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4.2 tbi upgraded, but now i have issues. HELP!

13K views 218 replies 13 participants last post by  motormike24 
#1 ·
hey guys. i've used this forum exclusively to do the complete GM tbi upgrade to my friend's 4.2 wrangler. it had the usual motorcraft carb swap already due to the crap carter carb that it came with smoked the old motor.

heres a brief rundown of what i've done til this point:

he had a rebuilt engine shipped to a shop that did his motor swap. drove it 200 miles or less with the motocraft carb. and burned up a piston in cyl 6. wasnt happy. called me cuz he was sick of the bs with the shop, and nobody would honor any warranty. I overnighted another engine kit, it has .060 over pistons in it, new rings, bearings, etc. then got it fired up, only to find the head musta been warped too. basically he got a junk rebuilt motor. so i swapped the head with a freshly machined head.

then he decided that since we could NOT get that damn ford carb to run worth a crap so he wanted to go FI. i researched options vs costs, again, from this wonderful site ;) and opted for the GM 4.3 tbi swap. i took the computer, MAP sensor, TPS, IAC, TBI unit, and temp sensor from a 92 chevy blazer 4.3. had a machine shop custom make me an adapter plate for the TBI.... but it wouldnt fire. found i had no injector spray. so i goosed it with some starting fluid, it fired, and like magic i suddenly had injectors! ran like a champ after some minor distributor adjustments. after we ran it around town we discovered it would lurch and pop and sputter at lower rpms, such as when driving 25-30mph in town in 3rd gear. but it ran perfect anything above 2500 rpms. never had a problem starting it again.

THEN, a few months later he decided he wanted to upgrade the distributor. i read about the HEI upgrade, and tried to do that. but could not obtain the proper distributor gear to run that set up within the time frame i had to work on his jeep. so we bought a brand new stock distributor, but got the ford distributor adapter and the ford 300 c.i. inline 6 distributor cap (because of it being bigger and farther spacing between posts). also ran with the TFI coil for better spark. went to fire it up, and no go. again, no injectors. so once again i goosed it with some spray, and it fired right up, and had great injectors as soon as it fired! kinda confused me, but figured it happened the first time, so no biggie. got the distributor timed properly, let it run a bit, then shut it off. i fired it up a few times, it was GREAT. i literally put a glass of water on the valve cover and it didnt move. went inside, drank some beers, and 4 hrs later came back to start it, no injectors. no matter how long it cranked. so i sprayed it AGAIN, and fired up and drove fine. shut it off, and it fired right back up. after lots of playing with it, i've discovered it will give injector signal every time to start it as long as its at least remotely warm. as soon as this winter weather cools it down, it loses its initial pulse signal to get it started. i dont understand. at all. ive changed the temp sensor with a new one, no change. the old distributor was JUNK i found out as it had many floppy parts and the magnetic deal that reads the star wheel under the rotor was constantly touching. but now that its got a good distributor it does this ****. HELP. im only here in town to help him out for a few days. im going the yard tomorrow to get a different computer in hopes maybe it was a freak coincidence that it went bad the same time i swapped the distributor, but i doubt it. please help me!

thanks, mike
 
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#43 ·
Referring to the orange and purple wire scenario, I wrote this in another thread where a guy was having problems with his Howell TBI system.

Did you make sure to have both your purple and orange wires go all the way from the dist to the ford duraspark module? If I remember right the purple wire was the one that needed to be "added" on to and extended over there.

Also make sure the black wire from the duraspark module is grounded to a known good ground. stock it used the dist for ground, but in moving everything around you might have got it moved. i ran a 3ft section of wire from the battery ground into this harness just to be sure.
 
#48 ·
everyone keeps mentioning the duraspark module... can anyone give me a picture of what it looks like? because all i have seen on this jeep is what i believe is being referred to as the "MCU". its a metal box that was originally mounted down by the firewall and fenderwell on drivers side, but ive relocated it to an easier to access location. thats where i ran the wires from to the distributor. maybe this is why im having issues, maybe i am mistaken on what is what here. so yea, a pic of the duraspark would be very helpful. also where would it have been located.
 
#46 ·
motormike24 said:
yes orange and purple, but im not sure exactly where this duraspark thing is ur talking about. maybe i did that part wrong too, cuz i just ran new wires directly from the mcu to the coil.... X( maybe i got it alllll kindsa goofed.
It's on the drivers side inner fender below the mastercylinder. The nutter bypass is taking the orange and purple wires that come from the distributor and run them directly to the ignition module which effectively renders the factory mcu useless by "bypassing it" hence the name.

If your orange and purple wires go from the distributor to the 7pin HEI that's it. Did you twist them like they are in the factory harness and they are not anywhere near the spark plug wires.
 
#52 ·
The purple and orange wires should go from the distributor directly to the 7pin HEI ignition module

Nothing more and nothing less.

CSP the only reason I keep talking about them is because he seems to not have a clue what they are and where their at. He just may have a better understanding of what they are and what he should not be using anymore. I will speak of them no more.
 
#55 ·
it appears that site is dedicated to international harvesters.... 0.o
i searched TBI and EFI and it said no results. so yea, not sure about that one. but im at such a loss right now, because we just ran all completely new wires for the entire ignition module after eliminating the duraspark, and now not only dont have fuel, but no spark either. this is getting worse by the moment.
 
#59 ·
I don't think you understand that the OP is using a GM TBI computer to control spark. He does not need, and should not even be considering the Duraspark module. He's using the computer to control a GM 8-pin ignition module. The only Duraspark part needed is the distributor.

motormike that site is dedicated to IH Scouts. The thing is the wiring etc. doesn't change with the make of the vehicle it's installed in. The only thing that the make of the vehicle it's installed in is the location of the source of power and where sensors are installed. GM TBI is GM TBI whether it's installed in a Chevy, Jeep, IH, or whatever. You could install it on a riding lawn mower if you really wanted to.
 
#62 ·
ok guys. thanks for alllll the help despite my lack of electrical expertise. i think we got it figured out. had a loose butt connector in one of the ECM wires, and now it has injector pulse and spark, but i think i have to super adjust the distributor now because when it cranks over and tries to fire it basically stops the motor dead in its tracks, as if its extremely advanced or something. might be due to having adjusted the distributor with both modules trying to feed the distributor previously. hoping so anyway. will let ya know after i re charge the battery as i ran it dead, LOL. thanks again you guys, you are a huge help.
 
#63 ·
There's a connector to unplug to set initial timing. It has to be unplugged to take the computer out of the loop or you'll never see it stay at a certain setting while you try to get it set. I know where the connector is on a GM vehicle, but no idea where it might be on your setup.
 
#65 ·
CSP said:
There's a connector to unplug to set initial timing. It has to be unplugged to take the computer out of the loop or you'll never see it stay at a certain setting while you try to get it set. I know where the connector is on a GM vehicle, but no idea where it might be on your setup.
Google says its a tan/single wire connector

Edit: tan/black
 
#68 ·
That wire is a part of the GM harness and you do have such a wire if you left the TBI harness intact.

The distributor was originally vacuum and mechanical advance. I sure hope you've disabled both types of advance since you're now letting the TBI computer do the timing advance for you. If not, you're in for more trouble with it running correctly.
 
#70 ·
If I understand the OP, he has built his own harness instead of splicing one from a donor vehicle. So, in that case, Mike will have to disconnect the wire that travels from D5 on the ECM and goes to "C" terminal on the GM 7 pin spark module. If the vacuum and centrifugal advances have not been disabled on the stock distributor then as you say," he's in for a lot of trouble to get the engine running correctly." God bless.
Jon In Tucson
 
#74 ·
7 pin, 8 pin, they both do the same thing...
An easy way to lock the mechanical advance is to take the top plate off the distributor, remove the springs and weights, safety wire the advance arms together if you don't want to weld them. Put it back together and perform the 0 degree base timing procedure. You should be golden... God bless.
Jon In Tucson
 
#73 ·
I've welded the weights to the arms.

You really should look at least at the sticky posts on the binderbulletin's EFI forum. You might find other things you've missed that aren't obvious in this thread. It seems like you're missing a lot of the basics.
 
#76 ·
Yes, the computer controls the timing now. You set it to zero and the computer takes it from there.

I've pointed you to the Binderbulletin site and you've rebuffed it based on thinking it's for IH only, but there's a ton of info in this link that you could use. There's a link for converting the Duraspark distributor and one for initial setup procedures as well. You've got the basics of the TBI setup, but are missing some critical knowledge. At least have a look at the links contained in this one as I'm sure there's more things you haven't thought to ask about in this thread.

http://www.binderplanet.com/forums/showthread.php?t=47254
 
#77 ·
X2. I strongly recommend what CSP said...

Mike, since you are using the GM module, the ECM will control the spark timing electronically. If there is any mechanical or vacuum timing advance, the ecm cannot override it. That is one of the run-ability problems you are experiencing.
It appears that you are at a crossroads. Either modify the current Duraspark distributor to be controlled by the GM ignition module and ECM, or use the Ford style ignition module with mechanical and vacuum advance. If you choose the latter you will need a tach filter to interface the Duraspark signal with the ECM.
If it were me, I would modify the existing distributor. I did it and it only took about 30 minutes and I didn't have to take the distributor out of the engine. God bless.
Jon In Tucson
 
#78 ·
sounds good and thank u all so much! i have the jeep running great as of now. fried the ignition module by accidently hooking the coil primaries up backwards, but got a new module and it runs great. i have blocked off the vacuum advance as of now, and with the timing set at 10 degrees it runs fine, except stumbles hard at low rpms with a load on it (eg. taking off in first gear), which im fairly certain is due to the mechanical advance not being eliminated yet as you all were telling me. so that will be my next task. the only other thing i havent quite figured out yet is which wire i either need to add or splice a disconnect plugin for setting base timing to the ecm... but i will figure it out eventually. it at least starts on its own every time now and the duraspark module is 100% eliminated. so thanks again for all that help. it saved me many migraines and a bottle of asprin :p
 
#80 ·
so ive found and installed a disconnectable connector for the ignition bypass wire, which as im understanding is the tan with black tracer from computer to ignition module. however, it does nothing when i disconnect it. warm or cold, no change. it fires up great, idles super high (around 2000 rpm) for a few moments, then the iac seems to attempt to bring it down to an idle, and instead it seems to drop too far, like 400 rpms or a little less, to the point where it nearly dies, but struggles a bit til it throws it back up to 2000 rpms or so, and it repeats that about 4 or 5 times and then it will go down to around 1400 or 1500 and stay there til it warms up more. and when it idles close to normal, the timing light shows 0 degrees, which is where it should be. it just acts like its too advanced to handle it so it idles way higher again. GRRR. ive even bypassed both mechanical and vacuum advance at this point. im lost again.
 
#82 ·
If you have 0* timing with the bypass wire disconnected, that is good. That is what you're looking for. After turning off the engine, reconnecting the bypass, starting again, are the symptoms you describe still happening?

I have copied and pasted the IAC reset and minimum idle speed and the TPS voltage setting procedures from the Injection tech forum found on binderplanet.com. I would follow those procedures before doing much else, It will result in a lot less heartburn, I know, I been there...

2. IAC reset/min idle speed- This sets the throttle plate on the throttle body to a specific rpm. I recommend about 500 rpm for most engines. A little common sense goes a long way. Obviously a cold engine will not properly idle when you disconnect the idle control. So ensure your engine is up to temp prior to setting the min idle speed.
Procedures- Go to sheet 7 of the pinout diagrams. At the top is the ALDL connector. You need to put a jumper between pins A and B of the connector. These are pins A9(wht/blk) and A12 (blk/wht) on the ECM. This puts the ECM into aldl mode. Turn the key on (not start) and the IAC should drive completely closed. You will normally hear a buzzing from the IAC. If you have the winaldl up and running on your laptop, you should see the IAC went from 145 to 0. Now unplug the IAC connector. turn the key off. Remove jumper. Start motor. If the idle is too low you may have to keep it running. On the front drivers side of the throttle body is the adjustment screw. It may be behind a silver plug. If so just use a nail or punch to poke it and remove it. Then use a #20 torx bit to adjust the idle speed to at least 100 rpm less then your warm idle speed. if 600 then set to 500 rpm. You are looking for the lowest consistant idle your motor will do. When set, turn off motor and reconnect the IAC. I try to keep the IAC count to about 40 with the motor warm and idling. If the counts drop to 0 then the IAC can no longer adjust the idle down.

This is a good time to verify the operation of the IAC. When the jumper is in and the key is on the IAC is driven closed. So while it is idling to set min rpm put a finger over the IAC port just above the IAC. There should be no air being sucked in and you should be able to see the pintle on the IAC.
When the IAC is connected and operating there should be a small amount of air being sucked in the port at idle and should increase as you apply some throttle.

3. TPS-throttle position sensor. With the idle set, you need to now set the TPS. This need to be set to about .54V. I normally shoot for about .6V.
The TPS is on the passengers side and will have 2 screws holding it on. The factory TPS will not have much room in the holes for adjustments so I use a drill bit or file to elongate the holes as needed. To adjust, just loosen the screws and trist the TPS. You can monitor the voltage on Pin B of the connector with the key on or at pin C13 of the ECM. You can also see it on the sensors tab of winaldl!! Anything away from .54V will also show as a percent of throttle. Such as .2 percent or 1.7 percent...depending on how far from .54 you are. I try to keep the idle setting to within 1 percent.
This is also a good time to check your TPS. Once it is set, just watch the voltage as you open the throttle. you should see a steady rise in voltage up to about 4.5-5V at WOT-wide open throttle. If it jumps up and down or skips some then you may want to replace it.

A big thanks to Billusn-1 at Binderplanet.com for maintaining this information.
God bless.
Jon In Tucson
 
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