Missing and no power a high rpm 4.2

[Jesse10]

Hey guys my old man has a 2000 model 4.2 wagon, and he's been having problems with it lately. We recently went on a trip to our farm out at stanthorpe, and it was fine on the way there all good and driving around all the very hilly country all low range work. Not a problem, but on the way home I started missing and coughing and it wouldn't rev above 2500 rpm, so if you changed back down a gear to go up a hill it wouldn't rev at all. So we pulled over changed the fuel filter. Off we went was ok for a bit but still doing it. But problem and basically gone. We went put there again the weekend just gone, and the thing started doing it again. So we changed the filter again got about 1 I'm out of warrick and it was still doing it. Pulled over checked all the fuel lines, they were all good, but there this one like little filter looking thing, which Nissan call a control valve just after the tank. We took that off blew it out with the compresser little bit of shit come out but not really much. But it's still doing it, he's ordered a new one of those control valves, ($95) for a tinny little plastic thing from Nissan. I was just wondering if anyone else had any ideas to try, or if anyone else has had a problem with that part?

Any help would be great its gotta be something simple. regards Jesse

[Glort]

I would say it's a fuel problem without doubt. it has all the symptoms my 4.2 has when something clags up on it.

I only gave mine a filter change and clean up yesterday.

I found when I first got the vehicle on mine the pickup in the tank had a lot of crud on it. The thing really dosen't have very big openings and wouldn't be hard to block with a few bits of crap. I drilled mine out a bit to give it more ability to flow and pass bigger bits of crud to the filter. I also wrapped it in a few layers of fly wire to increase the surface area of which the fuel is drawn from.

I would start at the tank and work your way forward. Blow the lines out with compressed air and make sure they are not restricted.

Check the soft lines near the tank and under the engine bay for cracking and leaks right up to the Filter and IP. I had some problems with the short bit of hose that connects the 2 hard lines under the bonnet. The hose was probably original and was cracked and hard. I missed it at first but due to putting the clear woven vinyl line in further up I could see I had an air leak from the bubbles in the line and traced it back.

Also some 4.2's have a very fine gauze mesh IN the IP under the banjo fitting. I believe at some point these strainers were deleted but I don't know what year model. It is a common problem for them to get clogged and restrict fuel flow. Can be impossible to detect if you don't know they may be there. I know a guy that was told his IP was stuffed by a diesel Mechanic and he bought a new pump and had them fit it. He got the old pump back and a few weeks later stripped it down and found it looked fine. He had since heard about the gauze screen, pulled it out to find the thing near solid.

Amazingly he did manage to get a worthwhile amount of money back off the incompetent diesel dim wits.

The best thing is to remove the fuel inlet fitting and make a small hook out of some wire and see if you can pull the strainer out. If it has one you can either clean and replace it or chuck the thing. I'd do the latter myself.

There seem to be a number of people that fit electric pumps to these vehicles. Perhaps the internal pump weakens a bit with age as clearences open up due to wear. I fitted an electric Walbro pump to mine under the bonnet and think it is extremely worthwhile. You can take the fuel line off at the IP, turn on the Ignition and see how much fuel your getting... or not. Also is very handy in priming new filters.

I have also found that clamps on fuel lines tend to loosen up fairly quick when you replace fuel lines. I always go over mine about a week after I change them and often find what was once tight can now be spun round on the barb without too much difficulty. Once nipped up the 2nd time they tend to stay tight.

Fuel problems arent difficult to fix but I reccomend if you haven't done anything much in the way of cleaning or replacing, start at the tank and work your way forward so you know you have eliminated all the possibilities of problems and know you have good flow.

The beauty of mechanical diesels is unless something goes bang, 9 times out of 10 the problem is fuel related.

[Jesse10]

Very helpful comment, thank you very much! Yer I think that's what we will do work our way up. And thanks heaps for the handy tips. And yea thatnis the beauty of these motors it's normly air or fuel related! Gotta love em! Thanks again

[Cuppatea]

I'm interested in this control valve your talking about.  What's it do and are they something I would expect to have to replace one day?  Can I chuck it?