When I had my 167K miles engine replaced last year, the 72K miles replacement engine came with multiple components (loaded intake manifold, sensors, wiring harness) in addition to the core engine. So I kept several of the components from the original engine as spares.

One spare from the original engine is the fuel rail and its six injectors. I never had the confidence to remove the injectors from the original engine while I still needed the use of my daily driver. But holding them in my hand now offers a convenient opportunity to perform some testing and measurements. I'm going to share some of my results with you as they may be helpful if you're testing your own components, either for troubleshooting or just to record a baseline (a good practice).

These injectors are Denso top-feed injectors. The LR part # is LR001982. The Volvo part # is 30777501. The Denso part # is 297500-0250.

There is one very simple test you can perform on your injectors without removing or disturbing them. That test is to measure their internal resistance. Just unclip the wire harness cable from each injector and apply a multimeter to its two contacts (of the injector, not the wire connector). Typically, this type of injector will measure between 10 to 16 ohms. All of the injectors in the set should measure within 0.500 ohms of each other (500 milliohms). My injectors from the old engine measured at 12.2 to 12.3 ohms. On my replacement engine, the injectors measured at 11.8 to 11.9 ohms. An injector which is far off from the others in the set should be replaced.

On my original engine, I had a long-term intermittent issue with a misfire on cyl 6 during a cold start when the ambient temp was in the 60's (F) or below. I replaced the obvious things (spark plug and coil pack), but I never solved it. I suspected the valve seals or a clogged injector, but those were guesses.

Now that I have the cyl 6 injector in hand, I decided to put my mind to rest and check it out. I mailed it to a fuel injector inspection and cleaning service, along with two additional injectors for cyl 4 and cyl 5 so there would be a reference to compare against. Note that you would typically send all your injectors for service under normal circumstances. But this was an autopsy, not a normal situation, and I didn't want to spend the extra $ for the other three injectors. I marked each injector and explained my situation to the technician so he understood why I was sending him only half of the six.

They test each injector for flow and spray pattern before performing a sonic cleaning. Then they run the tests a second time to provide before and after measurements. They also replace the small parts like o-rings and the filter. There are a bunch of videos on Youtube showing the process if you're interested.

Sure enough, injector #6 was partially clogged. There was an obstruction causing a 5% reduction in static flow. To PASS, the allowable limit is 3% for a daily driver and 1% for a performance car. The sonic cleaning restored this injector to full flow as the after-test showed.

The 5% flow restriction doesn't sound like much, but with the tight tolerances the computer is looking for, who knows? Maybe it was the cause of my problem, or part of it.

So that adds a little more data to the mystery of my intermittent misfire. And now I have three cleaned and tested injectors as reliable spares.

 

This is why every year (15k miles, 24k km) you're supposed to drain any water from the fuel filter, and every two years (30k miles, 48k km) you need to change it.

But of course, some jackass decided to make it so that if you want to change the fuel filter, you have to drop the entire *&&$!@!-0(! fuel tank, so nobody does it.

 

Just to see what it takes, I bought an inexpensive aftermarket fuel injector rebuild kit on AliExpress and went to work on one of my spare injectors. As shown in the pic, there are six parts to replace.

The OEM version (LR003579) includes only the two o-rings, not all the other parts. LR regards these two seals as essential to replace when removing and reinstalling an injector. They slip on and off easily with a little lube.

The aftermarket kit (the one I got) has all six pieces. Replacing the filter basket makes sense as that could be dirty. The standard technique is to use a screw on the end of a fixed handle. Insert the screw in the filter and then give it a good yank to pull out. This simple method did not go smoothly for me (nothing does) and took several attempts. The filter got ripped up so that I finally had to pull it out with pliers. Once out, the new one went in with a soft tap from a hammer. All good.

The other plastic collars and cap are optional to replace. If you remove any of them, you may deform the plastic so leave them be unless you have replacements on hand. Also take a close-up photo of the injector before pulling things off so you have a reference for how they go back on (some are directional).

If I had a large ultrasonic cleaner, I would have given it a sonic wash before installing all the new parts. Anyway, another satisfying DIY job.

 

What's the logic behind doing that?

 

And BTW, it is also considered incredibly rude to put hidden links in your messages to malware downloads. If you do it again I will recommend to the moderator that your account be terminated.