BMW 5.25TD Starting Problems - KingUz
Hello,

My father has a BMW 5 Series, 2.5 TD 1996. In the past week he has had problems when starting the car first thing in the morning. The car will start, then after a second, suddenly cut out, and it takes an age for it to start again. When you try to start it again, the engine turns over, but does not start.

Once it has started however, it works fine all day, just curious if anybody has any ideas?
BMW 5.25TD Starting Problems - sean
One, or two, my friend.

Questions first, then I will give you answers.

1. Where are you? Winter or summer?
2. When was the car last serviced?
3. Independent or franchised dealer?
4. Mileage car has travelled, please?
5. Vehicle parked on a slope, yes?
6. Nose up / nose down?
7. Any recent work done in fuel delivery area? Service etc?

There are some bright people, and me, here, friend.

We will help you.
BMW 5.25TD Starting Problems - KingUz
1. Car is in UK, North West, so I guess Summer
2. Last Serviced about 6 months ago.
3. Don't know, car bought at a garage over 2 years ago, been serviced at BMW specialist though.
4. Mileage is 110k I think.
5. Car Parked on flat surface, although the problem first started last week when it was parked on a slope, nose up for about 5 hours.

Oh, and its an Automatic

Thanks in advance for any help.
BMW 5.25TD Starting Problems - sean
Right then.

It's summer, even near Wigan. The rain is warm. This means the glow-plug circuit is largely redundant.

The change is parking nose-up, with a leak of air into the fuel system.

Dead easy, now, isn't it? Just park nose-down.

Well, no. You have a leak into the fuel system. Buy yourself some Vaseline and smear some around each joint on the pipework, right from tank, through filter, to lump of an engine.

One at a time to find the leak, or all at once, to fix it.

This is rather a good engine. The Quandts are proud.

If you park nose-up, the air runs up the delivery pipe and forms a bubble.

Try this, then please write back. This is a known problem, BTW, and the bright folks here and me will help you.
BMW 5.25TD Starting Problems - DL
The BMW unit will need glow plugs to start, even in this weather. Father in law\'s Range Rover with the same engine will not start without a 5 sec warm-up time in this weather.

I\'d suggest checking each glow plug in turn.
BMW 5.25TD Starting Problems - sean
DL,

You are a very bright poster.

We have both helped folks in this area previously.

I think you know me, and my designs.

Why do others need their plugs this weather?

A list of makers whose designs require this would really help all of us.

Thanks, greatly.
BMW 5.25TD Starting Problems - DL
I would think all IDI Diesel engines would need glow plug activation to start in this hot weather.....I\'ll try it tommorrow morning on something IDI and report back :-)
BMW 5.25TD Starting Problems - Aprilia
IDI engines lose significantly more heat during compression than do DI engines. This is due to the air running down the small channel into the prechanmber and swirling around in the prechanmber - it loses lots of heat (hence also you need significantly higher compression in an IDI vs. a DI).
Prechamber temperature needs to be a minimum of about 50 deg C for good ignition - hence an IDI needs glowplugs even in summer (unless in Iraq!). Some engines have a temp sensor to shut off glow plug cycle when engine temp is over about 50 degrees.

I'm not a Diesel expert, BTW, just what I've picked up from engine design bods.
BMW 5.25TD Starting Problems - DL
I didn\'t think the compression ratios between IDI and DI were radically different? I\'ll check some figures tommorrow.
BMW 5.25TD Starting Problems - Aprilia
Like I said, I'm no expert. Working from memry most IDI are 20-24:1, most DI are 15-18:1. Heat loss is the reason, I think. (Picked up from working with some guys on DI design team - could have remembered it wrong)
BMW 5.25TD Starting Problems - DL
No, all Diesels are in the region of 20 - 24:1

I will look up some info later
BMW 5.25TD Starting Problems - Sooty Tailpipes
Yes DI are usually around 18:1 and IDI 22:1.
If my X25TD engine, which has good compression, light oil, a good battery to turn it over quickly and the weather is fine, it will start after just a few seconds, with the glow, it starts straightaway.

I had a leak around two injectors, it was the braided flexible leak-off pipes coming from the injectors, the diesel was building up in the injector well, when this happened, it was harder to start, as air was drawn in allowing fuel to run back to the tank.

I replaced all these pipes, and the glowplugs, also noticed how vert dirty (PCV oil and EGR soot) the intakes were around the valves, so cleaned those with a bottle brush and a very small amount of spray (very easy to hydraulic these engines, there is about 2-3mm clearence at TDC!!!



Good luck!
BMW 5.25TD Starting Problems - Fullchat
Only needs one faulty glowplug on this engine and things start to go downhill rapidly!I had same problem with an Omega with same engine.


Fullchat
BMW 5.25TD Starting Problems - DL
I concur - the 6 cylinder BMW lump seems to need glow plug activation even for a warm start. The engine spins over for a while before firing, compared to the usual quick fire-up of a PSA XUD engine.
 

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