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koukouvagia

BMC 1.8 Diesel leak into sump

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After a recent oil change (15/40) I've covered about 60 hours.  The oil level in the sump has risen by about 1/2".  It's now showing just above max.   The engine is in otherwise good nick - it's has a top end rebuild, skimmed head etc.)

There is definitely a diesely smell on the dipstick where the top inch of the oil is less viscous.

 

Before calling in an engineer, I thought I ask for a few pointers as to what might be causing this.

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2 minutes ago, koukouvagia said:

After a recent oil change (15/40) I've covered about 60 hours.  The oil level in the sump has risen by about 1/2".  It's now showing just above max.   The engine is in otherwise good nick - it's has a top end rebuild, skimmed head etc.)

There is definitely a diesely smell on the dipstick where the top inch of the oil is less viscous.

 

Before calling in an engineer, I thought I ask for a few pointers as to what might be causing this.

Check fuel lift pump diaphram first.

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Even more consensus - fuel lift pump highly likely!

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Its the only place it can come from unless the engine is so knacked that it won't run.

If you are lucky the lift pump will be the old type that you can get a repair kit for, the later ones are a chuck away job.

To get you running, open the pump and put a thickish piece of polythene on top of the diaphragm and reassemble, will work for months.

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No its not and many, if not all BMC lift pumps have a drain in the base of the pump so is any fuel leaking out of the base. Not a 100% test but a guide and the first thing to check. Since low sulphur diesel has been mandatory the older "rubber" seals that swelled with the sulphur as they wore so kept fuel tight have been slowly shrinking. This has lead to an increase number of injector pumps leaking fuel into their engine from the main injector pump shaft seal.

 

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Its possible Tony but I have never seen a master splined horizontal 1.8 leak into the chain case, they usually drip from the body on the very rare occasions that they leak at all.

Now 1.5 vertical pumps, that's another story.

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1 hour ago, Boater Sam said:

If you are lucky the lift pump will be the old type that you can get a repair kit for, the later ones are a chuck away job.

If you look at the picture on the ASAP supplies web-site, if accurate, they are now selling again the type that can be dismantled.

The good news is they aren't very expensive.

 

Linky

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3 hours ago, Boater Sam said:

Its possible Tony but I have never seen a master splined horizontal 1.8 leak into the chain case, they usually drip from the body on the very rare occasions that they leak at all.

Now 1.5 vertical pumps, that's another story.

I suspect its because the 1.8 is a newer engine so less time for wear to take place. A 1.5 could be 50 or more years old.

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I Had the same  problem a couple of years ago.  Various diagnoses were lift pump (replaced but didn’ cure the problem), worn injectors dripping (replaced - didn’t cure the problem) and then TB suggested the seal on the injector pump.  Pump was replaced and problem solved.  One word of warning though, if the problem isn’t sorted the diesel level can get to a point in the sump where it self ignites, the engine runs away and is virtually impossible to stop until it self disintegrates!  Drastic, I know, but apparently it can happen.

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If you ever suspect a lift pump diaphragm problem they can be tested fairly easily (that is apart from trying to put the pipe unions back in!).

 

1. Remove both pipes.

2. Turn engine into the position the priming lever gives maximum pumping throw.

3. Thumb over outlet port and   pump priming lever several times.

4. Stop & wait about 30 seconds.

5. Remove thumb and air trapped inside the pump should escape.

6. Carry out 3 to 5 above but this time you should hear air being sucked in.

7. Refit pipes.

 

If it fails the above tests it may be fouled valves rather than the diaphragm but you then know its time to take the pump off & try to strip it.

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37 minutes ago, Tony Brooks said:

If you ever suspect a lift pump diaphragm problem they can be tested fairly easily (that is apart from trying to put the pipe unions back in!).

 

1. Remove both pipes.

2. Turn engine into the position the priming lever gives maximum pumping throw.

3. Thumb over outlet port and   pump priming lever several times.

4. Stop & wait about 30 seconds.

5. Remove thumb and air trapped inside the pump should escape.

6. Carry out 3 to 5 above but this time you should hear air being sucked in.

7. Refit pipes.

 

If it fails the above tests it may be fouled valves rather than the diaphragm but you then know its time to take the pump off & try to strip it.

Thanks, Tony.  I'll report back.  I've got a new lift pump on order, so I may as well fit that.

I note the comments about a failed seal on the injector pump.  I would think this unlikely since I had a new pump fairly recently.

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On 05/07/2018 at 19:06, Tony Brooks said:

Since low sulphur diesel has been mandatory the older "rubber" seals that swelled with the sulphur as they wore so kept fuel tight have been slowly shrinking. This has lead to an increase number of injector pumps leaking fuel into their engine from the main injector pump shaft seal.

 

Just to complete the story.  You were spot on, Tony.  It turned out that it was the injector pump seal, not the lift pump diaphragm that was leaking.  I was told by an engineer at Calcutt that the fact that the engine hadn't been used for a year while the boat was being restored would have exacerbated the problem.

So, this has meant a  refurbished pump. ☹️

Is there any way to stop this happening in the future? 

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8 minutes ago, koukouvagia said:

Is there any way to stop this happening in the future? 


Try to avoid periods of a full year whilst you are having half the boat rebuilt?

Sorry - couldn't resist!

  • Haha 2

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1 minute ago, alan_fincher said:


Try to avoid periods of a full year whilst you are having half the boat rebuilt?

Sorry - couldn't resist!

?

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24 minutes ago, koukouvagia said:

Just to complete the story.  You were spot on, Tony.  It turned out that it was the injector pump seal, not the lift pump diaphragm that was leaking.  I was told by an engineer at Calcutt that the fact that the engine hadn't been used for a year while the boat was being restored would have exacerbated the problem.

So, this has meant a  refurbished pump. ☹️

Is there any way to stop this happening in the future? 

 

I will send you a PM about one aspect of this but how do you stop it happening again?

 

First of all it should not happen after just one year but if the old seal had been exposed to high sulphur diesel the it would have swelled taking up any wear. If the run or left standing with low sulphur diesel the seal would shrink and thus leak.

 

I think regular use is the best answer because we do not know how old the leaking seal was (even if in an "overhauled" pump and we do not know it was made from a diesel tolerant materiel. That is before considering wear in the shaft/bearing that may have gone unnoticed during the overhaul.

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I've learned something today. Thank you Tony, & Koukouvagia. Now I know why I have been carrying a full seal and gasket set for my CAV pump for 15 years. I've seen pumps leak from the rear high pressure end but not from the low pressure end, the explanation seems perfectly sound.

Sam.

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Sam, I think that we can expect this to become more and more common on the DP series of pumps, not only on BMCs but also anything else that uses one like the Perkins 4-10x etc. To be honest I think this will apply to Rotodiesel and given time the Bosch rotary pumps.

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Well Tony, you have awakened the devil, but what is the solution? Are the new seals less susceptible to this swelling and shrinkage?

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16 minutes ago, Boater Sam said:

Well Tony, you have awakened the devil, but what is the solution? Are the new seals less susceptible to this swelling and shrinkage?

I understand that new (not new old stock) seals are less likely to be attacked by bio-diesel but the swelling was an advantage in that it took up a degree of wear. It was the sulphur in the old diesel that caused it so now we have low sulphur diesel normal wear will cause leaks sooner than it would with high sulphur diesel. I am talking about years and years not just a few years, probably decades. So not a problem for the automotive industry but certainly a potential problem for inland marine engines.

 

Still look on the bright side, at least the cap seals on BMC lift pumps should be easier to get back in if you are unlucky enough to pull one out!

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