Upgrade Projects

Early Bronco

Late Model






Installing a 5.0/5.8L EFI Engine
In an Older Truck

All of the Early Ford Broncos on the road are at least 20 years old. Many of them driven by motors equally old and with 150,000+ miles. While rebuilding these older motors is certainly an option, a popular alternative is to install a late model, Electronic Fuel Injected motor. These motors are relatively cheap and with modern electronics are incredibly reliable. This guide will help you to install a late model EFI motor into an older truck, with an emphasis on installation in an Early Ford Bronco.

Engine Removal
Power Steering
EEC Installation
Fuel System
Fuel Pumps
Selector Switch
Relay Wiring
Throttle Pedal/Cable
Issue Summary
5.8L Notes
Related Technical References


You will need virtually every piece of the doner EFI engine. It's much better to find a doner car and go there yourself to get all the little pieces. We have included a parts list for you to use as a guide. Basically, get everything that is attached to the wiring harness. While you may not be able to get everything on the parts list, try to get as much as you can.

Make sure you have all the parts and any tools you will need close at hand before you begin. You could also consider purchasing a complete crate motor from Ford or Summitt Racing. Summitt had them for $2495.00 not so long ago.

We recommend replacing any small bolt, hoses, etc. with new, high grade hardware at this time. There isn't much point in installing a highly realiable motor, only to bust a radiator hose that's 10 years old. Spend the time/money now, and save even more down the road.

Engine Removal

The older, carburated motors were pretty simple. At this stage we simply want to prepare the car to accept the new EFI engine. Therefore:

  1. Remove the old Bronco engine, but do not remove any of the wiring at this time.
  2. Remove the linkage from the firewall where the throttle pedal comes from inside the vehicle.
This would also be a great time to replace your motor mounts - particularly if they are original.


If you have bought a complete EFI motor, including the engine's water pump, alternator, power steering pump and air pump (if you have one), then you can used them all as well as the serpentine belt. In most instances, the modern parts are far superior to the originals. Even the air conditioning compressor (or air compressor) will fit without any extra effort.

Note: You will need an air pump on the engine if it orginally had one in order to meet emissions laws.

The 5.0L engine will fit with slight modification to the hood braces, small dimples on front and rear braces to clear the EGR fitting and A/C comp. The firewall may need very small dimples at the air injection pipe (usually not necessary if you install engine with motor mounts attached then put them on afterwards). The 5.8L motor will fit if you use Mustang shorty headers, change the upper intake manifold (or use a hood scoop) and modify the smog tubes at the back of the heads. You will also need to remove the fan clutch. That's about the extent of the clearance problems you will encounter.

If you decide to use the Bronco parts, put both engines next to one another and remove the EFI engines alternator, air pump and bracket. Remove the A/C, power steering pump and bracket, and the water pump. the install the Bronco water pump, alternator, air pump, power steering pump and put it on the EFI engine.

Power Steering Hoses

If you are using the EFI accessories then either take the ends off of the late model hose and your hose in order to get a new custom hose made up at any hydraulic shop. You could also get an AN adapter from one of the parts houses. (Lee Manufacturing, Sun Valley, CA makes these, there are others.)

You may also want to consider a new flow control valve to better match a truck power steering box as opposed to the doner vehicle's (this might be the case when using a 5.0L out of a Mustang). These flow control valves are exactly the same on the pump end, but is different on the hose end. Also needed will be a seat for the valve adapters and two fitting adapters, one for the valve and one for the seat and the other for the hose and power steering box. The cost is about $25 for the valve and adapters and $30 for the hose.

Those of you installing an EFI into an Early Bronco with the popular 2WD Pickup Power Steering Conversion may have a problem with the power steering pump pulley not clearing the box. This will only be true for certain setups with A/C. A EFI motor without A/C will have different brackets (available from Ford, $69) which does not have this clearence problem. By grinding of the front of the PS/AC bracket and two very simple custom brackets you can get a bolt on setup. A longer belt than stock will be neccessary (a 6-groove 915 serpentine belt)


A reverse rotation flex fan is required and many people use the Flex-a-lite 1517. With this fan no radiator modifications are required. To use the larger 1518 requires a 1.75" spacer and moving the radiator forward. It is reported that the Hayden 3528 is the same size as the Flex-a-lite 1517.


Depending on the fan you use, you may need to modify the radiator and it's mounting. Most 4-row core radiators are too large and come too close to the fan blades. The radiator modification requires moving the top radiator host inlet from the right to the left side, and the bottom radiator outlet from left to right. (The 5.0 water pump exits out the driver's side instead of the passenger side.) Many people build custom hoses, but the procedure described above is easily done by a radiator shop for usually under $50, and very clean.

If you decide to use your old Bronco accessories, then put both engines next to one another and remove the EFI engines alternator, air pump and brackets. Remove the A/C, power steering pump and bracket and the water pump. Install the Bronco water pump, alternator, air pump power steering pump on the EFI engine.


Wiring the EFI motor is straightforward. Simply take the time to layout all the components, and make sure you consult your wiring diagram.


You will need a wiring diagram for your Bronco. Each year is a little different. It makes the wiring much simpler if you get the wiring harness from the same year and model car that you got the engine. You will also need the 5.0L wiring harness for the year of your engine. This is essential! If you don't get the wiring you must get a wiring diagram for the year of car you got the engine from.

  1. In the engine compartment, mount the canister purge solenoid. (Note that you may pick your own location.) A good place is on the passenger side of the firewall. Mount the Thermactor Air Converter (TAD) solenoid and Thermactor Air Bypass (TAB) solenoid. Mount these units as close to the canister purge solenoid as possible.
  2. Put in the EFI wiring harness in the Bronco and route across the fire wall and wheel wells.

EEC Installation

  1. You can pick your own location, but to keep the electronics out of the engine compartment heat, it is recommended that you install the computer unit under the dash, on top of the heater. to do this remove the glove box, drill a hole between the top of the heater and the bottom of the dash into the engine compartment.
  2. From the engine compartment, make an oval hole 2-1/2" by 1-1/2" for the rubber plug and wiring.
  3. Put the EEC control wiring plug and the EEC power relay through the hole and install the rubber plug (which should already be on the harness).
  4. Mount the EEC control unit to the left of hole as far as possible to make clearance for the glove box for fuse box.
  5. Plug in the EEC control unit to the wiring plug.

Wiring the EFI alternator

If you use the alternator from the EFI motor you will need to wire the alternator into the Bronco system. First remove the voltage regulator from the Bronco. Do not remove the wiring at this time. From the EFI engine you will need the fusible links. the fusible links are on the starter solenoid, there are about 4 of them.

Hook the wires up as follows:

Black w/orange wire goes to the black w/red on the Bronco.
Yellow w/white wire goes to the green fusible link on the starter solenoid.
Light green w/red goes to the Amp gauge on the dash.
Grey w/yellow wire from the heated exhaust gas oxygen sensor goes to the run position of the ignition switch.
Mount the coil on the left fender well and attach the red w/light green wire from the coil to the start side of the ignition switch.
The following wires are also in the harness, but their use is optional:
Clutch cycling pressure switch.
Air change temp sensor.
Neutral sensing switch.
Air Conditioning wide open throttle relay.
The following two are variable. Some 1988 engines with the Mass Air Sensor seem to require them, but not other engines.
Engine coolant temp sensor.
Air change temp sensor.

All red wires to the run and start side of the ignition switch. In the wiring harness there is a group of red wires tied to one common red wire that goes to the ignition switch.


Now that you have all of the engine accessories and wiring harness installed, it's time to bolt up the transmission. Using a hoist, manuever the engine into the engine bay. Early Broncos came with both standard and manual transmissions, and each has a slightly different set of requirements.

A custom speedometer cable is needed to fit the stock Bronco speedo head and the vehicle speed sensor (VSS) found on the EFI motors ($25). The VSS plugs into the transfer case. Take the gear off your old cable and put it on the VSS and fabricate a simple holding bracket.

Automatic Transmission

If you use an automatic transmission then you will probably be able to use the exhaust headers from the doner engine. Mustang headers are known to work. (The clutch linkage of the manual gets in the way.) You may find a small interference fit between two of the hood braces and the EGR valve/air conditioning service valve. A hammer will fix this. Install the space plate and then the flex plate.

There is also a compatibility problem with flywheels. The older engines have an 28.2 oz-inch imbalance, while the newer '85 (maybe '83) and newer motors have a 50 oz-inch imbalance. You must either obtain a new flex plate or have your old one rebalanced.

Manual Transmission

If the engine comes with a flywheel, check and see if it is the larger 164 tooth flywheel for an 11" long style clutch. You can reuse the old flywheel if you get it rebalanced. The new engine probably doesn't have a boss for the bellcrank bracket. You have two choices:

Create a custom bellcrank bracket. You could also use a custom hydraulic or Morris cable setup. Or
Mount the space plate and bell housing to the EFI engine, then bolt the clutch bell crank pivoting bracket to the bell housing. Compare with your old block, and mark the 5.0L engine block where the second bolt must go. Drill and tap for a 1/2" bolt.
This is difficult to explain in words, but obviously you don't want to drill in the wrong place. Make sure you get this right!

Now install the fly wheel, spacer plate and pressure plate. Then install the bell housing.


Fuel systems have progressed over the years just as the electrical systems have.

Fuel Pumps

Review this for accuracy

Ford has used several different fuel systems over the years. The early '84-'86 Mustangs used a externally mounted high pressure fuel pump as well as the '83-'87 F series pickups. For the first year of these pumps they were used alone. Later, a low-pressure "pusher" pump was added. The current system uses an in-tank high pressure pump, so if the doner is a later model you will need to obtain at least a high pressure fuel pump.

High Pressure Pump

Here are some part numbers for high pressure fuel pumps. If used alone these pumps should probably be mounted as close to the tank as possible. There are a number of people reporting success using these pumps after the selector valve, toward the engine. A good location is on the outside of the right frame rail, under the passenger side.

High Pressure Fuel Pumps
Manufacturer Part Number
Ford E4ZZ 9350B
Federal Mogal P74-028
Airtech E2000
Holley 512-101 512-101

Low Pressure ("Pusher") Pump

A low pressure "pusher" pump will ensure that your high pressure pump is well fed. They are usually rated at 5-7 psi. The Federal Mogal P4594 pump (same as the AC Delco EP247) is a rotary-vane style pump rated at 7psi and 72gph. It's not great at pulling fuel from the tanks, but if located close to the rear main tank should work fine.

Fuel Selector Valves

If you have dual tanks you will need a 6-port electric solniod valve to switch supply and return lines from each tank. A company, Pollak, makes such a valve, part #42-159 for the selector and 42-203 for the electrical connector. Although the valve is all plastic, we have had no reports of problems. The valve has 3/8" tube fittings for the supplies, and 5/16" tube fittings for the return. Pollak also makes a marine unit, part #42-159S, which is of stainless construction. Pollak can be reached at (617) 282-9550. They run about $40. NAPA also makes a valve that looks similar.

Fuel Relay Wiring

If using the Ford fuel pump (E4ZZ 9350B) you may hook up the fuel relay pump as follows: The fuel pump relay is mounted next to the EEC control unit under the dash. From the relay the pink w/black wire goes to the fuel pump on the power side. the black wire from the fuel pump goes to ground. The orange w/light blue wire goes to the brown fusible kink. the red w/black goes to the inertia switch. From the inertia switch, the red wire goes to the red group of wires. You can mount the inertia switch at a location thaty is to your liking. The tan w/light green goes to pin 22 on the EEC control unit and the EEC IV SELF TEST CONNECTOR. The fuel pump relay is located under the driver seat in the Mustang. You will need this and the inertia switch from the trunk.


On the Broncos accelerator pedal linkage rod, drill out the ball end on the rod, where the linkage through the fire wall connects, to the same size as the Mustang throttle cable. Now heat the shaft below the hole you drilled (at the dog leg) and turn it 90 degrees. Cut a "V" notch the same size as the cable so the cable will fit in the hole that you drilled. Now mount the mustang throttle cable to throttle peddle mounting bracket, squeeze the "V" notch together. Use the screws that were used to hold the rubber boot on the Mustang to mount metal plate and throttle cable to the accelerator pedal brakcet. Put the cable through the hole in the fire wall and route the cable behind the engine to the left side and put the cable on the throttle body.


You will need to install Oxygen sensor bosses in the exhaust. A good exhaust shop should have the bosses available and be able to install. On some systems the O2 sensors can tell which cylinder in that bank is running rich/lean. You should try to locate these sensors as close as possible to the stock position.

The situation of a transplanted engine in California is unclear, even to those people who live there. The best advice for someone in that state is to discuss your plans with the shop who will be performing the smog check. Note: If you bring in your vehicle from out of state, do NOT tell that you drove it into the state. This will save you about $100. (They will give you a wavier to drive it to the smog shop.) As far as is known, if you bring in a car from out of state and it passes emmissions for that year you are legal.

There are some who claim that a car/truck can pass only if the engine is one of those the model was originally produced with. Thus, a Bronco with a 302 could not be upgraded to a 351W, but a 200ci I6 could be upgraded to a 302. In the case of two very similar motors such as the 302/351W, it is likely that putting your original 302 smog equipment on a 351 will pass you as a 302. Of course with the EFI you are passing emissions for the year of the engine.

Others claim that their 302->351 Broncos have legally passed emissions. It must be taken to a referee station, where it will be inspected and a new smog identification plate added to the door frame to identify the swap and the type of equipment that should be on the vehicle. Again, the best thing is to check with your local smog station.

An interesting note for owners in California who have manual transmissions (at least on the early models). It seems that the thermactor air injection system is not needed for an automatic transmission. Therefore if you swap in an automatic you can pass smog without the TAI system. Again, check with your local emissions office.

Still others state that the emissions must only meet the newer, of either the vehicle or engine. This means that you must use the entire original exhaust system: pipes, catalytic converter, muffler, and all engine mounted smog accessories. (This might not be neccessary if you use an older block with the newer fuel system. California has recently proposed additional emission regulation. You can read a review of the new EPA Smog Check II online.

Before Starting

Check the radiator, power steering and other fluids and turn the ignition to the on position. Check for fuel leaks with each tank on line. You will have to pressurize the fuel injectors the first time. After the motor starts check for oil pressure. It should be around 45 psi at idle. Observe the temperature gauge (you did take this opportunity to install an accurate set of guages, didn't you?) and allow the motor to idle until the temperature stabilizes.

Issues Summary

You must either obtain a new flex plate or have your old one rebalanced.
Fuel Pump
Your ols mechanical fuel pump will not adequately supply an EFI. You will need an electric fuel pump.
Clutch Bracket
The EFI motors do not have a mounting hole for the clutch linkage.
HEGO location
You will have to add O2 sensors to your exhaust system.
The 5.0 water pump exits out the driver's side instead of the passenger side. You will need to modify the radiator or make up some costom hoses.
Power Steering
You will need to install new ends on the power steering hoses.
Speedometer Cable
A custom speedo cable is needed for the vehicle speed sensor (VSS)

5.8L Notes

There are a few considerations when installing the 5.8L motor. As mentioned in the accessories section, the 5.8L motor will fit if you use Mustang shorty headers, change the upper intake manifold (or use a hood scoop) and modify the smog tubes at the back of the heads. You will also need to remove the fan clutch. That's about the extent of the clearance problems you will encounter. You will also need an oil pan to fit in the Bronco.

Parts List
E8FZ 12A664 A Bar Pressure Sensor
E8ZZ 12A690 A O2 Sensor Pig Tail
F03Z 9F472 A O2 Sensor
E6AZ 9B989 C Throttle Pos. Sensor
E6DZ 11433 A Relay Assembly
E8ZZ 12A650 DB Computer
E6PZ 12286 V Coil Wire
E4ZZ 9350 B Fuel Pump.
E6ZZ 9A750 A Throttle Cable
E8SZ 6750 A Dip Stick
E6LY 18472 C Heater Hose
E7SZ 18472 A Heater hose
E5ZZ 3C11 A Support P/S Pump

Related Technical References

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