Howell TBI Conversion for a 1986 California Legal Jeep CJ7

[TwoFiveEightDad]

Hi!  Hoping someone can give me some  good advice on a Howell TBI conversion on a 86 California legal cj7, 258.

Just finished the swap and everything looks right according to the directions but I have to say, the electrical instructions are a little thin compared to the rest of the directions.

I'm not getting spark yet and I’m wondering if there is a good ignition section wiring harness (like a painless harness but ignition only) to match up with the nice new Howell TBI one.

Anyway- either help getting started or help with finding an ignition harness would be great!

Thanks!

Jim

 

 

[Moses Ludel]

TwoFiveEightDad...Hi, Jim...You made a good fuel system choice and upgrade here.  The easiest way to troubleshoot spark is to envision the Howell system as EFI/TBI related only and nothing to do with the OEM ignition.  Your ignition still operates from the factory devices and wiring harness. 

If you're running the stock distributor, you need the OEM Motorcraft module or the conversion to a 5-pin Chrysler module like many do.  (I did this upgrade even with stock Motorcraft/Jeep ignitions and also added the broad diameter distributor cap, spacer and rotor ala Ford/Motorcraft version.)  The 5-pin Chrysler module is a more reliable setup and simplifies the wiring as well.  It's clear, you have five designated lead wires. 

Not to confuse, you can use the entire original wiring, module, coil and such if you prefer.  However, the OEM system includes spark retard and other emission related devices that were not required nor of any value with the Howell conversion.  The Motorcraft distributor, without the electronic retard functions, has a fully capable centrifugal and vacuum advance system.  The spark advance curve is sufficient for performance and fuel efficiency. 

Some do opt for an MSD or other aftermarket distributors, including inexpensive, easy to wire HEI type distributors for the 4.2L six.  Be careful here, as to your point, an aftermarket distributor may require an E.O. exemption number to meet California emissions.  Usually, California inspectors are content with the Howell E.O. number/sticker and the fact that the EFI conversion has cleaned up the tailpipe emissions considerably.  You will likely need all of the factory chassis related components, in particular the catalytic converter system.

You should be able to get spark unless you cut out wiring or circuits during the Howell EFI installation.  If you have an '86 or similar OEM factory workshop manual with wiring diagrams, you can trace out the wires needed for ignition.  This includes the module leads, feed to the ignition primary wires (check here for a voltage signal) and such.  If you deleted the ECU for spark and carburetor control, this could be the break in your wiring...See whether you have primary ignition current with the key on.  This is a simple test with a voltmeter at the coil primary positive terminal.  

Make sure you have not eliminated any hot leads or grounds.  Grounds are equally important on a 12VDC system.

We can walk through this if these suggestions do not resolve your issue.  I've discussed the big cap conversion and 5-pin Chrysler module in my books...

Moses

 

[TwoFiveEightDad]

Hi Moses- Thanks very much, this is helpful.  Beyond the Howell TBI, I’d like to stay as stock as possible to simplify passing emissions.  It feels like there will be less to explain to the emissions people…

 

In the process of removing the unnecessary wiring to install the Howell TBI, I think I took out too many other lines.

 

So- a few questions:

For the ignition circuit to get the right voltage from the Motorcraft module, I think I need a resistor wire and relay setup.  Is the Painless wiring kit good here:  https://www.summitracing.com/parts/prf-30819?seid=srese1&gclid=CjwKCAjwp6CkBhB_EiwAlQVyxY7ZKGrOBjsdys4O8kFVE7DB-NTgsp1Jj8s0jFwoi68kK3kGs4VpwBoCYsoQAvD_BwE

 

Next, I’m now missing the manifold heater circuit.  Painless also offer one of those: https://www.summitracing.com/parts/prf-30717?seid=srese1&gclid=CjwKCAjwp6CkBhB_EiwAlQVyxYMPkaep0uqDs2EHJLAttwDoGZC9L1pfw81O-AtQ1t1oRL1avTcBQRoCmHAQAvD_BwE

Good idea?

Next is the right place to pick up correct voltage for the replacement Howell computer.  Is there a really obvious spot on the harness?  I heard going to the positive side of the coil was good but that doesn’t sound right now bc it goes low (6V) during normal running…

 

Last thing is a lead coming off of a component on the forward part of the intake manifold.  Single red wire with a white stripe.  Don’t know what that is or where the wire goes…

 

Thanks again, I really appreciate the help!

 

Jim

[Moses Ludel]

Jim...See my comments below in red for easy access:

16 hours ago, TwoFiveEightDad said:

Hi Moses- Thanks very much, this is helpful.  Beyond the Howell TBI, I’d like to stay as stock as possible to simplify passing emissions.  It feels like there will be less to explain to the emissions people…

You're welcome...

In the process of removing the unnecessary wiring to install the Howell TBI, I think I took out too many other lines.

 

So- a few questions:

For the ignition circuit to get the right voltage from the Motorcraft module, I think I need a resistor wire and relay setup.  Is the Painless wiring kit good here:  https://www.summitracing.com/parts/prf-30819?seid=srese1&gclid=CjwKCAjwp6CkBhB_EiwAlQVyxY7ZKGrOBjsdys4O8kFVE7DB-NTgsp1Jj8s0jFwoi68kK3kGs4VpwBoCYsoQAvD_BwE

So, this looks like a conversion harness to enable installing a DuraSpark II into an earlier Jeep engine (232 or 258 six) with an OEM breaker point ignition.  The coil clip-on and harness plug to the module look like your stock system.  If you have lost the OEM harness, this could restore your system or serve as a by-pass of the extra devices (like the original ECU/MCU for spark retard and carburetor emissions functions).  Likely, this harness gets used for that purpose.  It would streamline the module/coil interface and likely connects directly to your ignition circuit.  You should have the OEM wiring, a module plug connector and a coil clip that looks like this.

Next, I’m now missing the manifold heater circuit.  Painless also offer one of those: https://www.summitracing.com/parts/prf-30717?seid=srese1&gclid=CjwKCAjwp6CkBhB_EiwAlQVyxYMPkaep0uqDs2EHJLAttwDoGZC9L1pfw81O-AtQ1t1oRL1avTcBQRoCmHAQAvD_BwE

Good idea?

Not sure whether Howell EFI would need the manifold heater, it could be a liability.  EFI has an enrichment or open-loop phase during warm-up.  OEM carbureted emissions engines benefit from the heater, it quickly warms the intake manifold to enable faster opening of the choke and better cold engine performance.  Mopar EFI and GM's TBI, which forms the base for the Howell kit, do not heat the manifold nor do they use manifold cross-over heat or a heat riser valve like earlier carbureted engines.  I'm surprised Howell does not discuss this device in the instructions and whether to disconnect it.  Worth asking Howell before restoring the manifold heater.

Next is the right place to pick up correct voltage for the replacement Howell computer.  Is there a really obvious spot on the harness?  I heard going to the positive side of the coil was good but that doesn’t sound right now bc it goes low (6V) during normal running…

If the Howell EFI operates from a full 12VDC source, you do not want to pick up resisted current (typically 6-9 volts, depending on the system).  You can check the voltage reading at the coil positive terminal to see whether there is a resistor or resistor wire (Ford method) in place.  To simplify all this, tap into the Key-On position pole at the ignition switch or, better yet, a conveniently accessible feed from the Key-On pole of the ignition switch.  (Follow the circuit from the ignition switch Key-On pole to an accessible junction or splice point.)  This way, you have a clean, 12VDC source with the key on.  Make sure it's Key-On and not the Accessories pole, which would trigger the computer in Accessories mode as well as Key-On.  You want just Key-On.

Last thing is a lead coming off of a component on the forward part of the intake manifold.  Single red wire with a white stripe.  Don’t know what that is or where the wire goes…

The ignition module has a red with a white stripe lead.  Is the wire red with a white stripe or a tan stripe?  See whether this is a Key-On 12V source.  If the wire goes to a sensor, take a picture of the sensor and post it.  I'll identify the sensor.

Thanks again, I really appreciate the help!

 

Jim

 

[TwoFiveEightDad]

Hi Moses, thanks!

 

Here is a picture of the sensor.

 

Jim

[Moses Ludel]

Well, Jim, it took some digging to find this switch and wiring.  I eventually found the sensor in my Mopar parts catalog that covers your year CJ...This is the Knock Sensor. 

The sensor serves the electronic ignition spark retard process to prevent ping/detonation when the engine is under severe load or running poor grade (low octane) fuel.  Sensors like this typically complete a ground when triggered:

 Mopar Part Number 33000902 SENSOR, Knock, 1983-86

In the case of your ignition, the knock sensor is part of the MCU/ECU engine management system.  The sensor signals the ignition to retard when the engine is knocking (ping or detonation).  The microprocessor (MCU) resets spark timing to compensate.

Moses

[TwoFiveEightDad]

thank you Moses!

[Moses Ludel]

TwoFiveEightDad...You're welcome, Jim.  By now, the complexity of the OEM ignition system should be clear.  The MCU/ECU creates a primitive version of electronic fuel-and-spark management with the last Carter BBD-carbureted Jeep 258 inline six-cylinder engines.  You can see why many opt for an HEI (GM style) distributor to eliminate the array of devices and MCU that make up the SSI (Solid State Ignition) on your engine.

It would be worth inquiring (at a BAR referee station) whether the Howell EFI will pass emissions with a straightforward HEI style replacement distributor.  There are several replacement distributors available, with and without California E.O. numbers.  An E.O. version would have an exemption decal and number, which would be fully acceptable. 

You can research which of these distributors have E.O. numbers:  https://www.summitracing.com/search/part-type/distributors/make/jeep/engine-size/4-2l-258/engine-family/amc-inline-6-cylinder.  DUI and MSD may be E.O. exempted.  

Otherwise, the OEM Motorcraft distributor will work with a simpler Mopar 5-pin ignition module.  The OEM distributor and advance curve (without the MCU's input and array of sensors/devices) would be acceptable.  My 258s ran nicely with the stock distributor.  I routed a simple ported vacuum hose for the vacuum advance signal and relied on the OEM distributor's built-in mechanical advance mechanism with the stock mechanical advance curve...You would not have the knock sensor function, but that should not be an issue with Howell EFI.  If knock occurs, you could easily retard the base timing (and curve) with the stock distributor.  There would be no MCU/ECU interference.

I describe the Mopar 5-pin module conversion (and the Ford 300 big distributor cap, rotor and cap spacer) in my books.  Here are two versions of the 5-pin module.  Wiring is much simpler with this setup if you're still lost in the mire of your underhood wiring.  I learned about the 5-pin conversion from Jacobs Electronics in the eighties.  This was not only a reliable conversion (better than the OEM Motorcraft modules by a long shot) but also allowed for a very basic wiring task:

https://www.summitracing.com/parts/sum-851021

https://www.napaonline.com/en/p/MPETP50SB

Moses