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Noisy Bosch pump


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Hi,

I have a Bosch pump fitted to my 69 TR6.

As starting from cold seemed to require leaving the pump running for a minute or so before operating the starter before it would actually start and run, I spoke with Neil Ferguson who said it was a commomn problem if the cable leading to the pump was not uprated to at least 22 amp rating. The original loom cable is too small and there will be a voltage drop.

Having checked the voltage at the pump as advised when cranking sure enough the voltage was down to 8.5 volts.

An uprated cable has been fitted operated through a relay and wow the pump operates at a much greater output. The engine starts pretty well straight away.

Problem: with the pump operating a higher output the noise has increased considerably. Seems like its almost cavitating. The pump is mounted in the spare tyre well with rubber mounting clamps.

Has anybody else had this problem?

Cheers

Rich

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Rich,

I had this with a 996 pump, before I dismantled the car to do body-off work.

When I removed the tank I found a flake of scale/ rust stuck in the tank outlet.

You can install a bigger outlet to the tank without welding, think from Prestige.

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Rich,

 

The correct Bosch pump needs a bigger supply hose than 6mm -1/4" bore. The supply hose to my Bosch pump is 10mm approx. and my tank outlet hole was also modified. My pump is a 0-580-254-952 and I was told by Bosch UK that this pump needs 2.6 L/PM minimum at the pump for it to work properly. So you could have cavitation or hammering from the pressure relief valve also known as harmonic noise.

 

I don't know if this helps you?

 

Bruce.

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I keep hearing about the Bosch 996 pump on this forum and it being the one to have on the TR6 ...I believe I have one on my car and it was installed nearly 30 years ago... What makes the 996 so special compared to other pumps please?

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Just found out that the Bosch pump conversion kit I bought from the TR Shop isn't fitted with a Bosch Pump! The description in their catalogue says Bosch TYPE fuel pump conversion. Caught out again, misread the description. Spoke to them re noise and their solution is sell me a new type replacement matching PRV for use with this pump at £120! Apararently they claim Moss kits are also not Bosch.

As anybody had problems with the TYPE pump fitted to these kits re noise and has the solution been with a replacement PRV.

Rich

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The Bosch pump on my '6 (supplied by Malcolm at Prestige) has always been noisey. I fitted it nearly 10 years ago and it's always worked well but is clearly audible when the engine is not running.

 

It's wired through a heavy duty cable/relay and is fed from the tank through a 5/16" adaptor (also supplied by Prestige), so no problems with power or fuel feed, it's just noisey.

 

 

Nigel

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The MOSS roller cell pump fitted to my TR6 was excessively

noisy, fixed by fitting a longer 8mm return pipe from standard

pressure relief valve to top of tank.

 

Harvey S.Maitland

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Interesting, a longer return pipe from the PRV would be a easy mod, might help, will do it anyway.

Another question:

What is the usual order of pump and filter. I understand original conversions using genuine Bosch pumps, the feed from the tank went to the pump, then to the filter and then to the PRV.

The TR Shop/Moss kit, pre mounted on a plate for fixing to the old filter mounting bracket, has the filter first connected to the tank which is mounted above the pump.The pump, whether Bosch or look alike, should always I beleive be at the lowest point at the bottom of the spare wheel well in both cases.

Interested to hear the general opinion, and indeed if it matters.

Cheers

Rich

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Interesting, a longer return pipe from the PRV would be a easy mod, might help, will do it anyway.

Another question:

What is the usual order of pump and filter. I understand original conversions using genuine Bosch pumps, the feed from the tank went to the pump, then to the filter and then to the PRV.

The TR Shop/Moss kit, pre mounted on a plate for fixing to the old filter mounting bracket, has the filter first connected to the tank which is mounted above the pump.The pump, whether Bosch or look alike, should always I beleive be at the lowest point at the bottom of the spare wheel well in both cases.

Interested to hear the general opinion, and indeed if it matters.

Cheers

Rich

 

Rich,

You are correct that is how mine was set up on Bosch UK's advice 35+ years ago. Some people fitted a gauze filter between the tank and pump to catch the large crud like flakes of rust!

 

Bruce.

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The Moss conversion I bought about 16years ago was filter before pump. I have just had the pump replaced and the mechanic that did the work reversed it so the filter was after the pump. His first comment when he looked at it was the filter should be after the pump. He also put a small in line filter between the tank and pump.

 

The Moss kit also had a tight bend in the hose between the filter and pump which has pinched the hose a bit so the flow to the pump was probably not what it should have been.

 

Simon

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My Bosch conversion on my TR6 was done with I believe a 996 pump nearly 30 years ago by Enginuity.... The fuel comes out of the tank along a short piece of fuel hose then into a large Bosch inline fuel filter then another piece of hose to the pump which is mounted on the chassis down behind the rear wheel arch

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The filter needs to protect the pump, besides the other components ( PRV, MU and injectors) so should be upstream of the pump.

The disadvantage of this location however is that this reduces the available inlet pressure in the pump, which can lead to cavitation. This is why the filter needs to be "large" (low resistance at a given flow rate).

A small inline filter may not be sufficient to ensure sufiicient inlet pressure (NPSH-available), especially when the fuel warms up and requires more inlet pressure (NPSH-required).

Waldi

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Hi Guys,

 

Just fitting a new alloy tank manufactured by Alicool in the UK. Nice bit of kit.

 

I am also reversing the pump set up to have the pump first then the filter as advised by proffessionals that have considerable experience. This is how Bosch originally recommended it. Moss and TR Shop kit is the other way around!

 

Also intend to put a 'T' piece in the MU return pipe and feed this into the inlet pipe from tank to pump to provide an additional fuel supply to the pump. Having left the return pipe unconnected when running the pump :wacko: its surprising how much fuel is returned from the MU. This extra fuel must help the pump resist cavitating surely and perhaps make it run quieter?

 

Cheers

Rich

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Hi Guys,

 

Just fitting a new alloy tank manufactured by Alicool in the UK. Nice bit of kit.

 

I am also reversing the pump set up to have the pump first then the filter as advised by proffessionals that have considerable experience. This is how Bosch originally recommended it. Moss and TR Shop kit is the other way around!

 

Also intend to put a 'T' piece in the MU return pipe and feed this into the inlet pipe from tank to pump to provide an additional fuel supply to the pump. Having left the return pipe unconnected when running the pump :wacko: its surprising how much fuel is returned from the MU. This extra fuel must help the pump resist cavitating surely and perhaps make it run quieter?

 

Cheers

Rich

I wouldnt as it will heat the fuel quicker.I always fit a very large filter before the pump to protect it. no point in having the tank putting crap into the pump and the dinky filters do nothing for the flow.

Stuart.

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Rich

Before you get too 'into it', have a good 'push around' of all the hoses and pipework.

When I had my Bosch (Moss) setup apart for petrol permeation (stink) through the hoses, I found a lot of the noise is the pipework/hoses/PRV (original type) and not the pump.

Now it is all rewired on a new supply, the pump really only goes 'Zuuzzz' when running but the hoses sometimes ring like a bu**er until you touch them!!

 

If this is the case, see if you can move them around until you find a 'sweet spot' then fix them in that location using cable ties/similar.

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Rich

Before you get too 'into it', have a good 'push around' of all the hoses and pipework.

When I had my Bosch (Moss) setup apart for petrol permeation (stink) through the hoses, I found a lot of the noise is the pipework/hoses/PRV (original type) and not the pump.

Now it is all rewired on a new supply, the pump really only goes 'Zuuzzz' when running but the hoses sometimes ring like a bu**er until you touch them!!

 

If this is the case, see if you can move them around until you find a 'sweet spot' then fix them in that location using cable ties/similar.

 

The noise that you refer to is known as harmonic hammering and is promoted by the Lucas PRV valve opening and closing very quickly. It can often be cured by the way you suggest or a pig tail put the hose length or a cable tie used to anchor the hose pulled up tightly or a softer HP Hose used. Do not use one of these 1000psi smooth bore PTFE Hoses that are promoted by some of these PI Bosch Type Pump suppliers. If you want to use PTFE only use a convoluted bore Aerospace type type rated at 200psi. The convolutions break up the harmonic pattern caused by the pump action.

 

Bruce.

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I wouldnt as it will heat the fuel quicker.I always fit a very large filter before the pump to protect it. no point in having the tank putting crap into the pump and the dinky filters do nothing for the flow.

Stuart.

Stuart,

 

What make & part number filter do you use?

 

Bruce.

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I wouldnt as it will heat the fuel quicker.I always fit a very large filter before the pump to protect it. no point in having the tank putting crap into the pump and the dinky filters do nothing for the flow.

Stuart.

 

+1 for Stuart and the filter pre-pump. Mine is quite large to minimise flow restriction - Volvo part # 202711

 

post-14246-0-71225600-1493788581_thumb.jpg

 

Gavin

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+1 for Stuart and the filter pre-pump. Mine is quite large to minimise flow restriction - Volvo part # 202711

 

attachicon.gif14937883846040.jpg

 

Gavin

The one I quoted is an awful lot bigger than that, 100mm long by 74mm wide.

Stuart.

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The one I quoted is an awful lot bigger than that, 100mm long by 74mm wide.

Stuart.

I'm using the same sytec filter, mounted vertically with outlet at bottom.

 

Works great, can run tank down to empty without a problem.

 

They're cheap too.

 

Steve

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