Starting from the plug end, put the following together:
- 5/8ths spark plug socket with integral u-joint
- one-inch extension
- a second u-joint
- 12-18 in long extension
- socket wrench or T-handle

Drop the socket into the #8 plug hole until it engages the plug then remove the plug just like the other seven.

Tip #2: Clutch Safety Switch Bypass

You can jumper out the clutch safety switch to fix the problem of your ZR-1 not starting sometimes. Jumper out the clutch safety switch at the connector below the dash with a female spade clip jumper.

Tip #3: Alternator

You can save some money having your alternator rebuilt rather then buying a new one from GM which is rebuilt anyway.

Tip #4: Thermostat Replacement

The thermostat is behind the lower part of the radiator on the passenger side. It's easier to jack up the car and remove the right front wheel. The job would be easy except there's a bracket attached to a frame cross member that goes to the housing, so you also have to remove that to get the thermostat out. I used a crowfoot wrench to get one of those bracket bolts out. The taper side side of the thermostat goes toward the radiator. To get the thermostat centered start the bolts to the housing. Taking the short piece of hose off the housing that goes to the radiator helps. Then reattach the bracket to the frame later after you check for leaks.

Tip #5: RC Fuel Injectors

What are the part numbers for the LT5 injectors? Injector type: SAT 12.5. Injector make: Lucas. STDF (flow) 205 CC. You need 8 Primary and 8 Secondary, the difference between the 2 sets is you specify the flange to be grounded off, that is on the 375 hp. motor, it doesn't apply to the late model with the 405 hp.

Tip #6: Changing Fuel Filter

To depressurize the fuel system look for the cap on the end of the fuel rail on the passenger side. Use a can or bottle, remove the cap and push in the valve to release the fuel into the can/bottle.

Tip #7: Air Duct Collapse

You can use galvanized 5/16 wire to reinforce the air duct to keep it from collapsing.

Tip #8: Installing Serpentine Belt

When snaking the serpentine belt around everything, you have to ease it BEHIND the water pump pulley. That gives you enough room to slip it over the alternator pulley. Then you kind a, squeeze a hand down there, kind a twist a bit, gunt and groan, swear at the water hoses, kick your dog, but eventually, you can slip the belt over the water pump pulley.

Tip #9: Defeating the 1 to 4 shifting

There are a few ways to defeat the 1 to 4 shifting.

1. Disconnect the molex connector under the ZR-1 next to the transmission on the drivers side.
2. Look at Service Manual 8A-201-25 figure 52; then unplug "2nd and 3rd gear blockout relay" (CAGS relay). The relay is behind the battery.
3. Most of the after market performance chips with disconnect this feature.

Tip #10: Broken or messed up nut or bolt head.

If you somehow screwed up a bolt head or nut and your socket won't work anymore try a socket one size smaller and hammer it onto the bolt or nut. You should then be able to remove the bolt or nut.

Tip #11: Checking bad shocks.

If you have more than 30,000 miles on your shocks, they may be worn out. Go to the front shocks, remove the wire retainer at the top and pull the DC motor off. If you see oil inside the cup, the shock's bad, and also if you see ALOT of oil on the sides.

Tip #12: Removing primary injectors.

Use a large flat bladed screw driver, 3/8" wide tip. Using the Injector Housing as a fulcrum place the screw driver tip under the connector base on the injector and pried up on the injector at the same time pressing the injector firmly in to the screw driver. By pressing the injector in to the screw driver while prying up is important to keep the injector from cocking in the Injector Housing bore.

Tip #13: Repairing bad Fuel Pumps.

The ZR-1 uses two fuel pumps, a primary and a secondary. If one goes bad then you have to replace the whole assembly at a cost of around $1400. Instead you can replace the individual bad fuel pump for a cost of around $72. The '96 Suburban with the 454 engine uses the same fuel pump and is a direct replacement. GM part number is 25163473.

Tip #14: 1990 - 92 Oil Pump Replacement

The 1990-92 oil pump part number 10135871 and pump seal part number 10067512 has been discontinued from GM. Some people have used the 1993-95 oil pumps part number 10187763 by swapping the gear set from the new pump assembly into the old pump assembly. However note that the new oil pumps use the same oil seal which has been discontinued so do not damage the old seal.

Tip #15: Testing leaking fuel injectors

One test you can try if you think you have leaking fuel injectors is to simply remove all of the spark plugs and turn the ignition switch to the "on" position (which will cause the fuel pumps do come on and pressurize the fuel system).

Then wait for a few minutes and smell inside each spark plug hole- if you have injectors leaking you will smell the fuel inside the cylinder.

Tip #16: Changing Master Cylinder

Changing out the master is not a big deal really. The rod is just clipped in the clutch pedal and pops right off. Removing the actual master is a no brainer, however, you can do it the hard way or the easy way. The hard way is to get all kinds of universals and work your way down to the nuts that hold it on. Or, you simply remove the battery and everything is right there and it takes about three minutes to get the nuts off. Your choice.

As far as bleeding the slave just read the manual. In there is says you turn it upside down and stand on your head and point to the north star OR you can get the vast majority of air out by simply pumping the clutch pedal.

Tip #17: Engine oil life Monitor

To reset the oil life monitor:

A. Turn the key to the "ON" position, but don't start the engine.

B. Press the "ENG MET" button on the trip monitor and release. Then, within five seconds, press and release the "ENG MET" button again.

C. Within five seconds of Step 2, press and hold the "RANGE" button on the trip monitor. The "CHANGE OIL" light will flash.

D. Hold the "RANGE" button until the "CHANGE OIL" light stops flashing and goes out. When the light goes out, the engine oil life monitor is reset. This should take about ten seconds. If it doesn't reset, turn ignition "OFF" and repeat the procedure.

Tip #18: Replace your thermostat

One of my members starting testing every thermostat that he removed during the course of servicing by testing the used one against a new thermostat in hot water and comparing them. After testing about ten thermostats he found that every one would open 5 to 15 degrees late. Then when open, they would only open from 80 to 95%. After making these observations he started to install a new GM thermostat every time he encounter one that is over 2 years old. The owners' of the cars almost always commented that they notice that the engine was running cooler with a new thermostat.

Tip #19: Vetronix TECH1 or a Mastertech scan tester

This difficulty will be specific to 94 and 95s only.

If you attempt to use a Vetronix TECH1 or a Mastertech scan tester with the dedicated OBD II 16-pin connector (used on 96 or later cars) to command the SRC controller to flash codes via the "Service Ride Control" light or to clear codes in the SRC controller, you may find neither function works in-spite of the tester manual and the service manual saying a tester can be used for that purpose.

The problem stems from the fact that 94 and 95 ZR1s, while having the 16-pin connector, did not use the the OBD II standard pin layout.

To enable the T1's or Mastertech's SRC functions you need to use the old style 12-pin connector on the end of the tester cable and fit that with the 12/16p "non-OBD II" adapter (Vetronix PN 02001575). Connect the T1/MT cable in that configuration to the car's DLC and the SRC functions work properly.

Tip #20: 1990 Slave Cylinder

GM had a strange factory procedure to install the slave cylinder on '90 ZR-1's. Because the bleeder valve was positioned very close to the floor they used an aluminum bleeder valve and then purposely broke it off to make it shorter, thus clearing the floor. They discontinued the supply of the replacement bleeders when they specified the '91 - '96 (PN 12509313) slave cylinder as a replacement for the 90's. The bleeder is on the bottom of new part. It's harder to bleed but it doesn't have the floor clearance problem.

The '91 bleeding procedure is to let it hang by the hose and turn it upside down. Gravity bleeding usually works okay.

Note that when you go to re-install the slave, about two oz. of fluid will backup into the master cylinder. It's advised to lower the level in the master before installing the slave cylinder on the bell housing. This will avoid a fluid spill.

Tip #21: Headlight motor acetal (Derlin) bushings

I went to ZR1.net and found an article on headlight repair by Juan Sepulveda which indicated that the bushings were available at Mid-America. I went there and found that they were approximately $5 with approximately $20 shipping. I have two 1990 ZR1's so I needed 4 which would amount to about $40. The big catch was that I wanted it now so I racked my brain and remembered a plastics place on 190th and Vermont in Torrance CA and knew that they had Teflon there. I figured that would probably work. I went there and they told me that Derlin was Dupont's trademark for Acetal so I bought a 33 inch long rod at 7/16 diameter for a little over $3. I was so happy that I gave them $5. I checked the depth and found that it was .4805 in. and ended up cutting them and sanding to around .465 in. If someone has a unused one and wants to get the real value on a micrometer and send it to me, I will be happy to add it to this article. The headlight motor now works fine. I hear that the delrin bushings are way stronger than the factory nylon and should last forever. Jim Blanchard

Tip #22: Heater Core Replacement

Followed the Helms manual to remove the dash but two things came up worth passing along. One is that there is a plastic duct going across the front of the heater box with a snap on short duct going into the heater box. This duct goes on behind the main console which I had no intention of dismantling. I was tempted to cut the duct by the console and get a rubber tube to reconnect it later but restrained myself from doing this due to the many years (since 1980) of NCRS training. So I unbolted the heater box and pulled it out from behind the duct while pulling out on the duct. This separated the snap on duct that I did not know was there. Next time I will separate it first. The other thing to mention is that there are two rivets that look weird and not like rivets. These I pried up with a screwdriver. Even if I knew they were rivets, it would be hard to get in there to drill them out. (Bad design - GM should have spent a few cents more and used bolts. They could have use rivets to hold a nut plate on for the bolts.) I did not have the time to redesign it so I left the rivets out when I put it back together.

Hint on putting the heater box back together: Slip the heater box cover back in place but don't bolt it back on. Take some twine and tie it to the short duct that goes into the heater box. The twine needs to be long enough the be pushed down and off of the pipe after it is snapped into place. Put the tube in the box with the twine coming out over the duct. Get the fingers of both hands around the duct and pull the twine until you get the snap end of the inner duct in place. Put the key on first and snap the two together. Push the twine off the end of the tube and pull it back out of the box. I used a piece of spring steel to shove it off the end of the tube. This maneuver should not take more than 1/2 hour to get the tube snapped in place. P.S. I had to take the dash apart three or four times before I got it together right. Jim Blanchard

Tip #23: Rapid Fuel Pressure Decay and Long Cranking

You might traced rapid fuel pressure decay and long cranking times to a cracked fuel pressure tube at the pump/sending unit. A possible crack might be located where the tube is spot welded to the bracket a few inches BELOW the assembly mounting flange (inside the tank when installed). If you happen to replace both pumps and the pressure is not holding check this area. You may have to pressurize the tube with air and use a soap solution to find it.

Tip #24: GM Actuator Cylinders piston seal installed backwards

Many, if not all of the GM Actuator Cylinders recently produced (past 2 years) have had the piston seal installed backwards. With the actuator piston seal installed backwards, when actuated, the seal is expanded in such a way that the piston may bind before completing a full stroke. Until this information gets back to the manufacturer and corrections are made with production and inventory, all new actuator cylinders sourced from GM and NAPA should be carefully disassembled and the seal reinstalled in the correct direction if degraded performance of the cylinder is present. Click for More Info