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Discussion Starter #1
Having two starting problems with my 525d:

1. doesn't start when fuel level showing between quarter and half full, when brimmed starts okay, until down to 1/4 or 1/2 full

2. takes quite a few cranks to start (7 or 8) all the time whether hot or cold

Any ideas where to start?

Ta
 

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Id check the fuel pump in the fuel tank first as this is a common issue with the E34 TDS failing and causing poor starting at 1/2 to 1/4 tank, if ok i believe the E39 has a second inline fuel pump under the rear seat which can cause starting issues when faulty,
 

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Having two starting problems with my 525d:

1. doesn't start when fuel level showing between quarter and half full, when brimmed starts okay, until down to 1/4 or 1/2 full

2. takes quite a few cranks to start (7 or 8) all the time whether hot or cold

Any ideas where to start?

Ta
If it's consistently hard to start hot or cold, I'd suspect the inline pump is on it's last legs and is just about keeping the HP pump supplied.

I'd fix it sooner rather than later, costs 70 - 100 quid from GSF etc
 

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Discussion Starter #4
If it's consistently hard to start hot or cold, I'd suspect the inline pump is on it's last legs and is just about keeping the HP pump supplied.

I'd fix it sooner rather than later, costs 70 - 100 quid from GSF etc
Thank to you both for the really speedy replies. I've booked in with my local indie (not BMW specialist) for the weekend to take a look. His first thoughts were:
- pump/sender unit in the tank for the car not starting when less than 1/2 full
- compression test for the fact that it doesn't fire up with a a single crank at the turn of the key

I'll definitely tell him about the in-line pump. Any thoughts on the compression test?
 
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If your fuel gauge is working then I doubt it will be the fuel sender unit is faulty, but the relay that activates the intank fuel pump on cold starts may not be operating causing cold start issues not pumping fuel or operating the glow plugs also,

Definately make sure he knows your car has three fuel pumps, one in the fuel tank, one under the rear seat as well as the main fuel pump.

By compression test I assume he means checking the fuel pressure at both fuel pumps the one in the fuel tank and one under the rear seat first, as checking the cylinders compression would be misleading I would have thought if either fuel pump failing or at least rule fuel pumps out before looking elsewhere for problem i.e main fuel pump, blocked / poor injector spray pattern etc.
 

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Discussion Starter #6
Thanks for the advice, I'll have him check all the pumps as above first together with the relay and then I'll report back at the weekend.

Thankin' you.
 

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Discussion Starter #7
Well, my mechanic and I talked through the symptoms. One of which is that I can do a huge amount of miles until the gauge shows 3/4 full (around 250 miles) and then another 150 miles or so until it shows 1/2 full.

His view was to first take a look at the fuel sender guage, to see if it was operating smoothly. Then look at the relay before going on to testing the pumps.

I'll be dropping it off during the week.
 

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I had a problem starting my E320 Merc (now sold) recently, which got worse and worse until it wouldn't start at all. The problem was worn injectors which were leaking and preventing the fuel syatem building enough pressure to start. This is obviously worse case but thought I would mention it.
 
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