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TBI harness in a YJ.

1-tonmudder

1-tonmudder

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Building a YJ for my wife and I'm gonna use a tbi 350.Im wanitng to use a stock 88 up Chevy harness and would like to know which ones and how much I can take out of the factory chevy harness and it still work. Any links or first hand knowledge will be appreciated.The jeep had a carbed 6cyl.
 
I started pulling one apart. Ordered a Howell harness and plugged it in instead. So much easier. All new wires and connectors. Will never pull another used harness apart.
 
If there is a bolt in harness to interface with the Jeep's wiring - Do it!

I did a TBI 350 swap into a 91 YJ that had a 2.5L and it took me a solid 20hr of labour to pull off a clean swap. Everything plays nice together, but it is still a fair bit of work.

There is very little you'll be taking out of the chevy side of the wiring (if anything) and a whole bunch coming out of the YJ's harness.
 
I have gone the Howell route on 2 YJs a '89 & '90. It was acutally very easy, I do believe they sell the harness seperately. It took me a weekend to do, Russell is correct about the amount of wires you need to remove from the YJ harness. I also mounted an electric fuel pump on the drivers side frame rail instead of an in tank, if you go that route just make sure you use the higher pressure rubber line to make the connection to the hard line.
 
ktmoutfront said:
I started pulling one apart. Ordered a Howell harness and plugged it in instead. So much easier. All new wires and connectors. Will never pull another used harness apart.
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Russell said:
If there is a bolt in harness to interface with the Jeep's wiring - Do it!

I did a TBI 350 swap into a 91 YJ that had a 2.5L and it took me a solid 20hr of labour to pull off a clean swap. Everything plays nice together, but it is still a fair bit of work.

There is very little you'll be taking out of the chevy side of the wiring (if anything) and a whole bunch coming out of the YJ's harness.
Click to expand...
Its carbed so shouldnt be a whole lot compared to FI'd harness,basically all Ill keep will be the starter/alt/gauges wires??I used a AFI harness on my cucv and agree they are the way to go.The yj is gettin axles,wheels/tires a 350/400/241 w sye.Just lookin to save a few bucks if I can.

K588 said:
I have gone the Howell route on 2 YJs a '89 & '90. It was acutally very easy, I do believe they sell the harness seperately. It took me a weekend to do, Russell is correct about the amount of wires you need to remove from the YJ harness. I also mounted an electric fuel pump on the drivers side frame rail instead of an in tank, if you go that route just make sure you use the higher pressure rubber line to make the connection to the hard line.
Click to expand...

Yeah the harness is $350.Did you use a VSS and what pump did you use??? A frame mounted Ford???
 
I had a vss but ended up removing it , I had clearance issues with it mounted on the Atlas transfer case. Let me find out about the pump, can't remember right off.
 
I swear the title on the thread said TBI.

Carb is easy. You should be able to use just the yj harness and adjust the lengths a little. Or is there some thing I am missing?
 
1-tonmudder said:
The yj is gettin axles,wheels/tires a 350/400/241.
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I misposted it will have a 231 w a 241 input.

K588 said:
I had a vss but ended up removing it , I had clearance issues with it mounted on the Atlas transfer case. Let me find out about the pump, can't remember right off.
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I didnt use one on my CUCV but it wasnt street driven alot back then and is a trailer queen now so Im not sure if this will need one or not,depends on who you talk to.If I go to a VSS Ill probably just use a 241.The jeep has a 231(no VSS) and the sye is a little cheaper for it than the 241 so thats why Im gonna try and use it.

ktmoutfront said:
I swear the title on the thread said TBI.

Carb is easy. You should be able to use just the yj harness and adjust the lengths a little. Or is there some thing I am missing?
Click to expand...

Yeah it was gettin late when I posted so maybe I should have worded it better/different.:doah:The jeep is carbed and I'm wanting to use a factory 87 up Chevy TBI harness and 7747 ecm.Picked it up fri night less the engine for $1300
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I think that year of YJ will still have computer controls for emissions and timing equipment. You'll wind up removing the wiring for most of that stuff...

The YJ's gauges use the same sending units as the 350 does, you can simply plug them straight in and they will work just fine.

If you have a cable driven speedometer head (I am unsure when they went electric) you'll want to get an inline VSS from Jags that Run for the ECM. It uses it for a number of things and shouldn't be deleted. Yes, you can run without one, but you risk the engine stalling out in some really unopportune times like during emergency braking without it. It also controls the EGR system (which shouldn't be deleted, it helps the engine run more efficiently at speed under light loads and reduces NOx emissions significantly without affecting engine performance), transmission lockup control, stop and go traffic idle control etc. If you want the engine to perform like it should, hook everything up. GM didn't waste money putting the speed input on the ECM for no good reason. Its so dang easy to hook up, I dunno why you wouldn't!
 
1-tonmudder said:
The $100 VSS from jags and the extra $$ of the VSS sensor option when ordering the harness. :D
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You'll probably save the $200 in fuel by running more efficiently in the first year of operation :thumb:

If $200 will make or break your budget, you probably should hold off on the swap until it isn't!
 
TBI never used a VSS in 1987, or on the 1988-1989 R/V series trucks. I believe 1988 C/K series trucks did use the VSS, but I am not sure of that.

Martin
 
82355 said:
TBI never used a VSS in 1987, or on the 1988-1989 R/V series trucks. I believe 1988 C/K series trucks did use the VSS, but I am not sure of that.

Martin
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Yes, they did. Just took the speed from a different source. The trucks which were TBI and still had a speedometer cable have a VSS fitted to the back of the speedometer head. It is an optical sensor that generates 2 pulses per mile, the same signal that the DRAC sends to the ECM from the 40 pulse per driveshaft revolution signal generated by the hall effect sensor on 90/91 R/V transfer cases.
 
Odd, I'll have to look at one. My 1990 K5 has no VSS, and it runs fine.

Martin
 
Yeah, I went out and looked at a 1988 V10 Suburban in my yard. I forgot about that odd three wire connector held to the back of the speedometer with a screw.

Honestly though, my 1990 K5 does not have one. I assume that is a completely different signal than the 1987-1989 generate?

Martin
 
82355 said:
Yeah, I went out and looked at a 1988 V10 Suburban in my yard. I forgot about that odd three wire connector held to the back of the speedometer with a screw.

Honestly though, my 1990 K5 does not have one. I assume that is a completely different signal than the 1987-1989 generate?

Martin
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Yup, the 90 K5 will have the speed sensor on the tail housing of the transfer case (just a little 2 wire sensor). Those two wires run up to a module enclosed in clear plastic up behind the dash called a DRAC (Digital Ratio Adapter / Controller). The DRAC converts the signal from the sensor on the t-case into the signals your ABS (if equipped), speedometer, cruise control and ECM use.

The earlier trucks with the optical sensor on the speedometer head were used for the cruise control and for the ECM.
 
Yeah, I know how that all works. My '90 has an NP203/NP205 doubler though. The previous owner drilled and tapped a hole, and wired up a VSS sensor in the tail housing of the NP205, but there was no reluctor wheel for the sensor to actually read. Then I had a bearing go out on the output of my NP205, and I used a different rear housing, so the sensor isn't even there anymore.

Martin
 
My thought was I could easily use an old speedometer setup. I already redid all the gauges and installed a factory tach and mechanical speedometer (that I have yet to bother to hook up...). I just doubt that both setups generate the same signal.

Martin
 
82355 said:
Yeah, I know how that all works. My '90 has an NP203/NP205 doubler though. The previous owner drilled and tapped a hole, and wired up a VSS sensor in the tail housing of the NP205, but there was no reluctor wheel for the sensor to actually read. Then I had a bearing go out on the output of my NP205, and I used a different rear housing, so the sensor isn't even there anymore.

Martin
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Ah, that makes sense! As you well know, the ECM does run the engine without it, but it is definitely not the best solution, IMO!
 
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