Diesel pump trouble

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Vanny
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Diesel pump trouble

Post by Vanny » Sun Jun 11, 2006 7:00 pm

for a good 6 month now i've been going through a long winded process of having to prime the fuel system to start the car. Obvious thing to check was the piping for air. Thoguh issolation it doesn't seem to be the supply pipes return pipes or leak off pipes, i've also changed the priming bulb to a brand new one!

When primed up nice and firm, it takes about 4 seconds before you start to hear a hissing noise thena few seconds later there is a gurgling noise. The hissing sounds like its down the back of the pump and the gurgling sounds like it comes from the dome on the top (i realise there is no fuel in or near it).

I'm thinking that something in the pump has failed, but i REALLY dont want to have the car into bits all over again! Anybody have any bright ideas?


(Xantia Bosch pump, thus far hasn't been messed with at all!

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Post by jeremy » Sun Jun 11, 2006 8:16 pm

You presumably have a Bosch pump? If so it will be prone to problems from the leakoff/return system - and I suppose you could eliminate it by clamping a connection from this circuit to the pump and seeing if there is any difference.

The same can be done on the inlet side -- this time by substituting the last section of pipe to the pump for clear - and looking for bubbles.

Have you got the black plastic filter bowl? Have you checked the thermostat for the fuel heater? I think this is the bolt - like thing that can be seen at the base of the filter pointing to the offside when you look in from the front. I think its sealing washers can leak - there are some posts on the French car forum about it.

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Vanny
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Post by Vanny » Sun Jun 11, 2006 9:04 pm

As it says in the post it is a Bosch pump and being a xantia engine DOES have the plastic bowl type filter. I have clamped the leak off pipes and this has made no difference.

When the outlet is clamped it primes and holds its pressure/fuel quite happily so i DONT think its actually an air leak, i would have thought if there was a leak then under priming the pressure and fuel would leak out?

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Post by Stewart (oily!) » Sun Jun 11, 2006 9:43 pm

How old are your fuel lines Vanny, mine were rotten, perforated, hardly leaking though?
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Vanny
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Post by Vanny » Sun Jun 11, 2006 10:49 pm

metal fuel lines are about 3 year 26000 miles old. Same rubbers though, and the lines have been heavily waxoyled a number of times. Realistically everything has been replaced. Fuel filter is the metal top with rubber lip type and about 2 month old (made no difference!), have replaced a number of non original pipes that where showing cracking. Have known good jubilee clips on all connectors except the leak off pipes and return line to the tank.


Issue only started AFTER rebuild of engine, and the pump probably only has about 75000 miles on it!

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Post by AndersDK » Tue Jun 13, 2006 12:13 am

Cracked pump body or top cover ?
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Vanny
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Post by Vanny » Tue Jun 13, 2006 8:23 am

id have thought if that was the case then fuel might leak frm the sides? There is certainly nothing obvious (like a ruddy big crack), starting to really annoy me now! Fuel economy is down quite a bit but i think this is down to beltching out a cloud of diesel everytime i start her up! Its better on long runs!

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Post by jeremy » Tue Jun 13, 2006 4:54 pm

Vanny

Amongst their functions both the Bosch and Roto-diesel injection pumps function as fuel lift pumps - which means that over the majority of the pump it is working at greater than atmospheric pressure - and of course any leaks would be to the outside - rather than air being drawn in.

On the Roto-diesel the lift pump is in the form of a vane attached to the driveshaft on the drive end of the pump. I do not have a good diagram of the Bosch to hand but it may have a similar arrangement. If this is so then I suppose a worn drive shaft seal might admit air. - and this would be one about the only place air could get in. There may be a tell tale leak under the cam cover.

I have never heard of this but I think seals are readily obtainable and are cheap.

I would normally say have a look at the Range Rover and other 4X4 sites as they seem to spend forever tinkering with injection pumps. However some of those vehicles have lift pumps before the injection pump and so those pumps will NOT have the lift stage in them.

I still think you have a leak on the inlet side before the pump.

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Vanny
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Post by Vanny » Wed Jun 14, 2006 12:46 am

Thanks jeremy,

i've spoken briefly to a diesel specialist today who has said pretty much word for word what you have written here and that i just need to hunt the leak! Traditionally i have always found that the fuel leak will tell you where it is if you pump long enough, but even clamping the fuel return line and allowing the primer to go stupidly hard has not thus far shown a leak.

I would have expected given the speed with which the filter drains that there would be some fuel seapage under load but i guess not!

Watch this space while i find a spare day to tinker!

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Post by jeremy » Wed Jun 14, 2006 11:21 am

Vanny

The purpose of suggesting the return pipe system was clamped off was to try and eliminate the whole of it at a stroke as it were. What I envisaged was being prepared and when you shut it off one day, immediately clamping the system shut shomehow, then releasing the clamp immediately before startup.

The idea being that any air in the system has not come from the return pipe system.

Form various postings on the french Car forum it seems that some (ZX TD's?) have a non-return valve in the return pipework - and I don't know if yours has one or even really what its supposed to do. Rather than open this subject at this stage and cause confusion I thought that by clamping you would find out in which part of the circuit the problem lay.

I wonder how difficult it would be simply to bypass the proper filter altogether and use a disposable filter for a short while just to see if there is any improvement. Filters cost a £ or 2 and are readily available in accessory shops and would enable you to eliminate the filter/heater and its thermostat as the cause.

Just as a comment I was not impressed by the top seal on the black filter bowl when I replaced the filter on our ZX and thought the top would be prone to distortion by careless tightening. Mine did seal properly first time but I was not impressed!

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Vanny
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Post by Vanny » Wed Jun 14, 2006 4:10 pm

GET THE HELL OUTTA MY HEAD


Image


picked it up about an hour ago at the local factors :D Have a big long length of fuel pipe too, just need to find some time to tinker! Also gonna go order the seals while im at it!