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Breaking Pumps
I’ve broken two pumps (expensive mistakes). I’m sharing my experiences to
hopefully save you from making the same mistakes.
Mistake 1: I twisted the positive electrical connection off while tightening the nut.
The reason was that I was trying to thread a 6mm nyloc nut onto the #8-32 thread
studs. Don’t make the same mistake.
Mistake 2: I “rested” the motor on the fuel line leading to my left frame rail
mounted pump pre-filter. The stainless steel line didn’t give and ripped the
end of the fuel pump off (by the way, I did this at Topeka in impound). Don’t
make the same mistake (mount the pre-filter right behind the tank).In-the-Field Pump Flow Measurements
I frequently wondered if my fuel filter was clogged or if my pump was weak. I
measured a couple (with and without filters, both old and new) and here’s what I
found. The time it takes to flow one pint of fuel (from the time fuel starts to
flow, not when the pump starts) is between 13.5 and 13.75 seconds. This is at 70
degrees F and 13.5 volts.
Clogged Filters
The pump is not good at pulling fuel through a clogged filter (but it can really push
through one). One symptom of a clogged inlet filter (either the new external screen
style or the old “sock” in the tank) manifests itself as follows: With a
fuel pressure gauge connected to the fuel rail, the pressure should be around 30 p.s.i. at
idle. When “jazzing” the throttle, the pressure should momentarily rise to
around 40 p.s.i. (same pressure as when you disconnect the vacuum to the regulator).
Now, “jazz” the throttle 6 to 10 times. You are creating a demand
on the system for fuel. If the filter is clogged, after you release the throttle to
idle (after those 6 to 10 rev-ups), the fuel pressure will oscillate for about 2-3
seconds. With a free-flowing system, there may be one oscillation of fuel pressure
upon return to idle, but no more.
Pump Pre-Filter
Run one, you should have seen all the junk in mine after the 9 race 1997 Pro Season.
Tank Pump Out
I empty our fuel tank after every session (weight management). To facilitate this
I’ve run a short jumper wire from the positive terminal of the fuel pump to the right
side frame rail -- terminating in an insulated female connector. To empty the tank,
I just disconnect the fuel feed line at the fuel rail, connect a short hose to the fuel
feed hose and put the other end in a fuel jug. Then I jumper from the battery side
of the master switch to the jumper on the frame rail. Very simple and effective. |
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