BMW M51 with dead pump - options?

[BenzBoy]

I think the high pressure pump on my e39 BMW 525 TDS is dead. I lost all power and it won't restart. DDE light on. (On the motorway, at night, with a car full of people and luggage with no hard shoulder... yes it was as much fun as it sounds)
I'll get the thing plugged in and read the codes, but I'm preparing for the worst case scenario here and the electronics inside the pump have gone wrong.

I'm looking into converting to a mechanical VE pump and was looking for any advice or websites that have some good info. That way I can at least have fun upping the power and won't have the electronics to worry about any more.
Apparently the easiest way is to find a VE pump from the M21 diesel, but they aren't exactly easy to come by. Even then, I'm not sure if it's a bolt-on job with some fabrication of a throttle linkage.

Is it possible to use another VE pump (say, from a Cummins 6BT) or is there some sort of difference in the bodies that will stop me using it, or at least make it more difficult?

Is there an option to use the pump head from the original (dead) VP37 to make some kind of hybrid with a VE of some kind?

I'm on a learning curve with all this, but I'm not afraid to get my hands dirty and have a go. I realise opening up diesel pumps isn't something you can do on a gravel driveway with a screwdriver and claw hammer, but I'm keen to give it a go, get the pump on the workbench and learn something new.

[grahamk]

Aww man I feel for you. I had an e39 525tds touring and loved it. Its quite rare for the HP pump to fail so suddenly from what I am led to believe. The lift pump in the tank is the usual culprit.

It should be possible to convert to a non electronic pump. The Merc guys do it all the time. The OM606 from the w210 has electronic throttle gubbins and the pump from the w124 is cable. Dieselpumpuk should be able to answer questions, there are a good few people running the M51 as a mechanical pump but I believe you need a different ecu like a megasquirt or similar.

I resealed the vp37 on mine. I forgot to score the head of the pump with a stanley blade to line it up exactly as it was taken off. It was an absolute pig to get running right again. About 3 hrs of fine adjustments.

[BenzBoy]

From what I understand, the lift pump would make starting difficult, but once it's running the HP pump ought to pull diesel through on its own. There's fuel in the line between the filter and the pump, so I at least know that fuel is making it that far.
It's had an intermittent problem for a while where the throttle just stops working, usually between gear changes. It's as if you aren't pressing the pedal. This only happens a couple of times when cold, then it seems to sort itself out. I assumed that was due to a dirty throttle pot in the pump. My old e34 TDS used to do it too, and a dose of Diesel Magic now and then seemed to do the trick. This total loss of power and no throttle response seems to be related to that, although the engine cutting out and not restarting leads me to believe that the fault is more than just the throttle sensor (I would imagine the engine would continue to idle if the throttle sensor stopped working... but who knows?)

I'll be able to get a diagnostics computer on it tomorrow and hopefully see what's up. Whilst I like the idea of a mechanical pump conversion, if I can make the existing one work again with a cheap-ish repair I'll go down that route.

[ChasR]

I just re-read your thread and saw grahamk 's comments. IMHO he is on the right path.

My old man had a 1996 Pre-facelift E36 325TDS company car back in the day. He had the car cutting out alot. It initially did it when it was at the halfway point on the fuel gauge. It then became more random.

From memory this was done to it.
-Leak off pipes changed; no difference
-Lifter pump changed, an improvement but some things became worse. It became even harder to restart at times
-Found out the dealer fitted the one-way valve incorrectly.
-High pressure pump changed.

We look back and reckon the lift pump was buggered in hindsight; the car ran fine until the fuel level went low. but then of course many years later people found out that the fuel pump pickup would become holed and aerate the diesel as it dropped below a certain level in the tank.

But I've seen similar things happen to a few cars. Diesel fuel can congeal in the fuel tank and make the car very awkward to run, as well as burning out your fuel pump due to all of the congealed mess. I'd say going from that the lifter pump or plumbing within it is at fault, if you don't have the gunging problem, which is an increasing problem thanks to EuroDerv and it affects even newer diesels:

[ChasR]

One way to keep the diesel bugs from reappearing besides cleaning the tank out is to treat the fuel with biocide. Another is to always keep the diesel tank topped up to full; it is the exposure to air/water condensation within the tank which causes this problem.

Another mate of mine reckons V-Power Diesel is the way forwards. His story had a point.

1)His Passat has done 70k under his ownership. After a year it would be a pig to start, especially in winter.
2)His Wife's Golf GTTDI (same engine) was always fine but ran on V-Power for 80k.

One day they ran diesel purge through the system quite recently. The Golf had very fine grey particles present. The Passat? Tons and tons of black gungy curse word, despite both being serviced on time. It does start significantly better now I must admit! Veggie oil can have the same issue with the injectors believe it or not.

But you can guess what I run the Mercedes on! I do however top it up a little more frequently; a few Merc owners have been caught out with blocked filters!

www.octane.uk.com/diesel-bugs-biofuel/

[BenzBoy]

Hmm, interesting info thanks ChasR. I've changed the title since we're discussing the faults with the existing VP37 a bit more.

Before I owned it the car was run on all manner of curse word and stunk like a chip shop. The diesel pump sounded clattery and it had that intermittent throttle problem.

Since then, I've given it a new fuel filter, new leakoff pipes (which helped with the lumpy idle and diesel leaks) oil and filter change plus air filter.
I've ran it on straight diesel and a few flushes of Diesel Magic for 6000 miles. The throttle problem was still there occasionally but I put it down to a dirty throttle sensor and a dose of Diesel Magic every now and then seemed to sort it out.

The problem that left me stranded happened like this:

Before setting off I'd just put 3/4 of a tank of Ultimate Diesel (or whatever it was called) in. I don't normally use it but I wasn't concentrating and put the posh stuff in. I figured it might do it some good (ha!)

70mph on the motorway, had just done around 80-100 miles with only one little glitch from the throttle early on in the trip, which sorted itself after a second.

Car begins to slow, and behaves as if I've just let off the accelerator. Engine still running, no lights on the dash, temperature fine. No amount of pedal input makes any difference.
As I pull into the refuge area, DDE light comes on, and as I come to a stop the engine cuts out and will not restart.

If it's the lift pump then I'll be happy, as it's a cheaper fix. However I've never had difficulty starting the car, and I was under the impression that the lift pump doesn't really do a lot once the engine's running. I've heard about the airation of diesel at low fuel levels and never let it go below 1/4 tank as a precaution.

[BenzBoy]

I'm dragging the car back to my workshop tomorrow. I'll be able to borrow a diagnostics machine to hook it up to so I can read the codes, and I'll also be able to do a few tests like seeing if the lift pump primes at all, and have a bit of a better poke around.

[rollingcoal]

It seems to me like you have a blocked in tank filter (like the one shown above )
I used to run my cars on veg oil, biodiesel, diesel mix and the symptoms you have described are spot on
take the top off the tank and have a look in the tank before you spend any cash on the pump , cleaning the tank is going to be cheaper than the pump
some pumps also have a tiny inline filter in the banjo pipe joining the pump, check for that
also make sure the fuel lines are clear by blowing air down them with an air line

[BenzBoy]

We rescued the car yesterday and after some cranking on a fresh battery the damn thing fired up. Read the fault codes but the DDE light was off and there wasn't any code that suggested a problem with the pump or sensors apart from: 1 DELIVERY-CONTROLLER CONTROL DEVIATION. Could this suggest loss of pressure in the fuel rail?
There was however a load of air in the fuel. The engine ran fine, but had constant air bubbles flowing through into the HP pump. At 3k RPM it got worse (possibly due to the greater fuel flow).

I noticed that the fuel level had dropped to 1/4 of a tank - I've never let it go below that due to the possible curse word in the tank and the in-tank o-ring failure which could make restarting difficult. I'd never had either of these problems but I figured I'd play it safe and kept it pretty full.

I went and got 20 litres of diesel to see if it was that o-ring on the pump letting in air, but the problem remained and a look inside the tank showed that the pump and pipes were all well submerged so they shouldn't be able to pull in air. The fuel looked pretty clean in there too.

One theory is that the air has gradually built up in the HP pump until it cannot supply any fuel. I'm a little bit dubious as I feel the engine would stutter and run rough before dying, rather than just steadly decelerate until it cut out... but maybe I'm wrong.

The hose coming from the tank looks fairly old and cracked, so that will be my first step in trying to find the source of the air leak.

[ChasR]

On the Mercedes I changed a few hoses as the pattern items were deteriorating. It does start better now, even with a lack of the fuel thermostat, as I bypassed that at the same time.

Speaking of which, you can't go off R6 spec alone these days; rubber hose is curse word quality these days. The only one I've seen last is either Gates Barricade or Cohline hose. dickdasterdley sells the latter over at www.powersteeringstore.co.uk/

[BenzBoy]

Just updating this, I put a power probe on the lift pump - not a peep from it. The car is more difficult to start now too.

I think what's happened is, the lift pump died and the engine kept running with the HP pump doing all the work pulling the fuel up from the tank. The extra pressure difference caused by the high pressure pump meant that air is being drawn in from everywhere there's the slightest hint of a leak. Normally the pressure provided by the lift pump would mean that this air wouldn't get in.
The air built up in the high pressure pump faster than it could bleed it off and the engine essentially ran out of fuel.

I've ordered a new lift pump, so I'll fit that when it gets here and see what difference that makes.

[Rich]

Also a point I've encountered on the e46, not sure it applies to this but they have a saddle tank over the prop and to allow the fuel to get from one side to the other it has a Venturi system attached to the pump outlet in the tank, which draws fuel from the unpumped side. When the pumps get weak (or fails one supposes) the Venturi effect is lessened and it runs one side of the tank dry whist one stays moderately full. The car still registers It has fuel because the instruments average a reading from 2 tank senders. Not sure if this particular model used this system but worth just bearing in mind I suppose.

[BenzBoy]

Apr 11, 2018 19:43:24 GMT Rich said:

Also a point I've encountered on the e46, not sure it applies to this but they have a saddle tank over the prop and to allow the fuel to get from one side to the other it has a Venturi system attached to the pump outlet in the tank, which draws fuel from the unpumped side. When the pumps get weak (or fails one supposes) the Venturi effect is lessened and it runs one side of the tank dry whist one stays moderately full. The car still registers It has fuel because the instruments average a reading from 2 tank senders. Not sure if this particular model used this system but worth just bearing in mind I suppose.

Aha! Yes, it does indeed have the same set-up. That would explain the breakdown more than the air filling the distributor pump theory (in my mind at least), as it was on a long journey so the lessened transfer from one side to the other due to the failed pump would mean that one half of the tank had chance to run dry.

[Rich]

Apr 11, 2018 20:44:10 GMT BenzBoy said:

Apr 11, 2018 19:43:24 GMT Rich said:

Also a point I've encountered on the e46, not sure it applies to this but they have a saddle tank over the prop and to allow the fuel to get from one side to the other it has a Venturi system attached to the pump outlet in the tank, which draws fuel from the unpumped side. When the pumps get weak (or fails one supposes) the Venturi effect is lessened and it runs one side of the tank dry whist one stays moderately full. The car still registers It has fuel because the instruments average a reading from 2 tank senders. Not sure if this particular model used this system but worth just bearing in mind I suppose.

Aha! Yes, it does indeed have the same set-up. That would explain the breakdown more than the air filling the distributor pump theory (in my mind at least), as it was on a long journey so the lessened transfer from one side to the other due to the failed pump would mean that one half of the tank had chance to run dry.

In that case, get the delivery pump going and you'll have to get some fuel into the tank and then brim it to 'reset' it once it's running. Fingers crossed its something this simple!

[BenzBoy]

Cheers Rich, I'll do that. Hopefully it'll do the trick and the old bus will be back on the road

[BenzBoy]

Just an update on this: I replaced the lift pump in the tank - no more air bubbles in the fuel. The HP pump sounded a lot happier too. Brimmed the tank and did a 100 miles in it this weekend without a hitch.
I think we can call that one fixed. Thanks for your help and advice everyone