Diesel starting problem - update

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Hi All
I'm not 100% sure of the netiquette associated with providing an update to a recent thread. I'm sure, if you're like me, that you don't read old threads,
so I thought I'd make a posting under a new subject.
If you can recall, I have an old BMW that has an intermittent starting problem. It is not frequent, but has happened again. I'm pretty sure now that it relates to a less than 1/4 full tank. Certainly, in answer to another poster, there is NO cloud of black smoke when it does start. This would presumably indicate that no fuel is getting into the engine, and may suggest a pump or filter problem.
The local garage could not identify a problem, but did notice that there was a new fuel filter fitted. I guess this was at a BMW service (I'll ask them next week). My FIL also noted that their BMW (diesel) had a similar starting problem that had a fuel pump relay replaced as a first guess; later the whole pump was replaced which cured the problem.
Would this problem suggest that the fuel filter or pump is at fault? Why would a faulty pump only show up as faulty with an empty(ish) tank?
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I'd always prefer a followup to the original thread, if I'd been interested in the thread I'd have flagged it as interesting and it would have appeared at the top of the threads list when the followup got posted.
--
bof at bof dot me dot uk

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Updates are always welcome, as far as I'm concerned.

What's "FIL"? Do you remember my message about the postal van which wouldn't start in the morning, and on which a fuel _lift_ pump replacement cleared the fault? By the way, the diaphragm is the usual culprit. If it's damaged (often not easy to see) it lets air in. The 2 valves are usually trouble free. What I mentioned about fuel filter sealing rubber rings, also applies to fuel lift pump rubber rings. There are usually two of them; one large one which goes at the bottom, and a small one which goes at the top. You used to be able to get replacement diaphragms, but I don't know what the position is now.

I'm not sure about your particular case; but I believe that the longer (in length) the fuel pipe is to the fuel lift pump, the greater loading there is on it. I can only _suggest_ that a low level of fuel in the fuel tank will increase the actual length of the fuel line, and therefore increase the load on the pump (it has to work harder).
If your BMW has done a high mileage, and the fuel lift pump is the original one (as far as you know); then changing it could be accepted as long term _maintenance_, and be an acceptable thing to do. An example: An engine camshaft drive belt is usually recommended to be changed at a certain mileage (60,000 miles comes to mind). It might run much longer, but I would certainly change it as recommended, _for my peace of mind_ if nothing else. A broken belt can/will do a lot of damage to pistons, valves, and even connecting rods.
Sylvain.

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Sylvain VAN DER WALDE wrote:

Father-in-law
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Grumps wrote:

> If you can recall, I have an old BMW that has an intermittent starting

When the problem occurs try taking off the filler cap if a sucking sound is heard then try starting the engine now, if that cures the problem then that is your source right there, vacuum, 1mm hole in the cap usually fixes the problem.
//J
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Jan Larsen wrote:

Thanks for that (and to Silvain, yes I do remember your earlier comment). I've had a listen at the tank. To me, it doesn't sound quite right. A sort of gurgling, and screeching. Maybe this is what the fuel lift pump should sound like. If I can get the car going this morning, I'll take it down to our local garage again. I can't understand why the engine runs properly when it is going though.
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I had a faulty (genuine new BMW) lift pump fitted in my 525TDS and difficult starting was its result. I think it had no dip tube or it leaked slowly at the top, as it would only start when the tank was nearly full - i.e. was able to prime down to about 3/4 full.
I also fitted a set of new BERU glowplugs which weren't expensive but are apparently good I later discovered.
Nick
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You must remember that the _cranking_ speed is very low. If you were somehow able to turn your engine over at at least idling speed (500 rpm approx), it would probably start quite easily.
Sylvain.

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Any chance you have a small air leak at the inlet side of the fuel pump, or even across the pump itself?
--
Tony Williams.

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wrote:

Yes - would give the symptoms you describe as I said in an earlier post and is what happened to mine
Nick
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Grumps wrote:

How the hell are we supposed to recall this on a new thread, you dummy?
Is it diesel or petrol?
If petrol replace the condenser.
If that doesn't sort it, it might be the air vent to the tank; petrol or diesel. Run the tank dry till the problem starts then remove the cap to allow air into the tank. If that solves it, you need to clean the filler cap or replace it.
If that isn't the problem, run the fuel tank as low as you can, then empty it. If the tank has water in, you have found the problem.
While this does come under the remit of DIY, as with computer threads, they aught to be posted to newsgroups better suited to the problem. But of course the thing is, you are a dummy.
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Weatherlawyer wrote:

Well, silly me. Sorry!

Oh dear! I bet you wish you could crawl into a hole now. Did you read the subject?
<snip mostly quite useful stuff>
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Grumps wrote:

LOL well done !
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How bout now?
--
Need Mercedes parts? http://parts.mbz.org
Richard Sexton | Mercedes stuff: http://mbz.org
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"Manners maketh man". Need I say more?
Sylvain.
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Weatherlawyer wrote:

I have a lousy short term memory, but I remembered the original thread. Perhaps if you didn't find it of interest you wouldn't remember it.
I did, and appreciate the update.
--
http://gymratz.co.uk - Best Gym Equipment & Bodybuilding Supplements UK.
http://trade-price-supplements.co.uk - TRADE PRICED SUPPLEMENTS for ALL!
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We were somewhere around Barstow, on the edge of the desert, when the drugs began to take hold. I remember "Weatherlawyer"

You TTC.
--

Dave

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saying something like:

Don't forget to let us know the eventual outcome. I for one am interested. Don't forget that things get worse in the cold weather; so act _now_.
Sylvain.

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Hi, I had a 525TDS with similar starting issue. When fuel level came below 20 ltrs, starting became worse. Replaced in-tank fuel-pump,problem solved.
Regards, Kees.
saying something like:

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