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It will read the same at any speed unless it is under boost.

Under boost, the fp should increase 1# for each pound of boost. In other words, if fuel pressure, vacuum hose off, is 40 and you hit 20# of boost, then you should be reading 60# of fp.

My first statement is really not correct, as fp is normally read with the vacuum hose off and when you put the hose on, the pressure will drop a few pounds due to the vacuum lifting the diaphram inside the regulator. The more vacuum the engine generates, the less the fuel pressure you will read if you have your gauge taped to the windshield. When boost comes on, the procedure is reversed.

Confused you, huh?




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Discussion Starter · #3 ·
Originally posted by Steve Wood:
It will read the same at any speed unless it is under boost.

Under boost, the fp should increase 1# for each pound of boost. In other words, if fuel pressure, vacuum hose off, is 40 and you hit 20# of boost, then you should be reading 60# of fp.

My first statement is really not correct, as fp is normally read with the vacuum hose off and when you put the hose on, the pressure will drop a few pounds due to the vacuum lifting the diaphram inside the regulator. The more vacuum the engine generates, the less the fuel pressure you will read if you have your gauge taped to the windshield. When boost comes on, the procedure is reversed.

Confused you, huh?
Steve, with no vacuum to pressure regulator
I have 35psi,with no vacuum and 10# of boost
I still have 35psi fuel pressure.
 

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you have a bad regulator then unless the pump is completely gone.

Take an air hose and apply pressure to the port, the fuel pressure should rise accordingly...say you put 20 # to the port, the pressure should rise 20#.

Does the pressure drop to about 30# when you put the vacuum hose on? Wondering if the line is blocked.....there should be no check valve in the hose to the regulator.


[This message has been edited by Steve Wood (edited December 10, 2001).]



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Discussion Starter · #6 ·
Originally posted by Steve Wood:
you have a bad regulator then unless the pump is completely gone.

Take an air hose and apply pressure to the port, the fuel pressure should rise accordingly...say you put 20 # to the port, the pressure should rise 20#.

Does the pressure drop to about 30# when you put the vacuum hose on? Wondering if the line is blocked.....there should be no check valve in the hose to the regulator.


[This message has been edited by Steve Wood (edited December 10, 2001).]
The pressure with the vac hose hooked up is
26psi and there is no check valve on the vac line to the regulator.There is no fuel in
the regulator hose port. Where should I apply
the air to ? the port on the regulator that
the vac hose goes on.
 

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Yup.26 lbs,vacuum on sounds awfully low though.Is that a stock pump?Maybe time for an upgrade;hotwire kit,walbro 340,adjustable FPR.What kind of shape is the fuel filter in?Changed recently?

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Discussion Starter · #8 ·
Originally posted by The Radius Kid:
Yup.26 lbs,vacuum on sounds awfully low though.Is that a stock pump?Maybe time for an upgrade;hotwire kit,walbro 340,adjustable FPR.What kind of shape is the fuel filter in?Changed recently?
It is the stock pump,the car has 76000. miles
on it.The car has a stumble when you take off
does not matter if at part or full throttle.
I checked for codes,checked the coil also
checked the cam and crank signals.I replaced
the plugs,wires(GM PARTS)and the fuel filter.
Thats when I went to fuel pressure.The only
changes in the car are k&n filter,pulley kit
and a chip.Not sure what brand.o2 voltage does appear to be low,always around 300mv.
 

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Well, the stock pump is probably shot. Try the fuel volume test that I suggested above.

Also, with the car idling, pull the the hose off the regulator and add pressure to the regulator port. At idle the car should not be using much fuel and if the pump has anything left, it should raise the pressure when you add some pressure to the the port.

I suspect you need a new pump, a hot wire kit to get full voltage back to the tank...and, perhaps, a new regulator. If the regulator is not adjustable, it would be a good buy, anyway.

Steve




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Discussion Starter · #10 ·
Originally posted by Steve Wood:
Well, the stock pump is probably shot. Try the fuel volume test that I suggested above.

Also, with the car idling, pull the the hose off the regulator and add pressure to the regulator port. At idle the car should not be using much fuel and if the pump has anything left, it should raise the pressure when you add some pressure to the the port.

I suspect you need a new pump, a hot wire kit to get full voltage back to the tank...and, perhaps, a new regulator. If the regulator is not adjustable, it would be a good buy, anyway.

Steve
I am going to drop the tank tomorrow,should I
go with the a GM pump or a performance one ?
I am new to this site and think it is great.
Thank You for all your info,also,can you list
some places to get the hot wire kit and other
products that you mentioned.Thanks again.Robert
 

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Don't drop the tank until you run some tests...pull the schrader valve out of the rail and slide a hose over the end...put 12 volts to the pump test lead and see how it flows...

But, it is time for a new pump. If you want to improve performance beyond stock, you will need a new pump anyway....the stock one barely kept up with the stock set up as it was.....

I would suggest a Walbro 340 since I noticed that PTE was selling either the 307 or 340 for, I think, $85 for a special sale. The only difference in the pumps is the pressure relief spring. Either one will do, actually.

For the hot wire...you can either buy a kit, or simply wire it yourself for $10 worth of parts...a 30 amp relay and a 30 amp fuse holder and a piece of ten guage wire long enuf to run from the alternator to the rear of the fuel tank.

There are several adjustable fuel regulators but you can wait on that if the current regulator is good and you are not upgrading chips, etc. With an aftermarket chip you need an adjustable one or, perhaps, the one of the TTA which has a bit higher pressure.

I suspect your 300 mv o2s are from lack of fuel. Your off idle cut out is probably the same.




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Discussion Starter · #12 ·
Originally posted by Steve Wood:
Don't drop the tank until you run some tests...pull the schrader valve out of the rail and slide a hose over the end...put 12 volts to the pump test lead and see how it flows...

But, it is time for a new pump. If you want to improve performance beyond stock, you will need a new pump anyway....the stock one barely kept up with the stock set up as it was.....

I would suggest a Walbro 340 since I noticed that PTE was selling either the 307 or 340 for, I think, $85 for a special sale. The only difference in the pumps is the pressure relief spring. Either one will do, actually.

For the hot wire...you can either buy a kit, or simply wire it yourself for $10 worth of parts...a 30 amp relay and a 30 amp fuse holder and a piece of ten guage wire long enuf to run from the alternator to the rear of the fuel tank.

There are several adjustable fuel regulators but you can wait on that if the current regulator is good and you are not upgrading chips, etc. With an aftermarket chip you need an adjustable one or, perhaps, the one of the TTA which has a bit higher pressure.

I suspect your 300 mv o2s are from lack of fuel. Your off idle cut out is probably the same.
I did the fuel test and got just under 2
qts in 1 minute.Fuel volume seemed to slow
down after 20-25 seconds.Thanks Robert
 

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That will do it, but I prefer to put the relay up front under the hood beside the fan relays. One of the problems is there should be a fuse close to the alternator in case a short develops in the circuit.

1. take a 30 amp, heavy duty fuse holder and put a ring terminal on one end and attach to the battery post on the back of the alternator.

2. attach the other end to the power input terminal on the 30 amp relay.

3. On the power output side of the relay, run a 10 gauge wire down thru the frame to the rear of the tank. (you can run it thru the inside of the car as per the gnttype.org link above, if you like)

4. cut the power wire at the fuel pump connector and attach the 10 gauge wire to the side of the connector that goes to the pump. I use crimp on connectors and put one on the original wire that I cut so I can plug it back in if the new relay fails. Note that you must cut the original wire as it cannot be connected at the same time as the new hot wire.

5. run a wire from the trigger terminal of the relay to the fuel pump test lead behind/under the alternator.

6. run a short wire from the ground terminal of the relay around to the mounting screw of the relay.

7. Mount the relay in line beside the fan relays.

8. Run a ground from the corner of the gas tank over to something attached to the sheet metal. Note that our cars are not normally grounded to the frame but thru the body sheet metal. The frame is an indirect ground thru the mounting bolts (body cushions)

Be careful when routing the 10 gauge wire so it does not chafe on anything and short out. If it does, the fuse by the alternator will save you and the extra connector you stuck on the original power wire will be very useful.







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