Intermittent Misfire/Stalling 19TXD

[TheOtter]

Hi folks,

Tearing my hair out over this one, so hoping someone can give me some useful advice on here. The car is a 1993 BX with the naturally aspirated 1.9 XUD diesel engine, with the Bosch fuel pump.

I'll start off by saying that the car starts first time on the button and idles perfectly at around 1100rpm. Around 5-10 minutes after I start driving I'll be going along and I notice the car start feeling a bit lumpy, with a slight power loss and hesitation when I want to accelerate, and it will also idle slightly lumpy at about 900rpm (as opposed to 1100 normally). After 3,4,5 minutes of this, it'll eventually cut out on me, but only whenever I'm changing down gears or going in to neutral when approaching a junction/roundabout/stop in traffic. After it dies, it takes about 5-10 seconds of cranking (during which it's coughing and dying as soon as it fires, etc.) until it starts up again and all is well, idling at 1100rpm and with full power again. This might sound trivial at first, but it will always seem to cut out on me in dangerous places, like at a roundabout, junction, or during a traffic queue in a contraflow on the motorway (that was embarrassing...), or at some traffic lights. This problem then goes in a cycle - the car will be fine for another random period of time (usually between 20-40 minutes) and then I go through the lumpy running-stall-almost cause a crash-cranking-start-perfect again.

Now it's either coincidence or something to do with the following factors - it only started doing this after I did an oil/filter change and a fuel filter change. Also, about 100 miles before the filter change, I'd started using biodiesel. In those 100 miles the car ran perfectly but struggled to start, presumably due to a gummed up fuel filter - after the fuel filter change the car starts first time every time, but now has this really annoying stalling problem. I've done about 400 miles since the fuel filter change and the symptoms have stayed the same.

Does anyone reckon it could be the bio and I was just lucky not to notice the problem in the first 100 miles? Maybe the replacement fuel filter is bad? Maybe it's a coincidence and something unrelated is going funny?

I seriously can't drive the car like this for much longer, it's like Russian roulette, I know it's going to cut out on me at some point, I know it'll die when I'm coasting up to a junction or a roundabout, but I don't know when. I'm driving constantly on edge and am stressed the entire journey just watching the tacho waiting to see the revs drop to 0 and hoping I can pull off to the side whilst I spend 10 seconds cranking the engine over to start the thing again...

Any ideas before I drive the thing off a cliff?

Cheers

Sven

[electrokid]

Bio can clean out crud in the fuel system - even though your fuel filter is new it could be getting blocked from crud coming from the tank or anywhere upstream.

And / or you may have introduced an air leak at the filter housing either by not tightening or overtightening.

So check the filter for crud and the seal on the filter housing.

[MULLEY]

I'll put my 10p worth in, you've got a bad batch of bio diesel, you don't mention what % you were using, i wouldn't use more than 50% tbh. I had this exact same experience, started using biodiesel & it gummed up the fuel filter, no problem i'll change that, it was easy to do, still had the cutting out & down on power. I had to take the fuel tank filter out & it was covered in a nice sticky yellow slime, that was the biodiesel deciding to emulsify & turn into jelly. I had to manually drain the fuel tank out, pour 5 litres of diesel in to pick up the rest of the crap, re-prime the car, re-start, go for a quick drive to get some decent fuel through the system, open up the tank filter again, give it another clean, re-drain (suck out the jelly), do the 5 litres of diesel again & do another quick drive, then check the tank filter (it was fine), i changed the fuel filter again & then filled up with nice fresh diesel, no problem after that. Take your biodiesel back to the place you bought it from & get a refund along with some compo for the inconvenience. I don't ever use bio when the temperatures start to drop, it goes waxy/jellified & then you get this problem.

[themildbunch]

Yes, you do have to be careful where you buy your bio diesel from - properly made it should be fine in an older diesel... does your supplier test it to EN 14214, do they use additives in colder weather?

[TheOtter]

Thanks for the suggestions guys.

Firstly I tired changing the fuel filter, that seemed to make no difference. Then, from Mulleys experience, I checked the in-tank gauze filter and that was absolutely spotless, not a hint of any dirt/sludge on it. So, the fuel system "seems" to be okay gunk/dirt wise, but I have discovered something. Whenever the car starts to play up (idle dropping/misfiring) if I pull over straight away and shut the engine off, then get under the bonnet and press the primer bulb on the fuel line 10-15 times it seems to then start up fine after a second or two of cranking, with the bulb getting harder as I pump it.

If I'm not mistaken, this means I have an air leak in to the fuel lines somewhere? A very intermittent one obviously, as it's fine almost all of the time.

Anyone have any suggestions as to obvious/common points where air can get in to the system?

Oh and the Bio was from a proper supplier in Bristol (Bristol Bio Fuels - http://www.bristolbiofuel.com/contact.html" onclick="window.open(this.href);return false;), what with my tank filter being spotless and the car running beautifully 99% of the time, and because they have a good reputation, I'm not concerned about the fuel itself. Of course being £1.10 a litre probably sways my opinion on the stuff

[Mothman]

I reccon you have air getting into the system somewhere.
Sophie was like this initially, just got worse and worse but was sorted with a new filter/primer. OK, a MK 1 which has a different filter system but the principle is the same.

Andy

[mat_fenwick]

It does sound like an air leak,,,I've previously (and others) had a leak from the base of the fuel filter housing which I'm guessing will be the same as yours:



BUT, this was evident with a dribble of diesel, plus it caused starting rather than running difficulties so I'm guessing elsewhere. Other possibles include the pump seals, but again I've only known this cause starting trouble, the rubber primer bulb itself and the hoses to and from the filter. If you can temporarily replace hoses with some clear tube this may help in pinpointing the problem. I guess the hoses from the top of the tank could also be a suspect (if original), but they seem to last a little longer than the under bonnet hoses with their cooler location.

[Thread Bear]

Might this be a heat related air leak. A touch of hot running opening a fracture somewhere. Would that fit in with the occurrences at all? Not the experience to point at a likely offending part, but the bottom of the filter might be possible, if that type, as its near the water flow.

[MULLEY]

Isn't the priming bulb one of the main culprits as well for letting in air?

[electrokid]

I had an air leak just where the metal fuel lines come down from the fuel tank and bend forwards to go along under the car to the engine bay. It had rubbed on the bodywork at the bend in the pipe. The hole wasn't big enough to leak much fuel but, under suction from the pump, it was happy to let air in and cause very poor starting and occasionally the odd misfire as well.

[citsncycles]

2nd the metal fuel lines, plus check whatever fuel preheat system the car may have.

[Van gogh]

Air leaks in fuel highways near the fuel filter .

[Defender110]

There is also the possibility of a clogged pick up pipe in the fuel tank; I have had debris in a fuel tank collect and block the pick up pipe starving the engine of fuel and then the debris drops off when the engine / fuel suction stops. The engine then starts and runs ok again until the debris is once again picked up by the pick up pipe. The same can apply to pick up pipes with a filter on that gets clogged. I can't remember if the BX is just a pipe or has a pick up filter.

[TheOtter]

Another update on this problem - basically it's still there and I'm very frustrated after today...

It's gotten much more frequent over the past week, so I can't drive for more than about 5 minutes without having to pull over and turn the engine off. If I do that and let it settle for 10-20 seconds, then start it up again it'll be running fine. Sometimes the idle drops and it begins to stumble, but it never gets bad enough to stall and ends up going back to normal after a couple of minutes. Usually stalls though, and usually whilst I'm in heavy traffic...

Anyway, today's progress: firstly I changed the leak off pipes, just in case, and because they're cheap and easy. The old pipes literally fell to pieces as I tried to pull them off the injectors, so I was hopeful that renewing them would solve the problem - but nope, not a single bit of difference.

I then spent the rest of the day trying to find any air bubbles, putting bits of clear pipe in different places on the fuel lines in the engine bay:
- Started off with some before and after the primer bulb/grenade. No bubbles at all, so everything backwards of the engine is fine, and the primer is fine.
- Put some on the inlet of the fuel filter housing - no bubbles. So pipework to the filter is fine.
- THEN! I put some on the outlet of the fuel filter housing - many bubbles! A big rush of them go through when I rev it, with the odd few going through whilst it's idling.

So, as long as I'm thinking correctly, this means there's something up with filter housing... I took the lid off, checked inside, nothing obvious. The lid looked fine too, so I just made sure everything was spotlessly clean and put it back together. Obviously I paid attention most to making sure the plastic to plastic mating surfaces that seal the lid to the housing were clean, to make sure there was no air getting in between the filter lid and the housing.

Of course this made no difference - quite a demoralising days work there.

Please tell me there is a common issue with the filter housings?! Where can air be getting in - SOMEONE TELL ME! I've tried my hardest to find any fuel leaks around the housing, but I can't see any - I'll have a closer inspection tomorrow when it's light again.

Any ideas very welcome!

Just to clarify what filter setup I've got, here's a picture of the engine bay:

[mat_fenwick]

Apologies if you've already tried this, but did you see my photo above? If you haven't eliminated this as a possibility, try pumping the priming bulb while looking for leaks around the white thermostat valve. This allows diesel to flow through the heat exchanger passageways between the thermostat housing and filter during cold weather.

If it's leaking there when pumping, chances are the O ring behind needs replacing. I have an overhaul kit but rather would like to keep it on the shelf - I can give you the part no. or measure the relevant O ring for you if you need though?

EDIT - you mention plastic to plastic mating surfaces on the filter housing - there should be a rubber seal which fits around the rim of the filter, to seal between the lid and rim of the housing. If this is missing then that's likely to be the problem. Either way, you've successfully isolated it to the filter housing so that's a good start.