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The 4WD Mechanix Magazine article "iinstallation of a Mopar Performance MPI/EFI Conversion package" is referred to in the 4WD Mechanix Magazine MPI/EFI trouble shooting article. I have tried everything to find it but have been unable to. Can anyone provide a pointer to it?

 

Thanks in advance...

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Hi, Allonsy, welcome to the forums!  I have included Mopar EFI conversion installation key points in several articles at the magazine.  Could not go into great detail because my Jeep CJ Rebuilder's Manual, 1972-86 and Jeep Owner's Bible each contain details on the installation of a two rail (earlier) system.  (The Jeep CJ Rebuilder's Manual has actual installation steps, the Jeep Owner's Bible is a system overview.)  Copyright does not allow me to reprint from my Bentley Publishers books.  The CJ book would be valuable for your needs; if you have a 1987-90 YJ Wrangler, the fuel pump replacement article (shared in links below) would be a helpful supplement.

 

There are two basic Mopar EFI systems.  (Actually three, if you include the original Mopar throttle body conversion system with Electromotive components and a Holley TBI unit, available in the early 1990s from Mopar Performance.)   Of the two Mopar EFI/MPI systems, the earlier MPI version patterns from a 1994-95 Jeep YJ Wrangler or similar XJ Cherokee 4.0L, and this is a two rail system with a return line to the fuel tank from the engine.  The pressure regulator is at the engine.  This system, uniquely, uses mostly off-the-shelf Jeep YJ or XJ parts.

 

The later system is similar in many ways but is a single rail design with 1997-up TJ Wrangler and XJ Cherokee 4.0L off-the-shelf parts.  This system has a regulator that mounts near the fuel tank.  The modified regulator is essentially the (1997-up) TJ and XJ fuel pump module's regulator.  Single rail systems regulate fuel at the tank (or an externally mounted regulator in this kit), with only one fuel line going to the EFI rail at the engine.

 

If you're either troubleshooting an existing system or need details on the kits, see my links below for some highlights.  I am pleased to answer questions about these EFI/MPI systems if you're in a troubleshooting situation.  Post your question(s) at the forum, I'll be glad to answer.  Meanwhile, these articles should be helpful.

 

See these articles:

 

In this installation for an '87-'90 YJ Wrangler, I use the Mopar factory fuel pump module with an MPI conversion.  The "kit" comes with an externally mounted fuel pump.  This alternative, using the higher pressure designated pump for MPI, works with these models.  For a 1980-86 CJ, there is no provision for the in-tank fuel pump module, and you need an external fuel pump, mounted near the fuel tank: 

 

Jeep in-tank fuel pumps can be difficult to troubleshoot and service. In this article, Moses Ludel discusses fuel pump diagnosis, repairs and pump replacement steps.
 
Each of these articles will help explain or illustrate various features on the Mopar EFI/MPI systems.  You'll find some installation notes, too.  The step-by-step installation for an '80-'86 CJ (similar in many ways to the 1987-90 4.2L YJ Wrangler install) is in my Jeep CJ Rebuilder's Manual: 1972-86.  If you want specific answers about your project, just ask here at this forum:
 
The Jeep inline six stroker motor with EFI or MPI develops maximum performance when tuned properly. Selecting the correct MPI injectors and matching the fuel supply system to the bigger engine and higher horsepower output require the modifications described here.
www.4wdmechanix.com/How-to-Tuning-the-Fuel-Injected-Jeep-Inline-Six-Stroker-Motor.html
 
Here, I do an overview of the various aftermarket EFI systems, including Mopar MPI:
 
In this coverage, we install the MSD Atomic EFI system on a Jeep 4.2L inline six-cylinder engine. The retrofit is similar for all Jeep 258 engines built from 1971-90. See detailed how-to steps for this 1989 Jeep YJ Wrangler installation.
www.4wdmechanix.com/MSD-Atomic-EFI-for-Jeep-4.2L-Inline-Six-2.html
 
Should you convert your 4.2L Jeep inline six to EFI? In this feature, Moses Ludel contrasts the BBD carburetor and the Mopar Performance EFI conversion kit.
www.4wdmechanix.com/Carburetion-Versus-EFI-Conversion-for-the-4.2L-Jeep-Inline-Six.html
 
Fuel pump and system pressure is different for carburetion, TBI and MPI. In this article, Moses Ludel discusses fuel pressure requirements for various Jeep engines and chassis designs.
www.4wdmechanix.com/Jeep-Fuel-Pressure-Requirements.html

 

Trust this helps, Allonsy!  Please share details about your project...Looking forward to your participation at the forums...

 

Moses

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  • 7 years later...
On 7/29/2014 at 6:08 AM, Moses Ludel said:

earlier MPI version

I know this thread is old but I have this version I think. I am trying to troubleshoot the fuel pump and I cant seem to find any wire diagram for this. I can see the Brown with black line running from the positive connection on the pump but cant seem to find where it goes. Any ideas? I was told by the previous owner that the kit uses things off of the 94 yj.

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myndcrym...At its website, HESCO has the complete instructions for the EFI Conversion installation.  (Use this link and click on the download link for the set of instructions:  https://hesco.us/techtips.asp.)  The instructions would be for the later single rail EFI system but would overlap with the earlier two-rail system...This is a quote from those instructions related to your concern.  I highlighted the pump wiring in red:

"20.        Route the rest of the harness along the top of the transmission. The next plug will be the
vehicle speed sensor.   (Figure 19.)   Route the remaining harness along the frame rail to
the rear of the Jeep
® to connect the fuel pump power (+) to the green wire with the black
stripe.   The ground wire is brown with an black stripe.
Secure the harness all along its length in strategic locations with the tie wraps provided.  Make sure that there is clear­ance between any moving parts or areas of high temperature, such as the vehicle exhaust. You may want to use dielectric grease on the connections to prevent corrosion (Mopar part number J8126688)."

Moses

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Thanks! I have traced the green with black stripe back to the relay. I cant figure out why I dont have power to my fuel pump. It should at least have power for a second until it has pressure correct. I found what looks like the main fuse and its good. I hear the relay click on then back off but still nothing at the pump. Maybe a bad connection at the pump. I will pull wires and check just the wires for 12v.

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myndcrym...HESCO should have the replacement pump.  Whether you have the single- or two-rail system may not make a difference with the fuel pump.  (Confirm this at the HESCO site.)  If you take the specs (PSI and GPM or GPH) from the pump I.D. tag or stamping numbers, a Walbro or similar replacement pump would work. 

You need to match polarity and the pressure/volume output.  The pump trigger is the ECM/PCM.  Make sure you get the trigger from the PCM.  Simply put, don't bypass the EFI and PCM functions.  The pump needs its signal and power via the 60-way PCM and fuel pump relay.

Moses

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  • 1 year later...
On 8/31/2021 at 8:56 PM, Moses Ludel said:

myndcrym...HESCO should have the replacement pump.  Whether you have the single- or two-rail system may not make a difference with the fuel pump.  (Confirm this at the HESCO site.)  If you take the specs (PSI and GPM or GPH) from the pump I.D. tag or stamping numbers, a Walbro or similar replacement pump would work. 

You need to match polarity and the pressure/volume output.  The pump trigger is the ECM/PCM.  Make sure you get the trigger from the PCM.  Simply put, don't bypass the EFI and PCM functions.  The pump needs its signal and power via the 60-way PCM and fuel pump relay.

Moses

Moses,

  You seem to know quite a bit about this kit.  Since Ma Mopar is no longer producing this kit (P5249686), I've been trying to cobble together all the bit parts to install on my '86 CJ.  One part has stymied me so far is the wire harness.  Hesco doesn't make a replacement, but suggested I pull the harness out of a '94-'95 YJ.  Would you know what wires I can purge out of this harness, and how to make it work in my CJ?  Is there a wire diagram for this?  I've read other places that there are two relays that are in the MPI kit harness that attach to the firewall....from the posts up above I gather one is the fuel pump relay....what is the other?

 

Thanks

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Zimbar...HESCO did offer the wiring harness for years, sorry to learn that's no longer available.  The harness was a "missing link" for 4.0L YJ/XJ donor vehicle EFI conversions.  As for the two relays, yes, one is the fuel pump.  For your purposes, however, you'll be using the wiring and relay layout for a 1994-95 YJ engine harness.  The primary engine needs:  fuel pump trigger, EFI-to-PCM, all of the sensors (crankshaft position sensor, MAP, temp, IAT and so forth) and the vacuum circuits.  You need the 4.0L coil with bracket and the ignition distributor from a 1991-95 4.0L engine.  While the reference is to 1994-95 Mopar systems, this was for emissions testing.  1991-93 Mopar MPI 4.0L is similar and also uses the 60-way PCM.

To make your task easier, I am providing the HESCO installation details below.  (Fortunately, I archived a copy of these instructions.)  This has many illustrations that will help you identify parts, wiring and vacuum circuit needs.  Note that the fuel injection is later single rail type ('97-'99 TJ prototype), which HESCO substituted for the earlier Mopar EFI Conversion's two rail system.  The significant difference is the HESCO modified fuel pressure regulator that returns fuel into the fuel tank;  there is no engine-to-tank return with a single rail system.  I would avoid using a single rail EFI/MPI system and stick with 1991-95 era two-rail with the 60-way PCM.  This will require returning fuel to the tank from the 1991-95 YJ/XJ pressure regulator at the EFI rail.  You can use the CJ's existing return fuel pipe to make this easier:

 HESCO Mopar MPI Conversion Instructions for 4.2L Jeep Six.pdf

Note:  If you have a copy of my Jeep CJ Rebuilder's Manual: 1972-86 (Bentley Publishers), I devote a section to the two-rail Mopar EFI conversion, which includes illustrations and installation details.

Worth pointing out, the original Mopar EFI conversion was a two-rail system patterned specifically for use of 1994-95 YJ off-the-shelf-parts.  You need the 60-way PCM (1991-95), the donor engine/PCM harness and the intake manifold with sensors.  (Although the '94-'95 prototype is OEM, the 1991-93 systems are similar.)  You'll need the MAP sensor and relays, which can be remote mounted as you note.  (Relays were originally located in the 1994-95 YJ's power distribution box.) 

You need the right high pressure, inline fuel pump for the EFI.  The signal for running the pump is the PCM, which triggers the fuel pump relay.  The wiring harness feeds a PCM signal to the fuel pump relay, which then feeds current to the fuel pump.  This pump is not a simple key-on operation, it must trigger from the PCM and fuel pump relay.

Where possible, I fabricate steel fuel pipe for EFI high pressure systems.  Any use of fuel hose and clamps must be high pressure EFI rated.  Vacuum circuits will need to mimic the '94-'95 YJ, and this includes venting and vacuum for the EVAP system.  The HESCO PDF demystifies the vacuum circuits and interface.  My book adds further clarification of the venting/EVAP for a two-rail system.

A major concern for DIY installers is the crankshaft position sensor (CPS) signal.  An OEM Mopar EFI system from a donor YJ/XJ does not have the Mopar/HESCO-type crankshaft damper and pickup.  The CPS sensor/pickup mounts at the bellhousing, and the signal comes from a 1991-up OEM flywheel or flexplate.  Your CJ flywheel and bellhousing are not equipped for a crankshaft position sensor (CPS) as found on 1991-up 4.0L engines. 

The Mopar/HESCO EFI conversion includes a special crankshaft damper (shown in the installation PDF above).  A special crankshaft position pickup (attached at the front of the engine) triggers from this damper.  You need a CPS signal, or this system will not work.  As mentioned, you also need the 4.0L ignition distributor and coil for a 1991-95 YJ Wrangler or XJ Cherokee.  These parts appear in the installation instructions PDF.

Changing your flywheel to a 4.0L type would also require a bellhousing with the CPS mount.  Here, you have the issue of transmission differences:  the 4.0L bellhousings with the CPS sensor provision would be an AX15 transmission pattern.  (Advance Adapters makes a replacement bellhousing for the 4.0L, and the transmission pattern is also AX15/NV3550.)  If you keep your original transmission, this would open the need for a transmission conversion.  The easier route is to use the HESCO damper and CPS pickup that will mount the CPS at the crankshaft nose. 

Note:  If HESCO stops selling the crankshaft dampers, these CJ-era installations in vehicles with the original CJ transmissions will require something like an Edelbrock front pulley/damper trigger and pickup.  Automatic and manual transmission applications need a CPS signal.

This may seem daunting, but if you can make sense of a wiring schematic, the Mopar EFI Conversion harness was a simple four-wire hook up to the CJ chassis electrics.  (The harness did include the wiring to the inline high pressure fuel pump that came with the kit.)  The conversion kit's wiring harness could be easily mated to the CJ chassis electrics.  Your application requires the right inline fuel pump and wiring to that pump.

 Getting a donor harness requires the 60-pin connector harness, the 60-way PCM, all wires running to the engine sensors, the EFI injectors and so forth.  If you do not have the wiring schematic for a 1994-95 YJ Wrangler, let me know...I have the Mopar FSM for 1994 YJ/XJ in my library.  Wiring diagrams are in that manual.

Moses     

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On 9/15/2022 at 1:03 PM, Moses Ludel said:

If you do not have the wiring schematic for a 1994-95 YJ Wrangler, let me know...I have the Mopar FSM for 1994 YJ/XJ in my library.  Wiring diagrams are in that manual.

Moses     

Moses,

  Thank you very much for the info!  A lot there to read and re-read again.  I just ordered your book (3rd edition) and hope it gets delivered soon.  I will check out that section you spoke about.  Yes, I will need the wire diagram and appreciate you offering it.  

 

Many thanks!

Patrick

(zimbar)

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zimbar...Thanks for your interest in my books!  The "3rd Edition" sounds like the Jeep Owner's Bible, which you will enjoy.  It's a solid reference and armchair read for this coming winter. 

As mentioned in my September 15th reply above, the book that covers actual rebuild/restoration steps for your '86 CJ, and also includes details of the Mopar® two-rail EFI conversion/installation, is my Jeep CJ Rebuilder's Manual: 1972-86 (Bentley Publishers).  Do you have a copy of that book handy?

I compiled a PDF of schematics for your use.  In these 1994 Jeep YJ factory wiring diagrams, the wire color coding is indicated by letters.  Wire routing includes the junctions and EFI related "pinouts" for a 1994-95 60-way PCM.  (This should be similar for 1991-93 YJ Wrangler and XJ Cherokee models from 1991-95.)  The stock 1994/95 Jeep YJ Wrangler 4.0L EFI details will clarify the devices and wiring required.  Your donor wiring harness(es) and PCM will follow this approach.  I purposely made PDF scans so you can zoom into the diagrams for more detail: 

 1994-95 YJ Wrangler 4.0L EFI Wiring Schematic.pdf

This should all help.  The Jeep CJ Rebuilder's Manual: 1972-86 has illustrations and how-to for the Mopar® two-rail EFI kit installation into a CJ.  HESCO's installation instructions that I provided also clarify the installation.  The Mopar EFI kit eliminates some of the YJ Wrangler chassis devices but is otherwise 1994/95 YJ. 

The somewhat streamlined Mopar aftermarket EFI Conversion kit met emissions requirements for 1981-90 4.2L CJs and YJs with an included wiring harness that had only four significant wires to mate with the vehicle's chassis electrics.  This was a clean and relatively simple installation.  It's too bad the price has soared on the Mopar EFI conversion kit.  That package was a solution for altitude changes, provided 50 extra horsepower and cleaned up the emissions.  You can get there by your approach if you sort all this out. 

The 4.0L YJ intake manifold will require minor "massaging" to fit a 4.2L head and exhaust manifold.  Some perform a 4.0L cylinder head conversion, which requires properly blocking off a couple of cooling ports in the head to match the 4.2L block ports.  This head (1991-up version) will take the MPI '91-up intake manifold and factory steel exhaust header.  Worth considering, especially if the head needs service.  

Note, too, that your EFI system and PCM will require a speed sensor signal.  This comes from the speedometer drive at the transfer case.  Your Dana 300 has a mechanical speedo cable and drive.  The YJ Wrangler uses a transfer case sensor/drive to an electronic speedometer.  You will need the speed signal plus a speedometer drive.  To bridge this and provide both a mechanical cable to your CJ speedometer and a speed signal to the 60-way PCM, HESCO still sells the speedo/sensor assembly that comes with the Mopar EFI Conversion Kit.  Here is the HESCO product and an additional connector available for two-wire use:

https://hesco.us/products/30798/electrical-and-electronic/43100/speed-sensor-hes7015#.YzO7-z3MIuU  

For tuning or troubleshooting the MPI/EFI system, you can add a simple dash mounted MIL lamp ("CHECK ENGINE" light) and follow procedures for a 1994-95 YJ Wrangler.  The 1991-95 YJ PCM will store OBD (not OBD-II) codes.  Though not OBD-II level details, the codes are still a valuable troubleshooting aid for a scan tool that has OBD Mopar adapters.

Patrick, my aim is to provide enough detail for you to make some informed decisions about this swap.  Many have done it, and I trust this information illuminates key points.  Still others have opted for the 50-State legal, somewhat less costly GM TBI-based Howell aftermarket kit.  The Howell system does offer EFI virtues.  However, the use of a stock 4.2L ignition distributor, or even a retrofit conventional HEI distributor, does not have the same refinement as the full-on electronic fuel-and-spark management found in a Mopar EFI/MPI system.  Multi-point EFI comes at a price.  Weigh the merits.

Moses

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For those wanting information on the Mopar EFI Conversion Kit installation, my book with illustrations and how-to details would be the Jeep CJ Rebuilder's Manual:  1972-86 (Bentley Publishers) shown at right below.  This and the HESCO instructions will help with your installation.  Look for the book with the yellow AMC/Jeep CJ on the cover:

 Jeep Books by Moses Ludel-1.jpg

Below are all of my Bentley Publishers books.  Top row (left to right) is the Harley-Davidson Evolution V-Twin Owner's Bible™, the three editions of the Jeep® Owner's Bible™ and the two Jeep CJ Rebuilder's Manuals.  Bottom row is the German edition of the Harley-Davidson book, the Chevrolet & GMC Light Truck, Ford F-Series Pickup and Toyota Truck & Land Cruiser Owner's Bibles.  The German edition of the Jeep® Owner's Bible™ is at lower row to the right. 

TDR Issue 112 Photo 1.jpg

Trust this helps when we discuss these books.  Whether you do this conversion with a 1991-95 YJ/XJ OEM system or the Mopar aftermarket EFI conversion for a 4.2L engine, consider getting a CD copy of the factory service manual for a 1994 or '95 Jeep Wrangler YJ.  (Weighing the information contained in the FSM, this is inexpensive and available at eBay.)  Here's a current Bishko CD version example, a direct replica of the OEM print manual on my office reference shelf:  https://www.ebay.com/itm/132408367081.  CDs enable PDF printing and zooming, you can print pages to take into your garage.

The FSM will provide all of the service, maintenance and troubleshooting details for keeping a 60-way PCM, two-rail 4.0L EFI system in good operating condition...Moses

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