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Old 01-19-2020, 01:53 AM
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Howell efi hard start, rough idle problems

I bought my 88 yj 6cyl from a lady a year ago in California. She knew nothing about it except it was her late husband's "Beloved Jeep". It had some issues but the price was to good to pass up. Well the first thing i had to fix was the driveplate cause all the teeth were ground off. Once i got it back together i found out it hard starting so i got a repair manual. Thats when i figured out the PO had put a Howell efi on it. Since then ive done the following( to no avail )
Fuel pump
Fuel filter
Tps
Starter
Starter relay
IAC
Ignition module
Automatic trans
Fuel pressure regulator
Plugs,wires,cap,rotor

Nothing worked so i wired a toggle switch to the ignition module so i could turn it on and off which would dump more fuel in the throttle body then it would start. It's been running like that for 8 mo. till 2 days ago i change my fuel filter after that it wouldn't start but tries to so on a whim i put a spare fuel pump on now it will start( still using the toggle) but idles rough and has a loss of power. I feel like half a person when im not in my jeep any ideas would be greatly appreciated

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Old 01-19-2020, 02:01 PM   #2
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Well, replacing parts is never the best way to diagnose problems as sometimes new parts don't work out of the box(fuel pumps are notorious for this). The howell uses GM TBI injection which is stupid simple but I hated howell as it doesn't control ignition timing. I would get a fuel pressure tester and make sure it is getting 9-14PSI of fuel continuously on the feed line of the throttle body. If it is getting that, then go to this forum for a voltage checks excel file and information on conversion TBI:GM Wiring Harness (octopus) | BinderPlanet

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Build Thread 1989 YJ, Chevy 355 TBI, 4L60E, np231 ssye/wide chain/6 pinion planetary, D30/8.8/4.56, 33" A/T's, bds 3.5" springs, 1" Boom Shackles, crossover heim steering
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Old 01-20-2020, 03:35 PM
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Well after hours of testing i found that i have 12v to my ignition module with key on but when i turn key to start it drops to zero. Bad ignition module maybe?
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Old 01-20-2020, 04:19 PM   #4
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I had this problem too with my EFI conversion. I ended up having to remove a resistance wire that went to my ignition coil, but it is possible the ICM is bad and you could have it tested at a parts store but have them test it 3-4 times in a row
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Build Thread 1989 YJ, Chevy 355 TBI, 4L60E, np231 ssye/wide chain/6 pinion planetary, D30/8.8/4.56, 33" A/T's, bds 3.5" springs, 1" Boom Shackles, crossover heim steering
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Old 01-20-2020, 04:54 PM   #5
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Quote:
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Well after hours of testing i found that i have 12v to my ignition module with key on but when i turn key to start it drops to zero. Bad ignition module maybe?
Or it may be wired wrong. There are circuits that get 12v in the run position, but zero voltage in the crank position. What happens if you get a battery feed 12v to the ICM just for testing purposes?
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Old 01-20-2020, 07:46 PM
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Just so happens i just tried that and i got 12v to the IM and my injector tester started flashing like a xmas tree.
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Old 01-20-2020, 07:49 PM
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I work the swing shift so that where I'll start in the a.m.
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Old 01-21-2020, 09:26 AM   #8
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Originally Posted by Juice0420 View Post
Well after hours of testing i found that i have 12v to my ignition module with key on but when i turn key to start it drops to zero. Bad ignition module maybe?
Could be wired wrong or could be a bad ign switch.
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Old 01-24-2020, 09:21 AM
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Just an update.......found lots of splices in main harness and some very poor wiring decisions so i spent the last couple days with my FSM cleaning up and getting all the wiring right. After my battery gets charged up I'll continue my troubleshooting
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Old 01-26-2020, 06:46 PM
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Now that everything is wired right my fuel pump and injectors don't power up when cranking?
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Old 01-26-2020, 07:00 PM   #11
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Then it isn't hooked up to key on power, they're hooked up to a source that doesn't have power while cranking.
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Old 01-26-2020, 07:30 PM
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I only found one source that was hot in start and run from the ignition switch and i have power to ignition module when cranking
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Old 01-26-2020, 07:35 PM
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Im not sure what is supposed to provide power to both the fuel pump and injectors at same time. Check engine light is on both at key on and while starting so i believe the brain is ok
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Old 01-26-2020, 08:27 PM   #14
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So it sounds like the wiring is all good. Now run a fuel pressure test, if you don't have the 9-14 psi, it won't run. You can also run diagnostics on these setups with a program called Tunerpro RT and an aldl cable.

Tunerpro: https://www.tunerpro.net/

Aldl cable: Cheap ALDL Cable
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Build Thread 1989 YJ, Chevy 355 TBI, 4L60E, np231 ssye/wide chain/6 pinion planetary, D30/8.8/4.56, 33" A/T's, bds 3.5" springs, 1" Boom Shackles, crossover heim steering
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Old 01-26-2020, 09:12 PM
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Fuel pressure was good, my tech wire should be connected to the negative side of distributor along with the yel resistance wire correct?
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Old 01-26-2020, 09:42 PM   #16
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Incorrect, your tach signal should be on the negative post on your ignition coil. I want to say a green wire but I could be wrong since it has been a while. The GM ECM basically works by controlling grounds.
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Build Thread 1989 YJ, Chevy 355 TBI, 4L60E, np231 ssye/wide chain/6 pinion planetary, D30/8.8/4.56, 33" A/T's, bds 3.5" springs, 1" Boom Shackles, crossover heim steering
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Old 01-26-2020, 09:53 PM
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Still wondering if my ICM is bad, i believe thats what still controls both the injectors and fuel pump at start? Or maybe my starter relay?
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Old 01-26-2020, 10:06 PM   #18
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The ICM can be tested at an auto parts store. Have them test it at least 3 times back to back. I'm wondering if you have a genuine Howell EFI kit or something similar now. Maybe pulling the starter disconnected the crank signal wire for the ECM. This is really hard to diagnose without seeing the vehicle so you may have to spend some time head scratching and looking at wiring diagrams
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Build Thread 1989 YJ, Chevy 355 TBI, 4L60E, np231 ssye/wide chain/6 pinion planetary, D30/8.8/4.56, 33" A/T's, bds 3.5" springs, 1" Boom Shackles, crossover heim steering
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Old 01-27-2020, 11:54 AM   #19
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Maybe it is time to get rid of that stock type ford ICM and get an HEI distributor.
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Old 01-27-2020, 12:54 PM   #20
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Go back to the wiring.... i believe you still have issues there
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TJ dash speakers that actually rock! Kicker sub and amp in center console
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Old 01-27-2020, 10:53 PM   #21
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Maybe it is time to get rid of that stock type ford ICM and get an HEI distributor.
Or use the Chevy TBI ECM to control ignition timing too by modifying your duraspark to work with the chevy ICM and therefore ECM! Unfortunately this will require a new Chip and Tune for your ECM which is well worth it.

AMC 258 DS distr conversion | BinderPlanet

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Build Thread 1989 YJ, Chevy 355 TBI, 4L60E, np231 ssye/wide chain/6 pinion planetary, D30/8.8/4.56, 33" A/T's, bds 3.5" springs, 1" Boom Shackles, crossover heim steering
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