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Old 05-27-2012   #5
Paul Workman
 
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Join Date: Nov 2007
Location: Squires (near Ava MO in the Mark Twain N'tl Forest) - Missouri
Posts: 6,466
Default Re: Changing Fuel Pumps Tomorrow

Could be a pump, but it is easy enough to check them to be sure.

See LINK to post #7 in this thread re how to test to see if the pumps are both running. And, connect a fuel pressure gauge to the fuel rail.

A fuel pressure gauge connected to the fuel rail (Schrader valve) should be about 52# when you energize the test connector (key OFF).

The current draw is about 4-5 amperes per pump, so you should have approx 8-10+ amperes - will indicate both pumps are running, along with the 52# at the rail. If you have 4-5 amperes, it could be a pump or an electrical failure (fuse/relay, etc).

photo showing proper meter configuration and indicating over 8 ampers (pumps are drawing the proper current, at least).



A dynamic test will confirm or deny if the fuel system is working in real world situations. To do it, you can tape the pressure gauge to the windshield and monitor FP in normal and WOT conditions.



At low throttle the pressure should be in the mid to upper 40s. At WOT the pressure should jump to about 52# and remain steady to 7k. If it isn't holding pressure at that level, delivery is in question (fuel filter??).

Of course, you could just change out the pumps and not bother with what I've suggested. But, I DO suggest this logical approach cuz I had the pleasure of installing new pumps once and had a failure right out of the box, AND a clogged filter to boot (gotta love multiples...makes troubleshooting less mundane, doancha think?). The procedure I just described sorted out the pump AND filter issues at the same time, and will work for anybody contemplating a possible fuel delivery issue.

I'm just sayin!

P.
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