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double trouble or twice as reliable?
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peter scott



Joined: 18 Dec 2007
Posts: 7113
Location: Edinburgh

PostPosted: Sun Feb 14, 2021 10:01 pm    Post subject: Reply with quote

Ray White wrote:

The two pumps are also in tandem.
Worth doing? or overkill?


Paralleling the pumps will permit greater flow rate but I doubt that tht would be required with the XPAG. The 3½ litre SS Jaguar used this arrangement but I don't think it was even necessary there. Fitting the double contacts is well worthwhile though for reliability.

Peter
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ukdave2002



Joined: 23 Nov 2007
Posts: 4100
Location: South Cheshire

PostPosted: Mon Feb 15, 2021 12:14 pm    Post subject: Reply with quote

peter scott wrote:
Ray White wrote:

The two pumps are also in tandem.
Worth doing? or overkill?


Paralleling the pumps will permit greater flow rate but I doubt that tht would be required with the XPAG. The 3½ litre SS Jaguar used this arrangement but I don't think it was even necessary there. Fitting the double contacts is well worthwhile though for reliability.

Peter


The AUA26 (in the pic) pumps can individually pump more than 8 gallons an hour, it would take a very thirsty engine to require 2 Shocked

If the pumps were set up so that they worked in tandem they would be working against each other as it would be impossible to synchronise the phasing of the pumps action. Then if one did fail you would never know until the second one failed!

Dave
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Ray White



Joined: 02 Dec 2014
Posts: 6285
Location: Derby

PostPosted: Tue Feb 16, 2021 2:09 pm    Post subject: Reply with quote

Sound like overkill to me.

One question... if a transil in the pump fails will it stop pumping?
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ukdave2002



Joined: 23 Nov 2007
Posts: 4100
Location: South Cheshire

PostPosted: Tue Feb 16, 2021 7:01 pm    Post subject: Reply with quote

Ray White wrote:
Sound like overkill to me.

One question... if a transil in the pump fails will it stop pumping?

They tend to breakdown o/c so you would never know they had failed, occasionally they fail s/c , but in this instance given their low current carrying capacity will probably fuse and go o/c almost instantly.

Dave
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Ray White



Joined: 02 Dec 2014
Posts: 6285
Location: Derby

PostPosted: Tue Feb 16, 2021 7:33 pm    Post subject: Reply with quote

The reason I ask is I have some very expensive electronics which could be ruined so maybe it would be better if the pump just stopped working....

I suppose diagnosing such a fault would be technical.?
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ukdave2002



Joined: 23 Nov 2007
Posts: 4100
Location: South Cheshire

PostPosted: Tue Feb 16, 2021 9:06 pm    Post subject: Reply with quote

When I worked for Sharp Electronics we reviewed MTBF (mean time between failure) for component failure; comparing manufacturers spec to real world failures. Small Zener diodes operating in the correct application have MTBF's measured in centurys!, so I don't think you have too much to worry about.
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Ray White



Joined: 02 Dec 2014
Posts: 6285
Location: Derby

PostPosted: Tue Feb 16, 2021 9:23 pm    Post subject: Reply with quote

ukdave2002 wrote:
When I worked for Sharp Electronics we reviewed MTBF (mean time between failure) for component failure; comparing manufacturers spec to real world failures. Small Zener diodes operating in the correct application have MTBF's measured in centurys!, so I don't think you have too much to worry about.


You have put my mind at rest, Dave.
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Minxy



Joined: 22 Sep 2010
Posts: 272
Location: West Northants

PostPosted: Fri Mar 12, 2021 9:04 pm    Post subject: Reply with quote

With reference to the original post, when I worked for Audi sport back in the eighties building the works Audi Quattro rally cars it was standard practice to double up on many components. There were three fuel pumps, the car only needed two to run so if one dropped out there was always two to run the car. Two coils were standard on any rally car as was a second throttle cable strapped to the original. Double pulleys with two alternator belts were also standard
I don’t know about today but back then the driver and co-driver were expected to do run of the mill repairs so the car was equipped with spares such as rotors, caps, HT leads etc etc. We, generally, only attended the cars at service halts.
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