So, I just spent yesterday evening replacing my cam sensor in my '87 Grand National for the first time, and I figured since there are a lot of posts about the adjustment but none on the actual replacement I'd lay out some tips and tricks for the first timer that worked for me. Some of you more experienced guys might have a different method.
First I took off the up pipe and all the piping between the turbo and the MAF, and removed the MAF. I have a cold air kit so I just left the pipe between the air filter and MAF and moved it out of the way. Then I removed the small 7mm screws for the intercooler shroud and pulled that forward, I didn't need to remove it from the engine bay. I removed the intercooler by loosening the hoses and taking off the 3 bolts, two on the passengers side and 1 drivers side. I believe there should be a fourth underneath the intercooler on the passenger side brace, but I did not have that one, I'll need to look into that. I also removed the nut holding the top of the drivers side intercooler brace to the engine. Once the intercooler was out I was able to remove the 3 bolts that hold the fan on the engine. Leave the other 3 that hold the lower pulley. Then, in front of the plenum, all around the cam sensor, I unhooked most of the sensors to have some play in the wires. I didn't bother unhooking all of the sensors (there were 1 or 2 that went down into the engine and I didn't feel like chasing), I had enough room to work.
Now, the fun part. If you are replacing your cam sensor it should still be in the car - remove the cap only first, not the whole cam sensor. I used a 28mm socket on a half-inch rachet with a breaker bar on the lower pulley (which is why I removed the fan) to turn the engine until I saw the timimg marks. Yes, I said marks - my car has two marks, one for TDC and one for 25 degrees after TDC. I can only assume the second mark was put in there during the rebuild I had done on the engine about 15 years ago. If you have 1 mark, just measure out 1.45 inches on a piece of masking tape and put it on the balancer after the timing mark. It's easiest to do that when the mark comes up the passengers side.
Now, align the 25 degrees ATDC mark with the 0 (you'll need to look down to the left of the alternator to see the timing marks) and look at the cam sensor. If the window is pointed towards the drivers side, you are on the compression stroke. No need to pull the #1 plug or anything like that. The sensor makes a half turn for every 1 engine rotation, so if the window is on the passenger side, spin the engine over one more time and align to the 25 degrees ATDC mark. Of course if the cam sensor insides are broke and the car won't run you can throw that out the window - but my car was running when I started this job.
Now the fiddly part - getting the hold down bolt off. It's a 14mm nut but I used a wobble attachment on my extension to get it down in there - I found it easier to use a 15mm socket. I'm sure there has to be a better way. Once I broke it free a few turns I was able to get my hand in there and remove it completely. I think I was hindered by the fact that I have a water temp sensor for my aftermarket gague on the top of the "s" hose. Anyways, once I got the nut off I pulled the cam sensor free.
Now, for the new sensor. I removed the cap, marking on the body of the sensor which way should be facing front so that the wires on the cap face the drivers side. I don't think that matters but I didn't want to chance the cap not fitting right the other way. I then put the cam sensor in turning the window just slightly counter-clockwise from pointing to the drivers fender to account for the gear turn. Here is what drove me nuts - the cam sensor wouldn't seat completely. I finally figured that I had it right - when I moved the window to drop in on a different tooth I felt a hard stop on the oil pump. So I put it back - the manual says just put the window towards the drivers side, and I figured the oil pump was in the right location because I was basically putting in the new sensor in the same place as the old one. It didn't feel like it went in any lower than when I had the hard stop, but what I did was put on the retaining bolt and tightened that down and sure enough, that pulled it deeper into the block. Whew!
Then I installed the cap and backed off the nut, the sensor turned but it took some effort. It was definitely not as easy of a turn as I thought it would be. I turned the sensor so the cap wires were almost facing me. I stripped both ends of a thin piece of wire and put one end into the middle connection on the sensor then plugged in the connector to the harness, this is the way I probed for voltage. I plugged in all of the other sensors (don't know if I needed to do this, but whatever, I did), hooked up the battery, set the voltmeter to measure volts, turned the key to accessory, and put red to my thin piece of wire and black to ground. I read about 4.5 volts. Everything I read about this says 7 volts, but I was getting a reading so I was happy. I then turned the sensor counter clockwise a little bit at a time and checked the readings, I needed to use two hands to turn it so I would turn, check, turn, check - it would be easier if I had alligator clips for my voltmeter, but I worked with what I had. I stopped once I read 0 volts, turned the key off, and tightened the retainer bolt.
Now it was time to put everything back together. Fan, intercooler, pipes - I just reversed the disassembly. Moment of truth - reach in, turn the key - fires right up. Job done. Time for a shower and some dinner.
Hope this helps some of my fellow Turbo Buick enthusiasts.
Bob
First I took off the up pipe and all the piping between the turbo and the MAF, and removed the MAF. I have a cold air kit so I just left the pipe between the air filter and MAF and moved it out of the way. Then I removed the small 7mm screws for the intercooler shroud and pulled that forward, I didn't need to remove it from the engine bay. I removed the intercooler by loosening the hoses and taking off the 3 bolts, two on the passengers side and 1 drivers side. I believe there should be a fourth underneath the intercooler on the passenger side brace, but I did not have that one, I'll need to look into that. I also removed the nut holding the top of the drivers side intercooler brace to the engine. Once the intercooler was out I was able to remove the 3 bolts that hold the fan on the engine. Leave the other 3 that hold the lower pulley. Then, in front of the plenum, all around the cam sensor, I unhooked most of the sensors to have some play in the wires. I didn't bother unhooking all of the sensors (there were 1 or 2 that went down into the engine and I didn't feel like chasing), I had enough room to work.
Now, the fun part. If you are replacing your cam sensor it should still be in the car - remove the cap only first, not the whole cam sensor. I used a 28mm socket on a half-inch rachet with a breaker bar on the lower pulley (which is why I removed the fan) to turn the engine until I saw the timimg marks. Yes, I said marks - my car has two marks, one for TDC and one for 25 degrees after TDC. I can only assume the second mark was put in there during the rebuild I had done on the engine about 15 years ago. If you have 1 mark, just measure out 1.45 inches on a piece of masking tape and put it on the balancer after the timing mark. It's easiest to do that when the mark comes up the passengers side.
Now, align the 25 degrees ATDC mark with the 0 (you'll need to look down to the left of the alternator to see the timing marks) and look at the cam sensor. If the window is pointed towards the drivers side, you are on the compression stroke. No need to pull the #1 plug or anything like that. The sensor makes a half turn for every 1 engine rotation, so if the window is on the passenger side, spin the engine over one more time and align to the 25 degrees ATDC mark. Of course if the cam sensor insides are broke and the car won't run you can throw that out the window - but my car was running when I started this job.
Now the fiddly part - getting the hold down bolt off. It's a 14mm nut but I used a wobble attachment on my extension to get it down in there - I found it easier to use a 15mm socket. I'm sure there has to be a better way. Once I broke it free a few turns I was able to get my hand in there and remove it completely. I think I was hindered by the fact that I have a water temp sensor for my aftermarket gague on the top of the "s" hose. Anyways, once I got the nut off I pulled the cam sensor free.
Now, for the new sensor. I removed the cap, marking on the body of the sensor which way should be facing front so that the wires on the cap face the drivers side. I don't think that matters but I didn't want to chance the cap not fitting right the other way. I then put the cam sensor in turning the window just slightly counter-clockwise from pointing to the drivers fender to account for the gear turn. Here is what drove me nuts - the cam sensor wouldn't seat completely. I finally figured that I had it right - when I moved the window to drop in on a different tooth I felt a hard stop on the oil pump. So I put it back - the manual says just put the window towards the drivers side, and I figured the oil pump was in the right location because I was basically putting in the new sensor in the same place as the old one. It didn't feel like it went in any lower than when I had the hard stop, but what I did was put on the retaining bolt and tightened that down and sure enough, that pulled it deeper into the block. Whew!
Then I installed the cap and backed off the nut, the sensor turned but it took some effort. It was definitely not as easy of a turn as I thought it would be. I turned the sensor so the cap wires were almost facing me. I stripped both ends of a thin piece of wire and put one end into the middle connection on the sensor then plugged in the connector to the harness, this is the way I probed for voltage. I plugged in all of the other sensors (don't know if I needed to do this, but whatever, I did), hooked up the battery, set the voltmeter to measure volts, turned the key to accessory, and put red to my thin piece of wire and black to ground. I read about 4.5 volts. Everything I read about this says 7 volts, but I was getting a reading so I was happy. I then turned the sensor counter clockwise a little bit at a time and checked the readings, I needed to use two hands to turn it so I would turn, check, turn, check - it would be easier if I had alligator clips for my voltmeter, but I worked with what I had. I stopped once I read 0 volts, turned the key off, and tightened the retainer bolt.
Now it was time to put everything back together. Fan, intercooler, pipes - I just reversed the disassembly. Moment of truth - reach in, turn the key - fires right up. Job done. Time for a shower and some dinner.
Hope this helps some of my fellow Turbo Buick enthusiasts.
Bob
