low fuel pressure

**mdj** · 02-12-2014

In hard acceleration fuel pres. drops to about 5lbs.new pump(twice)3/8"supply line,pressured tank to help siphon(inline 2000 pump)pinched off return (helped a little but not enough)new filter,this has been going on for some time and tuning is impossible.This is on a built 350 with 90lb. injectors running just under 14lbs. of press.when at idle and when return is restricted, press. rise a kills engine like it should.

**EagleMark** · 02-12-2014

Where is pump located? Wiring to pump, what gauge? Charging system voltage when happening?

But more then likely... that pump sucks for more then a stock engine.

**mdj** · 02-12-2014

Pump is on frame apx. even with bottom of tank.fuel gauge is connected inline right in front of pump.voltage is 14 or above and wiring is factory wire from donor vehicle Pump is for a ford big block and it starts dropping off around 3000rpm.

**EagleMark** · 02-12-2014

Originally Posted by mdj

Pump is on frame apx. even with bottom of tank.fuel gauge is connected inline right in front of pump.voltage is 14 or above and wiring is factory wire from donor vehicle Pump is for a ford big block and it starts dropping off around 3000rpm.

If the wire is small gauge... it may not be able to keep up with voltage demands of pump under high load. Example there are Hot Wire kits for the LT1 vehicles with this issue.

But dropping to 5 PSI is pretty bad and probably more likely a combination of not enough wire gauge and pump just can't keep up.

You may also be experiencing the fuel line and/or filter between pump and tank collapsing? Or if plumbed to an old stock tank the inlet is usually 5/16 and the fuel pump feed requires a 3/8th line. I've gotten away with this if sock is removed from the tank in small low HP engines!

Your basing the pumps ability on the fact it's for a Ford V8 and BB too, but specs are Minimum Free Flow Rate (gph) 30 but that is at 70-95 PSI... and only 5/16th hose.
http://www.autozone.com/autozone/par...ntifier=386516

**mdj** · 02-12-2014

Looking into a in tank install for the fuel cell. Any suggestions on a good pump that is a reasonable price,Plan on fabricating some type of hanger in tank for pump.Apx, 400 horse in engine. Will be increasing pressure to about 18lb. when I get pump problems figured out.(81lb, injectors not 90 lb).this is in a crawler 5500rpm max

**EagleMark** · 02-13-2014

Carter p5000 is from TPI and handles all the TBI high pressure needs. But it does whine so lots of guys don't like it, should not be an issue on a crawler.

This is the best route:
http://www.gearhead-efi.com/gm-ecm-p...onversion.html

**beestoys** · 02-12-2014

Originally Posted by EagleMark

Where is pump located? Wiring to pump, what gauge? Charging system voltage when happening?

But more then likely... that pump sucks for more then a stock engine.

Tend to agree with Eagle and your symptoms back that up at idle it's able to sustain but loaded the duty cycle's killing your pressure. Depending on the vehicle and it's use you may want to research an in tank drop in pusher. It'll run cooler and live longer as well.