low fuel pressure

[mdj]

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]

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]

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.

[beestoys]

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.

[EagleMark]

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/parts/Airtex-Fuel-Pump/_/N-5yc1s?itemIdentifier=386516

[mdj]

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]

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-pcm-conversion/in-tank-fuel-pump-conversion.html

[1BadAction]

This is the best route:
http://www.gearhead-efi.com/gm-ecm-pcm-conversion/in-tank-fuel-pump-conversion.html
Is the factory mounting ring on a TBI tank the same as the mounting ring on a bucket style tank like that is from?

[EagleMark]

:confused:

[brian617]

Is the factory mounting ring on a TBI tank the same as the mounting ring on a bucket style tank like that is from?


Negative

[1BadAction]

Negative

Guess that shoots that idea in the ass. Thanks for the info.

[EagleMark]

But for a factory TBI tank you just change the pump to TPI or 96 Vortec...

[brian617]

Guess that shoots that idea in the ass. Thanks for the info.

Anytime I can squash your ideas i'm glad to help :laugh:

What year truck are you working on?

[1BadAction]

But for a factory TBI tank you just change the pump to TPI or 96 Vortec...
I like the bucket style better, they seem to have a more consistent fuel draw when empty but since it's not a somewhat direct swap then I'll just go ahead with a TPI pump in the stock type hanger. A new sender should help somewhat, at 1/4 tank on the gauge I have roughly 2 gallons in the tank, and with the way I drive 2 gallons doesn't get me far. :innocent2:

Anytime I can squash your ideas i'm glad to help :laugh:

What year truck are you working on?
Hey, it saved me some cash or time at the auto parts store fooling with it :wtg: Finally starting to get my Suburban (see sig) where I can start modding. Tune is spot on other than I'm running out of both fuel and air. With 102 atmosphere, at WOT it's 90Kpa at 3000 and vac increases to high 80s from there, at 13psi it's still wanting more fuel with the IDC into the 90s. The minute I put the ported edelbrock intake and bored TB on it, I'm going to need even more fuel.

I also suspect the fuel pump isn't holding pressure when I snap the throttle open, I have the AFPR adjusted to what should be 18psi but all it'll give me is 13. I have the fp gauge but don't have what I need to read it while in the truck with the hood closed.

[EagleMark]

I have the fp gauge but don't have what I need to read it while in the truck with the hood closed.Plumb it to a gauge on the hood you can see!

[brian617]

I like the bucket style better, they seem to have a more consistent fuel draw when empty but since it's not a somewhat direct swap then I'll just go ahead with a TPI pump in the stock type hanger. A new sender should help somewhat, at 1/4 tank on the gauge I have roughly 2 gallons in the tank, and with the way I drive 2 gallons doesn't get me far. :innocent2:

I've used both the TPI and the now the Vortec (96-97 style) and the Vortec pump fits the sender better. The foot on the TPI pump doesn't match the bracket on the TBI sender very well. Not a big deal, but if your'e picky like me it makes a difference lol.

Is your 91 Burb the older or newer style?

[Fast355]

I've used both the TPI and the now the Vortec (96-97 style) and the Vortec pump fits the sender better. The foot on the TPI pump doesn't match the bracket on the TBI sender very well. Not a big deal, but if your'e picky like me it makes a difference lol.

Is your 91 Burb the older or newer style?

I used a 92 4.3 CPI Astro van pump. At 50 PSI it supplied more than enough fuel for ~450 hp.

[1BadAction]

I've used both the TPI and the now the Vortec (96-97 style) and the Vortec pump fits the sender better. The foot on the TPI pump doesn't match the bracket on the TBI sender very well. Not a big deal, but if your'e picky like me it makes a difference lol.

Is your 91 Burb the older or newer style?
Old style, 73 to 91 :rockon:

Thanks for the tip Fast 355, I'm right around the corner from you at DFW just about every day. Great little country style diner we visit for lunch in Euless.

[buddrow]

Old style, 73 to 91 :rockon:

Thanks for the tip Fast 355, I'm right around the corner from you at DFW just about every day. Great little country style diner we visit for lunch in Euless.

Hell I have family in Dallas, maybe next time I drive down I'll pester you guys in person lol

[mdj]

called my salvage yard guy he just got a 2002 chevy truck in and I think those have the bucket style pump assembly.When the snow melts down going to go down and take a look.He said it has a good pump so I may try that one(6.0 vortec I think)

[brian617]

called my salvage yard guy he just got a 2002 chevy truck in and I think those have the bucket style pump assembly.When the snow melts down going to go down and take a look.He said it has a good pump so I may try that one(6.0 vortec I think)

Yes, bucket siphon type.

[mdj]

Found problem after fighting this for a year.In 90 deg fitting that screws on to top of cell had collected some debris that was in some gas from a fuel can about a year ago.I put a filter before the pump after I cleaned the tank and never saw any of the debris in the filter and thought I had got it all.These small pieces had packed in to the 90 so tight you could hardly blow threw it.I dont know how the external pump could suck fuel threw it at all.Engine now runs great and idle much better with no hunting.I now can finally fine tune my chip.Engine hit six grand in a heartbeat spinning 38" tires in the dirt.This may seem like a simple thing to have found but I would have never dreamed that junk could get packed in like it did.Now where can I get a 18 lb. spring for my regulator.