Diesel starting problem

[squelchy]

Hi

I dont know if anyone has mentioned this before but if it is a deasil the glow plugs need to suck quite allot of batery power for them to heat up before the fuel will light and start the engin if your battery is not in its best condition tha is the first place I would look if you notice the baterys on deasils are always heavy duty for this reason compared to a pertrol engineed car hense why they tend to cost more to replace (just the joys of a deasil) try to get the batery charged over night or see if you friendly garage will test out the problem with a new battery if you have a friendly local machanic they will do this for free as if you need a new battery they would hopwe for the sale.

I hope this helps

Paul Herber wrote:

[Bob Mannix]

Batteries for diesel engines are heavier duty because the compression ratio for diesel engines is significantly higher than that for petrol engines, and this requires more torque.

[Grumps]

Thanks for the reply. Problem is, the car starts normally 99% of the time. Only occasionally will it take longer. I put the battery on charge last night for about 12 hours. It was still not fully charged by morning. Even so, I'm not sure it is the battery. How does one test the battery? (the engine does turn over easily for sustained periods)

[The Natural Philosopher]

Yeah. Ive had three batteries gpo on me this year.

The symptoms are that they take forever to charge, won't start the car properly even when they are charged, and all sorts of ancillary equipment goes haywire..if te battery is > 5 years old I'd simply replace it before looking any deeper. As I said my wife's Freelander diesel with a BMW engine would barely start even when jumped..new batery and it now springs to life. They don;t regulate te voltage to teh glow plugs..and I suppose thats what it was.

I had a guy with an old diesel tractor working here for a while. His method was to remove a bit of air intake, tip a cupful of diesel into the air intake, and if the glo plug failed to set it alight, use a bit of lit newspaper. Then cranking that lot over sucked raw flames into the cylinders, and it usually belched and rumbled its way to life with clouds of black smoke.

I wouldn't treat an engine that way myself tho...

[Grumps]

Well, perhaps it is only the battery. Nothing lasts forever. It just seems funny that the engine cranks without any effort.

Well, I'm not quite at that stage yet.

Needs must, as they say.

[The Natural Philosopher]

The point is that the battery should be something you can fit for 50 quid yourself, and if it fixes it, well and good. If not when you DO take it into BMW, at lest thats something they won;t be able to charge you 200 quid to fit ...the wifes car also turned over.a bit lazily..but wouldn't start..when we jumped it, it turned over and DID start, but it was a few seconds spluttering before it finally fired on all cylinders, Now with a new battery, it starts every time..perfectly.

The other things you should ALWAYS do are check the fuel filter and the presence of water in the diesel tank. Some vehicles have a warning light for that..rough running and a white smoky output are symptoms. Again these are cheap things to do, and once done eliminate another few potential culprits.

Diesels by and large HAVE to be made to such tight tolerances to work at all, that the wear rates are extremely low. 200K miles without any major parts replacement and not even a valve regrind is the norm for a diesel ENGINE.

After that, its probably new bearings, injectors, fuel pump and valve regrind time.

Mmm. That one also ended up with water in the tank...drained it, fitted new fuel filter (I dinnt know you ad ter do that mate) and fuel, bled the bloody thing (no fun at all) poured a half pint into the intakes, lit it and it was running well when he took it back to warwickshire..

>

[OxSc]

Petrol will damage the fuel *injection* pump. The fuel injection pump operates at very high pressures, and is built to very fine tolerances. It relies on the fuel for lubrication; petrol doesn't fit the bill. (BSI BS EN ISO 12156-1 describes the assessment of diesel fuel lubricity, and I seem to remember that there is or used to be a BS specifying among other things the minimum lubricity for diesel fuel sold as such (as opposed to central heating oil, for example.))

The very high pressures also account for the precautions taken to remove water from the diesel before it reaches the injection pump; water in diesel fuel can easily become acidic, and at high pressures will rapidly dissolve pump parts and ruin tolerances.

[Clint Sharp]

In message , OxSc writes

Speaking as someone who used to control field engineers and having had to arrange for their diesel tanks to be emptied and refilled with diesel on more than one occasion (all within 15,000 miles of new) after the muppets filled them with unleaded and drove off, we never had a single incident that cost us more than two tanks of fuel and the garage costs for pumping out and disposal of the fuel (how much does it cost to put the fuel in a breakdown truck?). We ran the cars for over 100,000 miles and never replaced a pump, in fact we never replaced anything in the fuel system apart from the filters. 13 Peugeot 406HDIs, one Renault Espace 2.2DT and an Audi A6 1.9Tdi.

[squelchy]

[Grumps]

[Stuart Noble]

Didn't see the beginning of this and I'm no mechanic but, whenever I've had starting problems, it's always been the glow plugs. Cheap and usually easy to fit

[Grumps]

Indeed. Our old BMW had constant starting problems which was fixed with a new glow-plug set (but I don't remember them being cheap or easy to fit). The current car has just had the ok on its plugs.

[Sylvain VAN DER WALDE]

That's a possibility. I would check it out.

The frequent enemy of a diesel engine fuel system is _air entering it_. In the case of filters, there usually is a round detachable housing which is sealed by a rubber ring. You should _always_ replace that ring (supplied with the new filter element). Sometimes several different rings are supplied, and you should compare the new one with the old one. This rubber ring is not always easy to fit, and I always used a mirror to make sure that it was seated properly. The assembly that the fuel element housing fits to has usually an input connection and an output one. These don't normally give problems, but _sometimes_ they do (they allow air to come in). Cleaning these joints with petrol, drying carefully, and using some jointing compound (red hermetite is ok) on all the threaded parts, etc.. will usually work. I don't normally endorse using jointing compound, unless a part is unobtainable or excessively costly.

Sylvain.

Sylvain.

[Grumps]

Hmm. The BMW main dealer must've replaced this filter. You'd think they'd know how to do it! However, I'll get them to check.

Would this "fitting error" (if it is an error) cause an intermittent starting problem? The engine runs perfect otherwise.

[Richard]

Neighbour's newish-jag which is powered by some awesome twin-turbo Vee diesel does not have a glowplug symbol. He was warned (by Jaguar) that if he inadvertently fills it with petrol he must _under no circumstances_ even unlock the vehicle. Apparently it _does_ have some sort of preheat system, but it commences as soon as the doors are unlocked, thus there is no embarrassing pause once you have jumped into your sleek executive conveyance!

Richard

[Pete C]

You'd have thought that cars could have an RFID tag by the filler that a reader in the pump nozzle would check.

Then the pump would stop and flash a light to tell the driver they're about to make an expensive mistake!

Would be easy to retrofit to cars too, just stick the tag inside the filler flap.

This sort of technology has been around on London Buses for a while in the form of Oyster prepayment cards :)

cheers, Pete.

[dom]

AFAIK petrol can only damage a diesel engine once it gets as far as the high pressure pump. As the high pressure pump is driven off a pulley from the crankshaft (or directly from a camshaft with unit injectors), I can't see how that can happen unless an attempt is made to start the engine.

I know in the case of my VW (indirect injection, mechanical pump) the only fuel lift pump is part of the high pressure pump, so it would be impossible for petrol contaminated fuel to move from the tank without cranking the engine.

Whilst glowplugs may be linked to doors etc, it will have no effect on a misfuelled diesel vehicle - so is this "don't touch it" an urban myth or is there some other reason?

Maybe electric fuel lift pumps (that run indepedently of the engine for some reason) on some diesel vehicles?

[Sylvain VAN DER WALDE]

The answers I've supplied are general ones, and are not necessarely applicable to yourself. In my experience, you can't assume that all mechanics are competent. Some are not.

The "air in the system" fault can be a most elusive one to diagnose sometimes. I can't give you a definite answer.

I remember going many times (as did other mechanics) to a postal van (at a sorting office) which woudn't start first thing in the morning. Bleeding the fuel system (removing the air) got it started, and it ran alright for the rest of the day. The next morning it probably wouldn't start. Obviously the matter had been investigated in the workshop. If I remember correctly, fitting a new lift pump did the trick.

Sylvain.

[Grimly Curmudgeon]

We were somewhere around Barstow, on the edge of the desert, when the drugs began to take hold. I remember The Natural Philosopher saying something like:

Bit of bent wire, burning rag. Used to do that all the time with my S2a slug. Wouldn't do it with a CR diesel, mind.

[Grimly Curmudgeon]

We were somewhere around Barstow, on the edge of the desert, when the drugs began to take hold. I remember Clint Sharp saying something like:

Is the right answer for pre common-rail systems.

If the main dealer is going to latch on to this latest money-spinning wheeze and charge an arm and leg, you may as well do it yourself. After all, if flushing out the fuel system fixes it and you get another 40 or

50 thousand miles before the pump expires, you're to the good. If it doesn't, then your'e no worse off than paying the dealers' prices anyway.

I've heard of several who've done just what you did and had no further problems.

As far as CR systems go - I'd suck it and see. Pretty much the same applies as above. IMO, there is more of a risk, but it can often be got away with. Much of the FUD about this is put around by the makers and the dealers as just the latest money-making wheeze, designed to part hapless punters from their cash.