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

[cjracing15]

You my friend have a vacuum leak some where. Be sure to check everything you touched on the intake swap. Go back over all your vac. hoses and check all you bolts.

[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

[cheepin]

Just started wiring up my CJ/buggy.Does anyone have a diagram of what sensor is where on a 1988 7.4L bigblock?I think I know what is what but not sure.Thanks.

[rfmaster]

Originally Posted by cheepin

Just started wiring up my CJ/buggy.Does anyone have a diagram of what sensor is where on a 1988 7.4L bigblock?I think I know what is what but not sure.Thanks.

Welcome to the thread and happy new year.

Regarding BBC EFI wiring - it is nearly identical to SBC wiring commonly found on light and heavy duty trucks (use 1227747 as a guide). The two things to look for are:

1) IAC is different and unique to BBC application. It has been reported by some that two wires in one pair have to be swapped - I have not had a chance to verify this. I'll get to this once I get going on my 383 TBI project.

2) Some HD BBC applications did not use KS. Consequently timing tables are very conservative. This can be easily fixed by reprogramming EPROM to suit your engine needs. HD BBC applications used 1228747 ECM with various BCC EPROM's although there are others (7747, etc) can be found out there.

3) BBC TB is prized by some for its large bore size (2" vs 1-11/16) and higher flow injectors. Note that late model injectors (94+) operated at 30 PSI vs. 13 PSI for 87-93.

//RF

[68 TT]

Originally Posted by rfmaster

3) BBC TB is prized by some for its large bore size (2" vs 1-11/16) and higher flow injectors. Note that late model injectors (94+) operated at 30 PSI vs. 13 PSI for 87-93.

//RF

Is that only for the big blocks or did the small blocks also get this pressure increase?

[rfmaster]

Originally Posted by 68 TT

Is that only for the big blocks or did the small blocks also get this pressure increase?

The G/P series vans from 1995-1997 with the TBI 4.3 and TBI 350 used 28-32 PSI fuel pressure to counter vapor locking in high ambient temperatures. On a side note GM marine used the 28 psi fuel setup on the 280-315 HP 350 TBI marine engines. The marine engines also used small 45 lb/hr 4.3 injectors.

//RF

[pancake]

The Blazer lives again!!!

After replacing the intake that i f*#*ed up and taking my time with all the seals and gaskets the blazer starts again.

I did buy a new IAC and reset it as described by RF i another post....nice smooth idle...600rpm

When I pushed on the gas pedal it poped and wanted to die...can this be due to lack of fuel pressure?

I have the timing set at 0TDC with the connector unpluged .

Now for the fuel pressure....

When the engine was warm and running I kinked the fuel line and the fuel pressure gauge climbed very fast past 20psi and almost to 30psi before I unkinked the line...This would tell me the problem is my fuel pressure regulator. it also had a slight "clicking" noise when the truck was not running. It seemed the noise was coming from the TBI.

I did rebuild the TBI but do not remember if the kit came with a new spring?? I looked in the box of old TBI gaskets and there was not an old spring...maybe the kit did not come with it...either way I think I need to replace it.

Can I buy just the spring or do I need a "kit"?

does anyone have a part number for the fuel pressure regulator spring?

I can finaly see the light at the end of the tunnel for my TBI retrofit and I would like to thank EVERYONE who put up with me

Thanks to cjracing15 for starting this thread and RFMaster and 68TT for all the help you guys are great..

[rfmaster]

Originally Posted by pancake

The Blazer lives again!!!

After replacing the intake that i f*#*ed up and taking my time with all the seals and gaskets the blazer starts again.

I did buy a new IAC and reset it as described by RF i another post....nice smooth idle...600rpm

When I pushed on the gas pedal it poped and wanted to die...can this be due to lack of fuel pressure?

I have the timing set at 0TDC with the connector unpluged .

Now for the fuel pressure....

When the engine was warm and running I kinked the fuel line and the fuel pressure gauge climbed very fast past 20psi and almost to 30psi before I unkinked the line...This would tell me the problem is my fuel pressure regulator. it also had a slight "clicking" noise when the truck was not running. It seemed the noise was coming from the TBI.

I did rebuild the TBI but do not remember if the kit came with a new spring?? I looked in the box of old TBI gaskets and there was not an old spring...maybe the kit did not come with it...either way I think I need to replace it.

Can I buy just the spring or do I need a "kit"?

does anyone have a part number for the fuel pressure regulator spring?

I can finaly see the light at the end of the tunnel for my TBI retrofit and I would like to thank EVERYONE who put up with me

Thanks to cjracing15 for starting this thread and RFMaster and 68TT for all the help you guys are great..

Well - Happy new year and congratulations!

Lets take one step at a time before jumping to quick conclusions.
After you you set base timing to 0 deg (by disconnecting EST connector) did you reset your ECM by disconnecting negative terminal from battery (with engine off)?? If not, ECM will set Code 42 every time when EST connector is opened during base timing adjustment. With Code 42 present ECM will not provide timing control and overall timing will be limited to EST module built-in timing which is fixed to about 10 deg. This is by design and allows you 'limp' home in case of a failure. Disconnect neg battery terminal for about 30 sec (this will clear ECM faults) - reconnect EST connector (single wire) and thereafter you should see about 18 to 20 degrees of timing at idle (normal operating temperature) with a typical stock calibration - ASDU, ASDZ. Verify your timing with EST connected. Popping through the TB could be due to lack of timing and not because of low fuel pressure.

Fuel pressure - stock TBI system likes 13 to 15 PSI. Do you see this with your engine idling??? Your pump appears to be capable of supplying fuel pressure - (dead head test 20 to 30 PSI seem to be excellent).

For new spring Contact Sean at http://tbiparts.com/
You can call him 217-473-4998

We'll celebrate after your first full test drive....

//RF

[pancake]

Still having a fuel pressure problem

After I set the timing I did disconnect the battery and reset the codes. The truck starts and idles fine.

I called Sean and he did try to help me resolve the fuel pressure problem.

I removed the regulator from the TBI and checked the spring...it is not broken.

Sean recomended trying to adjust the spring tension be moving the screw in the regulator cup....which I did...I moved the cup up..or added tension to the spring. I also marked on the side of the cup, there is a slot with a tab sticking out, to see if it moves with the truck running. it does not move.

With the engine cold I started the truck. It started right up and idled great with a nice spray coming from the injectors.

The fuel pressure started out at ~12psi when I firsted started the truck and I could hit the gas and the rpms would increase with no hesation or falling on its face.

After running for a few minutes, maybe five, the fuel pressure slowley droped to 0psi. it took maybe 5 minutes to go to 0psi.

At 0 psi the truck still ran ok.

I changed the fuel pump and the same thing happenes. The truck seems to run fine except a backfire through the exaust that I think is due to an exaust leak.

I belive the fuel pressure gauge works ok...but I should try to test it...any sugestions? It will dead head to over 30psi so I think the gauge works.

After I checked the regulator spring it showed ~12psi...the most I have ever seen...usually it is around 7...or 0psi. It only showed 12psi after the truck sat overnight and I tried to start it the next day. If the truck sits for only a few minutes it will not go over 0-5psi.

Sean gave me a number to call and get another persons input....but I would like to know what you guys think.

Could this be caused by a vacuume leak?

Could it be because my return line is 3/8"?

Could it be from the -6an fitttinge coming off the TBI?

The fuel tank I put on the truck was used and not super clean. I did shake some rust and debris from the tank. The tank has plastic baffles in it. I replaced the sending unit so it woulld fit the used tank. I replaced the fuel filter when I did the swap, and whem I pulled the fuel pump to replace it the screen on the bottom of the pump did not appear to be cloged....could this be a problem? U ran for truck for about 30 minutes total with a new filter so I dought I could have cloged it already?

Any help would be greatly appreciated.....I am almost there.

[mcbassin]

Just curious if you developed the pressure bleed down started after the tbi rebuild? Also, I don't know which pump your using on your build but we have had great success with THIS tbi rated fuel pump. Consistant pressure and it will take wide open throttle with no hesitation. It's kinda pricey but it was worth it on our project.

[rfmaster]

Pancake

Couple of thoughts on your fuel pressure observations.

1) 3/8" return line is just fine - I run 3/8" return line in my setups without any issues. TB fuel pressure regulator does not work well against return line back pressure.

2) Fuel pressure should be measured right next to TB inlet port. Take a look at my video:

YouTube- Carb to TBI conversion

3) Vacuum leaks do not affect fuel pressure. Fuel pressure gauge may have a air pocket that effects displayed values. -6AN = 3/8" should not affect fuel pressure.

4) Clogged Fuel filter or fuel sock - that may affect fuel pressure and volume.

Can post photos of your setup - how you routed fuel lines???

//RF

[68 TT]

Do you have any rubber fuel lines in the system?

I have seen them work fine when cold but kink when they warmed up. Makes for some interesting trouble shooting.

Is your pump in the tank or in-line? It could be a loose connection between the pump and the supply line to the TB at the pickup if it is in-tank. It is a rubber hose and could be losing its prime through the leak and/or losing pressure through the leak and gets worse as the pump heats up.

Just some thoughts based on problems I have encountered.

[pancake]

I do have rubber fuel lines in the system...the are rated for fuel injection and connect the tank to 3/8 alluminum line and from the alluminum lint to the TBI. The tank sits in the bed of the Blazer and the alluminum feul line is ran daow the fram rail to the fire wall tyhe goes to rubber. The line is not kinked anywhere...I checked.

My pump is in tank and new...I tried to switch the pump with no luck. There is a new sending unit with new hose and good fuel injection fittings.

I put the fuel gauge is by the Brake booster...between the booster and TBI....the gauge sits about 12" from the TBI, same place as RFmasters gauge

I did not know what the fuel pressure was before the swap ...I ran a carb and carter fuel pump.

After calling Brian Harrris at Harris preformance he told me to try a new spring...he said when the spring warms up it could lose pressure....I ordered a new spring from Sean.

If this does not work I might get a new fuel tank...change the filter and fuel pump screen and clean out the fuel line.

I am out of town right now but will be home this weekend and will take some pictures and post them.

Thanks for the input

[68 TT]

Originally Posted by pancake

The tank sits in the bed of the Blazer

I think it may be related to fuel tank elevation relative to the throttle body.

This non-stock configuration may need a helper pump to keep the pressure up.

If you can't lower the tank to below the bed try adding an in-line EFI pump to help pressurize the system and get the air out of the lines.

You never know what kind of weird things will happen when something as simple as the fuel tank elevation is changed.