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Discussion Starter #1 (Edited)
Hi All,

I have an 88 S10 with 2.8, all stock, 2WD automatic, usually used to haul firewood; performance is not a high concern. It runs, but EFI system has failed such that it burns super rich.

Most or all censors were replaced already. My mechanic friends are not interested in figuring out. I have been told cheaper to swap V8 or 3.4 than to keep chasing it.

I realize many options are out there for repair of existing system, motor swap, carb swap etc.. At this point I plan to replace with carb, likely Weber. I am not a mechanic, but have some skills. This likely will be the most ambitious project I have attempted.

However, here is a question before I spend more on the Weber than likely truck is worth at present:

Has anyone tried to put a 1bbl Rochester on a former EFl 2.8? What adapters exist, or would they need to be made? Do I need a distributor from the 1980 citation? What is to be done with TV cable? Would final result drive well?

I am sorry if this is a duplicate topic question, but I could not find it answered anywhere. All comments are appreciated. This forum is a great wealth of knowledge.

Thanks
Jeff
 

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Did you try a Search for 2.8 Weber carb? There are a number of hits.

Also...no need to submit your post for approval...just post it in the appropriate area.
 

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Discussion Starter #4
Hi Rhotpursuit,

I may have missed it in the 2.8 area, though I found much discussion on Weber, and other options, but did not see specifically anything on 1bbl Rochester.

Jeff
 

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Pull a schematic and teach yourself about this system. It’s not a difficult system. Heck, I installed a 91 EFI system in an 84 carbureted truck. It’s not hard. If the mechanics can’t figure it out then get a better mechanic. Swapping to a carburetor in my opinion is a step backward.

Please don’t that as some smart answer. I mean it really isn’t hard to grasp early EFI. There is very little to it. You’ll find lots of help here to fix a more than likely simple issue. If sensors are new and you’re that far into it, then it’s not time to give up.
 

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Oh. And you will major regret putting a Rochester 2SE on your truck. One of the very worst carburetors ever. That’s definitely a downgrade. If you’re going carbureted which I don’t recommend, do a Weber. The 2SE will make a slow truck even slower.
 

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The throttle cables are different. The lockdown cables might work. Maybe. But definitely not the other way gong to EFI from carb. The cable will be physically longer but same working length so it might be ok. You’ll need an S-10 82-85 distributor, You’ll have to plumb that with vacuum too. Honestly I still think you’d be shooting yourself in the foot and better off figuring out the root of the issue.
 

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Hello,

I converted my 1982 2.8V6 truck to TBI in the summer of 1995, and it was night and day better with TBI. I'd fix the TBI system you have. That will definitely be cheaper.

There aren't a lot of reasons for it to be really rich. One reason that's easy is the coolant temperature sensor on the top of the intake near the thermostat water neck. They are easy to break, and if that sensor is not working / not connected / bad wire or connector / etc. the computer thinks it is very, very cold and will add lots of fuel to compensate.

Failing fuel pressure regulator or injectors is another possibility. The fuel pressure regulator is an easy fix, too. There are TBI rebuild kits, which is mostly a gasket set and a fuel pressure regulator diaphragm. It's easy to "rebuild" a TBI since there's not much in them.

The TBI intake is a lot different than the old 2bbl. carburetor intake. I would expect installing a carburetor will require an intake manifold swap too.
 

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Discussion Starter #10
Thanks to all for the thoughtful responses! I appreciate the discussion as your view in this is a new lense on this situation. Here are some additional details and clarifications I may not have been clear on first posting:

I do not intend to go with the Rochester 2SE. Instead I had wondered if anyone has adapted the earlier Rochester 1 barrel carb, the type commonly found on earlier stock straight 6 motors.

Coolant temperature sensor had been changed and then later removed and jumped, with and without being connected. The only difference was the temp meter on dash would be on or off. Basically no effect on running rich.

Fuel pressure regulator, nor injectors have yet to be changed. They have been suspected by others but nobody with experience wants to touch it.

It is curious as I have taken the truck to at least 4 or 5 places, and nobody is interested in trying. "We can't plug it in to find out for sure." And "it is not worth doing" and "too busy" are the most common responses they say. Perhaps they just see it as an old farm/woods truck and don't think it supports the value of the repair.

Air flow censor is curious. It was the first thing that was tried to level it out. While cold it runs better when unplugged. Runs better when plugged in when hot. Doesn't make run great , just better... I thought I might run a switch to the dash as on/off to censor as temporary solution.

There is an exhaust leak after the manifold, but before the cat. I don't know if this would impact anything significantly.

I am in the Northeast, weather and seasons have no effect.

Looking forward to your responses.

Jeff
 

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Hello,

The 1bbl. Rochester would not be enough carburetor for your truck.

Inspect the vacuum lines for leaks and cracks, and replace as necessary. There aren't many vacuum lines on it.

Fuel pressure should be at least 10 PSI, no more than 15 PSI. Fuel flow should be at least a pint every 15 seconds.

If the ECM's coolant temperature sensor is disconnected, it will think the engine is -40 degrees F and add a lot of fuel. Shorted would read very hot, though I doubt the ECM cares other than maybe throwing a CEL. That sensor does not connect to the temperature gauge or temperature light on the dash. The gauge (or light) sensor is a different sensor, threaded into the cylinder head typically on the front driver's side. The CTS for the computer is threaded into the intake manifold near the water inlet / thermostat housing. If the sensor in the intake is what you're jumpering when it affects the dash gauge/light, then there is something else going on with the wiring.

With it being super-rich, and with your description of the CTS behavior, I still suspect a coolant temperature sensor or wiring issue. An exhaust leak could cause it to run poorly, if there is fresh air getting to the O2 sensor. It doesn't take much to affect it. You could disconnect the O2 sensor to see if it helps. Disconnect the battery for 30 seconds or so before starting it to clear the ECM's memory.

If the return line has a restriction (one of the rubber connecting hoses has collapsed internally), that would drive the fuel pressure up and it would run rich. If the fuel pressure regulator has failed, that could also make it run rich.

What air flow sensor? TBI trucks don't have one. Are you talking about the MAP sensor (small black rectangle, 3 wire plug, one vacuum line from it to the TBI)? The MAP sensor can fail, and it's vital to the system operation. They really don't like backfires. I've seen them fail and not throw a CEL, but it will not run correctly (often resulting in a stumble on throttle tip-in).

The TBI system on this truck is very simple. There aren't many sensors, there are very few vacuum lines, and there isn't much to the TBI itself. If you are comfortable doing a carb. swap, then you should have no problem rebuilding the TBI. A TBI rebuild kit is cheap, and consists of mostly gaskets and the fuel pressure regulator diaphragm. It's probably an hour of work to remove, rebuild, and reinstall if you've had one off before (3 bolts, throttle cables, unplug a few lines/wires, and disconnect the fuel and return lines).

I suspect that since it's older than 1996, it doesn't have an OBD2 port so garages either don't have the scan tools any more for the older engines, or they never did. You really won't need one to fix it. A good tune-up (distributor cap and rotor, spark plugs and plug wires, air filter, fuel filter, PCV valve, inspect/repair vacuum lines) to start, then check injector spray pattern, and fuel pressure and flow. Ensure that all electrical connections are good and there aren't any broken wires or bent pins on connectors.
 

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Don't waste your time on the 1 bbl, easier to fix the tbi. you can connect a good code reader to pin point your problem. As for the 3.4 swap, I did it to an 87, basically a bolt-in and the best thing you can do for a power boost 120 hp 2.8 to 160 hp 3.4 you will feel the difference, and you can up it about another 15/20 by adding the 4.3 tbi.
 

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All of this is good advice. It’s honestly very easy to troubleshoot once you understand how it works. What I recommend is looking for a diagram of it and watching where the wires go and studying it thoroughly. That helped me really get a grasp on how the system is wired and how it worked when I did my swap. I also concur that rebuilding a fuel injector is a really easy process. I think my cat could do it. It’s just a few pieces in that kit. Certainly simpler than rebuilding a carburetor by any stretch! It’s just a few pieces in that kit. No offense, but It sounds like your mechanics rely way too much on OB2 doing the troubleshooting for them instead of using their brains to figure it out. It sounds like to me that you need to find somebody else to work on the truck is they’re that freaking lazy or inept...If they cannot troubleshoot the system as simple as a OBD1 they probably aren’t great mechanics.
 
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