1989 Jeep YJ EFI Conversion Computer Question - JeepForum.com
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post #1 of 67 Old 11-09-2015, 07:44 PM Thread Starter
jlavigne
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1989 Jeep YJ EFI Conversion Computer Question

I own a 1989 YJ and the previous owner put a fuel injection conversion on it. I have a couple of questions about this:

Is it possible that it still has the original MCU under the dash and a new model computer and ECM mounted to the firewall on the driver's side?

I am having trouble with the fuel pump and spark. I re-did the ground to fuel pump and that seemed to help but now I am having issues where the fuel pump won't turn on and there is no spark. Then sometimes the pump will pump and the car will be flooded and I hold down the pedal and I will get a rough start and after that clears up it will start as many times as I want but if I let it sit for a while I am back to no fuel pump engaging?

I would appreciate some input into this situation.

Thanks!

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post #2 of 67 Old 11-09-2015, 09:31 PM
timatoe
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What type of fuel injection kit did they put on? It's possible the stock ECU is still there, but it won't do you any good because that never controlled any of the things you've got problems with.

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post #3 of 67 Old 11-11-2015, 12:45 PM
Berniebikes
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What timatoe said! The old ECU was mainly a control for emissions stuff and timing (IIRC). Once you change from the stepper motor controlled carb, or switch the ignition, the ecu and everything connected to it are just excess weight in your vehicle. If you tell us what sort of EFI system you have there is probably some advice available.
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post #4 of 67 Old 11-11-2015, 07:10 PM Thread Starter
jlavigne
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Not sure how to identify what kind of fuel injection system it is? With the old ignition on I was still getting signals to the MCU? All the videos I watched on doing the conversions showed removing the harness from inside the vehicle.
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post #5 of 67 Old 11-11-2015, 10:08 PM
timatoe
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If you don't already, get an account on photobucket or the like and take some pics and host them there. Copy and paste the "img" link here.

That's probably the best start.

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post #6 of 67 Old 11-12-2015, 06:10 AM
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You need to post some pics.
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post #7 of 67 Old 11-12-2015, 06:26 AM
jay-h
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If it's the Howell conversion ( injectors at the old carb location as opposedto the Mopar which has injectors by each cylinder), the ECU does not control the spark at all,however if your spark module is bad, it can confuse the injector control and may cause flooding when starting. Normally the fuel pump shoud run for 2 seconds at startup, but even if it does run longer it should notflood unless you have some leakage at the injectors.

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post #8 of 67 Old 11-14-2015, 03:31 PM Thread Starter
jlavigne
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Here is a pic of the after market injection setup...if anyone can identify it please let me know.


http://drive.google.com/file/d/0B0xP...ew?usp=sharing
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post #9 of 67 Old 11-14-2015, 03:58 PM
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That looks like a Chrysler multiport. Is there another computer in the engine compartment? If not then you might have the pre 91 renix from a Cherokee.
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post #10 of 67 Old 11-14-2015, 09:41 PM Thread Starter
jlavigne
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There is the original computer in behind the glovebox and there is a computer on the firewall. It was running great one week ago. Now have no spark or fuel. I replaced the Crankshaft Position Sensor and the distributor. The wiring is a mess. I wish I had someone in my area that I could pay to take a look.
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post #11 of 67 Old 11-14-2015, 10:03 PM Thread Starter
jlavigne
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yeah it definitely is this mopar injection system... http://www.fourwheeler.com/how-to/12...on-258ci-jeep/
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post #12 of 67 Old 11-14-2015, 10:04 PM Thread Starter
jlavigne
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fuel pump works if i jumper a wire from ignition into the wire that goes to fuel pump...but without that jumper it does not come on when turning key on or when cranking
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post #13 of 67 Old 11-15-2015, 11:32 AM
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Can you take a pic of the computer on the firewall? No fuel pump or spark is a power problem. You probably need a.meter to check voltage.
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post #14 of 67 Old 11-16-2015, 03:53 PM Thread Starter
jlavigne
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I have a meter...the computer on the firewall is from a 1992...If I ground terminal 85 on the fuel pump relay the fuel pump comes on but still no spark? I do have 12v to the green/red wire at the coil and 12V at the grey wire on the coil....but no spark our of the coil. I am starting to suspect the computer, because I am running out of other things to test.
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post #15 of 67 Old 11-16-2015, 05:13 PM
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Disconnect the 92 ecu and with key on check power at pins 3&9 to battery negative.
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