Thread: Super rich!
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mark houghton mark houghton is offline
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Join Date: Jul 2008
Location: Central Washington State
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Originally Posted by RarlyL8 View Post
If the rear fuel pump was not working you would be down on power on boost.
If the WUR was also not energized (all CIS components are daisy chained to the run sequence) then you would also be rich when not on boost. The car would run very badly. Rich off boost and insufficient pressure on boost.

Two fuel pumps are not mandatory for these cars. The fuel delivery system can support twice the stock power level (can you say homologation racing advantage?). The problem with single pump failure is that the failed pump then becomes a drain on the remaining pump. The front pump cannot push enough fuel through the dead rear pump and a dead rear pump cannot pull enough fuel through a dead front pump.
Good explanation. The solution: Plumb a valved shunt around each of the two pumps, so if either one dies you can shunt around it. Or better yet, take the rear pump out and run with just the front (or vice versa) and save the extra one for a spare.
Do both pumps output the same? Doesn't one of them (the front?) have a check valve in it?
Mark H. 1987 930, GP White, Wevo shifter, Borla exhaust, stock everything else. The result of a massive Pelicanite good will fire recovery effort. Truely an open book, ready for the slippery slopes to modification.

Last edited by mark houghton; 10-14-2009 at 12:50 PM..
Old 10-14-2009, 11:53 AM
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