My 406 Break - bought it for work, but already love the car

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joydivision
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Re: My 406 Break - bought it for work, but already love the car

Post by joydivision »

I finally found the time to install the one-way valve into the fuel feeding line, right after the primer bulb, so to end the fuel running back to tank issue when parked uneven. I'm certain that I did it well, the tubes are sitting really tight and I installed hose clamps on both sides, no leaks. But I wasn't aware of the problem of air entering the fuel line with the intervention (first time...). So, after installing, I was observing a real lot of bubbles in the return line (the feeding line is black, so I can't observe it). It started ok, though, but the first kilometres were a nightmare, constant hiccupping and ridiculous loss of power once I would accelerate just a bit. I barely made it to the destiny. Then, after like 20km, it started to improve slowly. It was only then that I researched on the net and understood that the problem was in fact these air bubble that could clearly be seen in the return line. I read that ideally the system should be bleed but that air will also slowly be purged out of the system through the injectors.

In fact, it is now driving much better, if you don't push hard, it drives with normal power, but on hard acceleration, it will accelerate fine for a couple of seconds, reaching higher RPM, and then cut back and start loosing rpm and power, it simply "stops" evolving, if you change back gear into a higher gear and ease the throttle and wait some seconds, it comes back to normal power. I've had a look at the fuel return line, the bubbles do exactly accompany this, first there are just a few or none, then if I accelerate hard, there appear a lot and take some time disappearing afterwards. This is exactly the same when done without gear. So I'm wondering: do I just have to have patience and it will purge what's left of air eventually through the injectors, or do I have to bleed it? It has done now around 60 km since the intervention. If bleeding is necessary, how is it done? The idea of loosening an injector to let the air out scares me a little bit...

I also had a look at Haynes manual, but as usual it just doesn't have any real precise description and no image at all for this, although it describes the procedure... just says to "loosen the bleed screw in the injection pump inlet pipe union bolt"... really helpful (NOT). But at least there seems to be a bleed screw?

So, I'm asking for a little help with this, if possible: do I have to bleed it or does the rest of air get out in a few dozen kilometres and I just have to be patient?
If it has to be bleed, where's that screw located??? Thanks in advance.

Btw: when it doesn't pull air, it accelerates really well, I'd almost risk to say that it runs smoother and better now that the non return valve is fit... also the cold start today went really well, after more than 1 day. So I guess all the trouble will be worth it in the end.

One more thing: I just found a thread where they were talking about a clogged in-tank strainer and it causing air bubbles.
In my car, I'm pretty sure no intervention has been done to fuel tank, so maybe that's the problem and is now being made visible due to the one-way valve?
If yes, how can this strainer be cleaned? I know where the fuel tank sensor and fuel lines exiting the tank can be accessed, I've seen it under the rear seat. But a strainer? Where is it, IN the tank????


On another note: I had to change the direction indicator lights control module (flasher), it decided to die a slow death. First I thought it could be the stalk, but as the hazards lights switch would also lead to failure, it had to be the module, and yes, it's fixed. Fortunately I remembered the thing with the access port on the left hand of the dash, but I also had to remove the panel with the headlights regulator to gain real access.
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Re: My 406 Break - bought it for work, but already love the car

Post by steve_earwig »

The Haynes doesn't cover the Siemens SID801 system! :(

I've had a look about but I can't find any information on bleeding the system. Obviously you'd be wise not to crack open any injectors (unless you have life insurance...)

The loss of power sounds like fuel starvation - something to do with the valve? (Was it ok before?) or maybe a blocked strainer. The strainer is in the tank yes. I've found myself that the hole in the floor of the car isn't big enough for the lift pump on the Bosch, I managed to get the locking ring off but I couldn't get it back on, necessitating the tank to be dropped. It appears PSA couldn't be bothered to change the pressing from when it was just a sender. I don't know about the Siemens, it's also just a sender but looking at the pictures it doesn't seem any smaller than a lift pump.
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Re: My 406 Break - bought it for work, but already love the car

Post by Doggy »

The system should be self bleeding once you have it running as you have now. I have heard of other owners suffering similar problems that turned out to be due to very, very small leaks at the fuel filter or low pressure pipe connections around it. It is entirely possible to have minor leak(s) that allow air to be sucked in but are too small for any fuel to leak out.

Any restriction at the in-tank strainer will make things worse, (more likely to suck air in and restricting fuel delivery). I would definitely check it.

Does the primer bulb get softer after being parked for a day or two?
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joydivision
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Re: My 406 Break - bought it for work, but already love the car

Post by joydivision »

Thanks for the quick replies. First, this engine has been modified: it has the Bosch pump fitted. I have NO idea if they fit the electric lift pump to the tank or not. I guess it's necessary for the conversion?

I'm going through this point by point.

- The valve was bought NEW from a auto parts dealer who I trust, it's specifically for diesel fuel lines, so I highly doubt it has a problem. Especially because when the car DOES accelerate fine (it happens more often now and for longer periods than right after installing it, that's why I though that the air is still being bleed from the system), it has all the power it had before (it even feels like it has more power, but that might be only in my mind).

- I supposed it was the air in the line, as the symptoms are like described on the internet for air in fuel lines. Also, it was much worse in the beginning, car was almost undrivable, now it drives fine when not pushed hard. And it also had a lot of more bubbles in the beginning, so I'm pretty sure it was the air I introduced in the system when cutting the line and inserting the valve. Now, it has solid stream of diesel in return line when idling and gets only a few bubbles when accelerating softly, but a lot of bubbles after a hard acceleration (which is why it will then hiccup afterwards or loose power). It only recovers solid stream when easing the throttle: if you remain hard on the throttle it will remain there or loose even more rpm and power. But overall this whole thing has been getting less worse, that's why I'm still hoping it could just be self bleeding and taking it's time?

- The strainer. Both of you refer to it. But Steve, you say that for the system that has the electric lift pump, it can't be taken out from the access port below the rear seat for it being to small? That would mean I had to take it to the mechanic, as I have no way of getting under the car to take tank off. But then again, how can I be sure it does have the lift pump?
You confirm that a blocked strainer causes worse air problems and other fuel restrictions; could it be that due to having the one way valve, this is a little additional restriction which wouldn't cause trouble itself, but allied to a blocked strainer could lead to worse air entering system through minor leaks in return piping or create fuel restriction? As clearly this problem emerged after installing the valve.

-Yes, the primer bulb would get softer, and engine might even get hard to start when cold, I have this problem since I bought the car, if parked on a ramp with engine higher than trunk, it won't start without manual priming, that's why I installed the one way valve, so yes, I was having a problem with fuel returning to the tank, but I thought that would be due to air leak in the tank or feeding lines. I haven't had the chance to check if this stopped happening now with one-way valve, as there's no ramp nearby my home... but the other day it was parked 2 days and when I started, it came to life quite quickly.


Bottom line, are you suggesting it might actually be caused by a small air leak in the return lines after the injectors/pump (too small to leak fuel), and now that I have the one way valve, the problem gets worse due to a preexisting restriction from clogged in-tank strainer, for example?

I think, for now I will continue to drive, tomorrow I have a small highway trip which I do twice a week to take my son to music classes, I will see how the car behaves, as at 120km/h it needs constant medium throttle to maintain the speed; yesterday I was driving on national road at around 100km/h in 5th without problems; this was totally impossible the day that I installed the valve. So, I still have hope that it's only the air that is still bleeding itself.
Then, after a few days, if it doesn't improve more, I will first investigate the in-tank strainer situation. Then we will see.
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Re: My 406 Break - bought it for work, but already love the car

Post by steve_earwig »

Gah! I forgot which car we were talking about, sorry. This is the 2.1td that's been converted to a Bosch pump from a 1.9. Forget everything I said, neither of these has a lift pump, you *should* be able to get the strainer through the hole in the floor no problem, cracking off the injectors will not kill you. I don't know where this bleed union is, there's no illustration in Haynes as you say, if you can't find it then I can only think you could crack off the union itself.
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joydivision
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Re: My 406 Break - bought it for work, but already love the car

Post by joydivision »

Thanks, no problem :wink:

That's good news, I will check the strainer if I can't get this sorted in the meantime.

Today I made some experiments and took some photos which I send attached.

First, the photo of the one way valve:
IMG_20211101_160207108_.jpg
I actually interpreted this situation wrong and described incorrectly, it's not a fuel return line. The bubbles appear in both lines that go to and from filter, the feeding line going to the filter (but much, much less, it often has a good solid stream) and in the line going from filter to pump, there the majority of bubbles appear.
Before doing the cold start today, I pumped the primer bulb and looked for bubbles, I could see very few, nothing serious, but it got in fact harder after pumping (which would confirm the initial problem - fuel going back into tank). I then started the engine, started nicely, no white smoke, no bubbles, solid stream. But then I accelerated a little and verified exactly what has happened lately (it's so bad that I never had tested or looked at this BEFORE fitting the valve, it could very well have been like this before or not, I will never know), stream of bubbles, especially coming from filter into pump, very little bubbles in the feeding line going into filter. The more acceleration, the more bubbles.
Photo:
IMG_20211101_164509791_.jpg
After a while they kind of settled and back to solid stream, until next acceleration. I then went for a short trip with my son (engine didn't have time to properly warm up). Parked the car. We remained there like half an hour and when we got back to the car, I looked before starting and there they were: a big air pocket right after the filter in the line going to pump and a small bubble right before the filter in feeding line, here are the photos:
IMG_20211101_160228314_.jpg
IMG_20211101_160310955_.jpg
I then primed by hand and they disappeared into the pump, back to solid stream in both lines.
Started engine and on the way home did some short time accelerations, it wouldn't hiccup at all, full power, perfect. It drove very well. BUT: I didn't push it hard and wouldn't accelerate for a long time nor repeatedly in short intervalls, so I guess the bubbles would always have time to sort out into solid stream before next acceleration....
So far the observations.

Now to the conclusions. I can only imagine two scenarios: there's still air in the system, which travels around (and which I managed to photograph) and likes to appear especially when accelerating, possibly due to suction of fuel. I remember that diesel on idle only consumes very little fuel. This air is being expelled really slowly through the injectors. And when left parked a long time, disappears into pump or some other hidden place, so in those lines solid fuel stream can be seen. In this case, I could bleed the system simply unclipping the upper hose that comes from filter to pump, it has simple metallic clips, and prime by hand, making sure solid stream comes out of filter, let this into some recipient (for example bottom of plastic bottle cut off) and then through a funnel insert fuel into tube that is disconnected, then while still priming, reconnect the tube, so that the minimum possible amount of air gets in.

There's another possibility, though: as I observe much more bubbles AFTER the filter than before it, could there be a tiny air leak IN the filter housing/seal? This would explain why the system still has air. But it wouldn't explain why it only started AFTER mounting the one way valve and why it would improve by itself over time, so I don't really believe in that possibility.
Let's see. If tomorrow with the high way trip it doesn't get sorted, I will first try the bleeding,only then study other possibilities.
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Re: My 406 Break - bought it for work, but already love the car

Post by Doggy »

I think your problem must minor leak(s) at the filter or the connections onto it, which allow air to be sucked in particularly when fuel demand is higher.
A restriction in the fuel supply, (e.g. blocked strainer), would result in higher vacuum in the low pressure fuel lines, increasing the liklihood of sucking air in through the tiniest of gaps.

I've just realised that the Bosch pump swap was a favourite technique of people wishing to use waste vegeatble oil as fuel - the original Lucas rotary pump was prone to failure when attempting to run on veg oil, whereas the reciprocating Bosch unit was much less likely to break. If it has been run on veg oil at some point, the strainer is very likely to be at least partially obstructed.

(My brother used to run his 1.9 406 on this stuff and became adept at changing a fuel filter or cleaning the strainer at the side of the road). :roll:
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2003 HDi 2.2 6-speed Exec Estate (2012-19) (also a gem)
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joydivision
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Re: My 406 Break - bought it for work, but already love the car

Post by joydivision »

What you're saying makes absolute sense. The one-way vale in fact acts as a added restriction, which would cause exactly what you're saying, if the strainer is blocked. It could even happen if it was not blocked, if in fact there were several small leaks. Good explanation!

Today I decided to make sure it wasn't air trapped in system after one way valve due to my intervention, so I properly bled it disconnecting the tube that goes out of the filter, then priming manually with the bulb until good stream of diesel came out (into a small jar I put below) and I then inserted a good amount of this fuel with a syrenge into the tube that goes to pump (as I could see the fuel level going down and air entering), until full, and only then connect the tube to filter again. I also removed those two clip clamps which I wouldn't trust, the tube could move by hand, and substituted by normal clamps with a screw which I tightened well. I also checked the other clamps, the ones I put at one way valve were tight, but at primer bulb they were quite loose.

I then tested. After standing a while, it would only have one larger bubble of air in line that goes to the filter. Then on idling it would not have much air bubbles, but as soon as accelerating, they increase. Then, if you leave it on idle again a bit, it would settle and you could again accelerate well. I test drove, it was doing the same, once I'd accelerate harder during a longer time, it would start loosing power or hiccup. Driving it normal you wouldn't notice any difference, engine runs smooth and well.
Now, after some time driving, I parked with running engine and observed the bubbles while accelerating the throttle cable, and now it is very clear: the air comes from the feeding line before the filter, every time you accelerate, more bubbles appear, then after the filter they are smaller, creating a stream of bubbles, probably due to further restriction from the filter they get divided like this and accumulate, while before it they appear as bigger bubbles in less quantity. So I think I can rule out the filter and connections to pump. Problem must be in piping before it or in fuel line from tank or could it be in the tank itself?

This leaves me a few options now:
- try to eliminate any possible air leaks in piping between primer bulb and fuel filter. This is a problem, as most of this is black, not transparent pipes. There are two of those bad metal clip clamps on a small hose piece, though, maybe a good idea to change them for proper clamps?

- get to the strainer and clean it, to reduce restrictions and make it work like before. Here I have two questions: any hints on how to get the thing out of the tank? Can it be taken out without the suction end of tube loosing contact with fuel? If not, I will have air in system again, which I have to bleed out, no? In that case, best place to bleed would be after primer bulb? Or after fuel filter like I did?

- take the one way valve out again so it gets back to as it was... this would be a pitty, as it would go back to cold start issue when on ramp, but the alternative of changing all fuel tubes in engine compartment seems quite some work, which I'm not sure I have time or skills to do (although it seems quite simple) and I'm afraid this might not be very cheap if I ask the mechanic to do this. But sure, it would be best to fix this problem once for all...

I'm kind of lost here right now.

One last question: this system doesn't have a return pipe to tank or does it? If it had, any air left trapped in system would travel back to tank, which could explain that it could come back into engine afterwards?? So, even if bled, maybe it's not bled enough (air could have been in pump or injectors) and could still travel back? This could explain all of it and in that case I wouldn't even have an air leak in piping after primer bulb, would explain why it slowly improved since installing one way valve.

I think for now I will just wait and drive more kilometres and see what happens. And also clean that strainer, if I manage to find out how. And hope it won't introduce more air in system. Then, if not solved, think of changing fuel lines bit by bit in engine compartment or maybe even the primer bulb, who knows it doesn't have a leak? I notice that when I pump it, it doesn't get totally firm, but I don't know if it should...
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Re: My 406 Break - bought it for work, but already love the car

Post by joydivision »

I just took a quick look at the fuel tank inspection hole under rear seat. I'm not sure if I can gain access like this, as the metal ring (it is supposed to be removed by unlocking it, with screwdriver and hammer or similar trick, right? or is this a different system?) seems to be bigger than the hole in the chassis?? :shock:
I will post photo later, I'm not at home right now.

Also, I just had a better look which answers my previous questions: yes, the car does have a return line into the fuel tank. So, in theory, this forms a closed circuit and air that was still trapped in system due to my bleeding technique not being really good, could travel around and come back through supply line? Or do I see that wrong?
If this appears about right, there might not be any leaks in fuel lines in engine bay, might just be trapped air, taking time to get out? For now I will wait and drive a few more days. Today on the highway I could go at 100km/h, maybe 110. In town, when going in low revs and then accelerating just occasionally, it pulls just fine, full power, until high revs. But only for some seconds. So, it seems to drive better than the day I installed the one way valve, which could further confirm that some of the air has already left the system? I mean, if it had an air leak, due to added restriction of the one way valve, it would constantly be sucking in new air and remain equally bad, no? So, let's see. I will report back in the next days.
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Re: My 406 Break - bought it for work, but already love the car

Post by Doggy »

Not a great picture but it may help:
https://catalogs.ssg.asia/peugeot/?lang ... aWVyPT0%3D
I think every fuel strainer/pump/level sensor I have seen has a large plastic retaining nut. I've tapped them round with a screwdriver, used a big pair of grips, whatever works for you.

I don't think you have to worry about air in the return line - the tank must be partly full of air in any case.
All that matters is that the suction inlet is immersed in fuel, the strainer is not seriously obstructed and there is as little leakage as possible between there and the injection pump.
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2003 HDi 2.2 6-speed Exec Estate (2012-19) (also a gem)
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2008 BMW E91 330i touring (great fun - murdered by a reversing SUV)
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joydivision
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Re: My 406 Break - bought it for work, but already love the car

Post by joydivision »

Ok, thanks, this is exactly like I have (I was looking for that drawing but didn' find it, don't know why)...
What you call a "big plastic nut", I can't find it in my car nor in the drawing, I only see the fuel tank ring (pos. 5 in drawing), which is exactly like in drawing, a large metal ring with holes in its side with which it must be locked in place. Probably it comes off like you say, with a little force, unlocking by rotation but what worries me is that it seems to be larger in diameter than the inspection hole, so if it doesn't fit through, I don't think I can remove the sensor/strainer/fuel lines connection plastic part that is contained in its centre?

Here's a photo:
IMG_20211102_141420529_.jpg
I made a larger trip as you already know, and it didn't improve :(
So I'm starting to think it really has an air leak. Might very well be the seal of the fuel filter housing, but I also see those bubbles before it, although much less. But before trying to hunt it down, I'd like to clear the fuel tank strainer hypothesis first...
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Re: My 406 Break - bought it for work, but already love the car

Post by Doggy »

I have not seen one with a steel ring, but the only cars I have seen have been a 1998 1.9TD, 2002 & 2003 HDi's all of these were plastic. The steel version is probably much better - the plastic ones can be difficult to refit without cross-threading.

Not sure about the size of the hole, some go through OK, others do not. Steve removed the fuel tank to change his one, my brother enlarged the hole in the floor.


Just had a thought. Very unlikely, but it is possible the tank vent is blocked making it more difficult to draw the fuel out.
You could try removing the fuel filler cap temporarily to eliminate this as a possible cause.
2002 HDi 2.2 Exec Estate, (2008-12) (wonderful)
2003 HDi 2.2 6-speed Exec Estate (2012-19) (also a gem)
2009 Citroen C5 2.0 HDi VTR+ Estate (godawful heap)
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Re: My 406 Break - bought it for work, but already love the car

Post by joydivision »

Thanks for all your very helpful input. Enlarging the hole in case the ring doesn't fit through sounds interesting, shouldn't be too difficult, avoids having to unmount the tank.
I'm determined to get this settled. The strainer is for sure one thing to check, so maybe I will need to enlarge the hole.
Regarding the vent of fuel tank, I doubt it, as today when filling it up at the gas station I paid attention while opening the fuel filler cap and there was no sound of air as if it had a lot of vacuum. But it's a possibility.

But in the meantime I think I'm on to something: so I've read some stuff on the net and come across something that made my "alert bells" ring in my head: someone talking about check valves adding restriction that is often underestimated. So I went further searching and found out that many of them require a minimum pressure to open and then I remembered that my car doesn't have a lift pump and the pump has to suck the fuel all up from the tank. Now let's imagine that: strainer in tank is partly clogged (maybe even the fuel supply output of the tank itself where the line is connected, might be worth checking!), the fuel filter itself is an restriction, so if the check valve is indeed such a big restriction in this circuit without lift pump, it might be enough to get air in through the most tiny leak that might be there (especially in filter housing), creating all these bubbles, especially after the filter.

So, I decided that tomorrow I will buy some inches of transparent fuel line, take the check valve and the two bits of black piping out again and install the transparent line after primer bulb to next junction before filter. Before connecting all this, fill both ends of piping with diesel to avoid much air. Then prime the whole thing with bulb. And then see what happens. If it works fine, but still has very few bubbles, then my theory would be just right: tiny air leaks with added restriction of check valve leading to fuel starvation on high throttle, while without it the amount of fuel versus air is just on the side of "enough". Then I guess it will be time to study what to do, but at least it will get me somewhere. Then I can investigate all the other things like possible clogged strainer, possible air leaks in filter or junctions close to it, etc. And only then I will think again what to do regarding the fuel returning to tank problem (maybe a check valve on return line would work?). Or leave it as it is and never park on ramp with nose facing uphills. At least the car will run properly. With the check valve I wanted to solve a (not so) severe problem, but just created a much more severe one... :roll:

Now, fingers crossed that it will be working fine again after removing the check valve...
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Re: My 406 Break - bought it for work, but already love the car

Post by joydivision »

Sorry for all the posts... but just found out that the primer bulb usually has a non-return valve fitted on one side as a standard??? :shock: I actually noticed a white plastic piece which something told me was looking strange for being just some kind of union... so when I installed the new valve not knowing this, I basically fitted a second non-return valve causing additional restriction? I mean, even if the old non-return valve had failed blocking in one direction, it would still represent some kind of restriction which was now doubled by the new one, am I thinking correctly? So, I definitely have to remove the old valve if I want to keep the new one! Will do this first thing tomorrow, as it is easy, no new tubing needed, just loosen clamp on primer bulb, pull out old NRV, remove clamp on one side of new NRV, remove bit of hose and connect new NRV directly to primer bulb. Maybe that will do the trick and I can still keep the new NRV?? Still all this means there's a tiny air leak somewhere, but this would give me time to find it, as engine would be back to prior quite acceptable performance.
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Re: My 406 Break - bought it for work, but already love the car

Post by Doggy »

Yes you are right - the priming bulb cannot work without the integral non-return valve, something we should all have realised. :oops:

I agree removing the extra valve is a good idea.

Don't worry about air bubbles in the return line I really don't think it matters, they will just add to the air already in the fuel tank
2002 HDi 2.2 Exec Estate, (2008-12) (wonderful)
2003 HDi 2.2 6-speed Exec Estate (2012-19) (also a gem)
2009 Citroen C5 2.0 HDi VTR+ Estate (godawful heap)
2008 BMW E91 330i touring (great fun - murdered by a reversing SUV)
2007 BMW E91 325i touring (slower smoother quieter)
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