I finally found the culprit

One month ago, my wife's car had a dead cylinder. It was cylinder #3. It passed all the usual tests: spark plug sparking, compression test showed 170psi across all cylinders, fuel injector ticking, presence of fuel injector signal. But it just didn't want to start.

Peering down the cylinder hole, I noticed a pool of oil on top of the piston. A leaking valve stem seal could put too much oil into they cylinder and foiled the proper mixture for combustion. So I replaced them and cylinder #3 was still dead.

I then wanted to double check the compression test figures. It showed 170psi for all cylinders. That was a good figure, but it measured only the peak compression and did not show there was enough compression at the right time. So I bought Harbor Freight Tool's leak down cylinder tester for $30.
   

But they showed minimal leakage.

I was desperate by this time. I decided to take a look at the fuel injector. Two years ago I replaced fuel injector for cylinder #3 because it went bad. So I was very doubtful that the fuel injector could go bad again within just 2 years. But I was desperate. 

Just for the record, it's possible to remove the fuel injector harness (fuel rail) without removing the intake plenum. You need to remove the bracket that secures the accelerator cable though. The bracket is secured by 1 bolt on the cylinder head and 2 studs on the intake plenum. Remove the bolt and twist open the studs with vice grips. Doing so will damage the studs. I replaced the studs with bolts. Good riddance since I hate dealing with studs in general. 

That's when I found the culprit. Compare cylinder 1 and 3's fuel injectors:

No wonder cylinder #3 was dead. The bad o-ring must had been leaking fuel into the cylinder.

It seemed that the replacement pintle cap I used was too wide. When securing the fuel injector into the harness, the smaller opening on the harness pushed the cap against the o-ring.

Fortunately I had spare pintle caps. It was a good thing I didn't cheapen out two years ago by ordering more than I needed. I trimmed the rim of one and installed it.

That's all it took to bring the cylinder operational again.

Installing and removing recessed valve keepers

Nissan Sentra GA16DE, as is the case with many other Japanese engines, have recessed valve. As such, a common valve spring compressor design like the one below won't work.

One tool that can work (or rather be made to work) with recessed valves is Leslie 36200.

To install the valve keepers, use it without the black attachment. Just position it on top of the valve keepers and push down. It has a strong magnet at the end so as you push down the valve spring retainer,  the magnet will capture the keepers. 

A valve spring retainer and valve keepers.

But as it was, its diameter was too big for the valve cylinder. So it needed to be filed. I didn't have a grinder so  it took me 3 hours while watching Pink Panther to file it down. Oh good times.

The yellow zip tie represented my target diameter. It was set to a slightly smaller diameter than the valve cylinder's.

 

I pushed the zip tie as far down as possible and marked places that were still thick.

1.5" was deep enough for GA16DE.

I don't have a picture of using it to remove the valve keepers, but here's one of me using the installation attachment. Just assemble the valve spring, retainer and keeper, and push down with the tool. Note that I was posing for the picture because I didn't take some while I was doing the actual installation. In a real installation picture, you should see an air compressor hose going into the cylinder or a string of nylon rope to float the valves up.

 

If you do not have enough power to push down the tool with your hand (awkward position, short stature, etc.), you can try pushing down the tool with your body weight as pictured above. Use a piece of wood to spread the pressure and push down. This works for the intake valves too which are positioned further inside the engine and may not allow you to push down effectively.

Water pump old vs new

From 1994 Sentra GA16DE 1.6L:

new vs old water pump. The old one had been on the car for 5 years and was leaking.

1994 nissan sentra fuel injector wierdness

We have two 1994 Nissan Sentra here, Put-Put and Pit-Pit. Put is 160K and Pit is 200K. They both still run strong but that is thanks to having 2 fuel injectors replaced.

It started last November when Pit's cylinder #1 fuel injector went bad. It was so unexpected because fuel injector rarely goes bad. I chalked it up to bad fuel filter. So I replaced the fuel injector and filter.

Then two weeks later, Put's cylinder #1 fuel injector also went bad. That was so surprising. What was the chance of two Sentras having bad fuel injector within weeks of each other. I can't blame it on gasoline because the other car, a 1991 Mazda Protege, was not experiencing any problem, and googling for the problem did not indicate that there was a widespread problem with Sentra's fuel injector. I replaced the fuel injector and filter.

The next day, Put's cylinder #3 fuel injector went bad. In less than 24 hours! I replaced it, and there is no more problem so far.

But last week, Pit's cylinder #4 fuel injector went dead again. By this time, I was so good at replacing Sentra's fuel injector, I did the whole thing from start to finish in under 30 minutes. For comparison purpose, the first time I did it I took 6 hours splitted across 2 days.