Tbi swap build thread

[jasons]

I have ground at the following plugs.

A12- blk/wht- System ground
B3- blk/red- Distributor plug
B10-orange/blk- park neutral switch wire
D1- brn/wht- system ground
D6- Tan- O2 sensor ground to engine

[jasons]

Installed the new IAC valve and did the reset procedure. Now it idles at 2,500rpm.

I'm at a loss. It's hard to search for a vacuum leak when you don't want to let the motor run.

Just a thought, but could too much fuel pressure cause this?

The fuel pump is rated at 29 GPH @ 12 PSI which should be right. Would a blocked return line boost the pressure? I ran into that on an 87 Dodge pickup once, but the increased fuel pressure caused it to shut down after a couple seconds, not run fast.

Any ideas? I appreciate it.

[rfmaster]

Originally Posted by jasons

The IAC did click when A&B pins were jumpered, I'm just not sure the plunger extended completely, the new IAC valve will be here in a couple hours.

The EGR valve is installed and the vacuum hose is connected. Should it be disconnected for this?

I will double check grounds at the ecm plug.

BY disconnecting EGR you'll make sure that EGR is not active at idle. This is just a precaution.

There are no grounds at ECM - there are two multi pin plugs that plug into dual row connectors. The grounds that I referring are harness grounds - 3/8 ID lugs in the engine bay.

//RF

[jasons]

Having run out of ideas and remembering late last night that a friends 87 body swap project was in one of my storage units I swaped throttle bodys. It now idles like it should. I must have gotten something messed up when I put the kit in my throttle body. I'll have to go throught it again.

Thanks for the help RF.

[BigrobDog]

all i got left is my drac to wire up . has any body got info on were to wire each wire to, 90 suburban 350

[jasons]

Originally Posted by rfmaster

Ok Guys.


Zooming into high temperature coolant area.


Cross over occurs right around 76 to 80C region.

AC Delco G1852 (found on Internet) data stops at 100C (212F) - I do not have this sensor at this time, but would like to re-run it to see how it behaves between 100 and 135C.

Next step is to validate SW5051 with the actual gauge.

Suggestions???? Questions???

//RF

Do you have the data for the SW5051 sensor broke down as to Ohms at a specific temperature? I have the data for the G1852 from the web, which is probably the same you found, but can't find it for the SW5051. I used the 5051 sender in my Blazer and the gauge pegs before the electric fan comes on at 185*. I think adding a resistor in line would work, but need to know what the difference between the two senders is to figure out how much resistance to add.

[rfmaster]

Originally Posted by jasons

Do you have the data for the SW5051 sensor broke down as to Ohms at a specific temperature? I have the data for the G1852 from the web, which is probably the same you found, but can't find it for the SW5051. I used the 5051 sender in my Blazer and the gauge pegs before the electric fan comes on at 185*. I think adding a resistor in line would work, but need to know what the difference between the two senders is to figure out how much resistance to add.

Yes, SW5051 is not a direct replacement.
RED line is the temperature curve for SW5051 with a series 22 Ohm resistor added. Below 75C (165F) the temperature gauge will be displaying very low temperatures due to higher resistance offered by SW5051. Above 75C with 22Ohm series resistor SW5051 appear to track TU5 very closely.



I have not had a chance to verify this, but test data supports this conclusion.

//RF

[jasons]

Thanks RF. I was thinking around 30 Ohm would be needed. I'll get a resistor to add and post the results.

[Jonboy]

Just a quick fuel question, for a swap into an older vehicle. I am getting ready to help a friend do a TBI swap into a '74 Blazer, but it does not have a return line. What is the best way to do one? Should I use rubber line going back to the tank, (and does the return need to be FI rated?), or does it need to be hard line. I am planning on using an inline fuel pump and using the original feed line. Also, where are you guys putting the fuel filter when doing an inline pump?

[rfmaster]

Originally Posted by Jonboy

Just a quick fuel question, for a swap into an older vehicle. I am getting ready to help a friend do a TBI swap into a '74 Blazer, but it does not have a return line. What is the best way to do one? Should I use rubber line going back to the tank, (and does the return need to be FI rated?), or does it need to be hard line. I am planning on using an inline fuel pump and using the original feed line. Also, where are you guys putting the fuel filter when doing an inline pump?

1) You'll have to become a plumber and install a new 3/8" supply line - for example SUM-G2538 aluminum fuel line which is easy to work with. Use your old line as return. Do not use rubber line - it will increase pressure drop and will deteriorate over time. As a minimum supply must be 3/8" and return 5/16". Return is a low pressure, but it still carries fuel. When plumbing vehicle for EFI keep safety and long term maintenance in mind!!!

2) If you have a baffled tank - use in tank fuel pump. In case of conventional tank use largest fuel filter you can find before inline FP inlet port. Large fuel filter will act as a mini surge tank and prevent fuel starvation when fuel sock gets uncovered. It is not a perfect solution, but it is as close as you can get away with without building a full surge tank system and lift pump.

//RF

[Jonboy]

Wow. I would have thought that the feed line would have been 3/8 already. Guess that's what I get for trying to engineer a TBI swap from 250 miles away. Thanks for the heads up.

[rfmaster]

Originally Posted by Jonboy

Wow. I would have thought that the feed line would have been 3/8 already. Guess that's what I get for trying to engineer a TBI swap from 250 miles away. Thanks for the heads up.

It probably is a 3/8" line, but after 40 years of service I would be leery to subject OE fuel line to high pressure. Fuel fires kinda ruin your day! In carb operation the fuel is sucked from the gas tank by the engine mounted fuel pump. In the EFI system fuel pump is working against FPR mounted in the TB, hence between fuel pump outlet and TB FPR fuel system is pressurized. Leaks are not good since today's gasoline is a nasty concoction of Gasoline and ethanol and other 'poop' that I do not care to remember.

//RF

[rfmaster]

Originally Posted by jasons

Thanks RF. I was thinking around 30 Ohm would be needed. I'll get a resistor to add and post the results.

22, 27 and 33 Ohms are standard values per E12 (10%) series resistors.... Use 2 Watt Allen Bradley resistors if you can..

//RF

[jasons]

I added a 22 Ohm resistor. The guage is now about 2/3 of the way up the normal range.

[rfmaster]

Originally Posted by jasons

I added a 22 Ohm resistor. The guage is now about 2/3 of the way up the normal range.

Earlier generation gauges may have been a bit off, but like you said you may try slightly higher resistor to dial it in.

//RF

[jasons]

I'm fine with where it reads now. I tried a 22 Ohm resistor, but it put the guage at about 1/3 of the way into the normal range. A 27 Ohm would probably put it in the middle, but the local Radio Shack didn't have one.

[k1blazer]

I apologize for coming in late in the thread. I have a 72 K5. What did you guys do to tackle the return fuel line to the tank?
Posted via Mobile Device

[jasons]

Originally Posted by k1blazer

I apologize for coming in late in the thread. I have a 72 K5. What did you guys do to tackle the return fuel line to the tank?
Posted via Mobile Device

I'm running an in tank fuel pump that has a return build into the unit. It's a little more than a frame mounted pump, but as far as I'm concerned it's worth it. It is as quiet as a factory setup and I've run it with as little as 3 gallons of gas in the tank with no starvation problems. This is where I got the pump
http://www.tanksinc.com/index.cfm/pa...prod/prd84.htm. It is item PA-TBI. The customer service was excellent also. For a stock Blazer tank let them know you need longer tubes for a 13" deep tank and you will have to improvise a little on mounting the sump pump to the bracket. I welded mine together and it works fine.

[k1blazer]

That's pretty awesome! So this one mounts directly to the stock tank?? I'll be honest, I've never actually seen the top if my tank.
Posted via Mobile Device

[jasons]

I didn't take any pictures while putting it together. You would cut about a 4" hole in the top of the tank, be careful if reusing your existing tank. I put the unit in just behind the existing sending unit which you will still need for the gauge. I had to move the tank forward about 2" to clear the crossmember. The fuel pump could be located toward the right front corner of the tank and then the tank could stay in the original location. Just make sure there is no interference between the pump unit and the sending unit for the gauge.

[k1blazer]

Thanks again!! I can't wait to start on mine.
Posted via Mobile Device

[k1blazer]

Guys! This is a very long thread and I've read through it. Thanks for all of the information! I have a question though. I probably just overlooked this in the thread but which intake manifold would I use on a '72 small block. The two center holes are at different angles on the later manifold.
Posted via Mobile Device

[rfmaster]

Originally Posted by k1blazer

Guys! This is a very long thread and I've read through it. Thanks for all of the information! I have a question though. I probably just overlooked this in the thread but which intake manifold would I use on a '72 small block. The two center holes are at different angles on the later manifold.
Posted via Mobile Device

1972 block is not your main concern, but cylinder heads produced from 55 to 86 had the four inner holes drilled at 90 degrees to the head flange surface. Starting 87 and up CI heads had the four inner mounting holes drilled at 72 degrees.

Holes in intake manifold can be slotted to accommodate 72 degree angle or manifold adapter bushings from Professional Products part number 52110 can be used in place of washers.

//RF

[iceship]

So what is the least about of componits you need for the engine to fire up. ....
Posted via Mobile Device

[rfmaster]

The thread has been quiet for a while! For those who are looking to upgrade TBI harness from JY pulled rat nest or contemplating clean carb to TBI swap Northern Autoparts has a special on Painless EFI TBI swap harness #60101 this week:

http://www.northernautoparts.com/Pro...ProductId=1468

//RF