GM tbi stalling issues & poss weak ignition (76 cj7 jeep)

[76cj7chick]

I recently upgraded from a 1 bbl carter carb to a gm tbi on my 1976 CJ7 jeep... With that, I installed a 2 bbl intake from an 85 CJ7 ...

Problem is, I've never been able to get it to run smoothly...

The main issue is that the engine stalls... It will keep running if I step on the gas pedal but as soon as I release the pedal it stumbles and dies... I checked the fuel pressure and it is at only 9psi... (I checked the fuel pump and it was 15psi at the tank... But I guess it dropped some psi toward's the throttle body?)

I also pinched the return line and there was no change in the idle...


I've heard that all GM tbi's have an internal Fuel Pressure Regulator... SO-----Is there a way to increase the fuel pressure regulator in the Throttle body?

I also tried to reset the IAC valve... And noticed with the IAC valve UNplugged, My tach read around 600rpms... But with the IAC plugged in... There was NO indication on the Tachometer of rpms.. (It was at 0) ---- Anyone ever get this? If yes, what would be a typical cause?

Could a weak (prestolite) ignition system be causing these, or even the Tach not showing any rpms? As, I have the tach - (neg) reference wire connected to my Ignition Coil - side... AND the GM TBI harness is also connected to the Coil.. (The power wire is on the + side of the coil... And the ECM wire is on the - side of the coil...)

Should I have an Ignition Switched relay for the TBI harness instead of connecting directly to the Igntion coil? (ALSO---I checked the Ohms on the coil and they are within the prestolite specs..)


I STILL haven't changed over to a duraspark distributor... So, my ecm continues to flash 42 and 43 codes.. These are for spark control... I hope to one day have the ecm control timing but for now am just focused on getting it to run as smoothly with fuel/air control. --Sooooo... Would the lack of "spark control" cause stalling? Or should I focus first on the fuel pressure, Pressure regulator and having the TBI power from an ignition relay verses off the + side of the coil?


Please help me trouble shoot these issues as I really want to keep driving the Peep... Any and all help is much appreciated....

 

[gert]

I recently upgraded from a 1 bbl carter carb to a gm tbi on my 1976 CJ7 jeep... With that, I installed a 2 bbl intake from an 85 CJ7 ...

Problem is, I've never been able to get it to run smoothly...

The main issue is that the engine stalls... It will keep running if I step on the gas pedal but as soon as I release the pedal it stumbles and dies... I checked the fuel pressure and it is at only 9psi... (I checked the fuel pump and it was 15psi at the tank... But I guess it dropped some psi toward's the throttle body?)

I also pinched the return line and there was no change in the idle...


I've heard that all GM tbi's have an internal Fuel Pressure Regulator... SO-----Is there a way to increase the fuel pressure regulator in the Throttle body?

I also tried to reset the IAC valve... And noticed with the IAC valve UNplugged, My tach read around 600rpms... But with the IAC plugged in... There was NO indication on the Tachometer of rpms.. (It was at 0) ---- Anyone ever get this? If yes, what would be a typical cause?

Could a weak (prestolite) ignition system be causing these, or even the Tach not showing any rpms? As, I have the tach - (neg) reference wire connected to my Ignition Coil - side... AND the GM TBI harness is also connected to the Coil.. (The power wire is on the + side of the coil... And the ECM wire is on the - side of the coil...)

Should I have an Ignition Switched relay for the TBI harness instead of connecting directly to the Igntion coil? (ALSO---I checked the Ohms on the coil and they are within the prestolite specs..)


I STILL haven't changed over to a duraspark distributor... So, my ecm continues to flash 42 and 43 codes.. These are for spark control... I hope to one day have the ecm control timing but for now am just focused on getting it to run as smoothly with fuel/air control. --Sooooo... Would the lack of "spark control" cause stalling? Or should I focus first on the fuel pressure, Pressure regulator and having the TBI power from an ignition relay verses off the + side of the coil?


Please help me trouble shoot these issues as I really want to keep driving the Peep... Any and all help is much appreciated....

From what I know..... start with the fuel pressure. You should not have a 6psi drop from the pump to the TB is your fuel filter clogged? the factory pressure spring in the TB injector hat is set to around 12psi so my first thought would be a clog in the fuel line. to low of pressure at the injector will cause a crappy spray pattern and bad running motor. Yes the TBI does have a regulator and it can be adjustable I am planning on buying these guys adjustable pressure regulator, pressure gauge adapter and injector hat spacer CFM Technologies take a look at their magazine article, Your high performance 'airflow' parts source for GM / Chevy Tbi / Vortec / Marine + Racing they show how to install the spacer and adjustable regulator as far as the ignition is concerned I do not know weather or not the computer will play nicely or not, someone else will have to chime in on that BustedJeep.Com - In The Garage

 

[GARGOYLEJEEPER]

76cj7chick,
Love the color. :rock:

First off you should have a model 220 out of a 4.3 V6
Fuel pressure : 9-13 psi
Throttle Position Sensor : 1 V
Minimum Idle Auto : 500-550 rpm Vac. Disc.

Distributor had 4 wires Electronic Spark Timing
Signal #423
Bypass #424
Reference Pulse High #430
Reference Pulse Low #453
Plus
Ignition #3
Tachometer #121

You should have :
M.A.T. Sensor
M.A.P. Sensor
Engine Speed Sensor
O2 Sensor
E.G.R. Solenoid
Fuel Pump Relay

Your problem is distributor related.

Will dig out my FSM and my big Electrical Diagnosis And Wiring Diagrams book and tell you what to do.

 

[Torxhead]

I would not be to concerned about that low fuel pressure, I have been running 9 psi for some time now with no issues. The fuel pump does put out a lot more pressure but the tbi regulator cuts it down. Underneath the tbi, between the inlet and outlet fittings there is an adjustment screw for fuel pressure. Screw it out slightly for more pressure. Your ignition problems could be from a bad ignition control module,
I believe it is that gold colored box, that could had gone bad. The prestolite and motorcraft icms will go bad if there is a poor ground, which is the black wire coming from them. If your icm gets hot to the touch that is a bad sign for sure.
Edit: after rereading your post, you could have an issue with a low idle adjustment, do you know how to adjust this?

 

[76cj7chick]

From what I know..... start with the fuel pressure. You should not have a 6psi drop from the pump to the TB is your fuel filter clogged? the factory pressure spring in the TB injector hat is set to around 12psi so my first thought would be a clog in the fuel line. to low of pressure at the injector will cause a crappy spray pattern and bad running motor. Yes the TBI does have a regulator and it can be adjustable I am planning on buying these guys adjustable pressure regulator, pressure gauge adapter and injector hat spacer CFM Technologies take a look at their magazine article, Your high performance 'airflow' parts source for GM / Chevy Tbi / Vortec / Marine + Racing they show how to install the spacer and adjustable regulator as far as the ignition is concerned I do not know weather or not the computer will play nicely or not, someone else will have to chime in on that BustedJeep.Com - In The Garage

WOW! Thanks for your quick and helpful responses!
The lines shouldn't be clogged or restricted since I recently installed new 5/16" stainless steel lines (feed and return)... So, shouldn't be clogged.. (Also recently bought a new mts fuel tank, internal fuel pump and inline fuel filter by WIX #33002 and the throttle body was a rebuild that I got off ebay.. The spray pattern appears to be good.. Not globby or drippy..

I Did install the fuel pump in tank... Just modified my sending unit to accommodate the pump... I don't have a bracket yet on the sender to hold the pump.. But hope to get someone (who welds) to barter with me.. Hopefully its not "swinging" around in the tank.. ROFL

I'm thinking about getting the adjustable fuel pressure regulator too.. Saw some youtube videos on how to install... But hope that I don't have to yet... (since the part costs money.. )

 

[76cj7chick]

76cj7chick,
Love the color. :rock:




Hi there GARGOYLEJEEPER! Thanks for chiming in too! ---I've always wanted a pink jeep... So I painted mine 'pearl Hot pink'...

Yes on:
First off you should have a model 220 out of a 4.3 V6
Fuel pressure : 9-13 psi
Throttle Position Sensor : 1 V
Minimum Idle Auto : 500-550 rpm Vac. Disc.


Unsure about this stuff.... (As I have the prestolite ignition system.. No timing control.. --Will one day.. Plan to get the later CJ7 "dizzy" installed with the gm 8pin module.. Still deciding on a coil..)

Distributor had 4 wires Electronic Spark Timing
Signal #423
Bypass #424
Reference Pulse High #430
Reference Pulse Low #453
Plus
Ignition #3
Tachometer #121

Is it okay to put my Tach reference wire to the - coil side? Or does it hog power from the ignition? (My coil tested at just under 9k.. Which according to the book is correct)




You should have :
M.A.T. Sensor
M.A.P. Sensor
Engine Speed Sensor
O2 Sensor
E.G.R. Solenoid
Fuel Pump Relay

Some of the above things that you mentioned I do have... Some, don't have.. Have all that you mentioned except----

Don't have the :
M.A.T Sensor..
E.G.R. Solenoid


Your problem is distributor related.

Will dig out my FSM and my big Electrical Diagnosis And Wiring Diagrams book and tell you what to do.

Please DO pull out the FSM book... As I am still unclear of what the issue is..

Thanks for your help!

 

[76cj7chick]

I would not be to concerned about that low fuel pressure, I have been running 9 psi for some time now with no issues. The fuel pump does put out a lot more pressure but the tbi regulator cuts it down. Underneath the tbi, between the inlet and outlet fittings there is an adjustment screw for fuel pressure. Screw it out slightly for more pressure. Your ignition problems could be from a bad ignition control module,
I believe it is that gold colored box, that could had gone bad. The prestolite and motorcraft icms will go bad if there is a poor ground, which is the black wire coming from them. If your icm gets hot to the touch that is a bad sign for sure.
Edit: after rereading your post, you could have an issue with a low idle adjustment, do you know how to adjust this?

GOOD TO KNOW about the screw for the pressure regulator... Which way do I turn it to increase the fuel pressure, if I can? (is "screw out".. .To the left/counter clockwise?)

I wouldn't doubt it if my ignition control module decided to fail.. Is there a way to test it? I have a multi-meter.. And I know how to use it..

You may be onto something... It could have something to do with the Idle (mixture) adjustment screw... Before I posted this thread----I was trying to adjust the screw properly and think I made it worse.. Which way should I go? I can't find anywhere listed or on the Internet which way the screw should be turned to make it run better... Is it dying because lack of air? Or too much? :dunno:

Thanks for your help! Hope to hear from you all soon!

 

[Torxhead]

Yes, screw out is counterclockwise(Like righty tighty-lefty loosey , if you have ever heard that) go easy on that also. I made a bunch of throttle body gaskets just for that. When an ignition module fails, from what I have seen, there is an ignition miss that can eventually cause a no start issue-you did not say that there was an ignition miss. I would recommend eventually removing the Prestolite anyway. To adjust the idle speed on a tbi, from what I understand, is engine off, disconnect the 4 pin idle air control connector from the tbi, start the engine, adjust idle, turn engine off, reconnect idle air connector. You should have close to full battery voltage to the fi system, if not it can affect the fuel pump and computer. I was able to achive that by running the sense wire from the alternator to the gas gauge hot line. If you completely close off the fuel return, it can overpressure the tbi and stall the engine, but with a 5/16" return line you should be o.k. I hope not having a computer controlled distributor is not affecting the computer signals to the tbi. On mine, with the Howell chip it is turned off, I guess since I do not any codes like that and have the Motorcraft ignition.

 

[bzahler]

I would go over to Binder Planet.com sign up and talk to Bill (he runs the injection forum) He will help you out Plus there is a ton of info in the FAQ'S

 

[007]

2 more cts here...

I'd have kicked that Prestolite out from under the hood way before the carb. BUT once you get it running get that done ASAP.

You'll be thrilled.


Sent from my iPhone using Tapatalk

 

[GARGOYLEJEEPER]

OK,
What I found out is it is your dizzy like I said either you need a filter between dizzy and ecm or a Duraspark conversion. The duraspark will be the way to go, or a dizzy shop to mate the AMC 258 i6 / 4.2l bottom to a 4.3 top. Your ECM is retarding the spark, electronic spark timing code 42, and electronic spark control code 43. You should also have the knock sensor and coolant sensor, besides what I said.
Your fuel pressure is fine 9-13. Leave the idle alone until you fix dizzy.

 

[76cj7chick]

Yes, screw out is counterclockwise(Like righty tighty-lefty loosey , if you have ever heard that) go easy on that also. I made a bunch of throttle body gaskets just for that. When an ignition module fails, from what I have seen, there is an ignition miss that can eventually cause a no start issue-you did not say that there was an ignition miss. I would recommend eventually removing the Prestolite anyway. To adjust the idle speed on a tbi, from what I understand, is engine off, disconnect the 4 pin idle air control connector from the tbi, start the engine, adjust idle, turn engine off, reconnect idle air connector. You should have close to full battery voltage to the fi system, if not it can affect the fuel pump and computer. I was able to achive that by running the sense wire from the alternator to the gas gauge hot line. If you completely close off the fuel return, it can overpressure the tbi and stall the engine, but with a 5/16" return line you should be o.k. I hope not having a computer controlled distributor is not affecting the computer signals to the tbi. On mine, with the Howell chip it is turned off, I guess since I do not any codes like that and have the Motorcraft ignition.

Thanks for your suggestions. I do hope to change out the prestolite ignition soon.. Just trying to figure out a good coil to use with the duraspark distributor and 8 pin gm ignition module... Looking at MSD, Mallory, GM coil and just stock jeep coils for later CJ7 years. Thanks for the clarification on the screw adjustment...

 

[76cj7chick]

I would go over to Binder Planet.com sign up and talk to Bill (he runs the injection forum) He will help you out Plus there is a ton of info in the FAQ'S

Hi there! Thanks for the suggestion.. I've been to binderplanet several times and have spoken with Bill about other install issues I was having... I may check it out again to see if anyone has asked my specific questions yet... But I don't recall seeing a thread on it..

 

[76cj7chick]

OK,
What I found out is it is your dizzy like I said either you need a filter between dizzy and ecm or a Duraspark conversion. The duraspark will be the way to go, or a dizzy shop to mate the AMC 258 i6 / 4.2l bottom to a 4.3 top. Your ECM is retarding the spark, electronic spark timing code 42, and electronic spark control code 43. You should also have the knock sensor and coolant sensor, besides what I said.
Your fuel pressure is fine 9-13. Leave the idle alone until you fix dizzy.

Would you know where this filter would be installed and what it looks like?
Yeah, so far don't have any ecm ignition timing on the jeep.. Hope to get it hooked up after I dump the prestolite ignition.. Just want to get it running as good as possible for now.. Then take on more with switching to a ecm that controls timing and fuel..

 

[76cj7chick]

I thought I'd mentions that my jeep stalling out issue seems to mainly happen since I switched out the inline fuel pump (gsl395 by walbro) and went to a carter P74000 in tank pump... Perhaps the psi is okay but maybe the gph or lph flow rate is not significant enough with the carter??????????


Anyone know of a IN tank equilivant to Walbro's gsl395 pump? Again, REALLY DON'T want in line, I prefer to have an intank...

ALSO---I DO have another intank fuel pump but is rated at 50psi... Would this be too powerful for my GM throttle body fuel pressure regulator? Or would it be okay to use instead of the 15psi pump?

Thanks again everyone for your help... Hope to hear from you professionals

 

[Torxhead]

You might want to contact Airtex fuel pumps tech line at 1-800-424-7839, after looking them up online. They do give advice to people with diy issues. I contacted them and was provided with the number of a fuel pump that is designed for my tbi system w/inline pump.

 

[GARGOYLEJEEPER]

Like Torxhead said Airtex E3902 (made in USA), from Shuck`s now O`Reily`s.
That is what I have in my S-10 w/matching Sock filter, replaced my OE pump just because of crappy gas. Need another running vehicle so I can swap in my 4.3 from my S-10 into my 7.
No pres. reg. is needed (it is in the TBI). So do not buy one.
Do not use 50psi pump.
You should put a relay to your ECM & TBI off the coil.
You should not have to mess with a rebuilt or new TBI.
And once you put in a better EST dizzy you won`t have to mess with that either.
Try swapping pumps. Since I missed that part some how.
Then buy a used 4.3 dizzy and have it mated to your dizzy way better then Ford Duraspark. If I was still at Mac`s Jeeparts I would do it for you, but since he passed I do every thing the hard way now.
My coil is a Accel Super Coil for the 4.3 and I haven`t looked back.
Sorry haven`t looked at my manuals, been doing yard work when I should be working on my CJ2a , to find out why you loose tach when disconnecting IAC.
Look at diagram.

 

[76cj7chick]

Like Torxhead said Airtex E3902 (made in USA), from Shuck`s now O`Reily`s.
That is what I have in my S-10 w/matching Sock filter, replaced my OE pump just because of crappy gas. Need another running vehicle so I can swap in my 4.3 from my S-10 into my 7.
No pres. reg. is needed (it is in the TBI). So do not buy one.
Do not use 50psi pump.
You should put a relay to your ECM & TBI off the coil.
You should not have to mess with a rebuilt or new TBI.
And once you put in a better EST dizzy you won`t have to mess with that either.
Try swapping pumps. Since I missed that part some how.
Then buy a used 4.3 dizzy and have it mated to your dizzy way better then Ford Duraspark. If I was still at Mac`s Jeeparts I would do it for you, but since he passed I do every thing the hard way now.
My coil is a Accel Super Coil for the 4.3 and I haven`t looked back.
Sorry haven`t looked at my manuals, been doing yard work when I should be working on my CJ2a , to find out why you loose tach when disconnecting IAC.
Look at diagram.

Hey thanks for your responses GARGOYLEJEEPER I know life can be busy and I appreciate your help!

Just a couple of things... .

Would you have a diagram of the tbi running off of a relay to the coil? If yes, please post or explain.. Assuming I would need a 5 pin relay.. But not positive which wires, besides ground goes. (I found a sample of relay wiring from gearhead-efi.com. Please let me know if it doesn't look right:If you use a bosch style relay here are the pins:
There are several different versions of the relay out there so look at the pin numbers before you buy one.

30-12v fused input(should also hook up your org ECM constant 12v to this wire)
85- Gnd
86- 12vdc from ign sw(black wire that was hooked up to the coil +)
87- pink/blk, pink(ignition, ecm power)
87- red, white(injectors)

there are 2- 87 output terminals on the SPST 5 terminal relay so you can use both.
Thanks. I'll check out the Accel Super coil.. Does the Accel Super coil require 12v always or does it need a balast resistor for start up? (I looked on line and from what I found is that the Accel IS a 12v coil, please correct me if I am wrong)
Just to clarify, I still have my Old prestolite ignition hooked up.. Haven't hooked up the gm module yet... Also have but haven't installed the duraspark ignition yet.
Really hoping to get the stalling issue fixed first then move to installing the timing controlled ignition.

 

[76cj7chick]

You might want to contact Airtex fuel pumps tech line at 1-800-424-7839, after looking them up online. They do give advice to people with diy issues. I contacted them and was provided with the number of a fuel pump that is designed for my tbi system w/inline pump.

I don't know.. Think that it might be a long shot. .Since I currently don't have their fuel pumps....

 

[76cj7chick]

Any one know the correct number of complete turns out/in for the Air Idle Mixture screw for the GM 4.3L V6 throttle body years 1987-1991? Or is there no set amount?

I know carburetors utilize a standard amount of turns for the throttle adjustment screw... So, just wondering what the standard is for the GM TBI??