Can't be the fuel pump.... - TCCoA Forums

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post #1 of 9 (permalink) Old 01-17-2017, 02:07 PM Thread Starter
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Can't be the fuel pump....

96 4.6L with +200k miles and the original fuel pump. Got a P0232 code. Checked all the wiring and relay. All is fine. Car runs. Can't be the fuel pump. It's the original one and you can hear it running next door! Guess I should replace it anyway... Car is stock so looking for opinions on which one to put in. What is the stock lph? Would going too big just cause it to fail prematurely? Ideas?
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post #2 of 9 (permalink) Old 01-17-2017, 03:09 PM
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Before you do that ... check the fuel FILTER which is on the passenger side, under the car, in line.

If it's plugged you'll get a lot of racket and not much fuel.

I'd also plan on replacing that fuel pump, but it's a lot harder than the filter.

Now. With a good filter, a higher flow pump won't cause any problems because the pressure regulator is a bypass style; the excess gets shunted back into the tank.

RwP

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post #3 of 9 (permalink) Old 01-18-2017, 10:17 AM Thread Starter
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Fuel filter is new. When I checked the pressure a month or so ago is was low (forget the exact #s but remember it being about 9psi low). Swapped another filter in and no change.

Planning on just the placing the fuel pump. Just haven't decided on which one. Can't find the stock values on the original but saw where the Mustang GT used a 110lph (though Ive read tests that showed 155lph).

Another question: whats the chances I break the bolts when dropping the exhaust? Should I plan for that and order new ones?
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post #4 of 9 (permalink) Old 01-18-2017, 10:42 AM
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Just get a walboro pump and call it a day. Just because it can flow more doesn't mean that it will until the need is there, and that way you don't have to drop the tank again just to change it out if you add more power down the road.
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post #5 of 9 (permalink) Old 01-18-2017, 12:34 PM
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Quote:
Originally Posted by Woodman View Post
Just get a walboro pump and call it a day. Just because it can flow more doesn't mean that it will until the need is there, and that way you don't have to drop the tank again just to change it out if you add more power down the road.
???
The tbird is a return based system (not return-less).
a larger (255lph) fuel pump WILL flow more fuel from your tank but the pressure regulator will just shunt the excess fuel back into the tank. Arguably, this will heat up your fuel. That fact doesn't particularly bother me but it is a valid difference between a stock and an upgraded pump.

In a returnless system (I believe some of the later mustangs have this b/c it was an option in the ECU programming), the ECU signals the pump to shut off when the desired pressure is exceeded. In THAT scenario, you would be correct in that a faster flowing pump will just spend more time idle vs. pumping.
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post #6 of 9 (permalink) Old 01-18-2017, 04:28 PM
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Quote:
Originally Posted by S4gunn View Post
???
The tbird is a return based system (not return-less).
a larger (255lph) fuel pump WILL flow more fuel from your tank but the pressure regulator will just shunt the excess fuel back into the tank. Arguably, this will heat up your fuel. That fact doesn't particularly bother me but it is a valid difference between a stock and an upgraded pump.

In a returnless system (I believe some of the later mustangs have this b/c it was an option in the ECU programming), the ECU signals the pump to shut off when the desired pressure is exceeded. In THAT scenario, you would be correct in that a faster flowing pump will just spend more time idle vs. pumping.
So the pump isn't a variable pump? It's either full tilt or nothing?

My mistake. I was under the impression that under low power demands, it wouldn't pump full blast, thus my comment.

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PI Swapped NPI motor with some port work on the heads, PI cams, 80mm MAF, CAI that feeds from fenderwell. Jmod, 3.73:1 TL in Mark VIII carrier, Mark VIII aluminum LCAs, 93 Mark VIII driveshaft, PBR brakes (soon to be Cobras), 18x9 wheels, 255/40/ZR18 Tires, Front and Rear strut/shock bracing, GR-2 shocks, Eibach 1.5" springs, 1989 SC front and rear sway bars.
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post #7 of 9 (permalink) Old 01-18-2017, 05:43 PM
No, Mr. Lemmywinks, No!!!

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Return-type and non-return type are different; you can really fuck yourself not knowing which you need.

A return type is a "Gearotor" type pump, similar to an oil or transmission fluid pump. it delivers whatever flow rate you paid for.

Stock is ~86lph, fwIr. The excess returns to the tank. 255lph will turn over the tank in ~5 minutes, ignoring what you would use idling.
Gas is a bad heat conductor, that volume cycling would increase the temp in a tank, but you could heatsink the return line easily, if that was important.

A non return pump is a turbine, with flow proportional to voltage, supplied by a fuel controller.

Like I always say, "Know your pump like you know your pimp"...

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post #8 of 9 (permalink) Old 01-19-2017, 07:26 AM
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Replace the fuel pump,filter,and tank sock. I put a 255LPH walbro one in, and have not looked back, car runs way better than it did before i put the new pump in. Only reason i went with that pump was that a friend hooked me up with employee discount and some cash for it, to make up for one that failed a week after install.
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post #9 of 9 (permalink) Old 01-20-2017, 08:59 AM Thread Starter
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Not sure how I missed this but per the '97 service manual:
"The high-pressure fuel pump on the 3.8L and 4.6L (2V) engines can supply 95 liters (25.1 gal) of fuel per hour at a working pressure of 269.0 kPa (39 psi) at 13.2V."

So that is equivalent to ~134lph free flow rate (@13.2V).

For anyone interested (or is as big of a geek/number-cruncher), I threw together a graph showing flow rate vs. pressure of the common fuel pumps available.
Attached Images
File Type: jpg FlowRate.jpg (174.9 KB, 4 views)

I did what last night?
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