5.3L Vortec V8 Conversion

[Team Willys]

Why? Is there a problem with doing that? Why did he "rip his out"?

 

[Frank Z]

Gauge issues, IIRC.

Look at this way, 2 computers and swapping sensors around is a lot more work than using an OEM GM PCM and sensors. The sensors are already installed, the wiring is already part of the harness, it's a known good system that works.

Adding a set of aftermarket gauges to handle the reporting duties doesn't have to be difficult or expensive. GM compatible gauges are everywhere and can be had for a reasonable price.

 

[Team Willys]

Yes, that's true, and I do agree to some extent. However, my customer really wants to keep the interior looking factory, including the stock shifters and stock gauges. I understand that it may be more work, but after market Auto Meter gauges would be about $600 when it was all said and done, and even then, the fuel gauge doesn't read correctly. The money saved on buying aftermarket gauges would help to off set the cost of the labor of the extra wiring. I know that the sensors won't all just swap right over, the GM stuff is metric, but I have a remedy for both the Oil Pressure sender and the temp sender already. Been there, done that on the last LS swap I did. The volt meter and the fuel gauge won't need anything done to function properly, and the tach should function as normal with the converter. I already mentioned that the Speedo isn't an issue b/c you just use the factory Jeep sender in the T-case. It may take more work, but its not like Im trying to install GM gauges into the XJ dash... I was just wondering why you all went different routes, if it was b/c it just absolutely wouldn't work, or if it was b/c it was going to be a lot of work and aftermarket gauges were just cheaper.

 

[Frank Z]

Aftermarket gauges can be had for around $350 for a full set of 6 gauges but you've got to be willing to spend some time shopping for the best price. Also, fuel gauges can be had to respond to a variety of sending unit resistance values.

John did a nice write-up on his gauge swap, here's the end result of his efforts:

His thread:
http://www.naxja.org/forum/showthread.php?t=1027402

I'll be doing the same with slightly smaller (3 1/8") VDO gauges.

If you've memorized this thread like everyone else () you'll recall that my attempt at adapting a GM gauge cluster met with complete failure. Turns out my cluster was bad but I think the end result would have been ugly anyway.

 

[Team Willys]

Yeah, that thing does look great in my opinion, but that's not the point. If it were my jeep, I would probably just do it that way b/c I do like the look of it. But he doesn't want that... he wants stock gauges, and since he's paying me and I am fairly certain it can be done, I will do what he wants. Luckily he doesn't want the GM cluster, b/c like you said, it really isn't possible with out a TON of wiring, or even possibly a complete custom dash. Lol, if he wanted that I would laugh at him.

Like I said, I personally have no issues with aftermarket gauges, but you have to admit there is a cool factor about using factory stuff... just like you making the XJ shifter work instead of swapping in a Blazer unit.

 

[John D]

John did a nice write-up on his gauge swap

His thread:
http://www.naxja.org/forum/showthread.php?t=1027402

Thanks Frank! You beat me too it.

Yeah, that thing does look great in my opinion, but that's not the point. If it were my jeep, I would probably just do it that way b/c I do like the look of it. But he doesn't want that... he wants stock gauges, and since he's paying me and I am fairly certain it can be done, I will do what he wants.

If you go there you will find my intentions were the same as your customer. I have countless hours invested as I really wanted it to work. I don't believe its possible, but you might find the magic bullet. Good luck.

 

[John D]

Team Willys,

Just thought of something... is this a '96 or older? If it is, then all the gauges except the tach will easily function doing what you suggest. If it is '97 up its impossible.

 

[Team Willys]

John, this is on a 2000. I have heard of this being done before so I told him it was possible... but I can't remember where I saw it. Pirate maybe? I am currently looking at your thread trying to understand what you went through. Maybe I can figure something out.

 

[John D]

John, this is on a 2000. I have heard of this being done before so I told him it was possible... but I can't remember where I saw it. Pirate maybe? I am currently looking at your thread trying to understand what you went through. Maybe I can figure something out.

Just go here http://www.naxja.org/forum/showthread.php?t=1027402

In this post I explain why I couldn't make it work. I would like to know if you find the work around for this.

 

[Talyn]

About the gauges... Has anybody thought about running both the XJ and the GM computer and transfer the gauge sending units off of the 4.0 onto the LS engine?

That may work with pre 97/OBD I gauge clusters but the OBDII PCM would bitch about having sensors unhooked. IIRC if the CPS is unplugged the gauges do nothing. Also, getting a tach signal should be interesting.

 

[John D]

That may work with pre 97/OBD I gauge clusters but the OBDII PCM would bitch about having sensors unhooked. IIRC if the CPS is unplugged the gauges do nothing. Also, getting a tach signal should be interesting.

Talyn,
I kept heading towards the CPS as the problem not allowing this to work. Just couldn't find a way around it.

 

[Team Willys]

I have an idea. I will see what I can do and will post up my results.

 

[kastein]

Team Willys,

Just thought of something... is this a '96 or older? If it is, then all the gauges except the tach will easily function doing what you suggest. If it is '97 up its impossible.

Not impossible, but difficult. You'd need to build some sort of microprocessor based circuit to take signals from the GM cluster electronics (or directly off whatever data bus the GM vehicle uses, I am not familiar with GMs at all) and convert it to the required signals to drive either a pre 97 XJ cluster, or the CCD bus messages required to make a 97 up cluster "come alive". My schedule is way too full of interesting XJ hacking projects already to take a look at this with any kind of reasonable time estimate, unfortunately.

That may work with pre 97/OBD I gauge clusters but the OBDII PCM would bitch about having sensors unhooked. IIRC if the CPS is unplugged the gauges do nothing. Also, getting a tach signal should be interesting.

Yeah, tach signal comes from the CPS... my bet is that you could pull a signal off the cam position sensor on the LS1 though, should be either 1/2 the engine RPM (if it pulses for only one cylinder) or 4 times the engine RPM (if it pulses every ignition pulse for every cylinder, if my math is right, 2 revs will get you ignition on every cylinder since it's a 4 stroke engine.) Then feed that into some sort of PLL or microprocessor circuit that would drive the 96-down tach, or into the same CCD bus message sender for 97-up.

 

[Frank Z]

I'm really getting frustrated with this project. I'm still having the same XXXXin' error code pop up constantly........and please pardon the language. I'm resigned to owning 4k lb piece of garage art at this point. I just sent Brendan Patton (www.ls1swap.com) the following and hope that he can get me pointed in the right direction.

HELP!

I'm really stumped and would like to tap into your expertise.

Here's the problem...P1518, over and over and over again. When I start the engine I get no throttle response at all. My first thought was a bad TAC Ground but that turned out not to be the case. I was able to get it the sporadically but that only lasted for a couple days. I've already tried a new (used actually) TAC Module with the same results.

my next step was to confirm proper wiring and voltage to the TAC module. 12vdc at Key On and 14+ vdc with the engine running.

Now the only way to get the throttle to respond to the peddle is to clear the code with an OBDII scanner. I can do it with the engine running and can hear a definite change in RPM's and then the peddle will work. I can drive the Jeep a little bit bt the code comes right back and I have the same problem when I try to restart the engine again.
AAARRGGGHHH!!

The only other error code I'm getting is a P0650 (MIL Control Malfunction). My sanner reports the error but when I test the mill circuit with the scanner it reports that the MIL should be off and the circuit is functioning properly

Lastly, major shifting issues.

I can get the Jeep up to around 20 Mph or so and it won't shift beyond second gear. I do have 12vdc to the tranny and 12vdc thru the normally closed contacts on my brake peddle switch. I have an OEM VSS located in the output shaft housing of my transfercase. I've also connected the 4wd circuit so that the PCM knows I'm not in 4WD.

Your thoughts?

I'm really getting depressed about this whole project to be quite honest and don't foresee ever driving the Jeep at this point.

If anyone has some brilliant insight or even a Scientific Wild Ass Guess, well I'm all ears.

 

[Frank Z]

Brendan already replied with some advice. I'll post up after I've had time to do a little more troubleshooting.

 

[John D]

Brendan already replied with some advice. I'll post up after I've had time to do a little more troubleshooting.

That's one thing you can say about Brendan, he always replies. Even when you are not paying him.

 

[Frank Z]

So after doing a little research, pouring over schematics and some very useful info from Brendan (www.ls1swap.com) I got the No Throttle issue resolved. Seems that if the PCM is powered up before the TAC Module, even by a millisecond, the PCM reports that the TAC is not communicating with the PCM. Clearing code while the engine is running allows the throttle to start functioning normally. A simple swap of 2 wires to allow the TAC to energize first cured the problem.

After checking the the wiring for the VSS for the umpteenth time I finally figured out that a VSS from a 97 or older GM simply won't work. The magnet in the VSS is much weaker and although I was getting a signal from the VSS to the PCM it wasn't what the PCM needed to see.

I picked up a new VSS and connector from the local parts house and surprise!!!!....it's a larger diameter than the '95 version. Since I'm a cheap S.O.B. I wasn't about to shell out more coin for another tail cone nor was I thrilled about buying another high dollar tap for 1 stinkin' hole.

My solution was to first determine the thread size, turns out to be a 22mm-1.5 which equals a 7/8-18. Sweet!! I figured I'd just buy a 7/8-18 bolt and booty fab a tap out of it. Wrong! Ever try to find a 7/8-18 bolt? They don't exist on my planet.

Hmmmm.....what to do, what to do? FZZZZZZZZZZZPLAT!! (That's the sound of a light bulb going on over my noggin, just like in the cartoons. ) chevy 3/4 ton tie-rod ends are 7/8-18! I threaded the new VSS into the jamb nut of my trail spare and it's a darn near perfect fit.

So I cut the TRE apart, weld a nut to it, cut a few grooves up the threads and bored out the tail cone on my drill press. The "tap" worked well in the soft aluminum and I had everything back together in no time last night.

Got up this AM and fired up the motor, turned on my speed-oh-meter (GPS for now) and slipped it into gear. drove around the neighborhood a little bit, seemed to shft just fine. Made my way to a road with a higher speed limit (45) and sped up and slowed down multiple times....shifted fine. So I cruise along at 40-45 and everything is working well, so it's time to really open it up. Yeah baby, I'm talking 55MPH here!!

I get to a stoplight and and make my gentle left turn and scan the road and gave the skinny peddle a tiny itsy-bitsty nudge.

Ho






Lee




Shit!

When I said tiny itsy-bitsty nudge I meant tiny itsy-bitsty nudge but based on the amount of time it took to exceed the posted speed limit (damn near 80mph) you'd think I put my foot through the floor. Jeebus H. Tap Dancin' Christ! This thing is a-freakin'-mazing. The available power is simply phenomenal!!

Wow! Just freakin' wow!!!

 

[Zapthepunctual]

Congratulations!! Been reading this thread for a while. I'd kill for a video or two.

 

[Frank Z]

Thanks.

Still have a nasty sqeal coming from the front end and a video would be unbearable at this point. So far I've replaced the front bearing in the alternator, replaced the idler pully, pulled the tensioner pulley and cleaned/repacked the bearing in it, checked for proper belt and pulley alignment...still squeals like a fat chick on Free Donut Day at Krispy Kreme.

Frustrating

 

[kastein]

So after doing a little research, pouring over schematics and some very useful info from Brendan (www.ls1swap.com) I got the No Throttle issue resolved. Seems that if the PCM is powered up before the TAC Module, even by a millisecond, the PCM reports that the TAC is not communicating with the PCM. Clearing code while the engine is running allows the throttle to start functioning normally. A simple swap of 2 wires to allow the TAC to energize first cured the problem.

Damn, that is all it was?! That sucks pretty bad! Glad you figured it out though.

Back in yonder olden days, memory chips had this same issue. There were some computer memory chips where if you fired up the 3 (yes, 3, one of them positive-ground!) power supply lines to the chips in the wrong order, or with the wrong delay between them, the chips would go :explosion - people devoted days and weeks to designing their power supply startup sequences such that they would come up in the right order naturally. So glad those days are over...

My solution was to first determine the thread size, turns out to be a 22mm-1.5 which equals a 7/8-18. Sweet!! I figured I'd just buy a 7/8-18 bolt and booty fab a tap out of it. Wrong! Ever try to find a 7/8-18 bolt? They don't exist on my planet.

Hmmmm.....what to do, what to do? FZZZZZZZZZZZPLAT!! (That's the sound of a light bulb going on over my noggin, just like in the cartoons. ) chevy 3/4 ton tie-rod ends are 7/8-18! I threaded the new VSS into the jamb nut of my trail spare and it's a darn near perfect fit.

So I cut the TRE apart, weld a nut to it, cut a few grooves up the threads and bored out the tail cone on my drill press. The "tap" worked well in the soft aluminum and I had everything back together in no time last night.

That's a ghetto fab to be proud of :gee:

I get to a stoplight and and make my gentle left turn and scan the road and gave the skinny peddle a tiny itsy-bitsty nudge.

Ho






Lee




Shit!

When I said tiny itsy-bitsty nudge I meant tiny itsy-bitsty nudge but based on the amount of time it took to exceed the posted speed limit (damn near 80mph) you'd think I put my foot through the floor. Jeebus H. Tap Dancin' Christ! This thing is a-freakin'-mazing. The available power is simply phenomenal!!

Wow! Just freakin' wow!!!

arty:arty:arty:

So it'll beat ricers at the light AND drive over their cars?