Fuel pressure and Voltage

[Turbo z28]

I notices as the voltage drops on my Scan master I get a drop in Fuel pressure, are they tied in together or should be looking for something else?

 

[TURBOPOWERED68]

I notices as the voltage drops on my Scan master I get a drop in Fuel pressure, are they tied in together or should be looking for something else?

Low Voltage and Low fuel pressure are directly related.
i am also dealing with low Voltage issues.
Good luck

 

[SHADOWII]

You should be able to locate a graph for the popular pumps, showing the sustained pressures @ differant voltages, like 12 to 16v. Should be able to go on the manf. web-site. May be able to use a caspers volt booster to help out.

 

[87GN_70GS]

If you're talking about a drop in fuel pressure while at idle, cruise, light throttle, etc, that should not be happening. Sounds like a ground or wiring or transducer issue.

But a drop in fuel pressure at WOT while under boost, etc. is directly related to supply voltage.

 

[Turbo z28]

It drops at WOT, it will go from 59 down to about 52-54 at 15psi. and then i start to see knock.

 

[Turbo z28]

and the voltage goes from 13.7 to about 12.5 volts

 

[SHADOWII]

The voltage should not be dropping off. Best to take the car and have the alternator/regulator checked for the output. It should be about 14.2-14.6v.

 

[kidglok]

heres what i found out: http://turbobuick.com/forums/threads/fuel-pump-output-and-voltage-deatchwerks.377992/#post-3026694

 

[RmvBfrFlght]

and the voltage goes from 13.7 to about 12.5 volts

My understanding is that there is something wrong with the alternator's regulator. As the RPM goes up the regulator decreases the voltage. There is a thread or two here on this issue. I'm not sure I could find the thread as I don't recall any of the keywords in that thread.

Maybe search/look for threads that recommend the Impala SS alternators. Supposedly bolt in.

The other side of the coin is that the fuel delivery is right on the edge. And that a better pump would be a good idea.

RemoveBeforeFlight

 

[Turbo z28]

Just got a new Powermaster 200amp alternator, Thanks for the help.

 

[696]

From looking at differnent peoples powerlogger files 13.2/ 13.6 is about right til WOT then I've seen most go to 13.0 and some drop to 12.8 or so. Only one I saw that kept 14.2 was with a volt booster...then your gonna get alot of opinions on doing that.

 

[Ttype6]

Just got a new Powermaster 200amp alternator, Thanks for the help.

When we look at the numbers on the Powerlogger they are coming from the Scanmaster which always reads lower than the actual volts that the generator is putting out. However,if the numbers you see are falling,your generator is falling. If this fall in voltage is making your fuel pressure drop,your pump is at the edge of its capabilities. I always recommend Red Armstrong's volt booster. If your new generator maintains good voltage,it should make a difference. You should still have a volt booster for as much cushion as possible. The volt booster also supplies more voltage to the ignition and that it good. Do you have your pump hot wired? If you don't,your pump is seeing much less voltage than the generator is putting out. Use only AC Delco fuel filter.

 

[Turbo z28]

Fuel pressure drops but not all the time, When I do notice the drop I also notice the Voltage on scanmaster drop.
I ordered a new Powermaster 200 amp adjustable voltage Alternator to hopefully rectify the problem.
Now my CK $2400. all billet transimission is slipping go figure!

 

[Chuck Leeper]

Wrong length belt will allow the tensioner to bottom out, allowing the belt to slip under hi rpm/load....
Bad grounds, poor connections, corroded cables, bad battery cell. All will do what u r reporting...

 

[SS/GN]

Fuel pressure drops but not all the time, When I do notice the drop I also notice the Voltage on scanmaster drop.
I ordered a new Powermaster 200 amp adjustable voltage Alternator to hopefully rectify the problem.
Now my CK $2400. all billet transimission is slipping go figure!

Alternator will not help,volt booster is the answer .Do a search Richard Clarke wrote a long and detailed fact finding mission on this.I like the Reds unit very simple but effective

Kevin

 

[Ttype6]

Fuel pressure drops but not all the time, When I do notice the drop I also notice the Voltage on scanmaster drop.
I ordered a new Powermaster 200 amp adjustable voltage Alternator to hopefully rectify the problem.
Now my CK $2400. all billet transimission is slipping go figure!

Do you have a volt booster?

 

[Turbo z28]

I changed and have the following,
Racetronix gss340 fuel pump( 2nd one in the car, thought maybe 1st one was bad)
New AC Delco fuel filter,
Hotwire kit.
Voltmeter reads the same at the back of alternator and the pump.

Motor:
212/212 roller cam.
Stock heads (ported and valves job)
TA62 Turbo
Adjustable Fuel Regulator.
60lb Injectors with TT Chip
Razors Alky (turned off until I can boost to 15lb with no knock)
RJC Power Plate

The only thing I havent changed is the alternator.

Do I need bigger fuel Lines?

 

[Ttype6]

The only thing I havent changed is the alternator.

Do I need bigger fuel Lines?

Like I said,you need more voltage. your generator is falling off way more than it should so you need to fix the one you have or replace it. When you get a generator that produces power like it should and doesn't fall off,it might be enough to solve your problem,but you'll still be on the edge with fuel delivery. More amps does nothing for you. You need more voltage. I would get a stock replacement. I actually prefer to find a good one in the junk yard,but an AC Delco reman will do. I recommend that you call Quad Air and order their volt booster. Your fuel pump and ignition system will love it.

No,you don't need bigger lines. I'm making 700 plus horsepower on E 85. that means I'm moving about the equivalent amount of fuel through the stock lines as a 1,000 hp motor on gasoline. Red Armstrong is trapping at 150 mph and he has the stock lines. When you're making much more power than you are now,you could drill out the four areas on the fuel supply line where the O-rings are to .299". You're a long way from needing to do that.I've watched many people needlessly butcher their stock lines .

 

[Reggie West]

You have 2 problems I can see.

Get a volt booster, that will solve the drop in voltage.

Set the alky system to come on at 8 psi. It is not spraying a lot at 8 but the system has a much greater range to spray progressivley more alky as you increase boost.

Good luck.

 

[Turbo z28]

I tried doing the alky, I set it to come on at 5 with same results. Six months ago I melted the valve guides on cylinder 6.
This is why I believe it is fuel issue. If I keep boost at 10psi I have no problems. anything over and i will get anywhere from 2-3 to 8-9 knock retard.