from the editors of:
GM High Tech Performance
LOG IN / SIGN UP
GET THE MAGAZINE
tech & how to
engines & drivetrain
Chassis & Suspension
paint & body
Best of the Best
GM High Tech Performance
How to Change Your Fuel Injector - Got Fuel?
We Inject More Fuel Handling Capacity Into An '87 C4
Jun 14, 2007
View Full Article »
VIEW FULL GALLERY
How to Change Your Fuel Injector - Got Fuel?
The parts collection for this project is from the Mid America catalog. Included are a set of eight new Accel high-performance injectors, a new fuel-pressure regulator, and a new diaphragm that should certainly be changed at the same time, new gaskets for the runner-to-plenum junction, a fuel pressure regulator for "before" and "after" readings, a new fuel filter, and a can of Red Line fuel system treatment. We also purchased an o-ring kit from our local Chevrolet dealer.
Before starting we wanted to have baseline fuel-pressure readings. This is the Schraeder valve to tap for our fuel-pressure gauge.
When checking fuel pressure, factory specs call for readings of 40.5-47.0 psi with ignition key on and engine off. Our reading was right in line at 43.0 psi. With key on and engine running, factory specs call for 3-10 psi lower than engine off readings. We found 36 psi, which was right in line at 7 psi below engine off readings. So we knew we had a good starting point.
Next step was removal of the clamps holding the inlet tube for the Mass Air Flow (MAF) sensor.
Then we lifted out the MAF sensor assembly.
We were careful to disconnect the wiring going to the MAF air flow sensor.
Next step is disconnecting the throttle linkage, including the cruise control connector as well as the throttle valve (TV) cable that was routed underneath the plenum of our '87.
We also removed the one intake runner bolt that holds the cable stay for the throttle and cruise-control cables.
When disconnecting the power brake booster vacuum line from the rear of the plenum it's best to use a 51/48-inch flare nut (line) wrench while holding the mating fitting with a 31/48-inch wrench.
Remove the four bolts that hold the throttle body to the plenum.
Two coolant hoses must be removed from the throttle body before you can lift it out. We had previously disconnected those hoses during an earlier modification. Their former locations are capped with a blue and a black plastic cap.
Note the different length of the lower runner bolts so you can be sure to reinstall them in the proper position.
With the upper (4) and lower (all 6) plenum bolts removed, you can carefully pry the top of the righthand runner assembly away from the plenum.
Likewise, you can then carefully pry the bottom of the righthand runner assembly away from the intake manifold.
The lefthand (driver-side) lower runner bolts are tough to access, so we chose to leave them untouched and only remove the upper runner-to-plenum bolts and the plenum, while leaving the lefthand runner assembly in place.
As we lifted off the plenum, we were sure to unplug the air temperature sender connector from the underside of the plenum.
Here's the right-side sixth runner-to-manifold bolt, shown with the plenum and runners removed. You'll have to use care and patience when removing it with the plenum and runners still installed.
Two fuel lines to the fuel rail and their retaining bracket must be disconnected before you can lift out the fuel-rail assembly. Be careful when loosening these lines since the fuel can be under significant pressure. Use caution and eye protection, and loosen them a little at a time until the pressure has been relieved. Use a 51/48-inch flare (line) wrench and a 31/44-inch open end to break loose the fittings. Two T40 Torx bolts hold the fuel line bracket to the intake manifold, and must be removed to allow you to lift out the fuel-rail assembly.
Carefully remove the vacuum line from the fuel-pressure regulator.
These tuned port injection engines use a "9th injector" bolted to the left-side runner assembly for cold start enrichment. GM refers to this injector as a "cold start valve," and it is no longer available. So we left this 9th injector in place and disconnected the feed line in order to allow us to remove the injector rail.
With the plenum and both side runners removed, disconnect the electrical connectors at each injector by pressing in on the retaining tang. While the locations for the connectors are intuitive, they are also critical, so it's worth a few minutes to label each connector in order to be sure you reassemble it into the proper location.
With the removal of the four bolts holding the fuel rail in place, you can now lift out the fuel rail/injector assembly. Note that the driver-side runner assembly has been removed to allow for a clearer photo. At this point, we now prepare for the actual disassembly of the fuel-rail injector assembly.
Small quarter-turn retainers hold each injector in place. The injector on the left shows the retainer in the disengaged position; the injector on the right shows the retainer turned to the engaged position.
Careful use of a screwdriver will rotate and disengage the retainer.
With the retainer disengaged, you can now lift out the injector. you'll have to tug slightly in order to overcome the friction of the o-ring that seals it in place.
At this point it makes sense to continue with full disassembly of the fuel rail assembly in order to replace the various o-rings that keep the fuel where it belongs.
During the disassembly process it is helpful to rotate the arms of the fuel-rail assembly in order to provide improved access to the bolts that hold it together.
During disassembly, the o-rings may come out with the fuel transfer tubes, or they may stay hidden within their fitting.
Careful use of a dental pick or other similar tool will help remove o-rings from their recess, but be especially careful not to nick or damage any of the sealing surfaces.
This photo shows the location of the o-rings on the fuel regulator block.
Here, you can see the relative locations of all the various components that make up the fuel-rail assembly.
We had to buy an o-ring kit for the fuel-rail assembly from our local Chevrolet dealer (PN 17111696). Twenty-seven bucks for nine little o-rings-at that price they ought to last forever!
Note the orientation of the retaining bracket to the fuel feed line.
The new o-rings will be a snug fit as they go together, so use a little Vaseline or other compatible lubricant to facilitate reassembly.
Now we proceed to the installation of the adjustable fuel-pressure regulator cover. It does not come with a new diaphragm, which must be ordered separately. However, the regulator cover does come with a metal disc that must be placed between the adjusting bolt and the diaphragm spring.
The original fuel-pressure regulator cover is held in place with special anti-tamper TT10 Torx screws that have a raised nub in the center in order to prevent access with a standard T10 Torx socket. However, the new adjustable fuel-pressure regulator cover does come with the necessary special Torx socket to do the job.
Note that the original fuel-pressure regulator cover included a retainer ring to evenly distribute the tightening load to ensure even compression and sealing of the diaphragm. The new adjustable cover incorporates a thicker flange that makes the retainer ring unnecessary; in fact, the new cover has a longer nipple for the vacuum line, making it impossible to fit the retaining ring to the new cover. During the install, we found that this nipple, which threads into the regulator cover, was only hand tight; we had to snug it up during assembly.
Here is the metal disc that provides for even distribution of the pressure of the adjusting screw across the new diaphragm spring.
We found that a small dab of Vaseline helped hold the disc in place during reassembly.
As we prepare for installation of the new injectors, we noted the different overall length of the new injectors in order to determine the correct groove for locating the injector locating ring. No instructions were included with the new injectors. A few helpful hints would have made the installation faster, easier, and less stressful.
Dirt is a major enemy of fuel-injection systems, especially because of the fine orifices throughout the system. any debris in the fuel system is a likely cause of a future leak, which is not a good thing on the hot engine of a plastic car, so be sure to clean all related parts and areas carefully with lint-free cloths.
Steady, even pressure is needed to squeeze the new injector into place, overcoming the friction of the new o-ring.
Freshly rebuilt, the fuel-rail assembly is lowered back into place to start the reassembly process.
To ensure that no debris contaminates our new fuel-system components, we replaced the fuel filter, which hides above the right front framerail, partially obscured by our previously installed cross-frame stiffener. We had to remove the bolts and the heat shield that protects the filter and lines from the heat generated by the catalytic converter.
you'll also need to adjust the newly installed fuel-pressure regulator. Recommended spec is 40.5-47 psi with key on, pump running, and vacuum line disconnected.
4.8L VS 5.3L Engine - Tech - Little LS Slugfest - Super Chevy Magazine
Most people look past the small 4.8L engine and go straight for the bigger ones. In this Little LS Slugfest, we compare both stock and modified versions of the 4.8L and 5.3L engines, now you be the judge!
Building a 700 Horsepower 454 On a Budget - Super Chevy Magazine
We take a junkyard 454 shortblock, and without taking it apart bolt on a new top end and other parts to make 700 horsepower for less than 2500 dollars - Super Chevy Magazine
Street Heat - Readers' Rides - August 2014
This month's Street Heat features our readers' rides including a 1987 Monte Carlo, 1997 GMC Sonoma, a 1998 Pontiac Firebird, and more!
Setting Idle Mixture The Right Way
Hey, how tough can it be? Just turn the screw and youre done, right? Theres a lot more to learn about setting idle mixture than just turning a couple of screws