Howell TBI installed and it won't fire up! - Page 2 - JeepForum.com

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post #16 of 30 Old 04-28-2013, 09:53 AM
SLO_Ken
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You said you bought it used? Was the previous owner running HEI, or was his a stock ignition?

You may need to bypass the Howell tach filter. I had to do that when I switched from the stock Duraspark to a MSD CDI. Clip the purple wire from B5 on the ECU and run your tach signal directly to that. This bypasses the filter, which is designed to clip and square-off the switching voltage from the coil on a stock setup. The tach signal from the HEI should already be a useable clipped square wave,so the Howell filter further filtering it makes it unrecognizable to the ECU.

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post #17 of 30 Old 04-28-2013, 10:29 AM Thread Starter
arg0413
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Okay I'm going to ground the grounds to the battery this afternoon. I don't know if the Po was running an HEI, but I'll email him. I've read just put the white wire on the tach lead, but I'm going to try what your saying, that deff makes sense why the ECM isn't telling the injectors to fire.

1997 TJ: 4.0/AX15, 4.11/Tru Track & 4340 Shafts in rear (D35) 35" MTR/K
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post #18 of 30 Old 04-28-2013, 11:24 AM
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I'm coming at this late, but two things you need to look for: #1 Are the injectors getting voltage when you turn the key on and #2 is your HEI module wired to the ECM as shown in the attached wiring schematic? That schematic is for the newer style HEI where the coil is external to the cap. Not sure if that is the style you have, or if you have the older style where the coil sits in the cap. I'm unsure of their differences. I only have access to that schematic I provided.

Take note that the HEI module is dual purpose. One function is controlling the ignition coil, the other is providing reference signal for injector pulse. Two separate functions. Hope that helps in some way.
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post #19 of 30 Old 04-28-2013, 11:32 AM
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Oh I see you tested the injectors with the ignition key on and then by manually grounding them. Ok well then they have power if they actuated that way.
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post #20 of 30 Old 04-28-2013, 12:44 PM Thread Starter
arg0413
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No I tested the injectors with a 9v battery and a interrupter switch, so I don't think they are getting voltage

1997 TJ: 4.0/AX15, 4.11/Tru Track & 4340 Shafts in rear (D35) 35" MTR/K
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post #21 of 30 Old 04-28-2013, 12:55 PM Thread Starter
arg0413
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Update : previous owner was running an HEI and had the system installed the same way. It's the older style HEI I have with the coil built into the cap. I've checked ground with voltmeter and it's excellent.

1997 TJ: 4.0/AX15, 4.11/Tru Track & 4340 Shafts in rear (D35) 35" MTR/K
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post #22 of 30 Old 04-28-2013, 01:45 PM
SLO_Ken
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If it is running through the howell filter, it's not unheard of for those filters to fail. Before I got the msd, I had my filter fail. The symptoms were the same as you are experiencing. Howell wanted $50 for a replacement. I was able to replace the damaged component for $0.19.

California 4.0 OBDII Engine Swap
http://www.jeepforum.com/forum/f8/california-4-0-obdii-swap-1530716/
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post #23 of 30 Old 04-28-2013, 02:05 PM Thread Starter
arg0413
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What filter are you speaking of? Please explain more..

1997 TJ: 4.0/AX15, 4.11/Tru Track & 4340 Shafts in rear (D35) 35" MTR/K
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post #24 of 30 Old 04-28-2013, 02:54 PM
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http://www.jeepforum.com/forum/f8/ho...oblem-1230390/

^ Posts 12 and 16.
There is a tach signal filter buried in the Howell wiring harness near the ECU connector. It's a pretty simple circuit board with a couple of electronic components that apparently are not too robust. Mine failed when I pulled and reinstalled my engine after a rebuild.
In post 12 of the attached link, I describe the diagnostic steps that Troy from Howell walked me through over the phone.
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post #25 of 30 Old 04-28-2013, 03:26 PM
graham33575
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I may be wrong, but doesn't the system require the tach filter? I've set multiple systems up now, and the one without ECM controlling spark needed a tach filter. Just my two cents. Good luck
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post #26 of 30 Old 04-28-2013, 05:10 PM Thread Starter
arg0413
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Problem solved! Thanks slo-ken! I was following your diagnosis of the tach filter and once I found terminal B5, I discovered that the wire was missing from the terminal! Installed a wire in terminal B5 and ran it to my tach feed on my HEI, engine fired right up! Runs excellent! These systems make such a difference! Thanks to everyone for the input to help solve the problem and get it running!

1997 TJ: 4.0/AX15, 4.11/Tru Track & 4340 Shafts in rear (D35) 35" MTR/K
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post #27 of 30 Old 04-28-2013, 06:10 PM
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Quote:
Originally Posted by arg0413
Problem solved! Thanks slo-ken! I was following your diagnosis of the tach filter and once I found terminal B5, I discovered that the wire was missing from the terminal! Installed a wire in terminal B5 and ran it to my tach feed on my HEI, engine fired right up! Runs excellent! These systems make such a difference! Thanks to everyone for the input to help solve the problem and get it running!
Awesome!
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post #28 of 30 Old 04-28-2013, 08:22 PM
SLO_Ken
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I'm glad it was something simple
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post #29 of 30 Old 04-28-2013, 09:19 PM
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So now I'm going to have to check out my Howell harness and look for this filter. I wasn't aware that the filters were used unless you were using a CDI type iginition like MSD. Glad it was that easy to find once someone knew the right place to look! Thanks for passing on that info SLO Ken.
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post #30 of 30 Old 04-28-2013, 09:29 PM
SLO_Ken
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Quote:
Originally Posted by CSP View Post
So now I'm going to have to check out my Howell harness and look for this filter. I wasn't aware that the filters were used unless you were using a CDI type iginition like MSD. Glad it was that easy to find once someone knew the right place to look! Thanks for passing on that info SLO Ken.
It's buried in the Howell harness about a foot or so from the ECU connectors, wrapped in tape, and covered in adhesive shrink tube.
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