XR4Ti Steering Racks, The Definitive Guide

Given these cars are 30+ years old, the seals in the steering rack tend to go bad. And/or the plastic boots crumble, leading to contamination of the rack and fluid, destroying the seals. Based on that, you're likely going to have to deal with some steering rack issues, regardless. You may also want to change the rack, or how it works, depending on your situation. For example, there are options for powering the rack hydraulics, such as Electrohydraulic Power Steering (EHPS) pumps from several manufacturers. I'm putting together another post for the known options there.

The XR4Ti came with two steering racks as standard, the TRW early on, and switching to the ZF for most of the production timeline of the car. Given these cars are 30+ years old, power steering rack seals and boots tend to fail, so knowing the rack is probably a good idea. 

TRW

Model years: 1985 - mid-1986
Lock-to-lock (L2L): 2.7 turns (According to what I assume is specs released early in the production of the XR4Ti, the rack was 3.6 turns, https://www.carfolio.com/merkur-xr4ti-99077?car=99077). 
Suitability: average driving, cruising

Note: Identifiable by a smooth surface on the rack housing. 

Note: Interchangeable with the ZF rack.

ZF

Model years: mid-1986 - 1989
Lock-to-lock (L2L) : 2.7 turns

Suitability: average driving, cruising, racing

Note: Identifiable by the waffle pattern on the rack housing.

Note: Interchangeable with the TRW rack.

Manual Steering Rack Conversion

Manual racks are desirable for road racing and drifting since you're aggressively turning the wheel and working the rack. These racks were never designed to take the abuse a rack will receive on a race track, especially drifting. 

Manual racks aren't desirable for a daily driver because you're having to do all the work yourself at slow speeds. Makes you realize just how heavy a car can be. 

A manual rack does simplify the engine bay by removing a pump and the belt(s) that run it. Looks great!

If you're going to run a manual rack, beef up the rag joint and steering shaft mounts, since they weren't designed to take the abuse of non-power steering forces on them.

Manual racks are not recommended if you're rally racing.

How to Order a New ZF rack at AutoZone (as of 2008):

AutoZone was $139.00, Advance Auto was $350.

"For example, the way to get the ZF rack from Autozone is to have the sales person phone ATSCO at the time you place the order. I had no problem getting them to do this. The Autozone sales person should tell ATSCO they want the Type 2 ZF rack. ATSCO will then link the order and the rack type to the PO# which Autozone also supplies.

ZF Rack: ATSCO p/n 6441 Type 2 $139.99 + $90 core

TRW Rack: ATSCO p/n 6441 Type 1 $139.99 + $90 core"

Note: Oreilly brand is A1 CARDONE part no 26-1921

Steering Rack Bushings

Stock, the XR4Ti comes with rubber bushings in the rack. You might be able to get poly or solid aluminum bushings, depending on timing and vendors:

MC2 Racing, a site by avid autocrosser Chris Grayson, has had poly and aluminum steering rack bushings available from time to time, but now recommends nylon steering rack bushings, available here. 

Steering Rack Fluid Cooling

You can use power steering coolers, akin to automatic transmission fluid coolers, purchased from many places, but Summit Racing as them for $25 (Item DER-13200). 

Steering Rack Rebuilds

You can get XR4Ti steering rack rebuild kits from: Power Steering Rebuild Kits, XR4Ti TRW Rack Kit, XR4Ti ZF Rack Kit

The size of the rack end seals (2 required) for the TRW rack are: 24-33-7 referring to the inner diameter, outer diameter, and thickness, respectively, in millimeters. Most industrial/pneumatic supply houses can provide these if you're inclined to just replace the end seals on the existing, early rack.

Other options

Ford Sierra (European) Manual Rack: 

Model years: unknown, all Ford Sierra's with non-power steering

Lock-to-lock (L2L) : 3.75+ Turns 

Suitability: average driving, cruising

Where to buy: http://www.kellybraysteering.co.uk/pages/manual_steering_racks_12938.cfm 

Requires manual steering shaft, European part: https://www.motomobil.com/en/products/steering-idler-shaft-not-for-power-steering-not-4wd-lhd-60959030-1 

 

Aftermarket Ford Sierra (European) Manual "Quick" Rack: 

Model years: aftermarket only.

Lock-to-lock (L2L) : 2.7 Turns

Suitability: racing, right hand drive (RHD) only.

Where to buy: http://www.kellybraysteering.co.uk/pages/manual_steering_racks_12938.cfm 

Requires manual steering shaft, European part: https://www.motomobil.com/en/products/steering-idler-shaft-not-for-power-steering-not-4wd-lhd-60959030-1 

Throwback: Ford Sierra Euro Headlight/Lamp Wiring for the XR4Ti (old article)

This was originally distributed as a file called litewiring.bmp through the IMON mailing list. I searched for it and couldn't find it, so I recreated it here, as well as attached the scan, of the copy, of the printout, of the attachment from the email. I'm about to do this myself, so I'm going to take this, as well as what's out on merkurencyclopedia.com and combine them into a new article.

Dec 2020 update: Here is what I did in a new 23turbo article.

Chris

Wheel studs for the XR4Ti, $28@Summit Racing, ARP Wheel Studs 100-7708

For the record, this is the wheel stud that works for the XR4Ti. Sold in a set of 5, which is annoying. 4 sets to create 16, with 4 spares.

ARP Wheel Studs 100-7708

                                          Brand:    ARP

Manufacturer's Part Number:100-7708

Part Type:Wheel Studs

Product Line:ARP Wheel Studs

Summit Racing Part Number:ARP-100-7708

UPC:672036000462

Wheel Stud Style:Press-in

Wheel Stud Thread Size:12mm x 1.50 RH

Knurl Diameter (in.):0.509 in.

Underhead Length (in):2.500 in.

Shoulder Length (in):0.315 in.

Quick-Start Nose:No

Quantity:Sold as a set of 5.

Notes:Fits late model Camaro, Corvette, and Firebird applications.

Notes:

• Application: XR4Ti,Scorpio
• These studs can be too long if you want to use a closed lug nut. Trimming may be required.

The infamous blower motor resistor issue

Why is my HVAC fan only working on one speed, or blowing a full blast? OR All about the thermal fuse, blower motor, and the parts number

If you have what appears to be the low speed, that may just be the air recirc. door opening due to a non-functional door solenoid. It is uncommon for only the middle speed not to work, since the failure of a blown thermal fuse is that only the top blower fan speed works.

The resistor pack is located beneath the plastic cowl cover behind the firewall in the engine compartment. Four or five screws to remove the cowl, and two screws to remove the pack, and a connector. The pack sits on top of the heater fan box. Just look for a plate held in with two screws and a wiring connector. Once removed, you'll see two or three coiled wires and a thermal fuse mounted on the other side. The thermal fuse is the culprit. 

You can either:

A) Repair with a 291.2 degree F (144 degree C) thermal fuse. (Radio Shack part #270-1322a or newer #270-1320). Don't solder it in. It MUST be crimped in, or the heat from soldering it will blow the resistor. You can cut the body of the old fuse off and twisted the leads of the new one to the leads of the old one. All speeds to the blower should work after this repair.

OR

B) Solder in series a 10 amp fast blow fuse. 

Repinning your harness to put an LA3 into a Merkur

There are more detailed, complete instructions at Merkurencyclopedia.com. 

These are the pins that you have to move to put an LA3 into your Merkur:
1. Pull out pin 43 and move it to pin 27. This connects the VAF signal. 

2. Pull out pin 25 and move it to pin 43. This connects the VAT signal. 

3. Pull out pin 32 and move it to pin 31. This connects the boost controller. 

4. Pull out pin 35 and insert it into pin 33. This connects the EGR solenoid signal. 

5. Put a spare pin into number 24 and run it to Signal Ground which is pin 46 for permanent premium mode. Or install a switch so that you can switch between premium and regular modes.

You don't need to hook up an Air Charge Temperature (ACT) sensor. You don't need to hook up the Brake On/Off (BOO) switch. And you don't need to do anything to keep the cruise control working. The cruise is a completely separate system from the EEC-IV in a Merkur. No modifications necessary. 

Throwback: MerkMeter User Guide

Since I have a gauge cluster with a MerkMeter and needed to understand what it was, how it worked and how to reinstall it, I had to go find information about it. I finally found information and had to pull this out of the WayBack Machine, I figured I'd post it here, so there's a live website for this content again.

Chris

MerkMeter User Guide

Rationale 

The exhaust gas oxygen (EGO) sensor is a crucial part of the engine management strategies of virtually all modern cars.  It basically enables the Engine Control Unit (ECU) to properly manage the fuel flow in response to changing engine operating conditions.  Responding to these changing conditions rapidly and accurately is a key component of the operating strategies employed by the software embedded in the ECU.  An improperly operating EGO can result in poor fuel economy, higher emissions, and poor drivability and performance.  Also, insight into the data a properly functioning oxygen sensor is sending to the ECU can be invaluable in monitoring the runtime health of the engine and diagnosing trouble when it occurs.  Just as a hot running engine, as indicated by the coolant temperature gauge in the instrument cluster, can be an indicator of serious problems, so too can an abnormal air/fuel ratio as indicated by the proper gauge.

Theory of Operation

The EGO sensors in our cars basically measure the difference in the oxygen content of the exhaust gas against that of the ambient air.  The air we breathe is about 21% oxygen.  The oxygen content of the exhaust gas of our cars is typically in the 0-2% range.  A small zirconium dioxide thimble in the oxygen sensor can generate a small voltage that reflects the difference in the oxygen in the exhaust (outside the thimble) vs. the oxygen in the ambient air (inside the thimble).  The greater this detected difference, i.e. the less oxygen in the exhaust gas, the higher the voltage produced by the sensor.  

For this type of EGO sensor to work, it must be heated above 600° F.  The exhaust gases passing over the sensor tip in the exhaust pipe accomplish this heating.  It generally takes about 2 minutes with the engine running above 2000 rpm for the EGO in an XR4Ti to be brought up to operating temperature. The Scorpio uses a Heated Exhaust Gas Oxygen (HEGO).  The HEGO, as the name implies, is brought up to operating temperature somewhat quicker due to an internal electrical heating element.  Output from both types of sensors is comparable. 

A new EGO sensor will output from zero to about one volt and can detect changes in the oxygen content of the exhaust very quickly.  These sensors are particularly sensitive around the ideal air/fuel mixture of about 14.7:1, which results in stoichiometric burn.  This is the ratio at which there is theoretically just enough oxygen to burn all the fuel.  (In practice the burn is never completely efficient and some residual oxygen will always be present in the exhaust).  The stock Bosch EGO sensors (or equivalents) generate approximately 0.45 volt at this mixture.  A voltage below 0.45 indicates a lean condition, while a voltage above 0.45 volt indicates rich. 

How does the EGO output voltage correspond to an air/fuel ratio value?  The answer to this question is dependent on many variables; the age and condition of the EGO, the fuel used, the operating temperature of the EGO among them.  Representative data from Bosch is shown below for a new zirconium dioxide EGO operating at 800-1200°F with an engine burning gasoline containing no alcohol:

Voltage	Approx. Air/Fuel Ratio
0.0-0.1	17.0:1
0.1	16.0:1
0.2	15.5:1
0.3	15.0:1
0.4	14.8:1
0.45	14.7:1
0.5	14.6:1
0.6	14.5:1
0.7	14.2:1
0.8	13.2:1
0.9	12.5:1
>1.0	12.0:1 or less

As a sensor gets older the maximum voltage it can generate and its sensitivity to changes may decrease.  Also if the sensor becomes contaminated with lead, silicone, or antifreeze residue it may become very inaccurate.  Bosch recommends that unheated oxygen sensors (XR4Ti) be replaced every 30,000-50,000 miles.  First generation heated sensors (Scorpio) should be replaced every 60,000 miles.

The sensitivity and responsiveness of the EGO makes it possible for the ECU to dynamically adjust the air/fuel ratio. When the engine has warmed, as indicated by the Engine Coolant Temperature (ECT) sensor, the ECU will go into “Closed Loop Mode”.  This is a feedback mode in which the ECU will actively vary the fuel supplied via the injectors based upon the EGO signal.  When a lean condition is indicated by the EGO, the ECU will increase the amount of fuel supplied by the injectors.  If the EGO shows the mixture is rich, the ECU will reduce the fuel supplied.  The ECU will make the necessary calculations and dynamically adjust the mixture continuously while in Closed-Loop Mode as much as several times a second.

MerkMeter Behavior

The MerkMeter is essentially just a small voltmeter calibrated to a range of zero to one volt.  Each LED indicates an increment of 0.1 volt.  The leftmost red LED will light when the voltage from the EGO is about 0.1 volt.  The leftmost yellow LED lights at about 0.4 volt and the leftmost green LED lights at about 0.7 volt.  The rightmost red LED will light at or above 1.0 volt.  There is about 10 millivolts overlap between adjacent LEDs.  For example, a value of 0.69 volts will light both the rightmost yellow LED as well as the leftmost green LED.

What the MerkMeter displays depends upon the operating conditions of the engine:

Cold Engine

When the engine is cold, the MerkMeter will gradually display an increasing voltage as the EGO sensor warms to operating temperature.

Closed-Loop Mode

The MerkMeter will show this mode as a display that oscillates from about 0.1 volts to 0.8 volts and back again. When at idle the crossover time from lean to rich and back to lean might be about one second. At part throttle cruise, the crossovers might occur several times a second. The range and speed of these Closed-Loop oscillations can be an indicator of the health of the EGO. If the range of oscillations is considerably less than normal, or is skewed toward one end of the range or the other, oxygen sensor deterioration or contamination might be indicated. The same condition could cause the crossover rate to slow. A car that never goes into Closed Loop Mode might have some other faulty sensor or ignition circuit. The XR4Ti will operate in Closed-Loop Mode only below 2950 rpm.

Open-Loop Mode

In this mode, the ECU does not use the EGO signal to calculate how much fuel to supply. It instead supplies a fixed amount of fuel based upon other parameters. The MerkMeter will display a stable, slightly rich reading normally in the 0.7 to 0.9 volt range. This will most often occur when cruising above 2950 rpm (XR4Ti PF2/PF3 calibration).

Wide-Open Throttle

At Wide Open Throttle (WOT) the ECU will also go into Open-Loop Mode. The MerkMeter will normally display a steady rich reading in the 0.7 to 0.9 range for the duration of the WOT event. If the MerkMeter drops into the 0.1-0.3 volt range at WOT, it is a good indication that insufficient fuel is being supplied to meet the engine demands.

Specifications

Display Driver:  National Semiconductor LM3914N

Fuse Protection:  0.5A fuse

Polarity Protection:  50V silicon rectifier diode

Voltage Requirements:  6-15V DC

Operating Current:

       No LEDs on -  ~5mA

                               One LED on -  ~15mA

                               All LEDs on -   ~95mA maximum

Signal Input Current:  Less than 100nA

References

The Complete Turbo 2.3L EEC-IV Handbook by Allan Slocum

Ford Fuel Injection & Electronic Engine Control by Charles O. Probst

Oxygen Sensor Technical Data Sheets by Bosch

Oxygen Sensor Diagnosis Olympic Imported Parts Corporation

Oxygen Sensor Information by Rick Kirchoff

Understanding Oxygen Sensors by Dave Cappert (broken link @  www.serviceinsights.com)

“What is an oxygen sensor?” from Bosch REPORTER: Written by Technicians for Technicians, October 1998

Oxygen and Air/Fuel Ratio Sensors by Jong Heun Lee

Throwback: About the MerkMeter

Since I have a gauge cluster with a MerkMeter and needed to understand what it was, how it worked and how to reinstall it, I had to go find information about it. I finally found information and had to pull this out of the WayBack Machine, I figured I'd post it here, so there's a live website for this content again.

Chris

MerkMetertm     Merkur Air/Fuel Ratio Gauge

 

Graphically displays the output of the existing oxygen sensor Patent pending design fits in the stock instrument cluster...No additional gauge pod is required! One year warranty Fits in all model year XR4Tis and Scorpios All wires and connectors needed for installation are included in the kit: Detailed and illustrated printed instructions included Installs with simple hand tools in less than one hour Three color display permits monitoring information in the driver's peripheral vision  10 segment display is calibrated for .1 volt per segment with a 1 volt range Built-in fuse protection Built-in battery reversal protection Display can be configured in Dot or Bar Modes High impedance precision circuitry will not effect oxygen sensor output to the ECU

Price was $74.99 (USD) for members of the International Merkur Owners Network, the Hardcore List, the XR4Ti List, the Merkur Club of America or any of the other Merkur clubs or organizations listed on the Merkur Desktop. Price for others was $89.99.