Tbi swap build thread

[rfmaster]

Originally Posted by 68 TT

I haven't messed with the stock early TBI mechanical speedo dashes that have the optical sensor on them before. All my other EFI conversions were port injected so they used different setups entirely.

How would that three wire module coming off the back of the speedo interface with the ECM? I know one wire is a ground and one is ignition on power so I'm assuming the one remaining wire goes into the ECM at A10 like the JTR module. How does this interface with the DRAC and how is it wired in?

I am no expert in DRAC interfacing - all my swaps were done using standalone inline VSS modules (non electronic dashes). DRAC - aka digital ratio adapter controller was used as a 'glue' module to get various early electronic controls working in some resemblance of a harmony. The following are good read on VSS /DRAC /ECM interfacing:

http://www.fullsizechevy.com/forums/...1-post279.html
http://www.jagsthatrun.com/V8-chapte...ed-Sensors.pdf
http://www.tbichips.com/drac/
http://www.syty.org/gallery2/main.ph...&g2_itemId=203
http://www.thirdgen.org/techboard/di...ico-trans.html


DRAC I/O
C15 2000PPM
C14 2000PPM
C13 40PPR (1:1)
C12 Signal in??? not sure
C11 2000ppm
C10 128000 PPM
C9 12V
C8 GRND
C7 VSS input
C1
C2
C3
C4 VSS cruise control

//RF

[68 TT]

Originally Posted by rfmaster

I am no expert in DRAC interfacing - all my swaps were done using standalone inline VSS modules (non electronic dashes). DRAC - aka digital ratio adapter controller was used as a 'glue' module to get various early electronic controls working in some resemblance of a harmony. The following are good read on VSS /DRAC /ECM interfacing:

http://www.fullsizechevy.com/forums/...1-post279.html
http://www.jagsthatrun.com/V8-chapte...ed-Sensors.pdf
http://www.tbichips.com/drac/
http://www.syty.org/gallery2/main.ph...&g2_itemId=203
http://www.thirdgen.org/techboard/di...ico-trans.html

DRAC I/O
C15 2000PPM
C14 2000PPM
C13 40PPR (1:1)
C12 Signal in??? not sure
C11 2000ppm
C10 128000 PPM
C9 12V
C8 GRND
C7 VSS input
C1
C2
C3
C4 VSS cruise control

//RF

Thanks for the links and info. I will do a bit of reading and see if I can get a handle on it.

I haven't found a wiring diagram that shows the DRAC, speedo sensor module and ECM connections under the dash. Anybody have one?

[68 TT]

Found another good thread on DRAC VSS.

http://www.coloradok5.com/forums/sho...d.php?t=124012

This one covers a bunch but does address the two-pulse optical buffer on the back of the speedo in some cases that I have and want to use.

http://chevythunder.com/fuel%20injec....%20pg%20B.htm

From what I have read I believe those with the 2-pulse optical buffer coming off the back of the speedo do not need a DRAC since the speedometer gears in the trans do the job of the DRAC in converting driveshaft speed into the proper 1000 rotation per mile output to the speedo. The optical buffer speedo has two trigger points the optical sensor sees so it outputs the 2000 ppm signal the ECM wants.

This type of optical buffer was also used on the early TPI cars and can be used with the later speed density TPI ECM if you do a little work in the program to change which input it is looking for and to convert the 2000 ppm DC signal from the optical buffer to the 2000 ppm AC signal the 730 ECM wants to see. Nice to know as I will eventually get my old TPI system installed into my Malibu and it has a newer dash with the optical buffer coming off the speedo.

[68 TT]

I just ran the numbers for calibrating a DRAC to my combination out of curiosity and I would have to install 33" tall tires just to make my setup come close to the highest pin setting calibration a DRAC can be configured for.

[pancake]

Hello again,

I finially had the time to re-install my old intake and put the TBI onto it using an adapter plate.

I got the truck started but it is ideling very high about 1900rpm and has a VERY loud whistling sound to it. I let it run for 5 min or so and it did not stop whistling. It is almost unbearable. If you remember from my other posts I eleminated the EGR. Does this have something to do with it?

I thought the whistling was coming from the IAC so I replaced it. no change.

The truck will also act like the idle is going to come down but then back fires through the TBI.

The truck starts fine but won't idle below 1800rpm unless I turn the dizzy to adjust the timing but then it backfires and dies. I can not get the idle low enough to use a timing light but I rechecked the rotor position in relation to TDC of #1 and I am close to "0" degrees timing.

I did not have this idle or LOUD whistling issue with the OEM manifold and EGR valve, but the truck would not idle correctly and would backfire out the exauet with it on. That is why I put my old intake "Edelbrock 2101" back on.

I did install a fuel pressure gauge and ran 3/8 allumminium? tubbing from the tank. The fuel pressure is only at ~ 6psi by the TBI. could this be the problem? The TBI is spraying a nice steady mist when the truck is running.

I found a post by RF on IAC adjustment....do I need to do this?

The truck did not have these issues with old OEM intake and EGR, I know I installed the new intake correctly and do not beleive that I have a massive vacume leak causing the LOUD whistling. I am at a dead end and any help would be greatly appreciated...Thank again, Pancake

[rfmaster]

Originally Posted by pancake

Hello again,

I finially had the time to re-install my old intake and put the TBI onto it using an adapter plate.

I got the truck started but it is ideling very high about 1900rpm and has a VERY loud whistling sound to it. I let it run for 5 min or so and it did not stop whistling. It is almost unbearable. If you remember from my other posts I eleminated the EGR. Does this have something to do with it?

I thought the whistling was coming from the IAC so I replaced it. no change.

The truck will also act like the idle is going to come down but then back fires through the TBI.

The truck starts fine but won't idle below 1800rpm unless I turn the dizzy to adjust the timing but then it backfires and dies. I can not get the idle low enough to use a timing light but I rechecked the rotor position in relation to TDC of #1 and I am close to "0" degrees timing.

I did not have this idle or LOUD whistling issue with the OEM manifold and EGR valve, but the truck would not idle correctly and would backfire out the exauet with it on. That is why I put my old intake "Edelbrock 2101" back on.

I did install a fuel pressure gauge and ran 3/8 allumminium? tubbing from the tank. The fuel pressure is only at ~ 6psi by the TBI. could this be the problem? The TBI is spraying a nice steady mist when the truck is running.

I found a post by RF on IAC adjustment....do I need to do this?

The truck did not have these issues with old OEM intake and EGR, I know I installed the new intake correctly and do not beleive that I have a massive vacume leak causing the LOUD whistling. I am at a dead end and any help would be greatly appreciated...Thank again, Pancake

Hmmm. My got feel tells me that you have several problems conspiring against you.

Idle at 1900 is not a good thing - you have a vacuum leak. Check TB to intake manifold gasket - there are different gaskets out there. Some seal better that others. Make sure that throttle plates are fully closed. I have seen post where throttle cable is too short and keeps throttle plates partially open!

YOU MUST RESET IAC - no if buts or whatever. This must be done as ECM has no idea where IAC is positioned, but if it was set to a known position it can make adjustments to adjust idle.

6 PSI is too low - it maybe enough for idle, but ECM VE calibration tables are setup for two injectors (62 lb/h) operating at 13 PSI. Injector delivery rate changes non-linearly with fuel pressure. Popping though TB is an indication that engine is running lean (or timing is way to advanced)! You need 3/8" supply line - soft steel or aluminum with a fuel pump rated at least 20 PSI and capable of moving 40GPH (aka GSL393, Carter P5001, others). Do you have carb rated pump by any chance??? 6 PSI is a carburetor rated working fuel pressure. Cheap fuel pressure gauges are also known to give false readings. (I had good luck with Summit SUM-800130 as it tracks within 2 PSI window of Auto Meter 2239). What is is the supply voltage at fuel pump - it better be around 12volts!

EGR - re verify that you do not have vacuum leak under block off plate!!

Take couple hi res photos (if you can) of your engine bay around TB and lets see if we can spot the obvious.

//RF

[68 TT]

The guys on the DIY EFI GM ECM list have had several different aftermarket TBI adapters leak at bolt points. Some went so far as to fill the bolt head areas with epoxy so the TB wouldn't leak.

Did you make your adapter or is it an aftermarket one?

[68 TT]

Originally Posted by pancake

Hello again,

I finially had the time to re-install my old intake and put the TBI onto it using an adapter plate.

I got the truck started but it is ideling very high about 1900rpm and has a VERY loud whistling sound to it. I let it run for 5 min or so and it did not stop whistling. It is almost unbearable. If you remember from my other posts I eleminated the EGR. Does this have something to do with it?

I thought the whistling was coming from the IAC so I replaced it. no change.

The truck will also act like the idle is going to come down but then back fires through the TBI.

The truck starts fine but won't idle below 1800rpm unless I turn the dizzy to adjust the timing but then it backfires and dies. I can not get the idle low enough to use a timing light but I rechecked the rotor position in relation to TDC of #1 and I am close to "0" degrees timing.

I did not have this idle or LOUD whistling issue with the OEM manifold and EGR valve, but the truck would not idle correctly and would backfire out the exauet with it on. That is why I put my old intake "Edelbrock 2101" back on.

I did install a fuel pressure gauge and ran 3/8 allumminium? tubbing from the tank. The fuel pressure is only at ~ 6psi by the TBI. could this be the problem? The TBI is spraying a nice steady mist when the truck is running.

I found a post by RF on IAC adjustment....do I need to do this?

The truck did not have these issues with old OEM intake and EGR, I know I installed the new intake correctly and do not beleive that I have a massive vacume leak causing the LOUD whistling. I am at a dead end and any help would be greatly appreciated...Thank again, Pancake

My 90 Z71 with the 5.7 TBI made a pretty loud whistle / sucking sound at idle when the air cleaner was off and only slightly muffled when the lid was flipped. With the air cleaner assembled like from the factory it all but disappeared.

If you have more than about 4 degrees advance and less than about 30 it should only pop or backfire if the plug wires are grounding out or connected wrong. Check the routing and condition of your plug wires after seeing what amount of initial advance you have. Your engine might like more advance too. My Camaro will start to pop & miss with less than 8 degrees advance due to the cam profile and compression.

[pancake]

Hello again,

Well you guys were right....it was/is a vacuum leak!!

When I installed the trans-dapt 2206 adapter plate, two of the bolts that hold the TBI in place are positioned directly over the edge of the spreadbore on the intake!! when I tightened these bolts down they crushed the intake where it sealed to the adapter plate!! I did not think I was applying that much torque, the bolts went in really easy..but did a lot of damage to the soft intake.

Well, I ordered another intake after finding the problem. I think this will "fix" my leaks.

As for the fuel pump...I do have a summit feul pressure gauge, 3/8 aluminum line to and from the tank, and a TBI fuel pump mounted inside the tank. I will check the voltage going to the pump and will also try moving the fuel pressure gauge closer to the tank to see if I have a kink or restriction in the line somewhere.

Is there a way to remove the intake so that no coolant gets into the oil? I am tired on buying 5 quarts of oil every time I pull the intake off. I do drain the raditor before removing but there is always some coolant left in the intake.

Thanks again for all your help and Happy Holidays.

Pancake

[68 TT]

Originally Posted by pancake

Hello again,

Well you guys were right....it was/is a vacuum leak!!

When I installed the trans-dapt 2206 adapter plate, two of the bolts that hold the TBI in place are positioned directly over the edge of the spreadbore on the intake!! when I tightened these bolts down they crushed the intake where it sealed to the adapter plate!! I did not think I was applying that much torque, the bolts went in really easy..but did a lot of damage to the soft intake.

Well, I ordered another intake after finding the problem. I think this will "fix" my leaks.

As for the fuel pump...I do have a summit feul pressure gauge, 3/8 aluminum line to and from the tank, and a TBI fuel pump mounted inside the tank. I will check the voltage going to the pump and will also try moving the fuel pressure gauge closer to the tank to see if I have a kink or restriction in the line somewhere.

Is there a way to remove the intake so that no coolant gets into the oil? I am tired on buying 5 quarts of oil every time I pull the intake off. I do drain the raditor before removing but there is always some coolant left in the intake.

Thanks again for all your help and Happy Holidays.

Pancake

Pulling the bottom bolt on the passenger side of the water pump should let the coolant in the top end drain out so there won't be any high enough to dump out of the heads into the intake valley. You can then pull the thermostat and use the shop vac to suck out all the coolant left in the crossover passage of the intake.

[rfmaster]

Originally Posted by 68 TT

Pulling the bottom bolt on the passenger side of the water pump should let the coolant in the top end drain out so there won't be any high enough to dump out of the heads into the intake valley. You can then pull the thermostat and use the shop vac to suck out all the coolant left in the crossover passage of the intake.

Great tip 68 TT

Any update on fuel pressure??? Another all too common reason for low fuel pressure is a bursted fuel hose between fuel pump output port and gas tank feed through (inside gas tank). Remember, that small piece of hose must be have fuel submersion rating - SAE 30R10! Anything less than that will result in a slow leak over time!

Happy holidays!


//RF

[pancake]

A little cold here (Colorado) so I have not worked on the truck too much latley....so no update on the fuel pressure. I did replace all the fuel line with 3/8 aluminum with 3/8 high pressure rubber fuel line attaching it to the tank and the TBI. I also replaced the fittings on the tbi so I could put -6an to 3/8 barbed of the TBI. I might be a weak fuel pump? I will have to see when it gets warmer. I did receive the intake and gasket kit so I will also be replacing them when it warms up a little

Happy Holidays....Pancake