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Changing injectors on your TPI motor (Part 1 of 2)
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Changing injectors on your TPI motor (Part 2 of 2)
- Submitted by: GARY 53
Remove the passenger side plenum and set aside. IF you have a CSI (cold start injector), which will be on the driver's side, you will need to first remove the nut holding the fuel supply tube from the fuel rail (using an 18mm end wrench), then you can remove the driver's side runner.
With many SBC motors, and TPI motors with heads from .87 up, there is a tendency to have oil leakage on the manifold between the two middle manifold-to-head bolts (on both sides), usually brought on by normal shrinkage of the intake manifold gaskets over time, as well as the failure to use thread sealant on the bolts. NOW is the time to remove the centre 4 bolts (at least those 4, if not all the bolts one at a time), and coat the threads with a sealant. Then re-torque the manifold bolts, first to 25 lb/ft, then to 45 lb/ft. IF you have aluminium heads, the torque rating is lower, 25 lb/ft. I believe.
Remove the 8 injector plugs, depending on your wiring harness (I have a Painless), by pushing in on the steel clips and pulling the plug upwards. Though the TPI system is not a sequential fuel injection system, and therefore all 4 injectors on each side fire at once, I suggest marking the locations (from 1-8) of the respective plug-to-injector, which will make it easier for reassembly and routing of the wiring.
The fuel rail is the next item to remove. First remove the vacuum line that feeds the FPR (fuel pressure regulator). I have an IROC fuel rail, which exits towards the driver's side, so the following directions are applicable to that type of fuel rail, but may differ slightly for a Corvette rail that exits to the passenger side. Remove the two fuel lines that connect the fuel rail to the supply hoses. In order to do this, I had to remove the T-40 bolt that holds my alternator to the serpentine belt system, loosen the other alternator mount bolt (15mm), and by using a ?. Breaker bar, take tension off the serpentine belt, and un-loop it from the alternator, allowing the alternator to rotate clockwise towards the inner fender. This will allow the room needed to remove the fuel line hook-up to the fuel rail, using a 5/8. Flare nut wrench (DO NOT use a standard combination wrench) on the fittings and a ž. End wrench to secure the fuel rail base. There will likely be some fuel dripping so I suggest having a rag under the fittings to absorb the fuel. Route the supply lines away and behind the alternator and set aside. There is a 9/16. Nut that secures the front of the fuel rail to the block, remove it. Then, using a 10mm socket, remove the 4 bolts on the fuel rail that hold it to the manifold. You can now carefully pry up on and wiggle the fuel rail until the injectors come out of the manifold. They are a press fit, held in by O-rings, so be careful you don't.t peel an O-ring as you remove the rail. Make sure all 8 injectors have the O-rings still on them, if not, use a small pick to retrieve them from the intake manifold). Take the entire fuel rail assembly (with injectors attached) to a well-lit work area for the injector swap.
Turn the fuel rail upside down so you have the injectors facing up. Using a flat blade screwdriver, rotate the clip that holds the injector to the fuel rail to the left (clockwise) only until it reaches the flat area, then grip the injector firmly and wiggle the injector while pulling up on it. It takes a fair amount of effort to remove the injector from the fuel rail, so be aware.
Using a pair of duckbill pliers (my favourite tool), remove the clip from the old injector, and install on the new injector. Using petroleum jelly, or a good O-ring lube, lubricate the new injectors O-rings (both fuel rail side and manifold side). Then install the new injector, just as you removed the old one, taking care to make sure the retaining clip is in the correct orientation. Then again with the flat blade screwdriver, rotate the clip back to the .starting. Position. Pay extremely close attention so you do not damage or cut any of the O-rings when reassembling. Do this process with all 8 injectors and you will be ready to begin the reinstallation.
Reinstallation is much the reverse of the disassembly. There are a few tips I learned that I believe are important.
When re-seating the fuel injectors into the manifold, you must ensure they all seat .cleanly. And in fact I heard a satisfying click (well, more a snap) that is not simply accomplished by tightening down the 10mm bolts. Do this in natural sets of 2, as you will see the fuel rail has each pair of injectors near each other. Failure to do this can and will result in fuel leakage and/or vacuum leaks.
Make sure you are re-routing everything such as the injector plugs very cleanly, and ensure no wires can be pinched.
Take the time while the fuel rail is off to clean all oil and dirt off the intake manifold using a lint free rag with brake cleaner.
Put the new Felpro (or equivalent) gasket sets on AFTER you do the clean-up of the manifold areas.
I strongly suggest you test the O-ring seals prior to putting the runners on. Accomplish this by hooking up the fuel rails and its. Supply and return lines, hooking the battery backup, and pressurizing the fuel rails by turning on the ignition switch for a few seconds. Then very carefully smell and visually search for leaks. This step is CRITICAL, for not only time saving if you do have a leak, but for your SAFETY and well-being. Don.t forget to unhook the battery again after pressure checking the injector seals.
I don't. recommend using air tools on reassembly except to run the bolts down, but not to tighten the bolts. The plenum is aluminium and can and will strip threads easily.
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