Fuel Injector Replacement Guide For 91 Zr-1 Models

To replace the fuel injectors of a 91 ZR-1, you will need to relieve the fuel system pressure by removing the fuel pump fuse and running the vehicle until the engine stalls. Disconnect the negative battery cable and remove the upper intake manifold. Disconnect the fuel injector electrical connectors and the fuel lines from the fuel rail. Pull the fuel rail straight up and out of the intake manifold, and inspect the condition of the fuel line sealing O-rings. Remove the retaining clip by sliding it off the fuel rail using a flathead screwdriver, and pull the fuel injector straight out. When reinstalling the new fuel injectors, ensure that the retaining clips are properly seated. Align the square slot with the tab on the injector and press the fuel rail with the injectors into the intake manifold until fully seated. Finally, install the fuel rail fasteners and tighten them.

You can purchase fuel injectors from various online stores such as Summit Racing, Southbay Fuel Injectors, and Pelican Parts. It is recommended to use Accel injectors with the part number 150821 from Summit Racing. These injectors require grinding off a plastic nub on the injector's connector for the secondary injector to snap in place properly.

Fuel Injector Types and Their Characteristics

There are four basic types of fuel injection systems: single-point fuel injection, multi-point fuel injection, sequential fuel injection, and direct fuel injection. Each type has its own unique characteristics and offers different advantages and disadvantages in terms of performance, fuel efficiency, and cost.

Single-Point Fuel Injection

Single-point fuel injection, also known as throttle-body injection (TBI), is the oldest and simplest form of fuel injection. It replaces the carburettor with one or two fuel injector nozzles in the throttle body, which supply fuel to all the cylinders simultaneously. While it offers better control than a carburettor, it can cause a slight decrease in performance at high RPMs and fuel wastage due to condensation outside the intake manifold.

Multi-Point Fuel Injection

Multi-point fuel injection (MPFI) or port injection provides each cylinder with its own injector located outside the intake port. This ensures a more precise volume of fuel for each cylinder, reducing the possibility of fuel condensation. MPFI offers improved performance and lower fuel wastage compared to TBI. However, the fuel may idle in the engine and port, and it may not sync perfectly with the rotation of the pistons.

Sequential Fuel Injection

Sequential fuel injection eliminates the disadvantage of MPFI by triggering each injector independently, ensuring that fuel is injected only when the intake valve of the cylinder opens. This system is the most widely used today due to its effectiveness and efficiency.

Direct Fuel Injection

Direct fuel injection bypasses the intake valve or manifold and injects fuel directly into the cylinder, maximising fuel economy. This type of injection system is commonly found in diesel engines but is also used in petrol engines, where it is known as GDI (gasoline direct injection).

Other Injector Types and Characteristics

In addition to the four main types, there are other variations and characteristics of fuel injectors:

• GDI (Gasoline Direct Injection)
• SDI (Semi-direct injection)
• FSI (Fuel Stratified Injection)
• SCI (Smart Charge Injection)
• HPI (High Precision Injection)
• JTS (Jet Thrust Stoichiometric)
• IDE (Injection Direct Essence)
• E-Tec (Evinrude, Ski-Doo, Sea-Doo)
• Semi-direct injection
• Optimax Air Injector

Fuel Injector Replacement Process

Step 1: Prepare for the Replacement

Before starting, disconnect the battery and let the engine cool down. Wear gloves and eye protection, and keep a fire extinguisher within reach. Relieve the fuel pressure to prevent unexpected fuel spray. Work in a clean area to prevent dirt and debris from contaminating the fuel system.

Step 2: Access the Fuel Injectors

Remove any parts that interfere with injector removal, such as the air filter box, intake plenum, engine covers, and wiring harnesses. Refer to your vehicle manual for specific instructions.

Step 3: Detach the Fuel Rail and Remove the Injectors

Disconnect the fuel rail if required, or unfasten and move it if possible. Gently wiggle and pull the affected injector out of its mounting location. The injector may come out with the rail, or you may need to wiggle the rail free from the injector.

Step 4: Inspect and Clean

Check the injector ports for debris and clean if necessary to ensure proper sealing of the new injector.

Step 5: Install New Injectors

Lubricate the new fuel injector O-rings with clean engine oil, then install them. Reattach the fuel rail afterward. Reinstall and connect any electrical items or parts that you removed during disassembly, ensuring each part is fully seated and secured.

Step 6: Post-Replacement Checks

After installing the new fuel injectors, run the engine and inspect for leaks from the fuel system. If the car doesn't start right away, allow it to crank for a few seconds to pressurize the system. Check that any fuses and relays are installed and working.

Fuel Injector Troubleshooting

Fuel injectors are designed to spray fuel in a fine mist to mix with passing air as it heads into the combustion chamber. They are crucial to your vehicle's performance and longevity. When they fail, it can lead to a cascade of performance issues, increased emissions issues, and even engine damage.

Common Fuel Injector Problems

• Clogged Fuel Injectors: Fuel residue can get stuck inside the injector or its filter basket, causing a full clog. This will require the injector to be removed from the vehicle and professionally cleaned.
• Dirty Fuel Injectors: Dirty fuel injectors will affect the flow rate of the fuel, which can result in poor idling, stalling, hard starting or sputtering, reducing your car's ability to accelerate effectively.
• Leaking Fuel Injectors: Externally leaking injectors pose a fire risk and need to be completely replaced.

Common Causes of Fuel Injector Failure

• Fuel impurities: Dirt, water, and debris can clog or damage injectors over time.
• Low-quality fuel: Fuels that do not meet industry standards can lead to the buildup of deposits within the injectors, affecting their ability to deliver fuel properly.
• Constant stress and high pressure: Over time, the internal components of the injectors can wear out, leading to a gradual decline in performance and eventual failure.
• Inadequate cooling: Coolant temperatures over 480ºF and exhaust gas temperatures over 1200ºF can cause injector components to expand and warp.

Common Symptoms of Fuel Injector Failure

• Poor Engine Performance: You may experience a noticeable decrease in power, acceleration, and overall engine responsiveness.
• Increased Fuel Consumption: Faulty injectors can cause an imbalance in the fuel-air mixture, leading to incomplete combustion and higher fuel usage.
• Long cranking or no-start condition: Weak or failed injectors often result in long cranking or a no-start condition due to poor combustion efficiency.
• Rough idling or misfire: If the injectors are not delivering fuel evenly, the engine may run unevenly, leading to a rough or shaky idle.
• Smoke and Increased Emissions: Excessive smoke from the exhaust is another common sign of injector failure. If the injectors are delivering too much or too little fuel, it can result in incomplete combustion, producing black, white, or blue-ish smoke.

Troubleshooting Steps

• Visual Inspection: Look for signs of physical damage, leaks, or corrosion. Check the condition of the fuel filters, as clogged filters can contribute to symptoms of a failed injector.
• Listen to Your Engine: Abnormal noises, such as clicking or knocking sounds, can indicate problems with the injectors or their components.
• Scan for Diagnostic Trouble Codes (DTCs): Use a scan tool to check for any DTCs related to the fuel system, which can help pinpoint specific injector issues.
• Fuel System Test: Measure fuel pressure, flow rates, and injector performance using gauges, observe spray patterns, and take fuel volume measurements.

Fuel Injector Maintenance and Care

Fuel injectors are crucial for your engine to work. They take the gasoline pumped from the intake and spray it into the engine using a fixed or electrical aperture, turning the gas into a fine mist that is easier to ignite. Fuel injector maintenance is as important as maintaining any other part of your vehicle. A clean fuel injection system ensures engine reliability, longevity, and proper performance.

Fuel Injector Cleaning

There are three main ways to clean your fuel injectors:

• Using detergents in the gasoline itself.
• Adding bottles of fuel-injector cleaner to your gas tank.
• Getting your fuel injectors cleaned by a mechanic.

Detergents in the Gasoline

This is the easiest way to keep your fuel injectors clean. Although detergent additives have been federally required for some time, the quantity of detergent can differ by brand. Look for gasolines rated as Top Tier, which have two to three times as much detergent as federally required. Some manufacturers specifically recommend using Top Tier gasoline, so check your owner's manual for guidance.

Bottles of Fuel-Injector Cleaner

If you don't always use Top Tier gas, you can buy a fuel-injector cleaning additive and pour it into your tank before filling up. There are numerous brands on the market for around $5 to $15 per bottle. Be sure to read the instructions, as some cleaners can be used at every fill-up, while others recommend less frequent use. Also, check your owner's manual to see if the manufacturer recommends against using any gasoline additives.

Cleaning Done by Professionals

If good gasoline and additives don't fix a running problem, or if you don't want to take the risk of using an additive, you may need to have your fuel injectors cleaned by a mechanic. This can be done with the injectors still on the engine or after removing them, but the former is usually less expensive. Expect to pay around $150 to $300 for this service.

When to Clean Your Fuel Injectors

It is generally recommended to clean your fuel injectors every 15,000 miles or every 30,000 miles, depending on your vehicle and how often you drive. However, if you start to experience issues like rough idling, stalling, misfires, sputtering, or poor acceleration, it's time to clean your injectors. These symptoms often occur in cars that haven't been driven for a while or are only run occasionally.

Other Fuel Injector Maintenance Tips

• Always use quality brand names when filling your tank with fuel.
• If you're storing your vehicle or gasoline-based equipment for extended periods, use a good quality fuel stabilizer.
• For marine or watercraft fuel injection systems, clean your injectors every six months or at least before the start of each season.

Fuel Injector Costs and Where to Buy Them

The cost of replacing a fuel injector can vary depending on the type of vehicle, the brand of the fuel injector, and the location of the repair. The replacement cost typically ranges from $300 to $900, with parts and labor costing between $150 and $400. Luxury vehicles can cost up to $2500 for fuel injector replacement.

Fuel injectors are electrical components that deliver fuel to the engine's cylinders, where it is burned to generate power. Each cylinder in an engine has a fuel injector, so the number of injectors depends on the engine's configuration (e.g., four, six, or eight cylinders).

You can purchase fuel injectors from various online retailers and auto part stores. One option is to buy them directly from the vehicle manufacturer (OEM parts), which tend to be more expensive but often have similar performance and lifespan to aftermarket or refurbished options. Here are some places to consider:

• CarParts.com: They offer a wide range of fuel injectors and provide a convenient vehicle selection tool to ensure you get the right fit.
• Summit Racing: They offer Accel fuel injectors suitable for ZR-1 vehicles.
• Jerry's Gaskets: They can provide new FIC (Fuel Injection Connection) stainless steel injectors and the necessary gaskets.
• FIC: They sell stainless steel injectors and offer a Viton gasket set.
• Atlantic Speed Performance Parts: They offer Accel fuel injectors at competitive prices and include a free t-shirt with your order.

It is worth noting that regular maintenance and cleaning of fuel injectors can help extend their lifespan. Cleaning kits, fuel additives, and professional mechanic services are some ways to maintain fuel injectors properly.

Frequently asked questions