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Beastrider *
Joined: 30 May 2019 Posts: 30 Location: Wales
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Posted: Sun Feb 09, 2020 0:17 Post subject: Spring stretch mod - fuel return valve |
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My KZJ95 has an irritating whine/buzz which seems to come from the passenger footwell. The noise follows the engine revs but not causing any driving problems - just annoying. From reading this forum, it seems the spring stretch mod in the fuel pump return valve may be the thing to try first.
Some people stretch it just a few mm, others say up to double the original length. I have also read that the spring weakens over time. Does anyone know the free length of a new spring? Or the part number for a new valve?
Increasing the spring force presumably increases the pressure required to open the valve. Could there be a detrimental effect on the pump by increasing the back pressure?
How much fuel is likely to leak out when I remove the 14mm blanking pkug from the top of the return valve? Do I need to use a hose clamp somewhere?
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Posted: Sun Feb 09, 2020 0:17 Post subject: Google Ads keep this community free to join! |
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diggerdave ****
Joined: 03 Oct 2014 Posts: 448 Location: Bubwith
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Posted: Sun Feb 09, 2020 0:50 Post subject: |
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If memory serves... I stretched it to about double its length. Everything has been fine (60,000m). I don't recall any fuel leaking at all, but keep a towel handy. _________________ 1997 KZJ90 3.0d, 2" suspension lift, 235/85/16 Cooper STT Pros. 217k hard miles |
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warwick lawley *
Joined: 11 Mar 2016 Posts: 29 Location: united kingdom
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Posted: Thu Feb 13, 2020 0:08 Post subject: fuel return line vibrating. |
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At low engine revs, there was this irritating buzzing noise from the rear nearside of the car. I found that the fuel return line was resonating thus setting up this dammed vibration. I fitted a non return valve in the engine compartment and the buzzing noise was gone. The non return valve fitted opened at the slightest pressure so did not impede the return flow but was sufficient to dampen the fuel flow pulses and cut down the resonance. |
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Beastrider *
Joined: 30 May 2019 Posts: 30 Location: Wales
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Posted: Thu Feb 13, 2020 22:52 Post subject: |
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Hi - that's interesting. I was also researching about fuel pulsation dampers which i believe are used in the feed line on some engines. I suppose your NRV is acting in the same way in the return line. Can I ask exactly where you fitted it and where you bought it?
Meanwhile, I have stretched the fuel return valve spring from about 13mm to 16mm and it has definitely reduced the irritating buzz noise. Probably I need to stretch it a bit more.
I also read that a longer length of flexible hose can cut down the resonance.
For me, the noise mostly seemed to come from the passenger footwell but also would come from the rear nearside floor area. |
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warwick lawley *
Joined: 11 Mar 2016 Posts: 29 Location: united kingdom
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Posted: Sun Feb 23, 2020 0:58 Post subject: Fuel return line pulsations |
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The NRV was an aluminium bodied device obtained from my local Motor Factor for under £5. I fitted it on the NS wheel arch in the engine bay and ran an extra short pipe to the fuel metering/pump unit. A damping unit with an internal rubber diaphragm would have been ideal and would have got one had I not had success with the NRV. |
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Beastrider *
Joined: 30 May 2019 Posts: 30 Location: Wales
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Posted: Wed Feb 26, 2020 20:59 Post subject: |
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Thanks for the reply. OK - I know the ones you mean. I have seen those NRVs too. Good to know it worked for you. I’ll try that if the noise returns. |
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