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Discussion Starter · #1 ·
i have a '85 with a 2.8/carb in it. the current engine is on its way out. it begining to smoke and burns some oil. i picked up a 86 for 90$ with a 2.8/TBI and it runs strong with good power. what do i need to salvage to convert the 86 2.8TBIto run in a 85 body. is it worth it? or can I change out the carb for the TBI on the 86 engine using the the 85 manifold? i dont know much about fuel injection systems.
 

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Discussion Starter · #3 ·
does the TBI produce more power and better milage than the carb? or did they just develop it for emissions standards. i heard both
 

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scuba2nd said:
i have a '85 with a 2.8/carb in it. the current engine is on its way out. it begining to smoke and burns some oil. i picked up a 86 for 90$ with a 2.8/TBI and it runs strong with good power. what do i need to salvage to convert the 86 2.8TBIto run in a 85 body. is it worth it? or can I change out the carb for the TBI on the 86 engine using the the 85 manifold? i dont know much about fuel injection systems.
Sorry I can't help you,but If you find an answer, please let me know. I have a 1991 S-10 2.8 TBI engine and my friend put it in a 1982 S-10 body using the 1991 harness and computer stuff. We are at our wits end trying to get it started. Mine is getting great fire to the plugs, but no fuel to the injectors. I bought this truck new in 1991 and know how strong it runs. (it's wrecked now) I am so ignorant on this subject that I don't even know how to test, or what to test to check the fire to the injectors. All I have is a test light. I am about ready to make a fish house out of the whole thing.
 

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The intakes will swap. So for an easy swap, swap the carb intake onto the new engine, and buy a cheap electric fuel pump. You can get one that will go in the engine bay. Search "3.4 swap" or "electric fuel pump for carb", both should yeild some results on what pumps have been used.

You can also swap the EFI in. It's not overly difficult, but will take some thinking on getting it all to run run right.

You'll have to drill/cut a rather large hole in the firewall on the passenger side and mount the ECM in the dash on the passenger side. You will also need to run a few wires through the dash, for ignition and mount the ALDL connector somewhere, mine is on the passenger side, so that once I actually get my truck running again (taken apart for some upgrades) I can have the laptop and everything on the passenger side, with no cables running accross my legs.

There will need to be a few minor changes to the connector at the driver side bulk head feed through, but I'm not exactly sure what pins need to be swapped where, since my sweap is quite different than a TBI upgrade, I ended up using the original harness and integrating it into the new harness I made.

You will need to swap out the fuel tank for a newer tank and also include an electric fuel pump, you'll need to run a wire for this.

You'll need to add a VSS to the cluster, you can pull it from teh '86 and it will fit in the '85 cluster. I did this to see if the optical VSS would work with the ECM I was using, unfortunatly it did not, but in your case it will, since you are using the S-10 ECM.

I'm sure there's other small details that I am forgetting right now, but that should get you started.

The upgrade to EFI is completly worth it.
 

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The_Raven said:
The intakes will swap. So for an easy swap, swap the carb intake onto the new engine, and buy a cheap electric fuel pump. You can get one that will go in the engine bay. Search "3.4 swap" or "electric fuel pump for carb", both should yeild some results on what pumps have been used.

You can also swap the EFI in. It's not overly difficult, but will take some thinking on getting it all to run run right.

You'll have to drill/cut a rather large hole in the firewall on the passenger side and mount the ECM in the dash on the passenger side. You will also need to run a few wires through the dash, for ignition and mount the ALDL connector somewhere, mine is on the passenger side, so that once I actually get my truck running again (taken apart for some upgrades) I can have the laptop and everything on the passenger side, with no cables running accross my legs.

There will need to be a few minor changes to the connector at the driver side bulk head feed through, but I'm not exactly sure what pins need to be swapped where, since my sweap is quite different than a TBI upgrade, I ended up using the original harness and integrating it into the new harness I made.

You will need to swap out the fuel tank for a newer tank and also include an electric fuel pump, you'll need to run a wire for this.

You'll need to add a VSS to the cluster, you can pull it from teh '86 and it will fit in the '85 cluster. I did this to see if the optical VSS would work with the ECM I was using, unfortunatly it did not, but in your case it will, since you are using the S-10 ECM.

I'm sure there's other small details that I am forgetting right now, but that should get you started.

The upgrade to EFI is completly worth it.
In my case, all of this has been done, except I don't know what a VSS is. He used hole saws to cut the holes in the fire wall for all that stuff. If I take the fuel inlet line off the Throttle Body, it will shoot gas all over the engine. But when I am trying to start it, there is no gas spraying through the injectors, or anywhere else that I can see. Is there any way to test the wires on top of the injectors with a test light? I've used my test light but can't get it to show fire anywhere near the injectors. How do you test the fuel pump relay in the engine compartment bolted to the fire wall on the driver's side? I took it off and ran a short, hot jumper wire to it and I could hear it click, but not when I put it back on and hook it up. I've never had this experience before and it is getting very frustrating.
 

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So if you pour some fuel down the TB, it will start and run for a few seconds?

The injectors get ignition 12V So when ever the key is on, there is 12V at the injector. The ECM will ground each injector, to open them.
You can test with a test light, but I recommend using a DMM (Digital MultiMeter), to very how much voltage is there and that pulses are happening.
IIRC, Red and white were 12V feed, while blue and green are triggers from the ECM.

VSS = Vehicle Speed Sensor.
 

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The_Raven said:
So if you pour some fuel down the TB, it will start and run for a few seconds?

The injectors get ignition 12V So when ever the key is on, there is 12V at the injector. The ECM will ground each injector, to open them.
You can test with a test light, but I recommend using a DMM (Digital MultiMeter), to very how much voltage is there and that pulses are happening.
IIRC, Red and white were 12V feed, while blue and green are triggers from the ECM.

VSS = Vehicle Speed Sensor.
When I pour gas in the Throttle Body while someone else turns it over, it almost starts, but not quite. It sure tries though. As long as the starter is turning over, it sounds almost like it is running. I'm assuming there is no fire to the injectors, but I will find out with a DMM. If not, can you guess where the problem most likely will be? Thanks for taking the time to explain things to me. I am completely illiterate when it comes to things like this. I overhaul, rebuild, restore antique IH tractors, but this is Greek to me.
 

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Merlin582 said:
When I pour gas in the Throttle Body while someone else turns it over, it almost starts, but not quite. It sure tries though. As long as the starter is turning over, it sounds almost like it is running. I'm assuming there is no fire to the injectors, but I will find out with a DMM. If not, can you guess where the problem most likely will be? Thanks for taking the time to explain things to me. I am completely illiterate when it comes to things like this. I overhaul, rebuild, restore antique IH tractors, but this is Greek to me.
You don't need a meter to check for injector firing, use a nerd light. Also check your fuel pressure
 

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poconojoe said:
You don't need a meter to check for injector firing, use a nerd light. Also check your fuel pressure
It's called a Noid light..... Hehehe anyone remember "Avoid the noid"?

Also it's better to use a DMM, that way you can see how much voltage is present, not just that there is voltage. Lights have a low accuracy. ;) Also a DMM can show you if you have a good solid ground signal, as well, not just that there is a ground signal, again "how strong".

I'd be looking at the ignition, maybe not getting power from teh ignition, which in turn is not sending signals to the ECM to fire the injectors.
These ECMs rely heavily on the trigger from the dizzy, for a lot of functions.
 

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The_Raven said:
It's called a Noid light..... Hehehe anyone remember "Avoid the noid"?

Also it's better to use a DMM, that way you can see how much voltage is present, not just that there is voltage. Lights have a low accuracy. ;) Also a DMM can show you if you have a good solid ground signal, as well, not just that there is a ground signal, again "how strong".

I'd be looking at the ignition, maybe not getting power from teh ignition, which in turn is not sending signals to the ECM to fire the injectors.
These ECMs rely heavily on the trigger from the dizzy, for a lot of functions.
I was half asleep, if you use a digital multimeter, make sure it's a decent one, a lot of the cheap ones don't like pulses.
 

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scuba2nd, I want to apologize for hijacking your post. And thanks for all the replies I received about the engine problem. A friend came over today and checked with his meter to see if I was getting fire to the injectors. He assured me that I wasn't. But neither one of us know what to check for or do now. If you aren't getting too tired of this topic and of an old man's rant, all other information will checked out and is very much appreciated.
 

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i swapped an 85 carbed engine into my 87 TBI.

besides the things mentioned, I had to swap over the timing cover and the distrib...
 

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For the original poster, I would swap in an Edelbrock manifold and a Holley 390cfm carb. Pretty straightforward. You will have to cut off the kickdown perch off of the valve cover (if it's an auto), switch the kickdown cable. I would also change the throttle cable to a one from a Pontiac Lemans 79. Trust me on that one. YOu will also want to grind the edge off of the drivers side valve cover so that the new cable bracket mount won't interfere when you want to replace a valve cover gasket. Jusst a tad off the lip where it contacts. It won't leak if you don't get carried away. That's all the bitchy stuff I wish somebody had told me about when I did the conversion I found out the hard way. J
 

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Discussion Starter · #15 ·
I like to do stuff cheap. my 85 2.8 has a lot of miles left in it for sure. but when the day comes the 85 croakes. i got a good 86 TBI 2.8. after hearing suggetions from many sources i'm going to switch the '86 engine to carburated. i just don't think i'm mechaniclly inclined enough to transfer over the TBI system from the 86' to 85' body
could I use the STOCK carb and manifold and bolt them on the 85 block? i;m really not concerned about performance just fuel economy.

P.S. merlin no hard feelings for hijacking the post.
P.s.s 2.8's arn't fun to drive
 

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Thanks scuba2nd. I moved mine outside and I am just going to cover it with a tarp until maybe someday put a carburetor on it. If not, just let it rot down. I'm definitely not taking it to a Chevy dealership because they would charge a lot more to straighten it out than it's worth.
 
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