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Noisy fuel pump


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Firstly is it abnormally noisy? They can become more noisy as they start to fail, gave restricted fuel flow (from a blocked filter or fuel line) or the PRV is set/stuck too high. Listen and compare to another car running a Lucas pump (might be tricky as many are now on Bosch pumps).

If it sounds like a low flying aircraft you may have resonance - bend the flexi high pressure pipe with your hand and see if all goes quiet. If it does change the pipe or at least loosen and twist and re-tighten to try and change the frequency out of the audible range.

You could isolate the cockpit from the cabin by fitting a firewall which will give better/additional sound isolation than the trim does. As you rightly say you can't really wrap the pump in sound deadening without likely ioverheating and cavitation.

Fit a Bosch or Sytec equivalent - they sit in the spare wheel well where the Lucas CAV filter is currently mounted

 

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55 minutes ago, Andy Moltu said:

Firstly is it abnormally noisy? They can become more noisy as they start to fail, gave restricted fuel flow (from a blocked filter or fuel line) or the PRV is set/stuck too high. Listen and compare to another car running a Lucas pump (might be tricky as many are now on Bosch pumps).

If it sounds like a low flying aircraft you may have resonance - bend the flexi high pressure pipe with your hand and see if all goes quiet. If it does change the pipe or at least loosen and twist and re-tighten to try and change the frequency out of the audible range.

You could isolate the cockpit from the cabin by fitting a firewall which will give better/additional sound isolation than the trim does. As you rightly say you can't really wrap the pump in sound deadening without likely ioverheating and cavitation.

Fit a Bosch or Sytec equivalent - they sit in the spare wheel well where the Lucas CAV filter is currently mounted

 

I would check the flow of petrol to the pump first. The original design of 1/4" bore pipework to pump is only marginal further restricted by the banjo bolt bore/ hole size into the CAV filter. Crud can cause blockages like rust flakes or rust flakes can sit on top of the exit hole in the tank. When was the filter last changed and have you bled the filter unit with the set screw on top of the filter? as air can build up in the filter body!  This happen to me once! Is the pump body getting hot?

Bruce.

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Well this leads me to my next question,having checked most of the suggestions through and found no problems I began to think I haven’t had the car running much though Revington tr had it for a while and didn’t mention the pump being overly noisy.So would a Bosch pump be less noisy in anyway,now I think of it the previous owner made no mention of pump problems so assuming it’s me being paranoid,my son in law runs a tvr chimera and although you can hear the pump when he switches the ignition on you would be hard pressed to hear it when running.What  is the noise difference between the two of any

regards Nige

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43 minutes ago, nigelcurry said:

Well this leads me to my next question,having checked most of the suggestions through and found no problems I began to think I haven’t had the car running much though Revington tr had it for a while and didn’t mention the pump being overly noisy.So would a Bosch pump be less noisy in anyway,now I think of it the previous owner made no mention of pump problems so assuming it’s me being paranoid,my son in law runs a tvr chimera and although you can hear the pump when he switches the ignition on you would be hard pressed to hear it when running.What  is the noise difference between the two of any

regards Nige

Hi Nige,

Im sure there is as much noise variation between different Lucas pumps as there is with Bosch conversions.

I fitted a Bosch type conversion supplied by Malcolm at Prestige and I consider my pump to be quite noisey. I have tried various things to reduce the noise with limited success. It isn’t a resonance issue just a noisey pump. I have heard others with similar set ups which are almost silent. For sure there is a reason for this but I haven’t found out what it is yet. Is it just the pump or something to do with the return line to the pump….. I don’t know. I’ve tried different mounting solutions and have big diameter outlet from the tank and through the filter in front of the pump but I can still hear the pump with the engine running on tick over, especially with the hood up. However once driving I can’t hear it. It runs fine by the way with no issues, so I’m not overly concerned.

Im not sure if this answers your question, but I think what I’m saying is that I wouldn’t change the pump setup just because the one you have seems a bit noisey.

Cheers, Rob

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Hi Nige

Maybe worth checking the armature end float of your Lucas pump, as follows.

Slacken the locknut at the top of the pump, screw the centre adjuster in until resistance is felt, then screw the adjuster back a 1/4 turn hold in place and tighten the locknut.

Cheers Steve.

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I'm of the impression that there are different flows of the different Bosch pumps, that have been used, and other makes for that as well, so at idle there will be much more noise, as the majority of flow will be returning thru the PRV and back to the tank.  It also depends if you still have a CAV filter fitted, the returning flow from the PRV is also feeding the pump under a bit of pressure, and not relying wholly on the pump sucking.

It would be really useful to know what pump numbers are fitted that do show the noise.  I know my Bosh pump ends in 996, so its the biggest flow, and does buzz a bit at idle, but is not so noisy at speed, and not heard as much, as there isn't so much going back from the PRV.

John

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IIRC Wheeler Dealers episode on the TR put the fuel pump inside the rear wheel arch... I think it was for better ventilation rather than noise. Can't remember if they shielded it from road crud or if I actually dreamt it all up anyway LOL!!!

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42 minutes ago, John L said:

I'm of the impression that there are different flows of the different Bosch pumps, that have been used, and other makes for that as well, so at idle there will be much more noise, as the majority of flow will be returning thru the PRV and back to the tank.  It also depends if you still have a CAV filter fitted, the returning flow from the PRV is also feeding the pump under a bit of pressure, and not relying wholly on the pump sucking.

It would be really useful to know what pump numbers are fitted that do show the noise.  I know my Bosh pump ends in 996, so its the biggest flow, and does buzz a bit at idle, but is not so noisy at speed, and not heard as much, as there isn't so much going back from the PRV.

John

John, Lucas pumps  suck but Bosch Pumps don't but rely on gravity feed this why they s/b be fed through a 3/8" bore pipe with a low resistance Bosch filter before the pump. Bosch's roller vane pumps do not like crud coming into the vanes as they can some times get jammed up.

Bruce.

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Nothing wrong with the Lucas Pump! As I have said many times before on this forum..."If it was good enough for 2 decades in Formula One on the Cosworth DFV, it's good enough for our Pi cars!" True unlike the Saloon Pi cars where it has the space to lay on it's side, the limited space in the Roadster means it's upright sitting on it thrust washer which can cause it to overheat if you haven't got a "Continental Cooling Kit" as Triumph named the Coil that surrounds the electric motor! Since fitting mine way back in 1972 I had no trouble with overheating. In fact I find the hum from the pump quite reassuring, as opposed to the 'Screech' which is quite distinctive when it did let me know it was overheated!DSCN0002.thumb.JPG.7d640fba8481e618414f7c6d907f379e.JPG

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On 11/5/2021 at 11:40 AM, Rob Y said:

Hi Nige,

Im sure there is as much noise variation between different Lucas pumps as there is with Bosch conversions.

I fitted a Bosch type conversion supplied by Malcolm at Prestige and I consider my pump to be quite noisey. I have tried various things to reduce the noise with limited success. It isn’t a resonance issue just a noisey pump. I have heard others with similar set ups which are almost silent. For sure there is a reason for this but I haven’t found out what it is yet. Is it just the pump or something to do with the return line to the pump….. I don’t know. I’ve tried different mounting solutions and have big diameter outlet from the tank and through the filter in front of the pump but I can still hear the pump with the engine running on tick over, especially with the hood up. However once driving I can’t hear it. It runs fine by the way with no issues, so I’m not overly concerned.

Im not sure if this answers your question, but I think what I’m saying is that I wouldn’t change the pump setup just because the one you have seems a bit noisey.

Cheers, Rob

Bosch type pumps often become noisy when they are being starved of fuel. Have you got a proper fuel supply to the pump? A genuine Bosch pump needs 2.6 liters per minute at the pump!!! The Lucas/CAV 1/4" bore system will no where near give this volume. This figure comes from Bosch engineering in 1982 when I converted to a Bosch pump. I had to increase my pipe work to 3/8" bore and modify the tank outlet and use a Bosch low resistance filter before the pump.

Bruce.

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Hi Bruce,

Thanks for your comments. I’ve done all I can before the pump I think, so this means bigger outlet from the tank and I’ve changed the filter from the one supplied with my “kit” to a bigger one with a mesh filter and bigger inlet and outlets.

 I don’t know why but I have a feeling it is coming from something the other side of the pump, a restriction in the return flow to the tank maybe? Car runs fine even on hot days. The original kit came with a small filter before the pump and a paper filter inside. After a drive on a hot day I got fuel starvation which stopped the car. Since changing the filter I’ve had no issues like this but it did not reduce the noise.

It isn’t too bad once driving, can’t be heard above the engine, but it is definitely noisier than some I’ve heard.

Rob

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