump to draw fuel from the tank into a large size fuel filter (which acted as surge tank) before being fed into high pressure FP. Volkswagen used a plastic surge tank - fuel filter part #533 201 511 A on some of their early 80 cars. I bought one of them in hopes of using in my system, but the fuel line size used by Volkswagen was too small (and metric to boot).
In retrospect finding a replacement EFI tank (with built-in baffles) is easiest and least expensive route one can take. Follow up question - is it possible to adapt a 1990 burban gas tank (GM14C Tank Dimensions: 28 3/4" x 28 1/8" x 12 3/4" in your 75 blazer? It looks like 75 blazer also used 31G tank (GM14A; 31 Gallon; Tank Dimensions: 28 3/4" x 28 1/8" x 12 3/4"). Filler neck size might be different.

//RF

Thank RF and 68TT,

I'm considering my options...

It's a 31 gal tank, and it is reletively new.

I had to modify it for this conversion already. I needed a 1/2" line for the filler vent so I had a port added.

I could easily cap the old return and install a 1/2" line between the surge tank and the filler vent tube. But I am worried about the noise of gas falling from the top of the tank while driving.

I could add another 1/2" port with a tube inside the tank to eliminate the noise.

I could scrap my new tank, get an EFI tank, then figure out how to retrofit/re-engineer the filler tube and vent.

I could get a 4-6 PSI intank fuel pump. Expensive! RF, are you using an in-tank fuel pump on yours?

I could engineer a baffle system like 68TT suggested. I think thats beyond my abilities. 68TT, How would you get it tight inside the tank so it doesnt rattle around?

And of course, the cheap way out is to make sure I dont ever let it get empty enough to have to worry about it!

Decisions, decisions..

Keith

[rfmaster]

Keith

You need to do a bit more research before turning a wrench or spending a dollar.

Just because I am very curious (not) I did a quick check on GM14C Tank

Rock auto has tank for $89.79
Fuel Pick up Part # SP12L1H Includes Fuel Pump, Sender, Float and Strainer (4 port) $122.79 or you could re-use your old pick-up with new tank.

About noise - I never hear noise of returning fuel - fuel pump makes more noise (engine is not running) and with a mild 350 idling into a pair of Delta 40 rumbling near by - well you can forget about it.

//RF

[kcblazer75]

Originally Posted by rfmaster

Keith

You need to do a bit more research before turning a wrench or spending a dollar.

Just because I am very curious (not) I did a quick check on GM14C Tank

Rock auto has tank for $89.79
Fuel Pick up Part # SP12L1H Includes Fuel Pump, Sender, Float and Strainer (4 port) $122.79 or you could re-use your old pick-up with new tank.

About noise - I never hear noise of returning fuel - fuel pump makes more noise (engine is not running) and with a mild 350 idling into a pair of Delta 40 rumbling near by - well you can forget about it.

//RF

Thanks RF,

Research is what this is all about. Havent done or spent anything yet. I appreciate the reminder though.

The noise I am talking about would occur if fuel was returned at the top of the tank, instead of the bottom of the tank. It would splash like filling a bath tub. That's the situation I would have if I used the filler vent. The stock return line outputs at the bottom, so you wouldn't hear it.

I appreciate the research you did! Buying equipment is always on the table. However, like everyone else, I'm already over budget, and trying to make due with what I've got.

I'm new to posting, and hope I haven't offended anybody, or asked too much.

Thanks

Keith

[rfmaster]

Originally Posted by kcblazer75

Thanks RF,

Research is what this is all about. Havent done or spent anything yet. I appreciate the reminder though.

The noise I am talking about would occur if fuel was returned at the top of the tank, instead of the bottom of the tank. It would splash like filling a bath tub. That's the situation I would have if I used the filler vent. The stock return line outputs at the bottom, so you wouldn't hear it.

I appreciate the research you did! Buying equipment is always on the table. However, like everyone else, I'm already over budget, and trying to make due with what I've got.

I'm new to posting, and hope I haven't offended anybody, or asked too much.

Thanks

Keith

Keith

There is no offense in asking pertinent questions - this is a discussion board and if you look through the threads all sort of questions are brought to the 'table'.

Back to your return line situation - couple of points of interest.

1) Return line should not have any back pressure - if I interpret your post correctly you were planning to install a return line bung into a filler neck. It is do able and I have seen it done before - putting a T into a vent line.

2) The bathtub noise - as I have mentioned before it is really a non issue in a running vehicle. I simply can not hear it in my truck with engine running! Both my tanks are equipped with a three port fuel pick modules - Fuel supply, fuel return and vapor vent (to CCP). The mistake I made during my conversion was to keep original non baffle tanks. I simply did not know any better. I used FG05C (right) and FG05D (left) fuel sending units with external fuel (low pressure) pump.

Interestingly enough return fuel line ports have a check valve that also acts as a fuel spreader (inside the tank) - this is probably the reason why I can not hear noise of splashing fuel! In your case you can probably achieve the same effect with a section of 1/2" ID SAE 30R10 fuel hose perforated (like a Swiss cheese) with many holes acting as a spreader, inside your tank. Note that everything inside tank must be rated for fuel immersion - fuel hose must be SAE 30R10 not commonly available SAE30R9 (fuel injection) or SAE30R7 (50 PSI fuel line).

//RF

[68 TT]

Originally Posted by kcblazer75

...I could engineer a baffle system like 68TT suggested. I think thats beyond my abilities. 68TT, How would you get it tight inside the tank so it doesnt rattle around?

I was planning on using some fuel tank repair epoxy to secure the baffle system to the tank sides & bottom so it doesn't bounce or slosh around. If cut to the right size the legs could be under a little pressure to keep the center pan / ring in place so the epoxy is just vibration & bounce prevention.

I considered separating the tank halves and welding the baffle & pan system in place but that is a whole lot of work that can be avoided by just spending $90 on a baffled tank. In a situation where no baffled tank is available this would be an option. I weld repaired a whole lot of used fuel tanks in the air force so I know how to deal with them and what to expect. I'd like to avoid that if possible though.

I guess I could cut a 12" square access hole in the top of the tank and cut down on the work a bunch vs. separating the tank halves.

[manimal]

OK, here are my findings......
Key off; .01 dcv between dark green/white and black/white
Key in run; 12 dcv, does not go off after 2sec
engine cranking/running; .66 dcv
* accidentally touched the tan/white wire instead of dark green w/DVM engine stalled
I cannot find a fuse link-also my FSM says that is only for the "CK" and not the "RV" vehicles. I am confused.....
I then followed the FSM for the test...
I hooked up 12v power to the FP test wire and pump runs.
disconnected the fuel module and removed the 12v to the test wire..key to run, pump does not run.
key on;checked the orange wire to ground I have 12v, then dark green/white to battery -, I have 12v,but when I use a test light between the two I get nothing????(test light is good) NOW I am really confused!
using the test light proceedure, my manual says there would be an open or short in the dark green/white wire or faulty ECM.
SO I continued on based on the DVM reading of 12v @ the dark green/white wire......
again key in run still no FP running.
Reconnected the fuel module engine running,disconnected the FP relay, engine still ran.
Key off, I probed the FP test socket, no power....Factory Service Manual says-NO TROUBLE FOUND.
Does any of this make sense? Cause I am REALLY confused.
Thank You

[kcblazer75]

Originally Posted by rfmaster

Keith

1) Return line should not have any back pressure - if I interpret your post correctly you were planning to install a return line bung into a filler neck. It is do able and I have seen it done before - putting a T into a vent line.

2) The bathtub noise - as I have mentioned before it is really a non issue in a running vehicle. I simply can not hear it in my truck with engine running! Both my tanks are equipped with a three port fuel pick modules - Fuel supply, fuel return and vapor vent (to CCP). The mistake I made during my conversion was to keep original non baffle tanks. I simply did not know any better. I used FG05C (right) and FG05D (left) fuel sending units with external fuel (low pressure) pump.
Interestingly enough return fuel line ports have a check valve that also acts as a fuel spreader (inside the tank) - this is probably the reason why I can not hear noise of splashing fuel! In your case you can probably achieve the same effect with a section of 1/2" ID SAE 30R10 fuel hose perforated (like a Swiss cheese) with many holes acting as a spreader, inside your tank. Note that everything inside tank must be rated for fuel immersion - fuel hose must be SAE 30R10 not commonly available SAE30R9 (fuel injection) or SAE30R7 (50 PSI fuel line).

//RF

RF,

That is a great idea! I hadn't thought of installing a "Swiss cheese" pipe inside the tank. That would properly allow air to escape while filling, and baffle the sound of fuel return. I will probably use brass pipe instead of rubber (as the filler vent bung I installed is threaded). I can "T" the vent on the outside of the tank, one for the filler vent, and one for the surge tank return.

I'll chew on this for a little while before taking any action.

Thanks

Keith

[kcblazer75]

Originally Posted by 68 TT

I was planning on using some fuel tank repair epoxy to secure the baffle system to the tank sides & bottom so it doesn't bounce or slosh around. If cut to the right size the legs could be under a little pressure to keep the center pan / ring in place so the epoxy is just vibration & bounce prevention.

I considered separating the tank halves and welding the baffle & pan system in place but that is a whole lot of work that can be avoided by just spending $90 on a baffled tank. In a situation where no baffled tank is available this would be an option. I weld repaired a whole lot of used fuel tanks in the air force so I know how to deal with them and what to expect. I'd like to avoid that if possible though.

I guess I could cut a 12" square access hole in the top of the tank and cut down on the work a bunch vs. separating the tank halves.

I was thinking about this last night.

Is there any way to just install the center pan / ring and secure it to the INSIDE lip of the 4" access hole at the top? Maybe with a few spot welds.

The spot welds would be on the inside of the o-ring, so you wouldn't have to worry about leakage. That would also avoid the trouble trying to assemble some big structure inside the tank.

Build the ring and arms on the bench, except leave one end of the ring open so you can collapse it to fit through the hole. Once inside, weld the ring solid (through the hole), then spot weld the arms to the hole.

Just throwing that out there!

Keith

[68 TT]

Originally Posted by kcblazer75

I was thinking about this last night.

Is there any way to just install the center pan / ring and secure it to the INSIDE lip of the 4" access hole at the top? Maybe with a few spot welds.

The spot welds would be on the inside of the o-ring, so you wouldn't have to worry about leakage. That would also avoid the trouble trying to assemble some big structure inside the tank.

Build the ring and arms on the bench, except leave one end of the ring open so you can collapse it to fit through the hole. Once inside, weld the ring solid (through the hole), then spot weld the arms to the hole.

Just throwing that out there!

Keith

It would be pretty tough to weld anything through the sending unit opening. No room to work and see too. I doubt I could get my hand and the MIG gun through at the same time.

You might be able to rivet the thing together in the tank but I would be worried about it coming apart from vibration.

A 12" access hole next to the sending unit opening and a fabricated sump pan welded in place would be the best option. This way you could fab up a proper sump pan and get both hands in there to weld it in place. This could be done with the sending unit installed so you could make sure it fit right and worked before you welded the sump in place.

[kcblazer75]

Originally Posted by 68 TT

It would be pretty tough to weld anything through the sending unit opening. No room to work and see too. I doubt I could get my hand and the MIG gun through at the same time.

You might be able to rivet the thing together in the tank but I would be worried about it coming apart from vibration.

A 12" access hole next to the sending unit opening and a fabricated sump pan welded in place would be the best option. This way you could fab up a proper sump pan and get both hands in there to weld it in place. This could be done with the sending unit installed so you could make sure it fit right and worked before you welded the sump in place.

What do you think the diameter and height of the ring/sump pan would need to be?

Once inside the tank, could you bring the seam you need to weld up to the hole? You could weld it without having to reach all the way inside.