Junction Stalling

[vulgalour]

For some background, my BX (17RD, non-turbo diesel) has been off the road for a month and today was the first time I'd used it. I was having an air ingress problem in the fuel lines which was found to be a worn fuel filter housing top and a bad fuel hose clamp.

On the advice of this forum's previous posts, current posts, and information from other forums, to cure the air ingress issue I have replaced:
- bad jubilee/worm drive clamps with new fuel hose specific clamps
- clear fuel hose (fitted to find the air leak) replaced with brand new rubber fuel hose
- worn fuel filter housing top replaced with brand new part
- Fuel filter housing o-rings replaced with brand new
- brand new fuel filter
- cleaned out all of the gunk inside the fuel filter housing

Today I had to do a short errand and on my return, while sat at a junction waiting for a gap in traffic, the idle started to gradually drop of its own accord and when I went to set off, the car stalled. The car tried to do this a second time as I slowed for a junction, and successfully stalled quite abruptly part way through a three-point-turn when I came to a stop to change gear and direction.

Afterwards, I attempted to repeat the conditions that the stalling occurred and the car steadfastly refused to oblige. I also left the car idling on the drive to look for leaks and to see if the idle would again drop off and again, the car refused to oblige.

Is it possible that this issue is some air working out of the system, or is it indicative of another problem? Unfortunately I can't do many miles at the moment because of current world events so more extensive testing to discover if this is a regular problem or actually just an intermittent one isn't really viable. Your feedback would be welcome, regardless.

[vulgalour]

I've posted this over on the build thread too, I'm posting it here for ease of reference in case I solve this issue and in case anyone else has similar issues in the future:

Had another look at this today to see if I could find anything amiss. The car isn't keen on starting, or restarting, and the injection pump is now making a wubbawubba sort of a noise so I guess that means something in the pump is on its way out. The wubbawubba gets quieter the longer the car is running, but it required two attempts to start with or without priming, as though the pump wasn't pulling fuel through quickly enough. The wubbawubba noise is similar to the one that a mechanical fuel pump diaphragm makes, that sort of wobble board meets air sucked through a straw type of noise. I couldn't capture it on my phone because the engine drowns out the rest of the noise.

No diesel leaking out anywhere and while I'd like to say there was no air getting in, since I don't have see-through fuel hoses I can't say that for certain. Once running the car is fine and try as I might I can't get it to repeat the stalling issue.

So I guess at a minimum an injection pump rebuild is on the cards to try and resolve this issue. My concern is that the badly filtered used veg oil remains I found in the bottom of the fuel filter housing has perhaps but excessive strain on the pump and simply worn it out, which would mean replacement is the only option. I don't know though, I'm learning as I go here on this one and not entirely sure what the wisest course of action is from here.

[Kaapelimies]

Have you carefully checked that there is absolutely no diesel leaking out from the throttle axle that goes inside the pump? That's a very common failure and it's only an inexpensive o-ring.

[Jaba]

Is the fuel coming through clean ? There may be a lot of stuff left in the tank from before. If it is just air then the metal fuel supply pipe is a known cause of bad starting - but priming usually gets round this. It might be worth getting a seal kit for the pump as an inexpensive lets try this to fix it thing to do.

[vulgalour]

There's no signs of leaks or even moisture on any of the connections, the pump and filter housing, and hoses, are all lovely and dry as they ought to be.

The fuel coming through doesn't have any sediment or visible particulates.

From feedback on other fora, and conversations outside of those, the following have been offered as potential issues:

Fuel pre-heater air leak, a common problem
Gummed injector due to evidence of veg oil
Blocked fuel tank strainer due to evidence of veg oil
Failed/weak lift pump (I'm still not entirely sure my car has a lift pump, I understood the injector pump was the only pump on the car)
Damaged metal or rubber fuel hose between the tank and the fuel filter hose
Cracked plastic fuel filter housing - discounted because it's a metal one on this car and not cracked
Inoperative injector pump waxstat
Water in the diesel
Damaged/worn leak off pipes

There's a lot of things this could be, so it's a case of working through and trying to eliminate these items. Because there's a good number of things other than the pump it could be, and the pump is probably the most involved and expensive component in this puzzle, I'm setting that aside for now and ruling out the cheaper/easier items instead.

Fuel pre-heater is not bypassed. I don't intend to bypass it until I've ruled other items out, if in the process of ruling other things out I cure the problem I will not bypass the pre-heater.

A gummed injector could caused intermittent fuel starvation and, from how it's been described to me, manifest as the problem I'm having. So, I've ordered some injector cleaner to put through the system and see if that improves anything, it's a cheap and easy fix so a very good place to start.

Fuel tank strainer/pick-up being blocked is very plausible too given what I found in the fuel filter housing, not the worst job in the world to do if so, and shouldn't cost anything. This might also explain why when fresh fuel is put in the car it normally runs better and fires up easier, presumably the fresh fuel disturbs the sludge theoretically blocking the strainer. I won't know until I get to the point I'm taking that apart and having a look.

I have no idea if, or where, the lift pump would be on this car. I was under the impression the only pump was the injector pump in the engine bay. Feel free to correct me if this is not the case.

Damaged fuel hose also a potential. All the fuel hose I could see and replace has been where needed. I've seen no signs of fuel leaking out anywhere else and no damage at joints I could see that would hint at air having a place to get in. This is something I'll replace if nothing else at all works.

I don't have a plastic fuel filter housing so I know it's not that.

I don't know how to test the efficacy of the waxstat, if there is one, and given how warm it is lately I doubt this is the cause of the starting problem.

There is no sign of any water in the diesel, so I don't believe that's the problem.

The leak off pipes were replaced with good quality hose a little over a year ago. They show no signs of deterioration or leaks so I don't believe these are part of the issue.

[vulgalour]

Car dumped a load of diesel on the floor today so I had to find out where it was leaking from.


With the engine not running there was no obvious leak, though the top of the pump was a bit greasy with diesel where it wasn't yesterday.


At idle, the leak became apparent, and from the braided hose I'd already inspected and couldn't find any issues with.


Apply some throttle and it starts putting bubbles out of the braided hose.


So that'll be an air leak then. It might have had an air leak here for a while, I just couldn't see anything amiss at all. Even with the damaged end trimmed off and inspected, the crack is barely even visible.


These leak-off pipes were fitted by the previous owner a little over a year ago and came directly from Mercedes Benz to be assured of quality. I guess that's no guarantee of anything after all. I've ordered new replacement leak off hose to replace all of them with new because if this one has failed, the others will likely not be far behind. The other thing I didn't see until sorting out the pictures was some cracking in the return hose, I could only see these cracks on the photographs, I couldn't see them at all in person.


So I've ordered a replacement length of hose for that too. On the plus side, trimming off the damaged section of braided hose did cure the leak and did improve the starting of the car, I couldn't trim the bigger hose down because there's not enough spare length. Car will not be used until the replacement hoses arrive as I don't particularly want another hose to fail and dump a load of diesel and potentially leave me stranded somewhere.

We shall have to wait and see if replacing these hoses cures the stalling issue which it currently does still have, though much reduced.

[Jaba]

Looks like you are on the case Watson!
BTW there is no lift pump, thats a modern development.
The waxstat wont have any effect on starting that you would notice and will not cause stalling. It just advances the injection timing a tad and lets it go back to normal timing as it warms up. Its easy to check by observing the operating cable. I have had them fail and never notice it for a year and the one on a Bosch TD I had never worked at all and I didn't bother to replace it.

[prm-comp]

Possibly your problems could stem from the previous use of vegetable oil.
Viewing the open end of the hose pic, I would question the type of rubber under the braiding, it would appear separation has occurred.
Certain types of rubbers deteriorate with veg oil, especially when other additives have been included. Even nitrile (Buna-n) can deteriorate over time.
I would check the fuel tank for contamination as Jaba mentioned. Look with a torch for any grey/yellow gum type sludge at the base, microbial growth, usually associated with the ingress of water and syphon these out with a small length of garden hose.

I would certainly try using an injector cleaner. This may reduce the noises coming from the injector pump and clean the whole fuel system.

Regards

[vulgalour]

I wish I had more history with the car to help figure out what was done before Dean owned it. Dean, the chap I bought it from, has been up front and helpful filling in what blanks he could from its time with him but he couldn't get much of anything out of the owner before and I suspect that's the owner that's treated the car poorly. There were lots of signs of neglect all over the car that Dean and I have put right again and I believe this latest round of issues is more of that neglect coming to the fore. It's fine to run a car on veg oil providing you take care with filters and clean fuel etc. and having done it myself in the past I've learned that there's not really much of a saving to be had at all over using regular diesel, certainly when it comes to all the extra faff, filters, and premature wear and tear.

At the moment I'm at the mercy of delayed postage (I'm frankly amazed anything is being delivered lately) so I can't crack on with repairs as quickly as I'd like.

[vulgalour]

Right then, small update. The potential cause of the leak was the o-ring on the throttle shaft as when I took the top off the injector pump to replace it I found the old one was loose, discoloured, and while not rock hard certainly didn't seem as flexible as it ought to be.


I had bought a kit so I could replace this seal and others and on reassembly managed to break some of the internal components so now I'm scouting out for a suitable professional I can send the pump to for a full rebuild once I've saved up for it.


I can get a new throttle spindle to replace the one I bent, the problem is the rod that holds the springs appears to have one end broken off and that part doesn't seem to be available, so I'm keeping an eye out for another 1.7 suitable pump (the 1.9 variants appear to be different) so I can rob the bits I need from that and send everything off to be redone by a professional.

[vulgalour]

Right then, let's bring this to a close (I hope) with a conclusion now that I have the car running again. Sent the injection pump away to be rebuild and on refitting I was having trouble getting the car to idle without stalling. Found the only way to get the pump to run was to have it turned fully towards the bulkhead and have the idle turned up. It was barely driveable, and would attempt to stall every time you came to a junction.

A proper headscratcher, I found that jacking the car up so the back was higher than the front helped, but it still wasn't running right, and I was prepared for dropping the fuel tank and replacing fuel lines at the rear, possibly clearing out the tank in case something had blocked a pick up.

To save work, isolated everything from the fuel filter back by running the car from a jerry can. Initially this showed some improvement even with the car on the flat, until the problem reappeared. That indicated the problem was probably between the jerry can and the injection pump which probably meant a blocked fuel filter.


Took the fuel filter off, emptied it out, found nothing of note inside, and reconnected everything. Now the car was unwilling to run as though the timing was wrong, so moved the pump back to about where it was before being reconditioned and the problem appears to be solved.


Certainly on the short test run it showed no hestitation, no attempt to stall, and it ran perfectly normally. Time will tell if this is the fix and I don't know exactly what taking the filter off and putting it back on again did, but that seems to be the thing that sorted out whatever the problem was. A bit of an odd one this.