[SOLVED] Yet another power loss and black smoke question (updated)

[user 10312]

Just clasping at straws now but spotted in your signature thing you have a DTI power chip have you thought about removing it and doing the same test?

Another easy experiment is get a 10 litre at least container ( a fair bit of fuel is returned to tank) and some 8mm fuel line. Hook up the fuel line to the the supply side of the filter. Shove the fuel line in the in the diesel filled container and repeat the test. This will categoricaly rule the fuel tank in or out as the culprit.

Always do one thing at time that way you know what fixes it.

 

[OldManBeard]

Thanks for the suggestions and I do agree with trying only one thing at a time. It wasn't apparent from my posts but that is the approach I use whenever possible. My list was merely a summary. The chip has been disconnected while I've been trying to sort this out. Perhaps I forgot to mention that.

It would have been very useful to be able to show and record the fuel flow while driving. Unfortunately, it appears that, and a whole lot of other, information is not available via the ODBII interface on mine.

Disregarding that the tank had been functioning fine, the idea of eliminating it at first appears to make sense but it's pretty impractical. The only places I could mount a temporary one is on the roof rack or inside the cabin (which would be most undesirable, as spillage could occur). Either way, that would remove the lift pump from the circuit and, especially having it on the roof, add gravity feed. This would replace one set of variables with a completely different set, meaning the results wouldn't be very meaningful at all.

An alternative way to get suitable results might be to add a flow sensor, perhaps in combination with a pressure sensor, in the line after the fuel filter and record that data during testing. I'll ask the diesel specialist if they have appropriate gear for this when I contact them.

 

[Old.Tony]

A trick some of us have used in the past is to add a small section of clear hose at this point. It's often the case that odd issues with fuel delivery are caused by air entering the line. Since there's not a large amount of pressure at this point it's rather easy to do and will reveal any air entering the system (which you don't want). Just in case that helps too!

 

[OldManBeard]

A trick some of us have used in the past is to add a small section of clear hose at this point. It's often the case that odd issues with fuel delivery are caused by air entering the line. Since there's not a large amount of pressure at this point it's rather easy to do and will reveal any air entering the system (which you don't want). Just in case that helps too!

Good idea and I conveniently have a roll of 8mm clear tubing in the shed. I just need to work out how to route it, without it getting pinched, so that it can be observed during road tests. The fit-up of the Navara bodywork is pretty piss-poor but I'm not sure the gaps are quite big enough.

I doubt I will find a problem with air in the line, as the fuel filter is always still fully primed when I check it. Nevertheless, I'm not in a position to discard theories without first proving them wrong, so will pursue this one. Thanks again.

 

[user 10312]

Either way, that would remove the lift pump from the circuit

There is no lift pump. All the lift and pumping is done at the injection pump itself that is not prior to the filter. I will admit probably not that easy using a seperate fuel container.

 

[OldManBeard]

There is no lift pump. All the lift and pumping is done at the injection pump itself that is not prior to the filter. I will admit probably not that easy using a seperate fuel container.

Perhaps not in yours. Mine has a small pump built into the fuel pickup/level sensor unit inside the tank and we were monitoring it's current (averaging just 200 to 300 milliamps) when we had the mechanic's professional scan tool connected. That current did, as expected, vary with different fuel levels on different test runs. I must say that it can't be doing very much, otherwise, why do I need to prime the fuel filter whenever I change that?

 

[Old.Tony]

The pump in the tank is an oddity, quite possibly an aftermarket thing - I've not heard of a lift pump in a diesel. Certainly the petrol cars have pumps in the tanks, but they run a lot lower rail pressure than the diesels. You'd think that a lift pump is there to push fuel to the front so that priming is unnecessary, but from what you're saying, it's offering little more than a restriction to the fuel flow - and these cars do pump a large amount of fuel through the system.

It might be an idea to remove the pump from the system (including electrically) and test without it.

 

[OldManBeard]

The pump in the tank is an oddity, quite possibly an aftermarket thing - I've not heard of a lift pump in a diesel. Certainly the petrol cars have pumps in the tanks, but they run a lot lower rail pressure than the diesels. You'd think that a lift pump is there to push fuel to the front so that priming is unnecessary, but from what you're saying, it's offering little more than a restriction to the fuel flow - and these cars do pump a large amount of fuel through the system.

It might be an idea to remove the pump from the system (including electrically) and test without it.

I can only say that the pump is there. This is my first Navara and my first diesel, so I have no idea what is normal on these machines and the workshop manuals are utterly useless in that area, as they are in many others. Yes, it is quite possibly an aftermarket thing installed by the previous owner but I have to say that it looked integral to me and the wiring and connectors looked factory standard, rather than modifications. If it was added, it was very professionally done.

I replaced the stock tank with a new 140 litre steel tank and the pickup assembly was removed from the original tank, float arm extended and installed into the new tank. The pump certainly wasn't installed at that point because I did that work myself.

The car had been driving perfectly well until fairly recently, both before and after I installed the new tank. It is of course possible that something has gone wrong with the pickup assembly in the meantime. I will be temporarily removing the tank at some stage, as I want to adjust the float arm for better accuracy, and will definitely check it all out then. But that's a job big job when you don't have a hoist, one I don't quite feel up to at the moment, and is not happening too soon anyway. I very recently filled the tank and I have nothing to hold that fuel, so cannot empty it, and wouldn't even attempt to remove the tank when full.

 

[OldManBeard]

I'd like to edit the subject of this post to include the word "solved" but I can't find an option to do so. Can a post only be edited once? Here's the latest result, at least as far as the performance issue is concerned:

After investigating a whole bunch of other stuff, including several red herrings, and after discussions here, I went out and purchased several jerry cans and borrowed a few more. I was able to empty the fuel tank and take it out of the car (a bugger of a job!). While I had it out I made some changes to where the rear strap hooks in on the outboard side. It will now pop back in relatively easily and without a lot of bending of the strap, head bumping, swearing, etc.

What I found was some kind of gunk that had the consistency of light grease. I won't try to guess what it is or where it came from, although I suspect it was in the fuel when I refilled the tank a second time after installing the tank because it was not too long after that that the car started mucking up. That gunk wasn't actually blocking the fuel pickup but, as far as I was able to determine, had worked its way up the line. The was no sign of it at the filter end, so I think it built up somewhere between the tank and filter and created a partial blockage. One which only had an effect when I had to put the foot down a bit going uphill, and therefore needed a bit more fuel flow. Anyway, while I had the two ends disconnected I fired up the compressor and blasted air through the line at the compressor's full 145PSI. I can't tell you what came out because I was on my own and can't see both ends of the line at the same time. Besides, with the pressure and volume of air that I used, I'm sure the gunk would have just sprayed everywhere and become indistinguishable from the fuel I had managed to spill all over the place.

My theory for the black smoke when the car lost power is that it initially starved of fuel. I then eased off the pedal and worked at finding a point where I still had enough power to go forward, but of course much slower than desired. At the same time, the computer was asking for the additional fuel and, because the engine was no longer using it as fast, I got a surge when the fuel caught up, creating a temporary over-fueling situation. While working to pedal to keep the car moving I think it was oscillating between being starved of fuel and being flooded with it. I am of course quite happy to be proven wrong about this if anyone has a better and convincing explanation.

About the lift pump I mentioned previously, I tested it and found it wasn't doing anywhere near enough to warrant keeping it. That, and comments posted here, made me suspicious about it being an OEM part or not, so I followed the wiring back and found the point where that had been modified. A very professional job indeed but I can't help but wonder why it was ever done if Navaras don't have a lift pump as standard. The absolutely most confusing thing for me was that the ODBII scanner was able to read the pump current. That can only happen if there is a suitable electrical connection point for the pump. I assume the Navara has support for such a pump but Nissan decided not to fit them. Anyway, that pump has been binned, the pickup assembly restored to stock condition and the float arm adjusted to give me an improved reading when the tank is near empty.

The car is now running very strong through the local hills, which have a few long steepish climbs that would most definitely have triggered the problem before. I'll repeat the testing with the camper attached but, for now, I feel confident enough to call the diesel specialists and cancel my booking with them at the end of the month.

 

[Old.Tony]

I've edited the thread title for you. Great news!

 

[tweak'e]

wonder why it was ever done if Navaras don't have a lift pump as standard. The absolutely most confusing thing for me was that the ODBII scanner was able to read the pump current. That can only happen if there is a suitable electrical connection point for the pump. I assume the Navara has support for such a pump but Nissan decided not to fit them.

the d23 have them afaik. nissan probably just went cheap on the d40's. it kinda depends a bit on what fuel filter they use.
but generally lift pumps are a good thing, however it sounds like that one probably got blocked up with gunk.

 

[user 10312]

Thanks for the update. This kind of info is really valuable. Interesting on the supplementary pump that was in the tank. I know a bloke locally with the same spec D40 as ours who fitted a small electrical pump just prior to the fuel filter as he was having surging problems on low fuel (like less than a 1/3) in the tank. It did sort it. I to get a little surging sometimes on low fuel tank level, like when the Suction Control valve is gummed up but replacing the fuel filter and doing a fuel pump reset sorts it.

I believe the fuel pump on these things are marginal on the suction side and any sort of restriction will cause issues.

 

[OldManBeard]

Thanks for the update. This kind of info is really valuable.

You're welcome. One thing that really pisses me off is people asking for help and then never coming back with any info on whether or not they resolved the problem. Even worse are the ones who change the subject line to mark it as solved but never reveal how. That's just so ungrateful and utterly useless for those who later come across the thread while searching for an answer to the same problem.

I'll keep that surging issue in mind. If I ever decide I need/want an auxiliary pump I'll most likely add an extra suction pump in between the pre-filter and the main filter. If there's ever anymore gunking up, it's a whole lot easier to replace the pre-filter element than it is to drop the tank to get to a clogged pump in there, especially when you're in the middle of nowhere.

 

[OldManBeard]

the d23 have them afaik. nissan probably just went cheap on the d40's. it kinda depends a bit on what fuel filter they use.
but generally lift pumps are a good thing, however it sounds like that one probably got blocked up with gunk.

You're most likely right about that pump being gunked up. It was a glued together body and I just didn't see that it was worth my effort to dismantle it to find out, as I had already decided to eliminate it.

 

[tweak'e]

If I ever decide I need/want an auxiliary pump I'll most likely add an extra suction pump in between the pre-filter and the main filter. If there's ever anymore gunking up, it's a whole lot easier to replace the pre-filter element than it is to drop the tank to get to a clogged pump in there, especially when you're in the middle of nowhere.

funny enough i have a vehicle at work that has filter issues and an electric lift pump.
it has a small lift pump by the tank and the pre filter and main filter is up by the motor. i guess they must of had issues with pump gunking up etc because they fitted a small petrol style filter in front of the pump. of course that clogged up and brought the vehicle to a halt.
so i have the job of rearranging it so the pre filter is in front of the pump.
tho there is other snags to that.

typically the intank pumps have a prefilter sock on them to stop gunk getting in and blocking it.
some 4wd's have that even if they do not have an lift pump. after 20-30 years they are known to block up.

 

[OldManBeard]

some 4wd's have that even if they do not have an lift pump. after 20-30 years they are known to block up.

That's fine by me. I don't expect either Navara or myself to be around that long.

 

[Jardsoooo]

Well that was quite a story - well done to all concerned for the advice given and the happy conclusion

 

[ericcs]

What I found was some kind of gunk that had the consistency of light grease. I won't try to guess what it is or where it came from, although I suspect it was in the fuel when I refilled the tank a second time after installing the tank because it was not too long after that that the car started mucking up

I had the same stuff completely clog my fuel filter, like black grease, which wouldn't dissolve in any solvent. was told it was from some sort of bacteria in the fuel, possible as i'd only returned from the cape 2 days before, and i didn't take a spare. Same surging issue on hills, fine on the flat, makes me wonder what my lines are like?

 

[OldManBeard]

I had the same stuff completely clog my fuel filter, like black grease, which wouldn't dissolve in any solvent. was told it was from some sort of bacteria in the fuel, possible as i'd only returned from the cape 2 days before, and i didn't take a spare. Same surging issue on hills, fine on the flat, makes me wonder what my lines are like?

That's interesting, as well as informative. I've got a can of "Diesel Algae Stop" and think it might be time to add some of that to the fuel tank.

I'm surprised you didn't take a spare filter with you. Some of the fuel up north can be questionable at best. When we take off I'm planning to take spares of all the filters and multiples of the ones I expect will need replacing more frequently. They don't take up so much room that I could justify not taking them.

 

[tweak'e]

i usually find diesel bug is a brown color, but i have heard of it being black. it may be because i see very little of it.
however it lives on top of the water layer. with most small diesels that water layer is in the water trap/filter rather than in the tank.
these engines flow so much fuel to the engine and back to the tank it tends to wash the tanks out quite well.

i suspect its something else. some garages are known to dump oil, trans fluid, missed fuel petrol etc into gas station diesel tanks.