Hello firstly I appoligize if this has already been asked in some form or another but I did search for awhile and couldn't find anything like my problem. That disclaimer out of the way here is the issue.

The other day put some royal purple fuel treatment into the tank after a fill up. Went into town and did some errands. Was running fine till turned on the AC. Then it started running really rough and noticeably miss firing. Turning off the AC seemed to make it go away. But after a bit about 10 min and almost home the missfire and diesel sound when taking off from a stop got worse. So limped her home and did some tests today. After it had thrown the cyl 6 missfire code. Checked the plug and made sure it was okay (cleaned and visually inspected) even swapped it out with another good plug and still missfire. So I checked the wire for gouges, and exposed wire. Nupe, even swapped it with another wire and same issue was there. Am getting good spark from the coil pack and at the pack itself. So spark isn't the issue. Am not sure what to do next and could use some help if anyone could. I really love my Discovery and would like to get her running at good condition again. Thank you in advance for any suggestions and help. It is much appreciated. PS.. also checked and cleaned the MAF even unplugged it at one point problem is still there.

 

Check the fuel injector, you'll have to remove it. Look in the top, might have a screen (some don't), clear it if it does. Shake it, if it rattles it's good, if not it's stuck or broken (maybe). If no screen you can try tapping it upside down on a hard surface to see what comes out. Aint gonna come out the nozzle side for sure....... The fuel rails on these early trucks are steel, it rots/flakes. You've learned a valuable lesson, don't mess with aint broke......

 

That may have loosened some crud in tank or lines and clogged that injector.

 

Thanks to you both I was thinking it was a possible block due to something breaking lose, but figured would check the usual suspects first. Will give that a try either later tonight or tomorrow and update ya on what I found. Oh did forget to mention, it's been a long day :P when I checked the pressure in the fuel line rail while running was at 30 psi. I checked it with a tire pressure checker. Also Thanks Again

 

30psi running is ok, few pounds low. That could be pickup screen, inline filter, fpr, or tire pressure gauge. 34-37 is delivery pressure. You want as high as possible for injector spray pattern and atomization = efficiency. Pumps are 40-45lb/ft rated. You'll have fun playing with the rail, get some rest......

 

So slight update looked into pulling the injector, and wasn't sure how so searched around. One place I found said just loosen the one side and pry on it. Well I tried a light pry around maybe 5 lbs of pressure and decided that I didn't like that idea. Then smacked myself in the head and looked in the shop manual I downloaded. Now I know why ya said will have fun playing with em. Didn't know that ya gotta pull all that stuff to get to em, but on the plus side while I'm at it may as well replace valve cover gaskets. So will probably end up getting to it early tomorrow. As smoke from fires is making working outside impossible. Just wanted to let y'all know I haven't forgotten bout ya and thanks again for the advice so far Will keep ya posted

 

Sorry for the long time between posts.. The smoke here has been so nasty it keeps me indoors, well that and my bad back lol. But to the update. Finally got the injector out after a fight with the rail (mostly cause forgot to take coil pack off lol) and no screen that could be removed. Tapped it upside down on a clean cloth and nothing that I could see came out. Did shake it however and it sounded like intermintently it would stick just a little bit. So pulled 8 and 4 and shook them as well 8 sounded fine but 4 sounded the same as 6 (the trouble one) So my question is does this sound like the injector might be bad? Thanks again

 

Hard to say, could be the pin or could be deposits. Now you know a little more about the condition and that's the point. They can be pro cleaned and flow tested, might want to ask around the local garages, see where they send em out to. Good on ya for going the distance with the rail, aint easy fo sho. Tom has a blurb about Volvo injectors in his build thread, you might be interested in that......

 

Ok will check the thread out, and will do the ol call around tomorrow. And yeah it was a pain but eventually it came out. Well the #4 injectors o ring decided to get stuck up inside, but was gonna replace all the o rings anyway :P Will update when I know a little more, tomorrow am gonna put er back together and test to see if there was some debris clogging it. And thanks again

 

No problem as always. Like to hear how things go.