| I recently finished replacing the last (what I can only assume to be original) fuel injector on my 1990 (11/89 build date) Nissan 300ZX Twinturbo. Every injector I removed has the code 1M50 stamped on top of the injector. The first one failed about 4 years ago and the last one failed a few months ago. The replacement OEM injectors I received had the code 1M51 stamped on their purple plastic caps. I had both flow tested. The 1M50's flowed at 372 cc/min while the 1M51's flowed at 370.5 cc/min these tests were done on functional injectors at the time. I decided to cut apart a 1M50 injector. On to the pictures: Here you can see both the cut injector and the original side by side (used a Dremel so the cut's aren't exactly perfect):
You can see that despite the brown color of the injector, they were originally purple. The next two show the details of the injector cutaway. Note the pintle assembly is in place in each. The spring between the upper copper plug (long coper tube down the center) and pintle assembly has been removed.
 
In the next two the pintle assembly has been removed. As in the above pictures you can see the solenoid windings. The heat from the cutting process has made each strand hard to distinguish but towards the edges you can discern individual wires. These wires are encased in a rosin like material. The windings are never actually exposed to fuel (directly).
It should now be clear that fuel enters the fuel injector from the side, goes through the mesh and enters the casing through the holes and into a chamber formed by the casing and the rosin/solenoid. The pintle assembly has about 1mm of play up and down. It appears that when the pintle is down (closed) the chamber in the top of the pintle can fill with fuel from the previously mentioned chamber. Then once the pintle moves up (open) the chamber is cut off from fuel and the fuel is free to move out the bottom of the injector. It's hard to tell from the following picture but the upper chamber of the pintle connects to a square section of the pintle shaft. Thus there are passages from this chamber down the pintle body. The long score marks are from my cutting the injector apart.
 So some speculation now. First, if ethanol is corroding the electrodes then it has to be seeping through the rosin (which is possible). Second, the spring which keeps the injector pintle in the down position (closed) is in direct contact with the fuel. The pintle assembly shows no signs to corrosion. Now here's my speculation part. These fuel injectors were manufactured sometime in 1989. At this time there was little to no ethanol in our fuels. They survived for 16 years which is pretty damn good in my opinion. Now I've see injectors go from 14 ohms to 140 ohms while sitting in a plastic bag (after being exposed to fuel). So I'm not a big believer that the constant current is a contributing factor to injector failure. I think there is good evidence to support the idea that the 1M50 injectors are failing due to ethanol (or some substance) seeping through the rosin to the solenoid windings resulting in high resistance. However what I want to know is if anyone has had issues with the new 1M51 injectors Nissan has received through JECS. I believe it may be possible that these injectors have an upgrade rosin. Does anyone have evidence of the 1M51 injectors crapping out at an unreasonably high rate (less than 5 years)?
"The 300ZX Turbo is a dance; it's a song; it's rolling, roaring automotive art. There is no color that doesn't suit it. There is no mood-lifting chemical substance it can't replace." - Automobile Magazine
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370cc 1M50 JECS Nissan Fuel Injector Cutaway - 
