1st TBI Conversion Help Needed

[MtBraun]

was this a carb engine you swapped to efi or did you swap in an entire tbi engine?

Carb swapped to TBI. Old gen 1 SBC. The engine has been overhauled at a minimum. I had to replace a head gasket last winter and the cylinder bores looked like new.

 

[4WDKC]

Did the truck idle smooth and run ok, not a power house before the head gasket went?

 

[MtBraun]

Did the truck idle smooth and run ok, not a power house before the head gasket went?

Yes, ran just fine before the conversion. Pretty gutless before and after conversion.

 

[4WDKC]

Yes, ran just fine before the conversion. Pretty gutless before and after conversion.

It is a smog era 350 so its expected. But it running smooth tells me it probably has a cam similar to the tbi cam.

 

[MtBraun]

It is a smog era 350 so its expected. But it running smooth tells me it probably has a cam similar to the tbi cam.

Yeah, could be. That or Dave tuned it accordingly.

 

[4WDKC]

only ways I know to cover up a lope of a cam is advance it in the timing set, advance it while its being ground and increase rpm.

 

[MtBraun]

This saga just won't end. Yesterday my son and I swapped out the transfer case which is detailed in another thread. We go to take it for a spin to see if it fixed our 4x4 problem and the truck has never run so poorly. It spit, sputtered, and eventually died to a no start. I'll go back and diagnose from the beginning (fuel pressure, spark, etc.), but obviously the TC has nothing to do with the TBI, so I think there is just a coincidental failure of some TBI component.

So a question here. I'm going to explore going back to a carbureted setup. This project has been an abject failure and disaster that I'm tired of messing with. One thing that comes to mind is the fuel pump. Are there newer carbs that can handle the higher TBI fuel pressure, or do I need to change out fuel pumps back to a mechanical? If I can stay with electric fuel pump, how do I control that in a carbureted environment?

And what about the dizzy? Just change back to the original?

@1987 GMC Jimmy @4WDKC

 

[4WDKC]

You would need to install a regulator to reduce the pressure to the carbs needs. Yes a standard height dist will be needed. Just a thought, did you put the tbi on a carb intake or tbi intake?

Sent from my Nexus 5X using Tapatalk

 

[MtBraun]

You would need to install a regulator to reduce the pressure to the carbs needs. Yes a standard height dist will be needed. Just a thought, did you put the tbi on a carb intake or tbi intake?

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The fuel pressure regulator makes sense. Is there a relay involved, or how do I power the fuel pump absent TBI control?

We put this system on an original 4 barrel carb intake. Used the Holley adaptor plate.

 

[4WDKC]

The fuel pressure regulator makes sense. Is there a relay involved, or how do I power the fuel pump absent TBI control?

We put this system on an original 4 barrel carb intake. Used the Holley adaptor plate.

yeah you will need to wire in a relay since the ecm will be absent, have you checked for vacuum leaks around the adapter plate? Some arent thick enough to keep the bolts from bottoming out on the intake manifold.

 

[MtBraun]

yeah you will need to wire in a relay since the ecm will be absent, have you checked for vacuum leaks around the adapter plate? Some arent thick enough to keep the bolts from bottoming out on the intake manifold.

I've used up a can of ether checking for leaks. The first adaptor plate I tried was a thin piece of junk. I sent that back and got the thicker Holley plate - it's 1/2" thick and worked great.

 

[4WDKC]

I've used up a can of ether checking for leaks. The first adaptor plate I tried was a thin piece of junk. I sent that back and got the thicker Holley plate - it's 1/2" thick and worked great.

I remember you saying you did the IAC learn did you do the tps learn also?

 

[MtBraun]

I remember you saying you did the IAC learn did you do the tps learn also?

I did not do the TPS learn. Put in a new IAC and did the relearn on that.

 

[1987 GMC Jimmy]

I’m not familiar with the TPS relearn procedure. I’m really upset in how this has worked out. Not because of you in any way, Matt, but it’s usually not that stubborn. People have had chronic TBI issues on here a few times before, but the threads usually die after a few weeks so we don’t see the resolution. Sometimes there is, and I can easily assume that sometimes there isn’t. It sucks to invest a bunch of time and money in something and have it flop. I thought of one thing here. Have you tried backprobing the entire TBI harness at the ECM to make sure all your voltages leaving and coming back there are to spec? I really want to nail this son of a bitch because you’ve been through too much to return to the old status quo. Or at least that’s how I feel.

You must be registered for see images attach

I’d go through and probe everything both in and outside of this chart that I could. After that, you’re confined with to more mechanical/conventional solution. That’s how I see it. Have you tried to run it with the MAP sensor port plugged off at the TBI? I may experiment with that, too.

 

[4WDKC]

I’m not familiar with the TPS relearn procedure. I’m really upset in how this has worked out. Not because of you in any way, Matt, but it’s usually not that stubborn. People have had chronic TBI issues on here a few times before, but the threads usually die after a few weeks so we don’t see the resolution. Sometimes there is, and I can easily assume that sometimes there isn’t. It sucks to invest a bunch of time and money in something and have it flop. I thought of one thing here. Have you tried backprobing the entire TBI harness at the ECM to make sure all your voltages leaving and coming back there are to spec? I really want to nail this son of a bitch because you’ve been through too much to return to the old status quo. Or at least that’s how I feel.

You must be registered for see images attach

I’d go through and probe everything both in and outside of this chart that I could. After that, you’re confined with to more mechanical/conventional solution. That’s how I see it. Have you tried to run it with the MAP sensor port plugged off at the TBI? I may experiment with that, too.

http://www.gearhead-efi.com/Fuel-In...tems-Min-Air-Adjust-TPS-set-and-Fuel-Pressure

With it being on an unknown cam this is the only thing i can think of. The plug over the adjustment screw is alum. I punctured mine with a pick and smacking it with my hand so I didnt damage the screw head.