This page will detail the removal and installation of accessory brackets, serpentine belt, fuel lines, fuel pump and the throttle cable.
3. Pulleys and Serpentine Belt 7. System Check, Start Engine and Set Timing
Remove the AC compressor and carefully set it aside, securing it to something solid. Remove the idler pulley to gain access to one of the three bolts holding the original bracket on. Also remove the lower radiator hose. To install the new bracket, you will reuse on short bolt and the long stud, but will have to supply a medium length bolt. In picture below, you can see the arrangement of the bracket bolts as they need to be installed. Install the bracket and re-install the AC compressor. Before installing the compressor, be sure to unbolt the small 10mm bolt holding the dipstick in place and pull the dipstick/housing up so that it will clear the compressor. You will have to give the tube a slight bend upward, but not enough to affect removal or reinsertion of the dipstick. Note: the original compressor bolts will not work with the new bracket. I had to "borrow" the bolts from the GTA to complete this swap. The correct compressor bolts did not come with the new bracket and pulley set, and I am not sure where to get these bolts. If you are planning this swap, think ahead and get these bolts prior to starting.
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Do not attempt to change out this bracket without first getting a good power steering pump pulley puller. I rented a nice piece from my local Autozone. It was free, with a $40 deposit. The parts sitting outside the box are the ones I used to pull and re-install the pulley. After the pulley is off, remove the three bolts holding the pump to the bracket, and the rear bracket where it attaches at the exhaust manifold/header. Once these are loose, you can gain access to one of the bracket bolts, otherwise inaccessible. Remove the bracket and the rear pump bracket (which is held on with two 15 mm nuts). Reuse the existing bolts and stud in the same locations. Install one bolt at the lower left (facing the vehicle) to hold the pump to the new bracket. Install the bracket on the top left stud. This will allow the pump to hang aside slightly for better access to the top right bolt. Install the stud nut and two bolts holding the bracket in place. Then complete the bolts that hold the pump to the bracket. Re-install the power steering pump pulley and alternator. NOTE: I learned this the hard way, but before installing the bracket, think about how the fuel lines will be run (see below). I ended up re-using the fuel line extensions from the GTA, and they must be installed before the bracket.
3. Pulleys and Serpentine Belt:
After I installed the AC bracket, it appeared that I could get away with leaving the original alternator/power steering pump bracket in place. But I soon noticed that the pulley projection between the new AC bracket and TBI pulleys/brackets was about 1/8" more. Therefore, I had to install both new brackets as well as the pulleys. I used the same belt routing pattern (using the dashed line below), by measuring the new length with the pulley tensioner in its tensioned position. This was easy to do using a flexible measuring tape (such as one used to measure for clothing). My length measured 95 3/8" (95.375"). The belts are measured in meters, so multiply the inches by 0.0254. The closet belt measured 2.425 meters, but was too tight. The next size up was 2.440 meters, or 96.06". This extra length (approx. 11/16") was just barely within the tensioner range, but was acceptable. NOTE: Be sure to torque the harmonic balancer bolt to specification after you install the belt. I prefer to wait until all the spark plugs are in installed an the belt installed to help hold the crank from turning when tightening the bolt. In previous pictures, you can see that I taped a note on the plenum as a reminder that it was not torqued.
4. Throttle & Cruise Control Cable:
To make this swap, I had to change the throttle cable to a TPI style end. The TPI end has a cylinder crimped on it, whereas the TBI end is more like a traditional carb that slips over a pin and is retained with a clip. The new cable has the same interior style end, but the firewall opening is different and the cable must enter the cab either angled up or down. Although the original cable was level, I installed the new cable angled up inside, for it presented less "bending" issues. I simply used a Dremel tool with a cutting wheel to oversize the opening. I made it a little too loose so I also had to install a couple of small sheet metal screws to hold it tight to the firewall. If you have to do this, be sure to pre-drill the firewall and oversize drill the cable flange. You would not want to split or crack it. When the new cable was installed, it was too tight and prevented the throttle from fully closing (about 1 1/4"). To fix this problem, I fabricated an extension to go between the throttle cable and throttle pedal. This worked out great. I built in some adjustment and set the tension and lock nut to the WOT. Since the extension has a section of rod and no nut behind the pedal rod, it has some free play for a natural feel. TIP: To get out the old cable, use an adjustable crescent wrench. Adjust it so that it will slip over and squeeze the lock tabs as you push on the cable housing. It will pop right out in no time.
In order to install the factory Suburban cruise control cable, I had to cut off the original press-in fitting and install a smaller fitting. I used parts left over from when I installed a universal Audiovox cruise control system on my 1981 Camaro. Be very careful if cutting so that you do not damage the cable itself. As you can see in the pictures below, I also installed a polished air-foil and TB cover plate from S&P.
I originally planned on installing two AN fittings directly to the stock TPI fuel rail ends (see first two pictures). But I soon realized that without getting some 90* or 120* fittings, etc., this was more complicated than it needed to be. So I pulled the fuel line extensions and bracket off the GTA. Be sure to install these before the power steering pump/alternator bracket. For my swap, I reused the high pressure, socketless fuel lines that came with the Edelbrock MPFI conversion kit. I do not have a great deal of detail here, but reworking these fuel lines would be a matter of planning ahead and getting the right fittings. For instance, the same AN fittings that I planned on installing at the fuel rails will also fit at the ends of the fuel line extensions. The fuel filter part number that fits the GTA is identical for the Suburban. Therefore, I will reuse the stock filter and not concern myself with the fuel pressure differences between the TBI and TPI. If it works on the GTA, it should be fine with the TPI conversion on the Suburban.
I do not have any fuel pump conversion pictures because it was already completed when I converted the TBI to the Edelbrock MPFI system. I will say this, for the 94' Suburban, a stock replacement in-tank fuel pump and sock for a 91' Pontiac Trans-Am GTA (5.7) will swap out with zero issues. From the exterior, the pumps are nearly identical, including the plug. The only thing to consider is using the short length of high pressure hose and metal clamps that comes with the new GTA pump. Never take the time to drop the tank and not install a new pickup sock. In fact, you will have to get a new sock to preserve and warranty that comes with the pump. Updated since original conversion: The truck died when going down the interstate. I knew that I had a fuel pressure problem when the pressure would not come up above 10-15 psi, even when crimping the return fuel line. I dropped the tank to find out that I apparently reinstalled the low pressure hose by mistake (NOT GOOD!) The hose split releasing pressure. I originally installed a Carquest pump, but had purchased a new AC Delco unit with strainer prior to dropping the tank, in anticipation that the maybe pump went bad. I decided to install the new AC Delco pump, strainer and hose, since I had already dropped the tank. Well, this time I took pictures. Never try to do this without a helper (lol). You can drop the tank under the Suburban without using jack stands. Drain as much gas out that you can. Remove the filler neck connection hose and loosen the larger vent hose. Position the a floor jack under the tank in a centered location. Support the tank and then loosen the strap bolts. Slowly lower the tank and let it drop to the driver's side. Disconnect the supply line, return line and small vent line. Slide the tank out from under the truck. Use compressed air and paper towels with a degreaser to thoroughly clean the top before remove the lock ring. Remove the sending unit and pump assembly. Change out the pump using the new rubber bushing (bottom of pump), new HIGH PRESSURE hose, clamps and strainer. Put a little grease on the new O-ring and re-install the unit and ring. Re-install the tank in the reverse order. Fill it with 5 gallons to test the pump before filling the tank with too much gas.
7. System Check, Start Engine and Set Timing:
After double checking all my harness and hose connections, I turned the key to the "on" position a couple of times to prime the fuel system. The engine started immediately. I soon noticed a slight issue with the idle, as it seemed to be searching up and down, almost like a vacuum leak. But according to S&P, this is normal when a computer chip is first installed as it will take the computer up to 10 starts to "learn", and will still be "learning" up to 85 starts. After it warmed up, I set the initial timing to 4* BTDC, and eventually set it at 6* BTDC. As with the TBI or any other TPI system, set the initial timing by disconnecting the EST plug. The procedure is to disconnect the bypass, start the engine, set the base timing, shut the engine off and reconnect the bypass, then restart the engine. Once it is set, tighten the distributor hold-down clamp, and check the timing with the bypass connected. It should be approximately 14* to 16* BTDC. Test drive the vehicle and check for shifting characteristics. Mine seems fine, so I would assume that if there were any issues with the 4L60E jumpers that I spliced, it would be apparent immediately.
TROUBLESHOOTING:
Check Engine Light: I quickly noticed that the original computer "check engine" light is on full-time now. This is because of all the original TBI engine harness connections that are not being used with the TPI swap. I will have to either disconnect the light or have the original chip returned to eliminate this problem.
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