Question for anyone who has a fuel pressure gauge on their sled

[TurboMatt]

I just hooked up a fuel pressure gauge on my sled. Is it normal for the fuel pressure to drop completely to zero every time I turn off tthe sled? I woulda expected it to hold pressure. I'm checking it through the shraeder valve fitting on the sending uniit.

 

[TRS]

It should hold pressure. It should not drop to zero after you kill the motor. Make sure you don't have a leak at the Schrader valve. It will drop over time but not to zero when you kill it.

 

[Kraven]

The CFI system is a recirculating fuel circuit.

Perfectly normal Matt..

If you think about it...the fuel pump feeds the fuel rail... that returns to the tank.

That end is open after the Pressure regulator on the return side of the PFA... so it naturally goes back to zero.

.

Eric,

Don't know if that's correct.

Every-time I change out a fuel filter, there's still pressure in the lines when I go to disconnect

 

[mountainhorse]

I think I'm on crack today or something... posting on too many forums today or eating funny food. Maybe I took the wrong meds today??

YES, it should hold pressure, for some time, as the others have posted above.

Is the bleed line on the tester weaping fuel or the connection at test port?

 

[mountainhorse]

First off...

Sled runs or does not run??

Is this a Pressure test gauge...or did you wire up a fuel pressure gauge for permanent install?

If it goes to zero after you kill the engine, but it still runs with the gauge hooked up and NO external leaks....

Possibilities:

Pintle stuck open in one or both injectors.

Check valve in fuel pump not functioning.

Outlet hose from pump to PFA cracked and leaking inside of tank.

Defective Pressure regulator in PFA head.

Leaking O-ring(s) on Pressure regulator. (leaks inside of the tank...you would not see it)

Are you turbo'd on this sled?... If so, does it have an external pressure regulator?

 

[TRS]

Eric,
Some days just go that way. The other day my wife asked me what the book with phone numbers is called....

 

[Merlin]

Matt,


As per Eric's list of possibilites, I found my original(blue) injectors to be bleeding off fuel pressure to O from 58/59 PSI as soon as the engine was shut off............

After installing the upgraded(yellow) injectors, the pressure would only drop to 50 PSI when the engine was shut off & would take several hours to drop to 30 PSI.................I'm assuming the pintle/s were gummed up & not sealing............


Hope this helps,


Glen

I just hooked up a fuel pressure gauge on my sled. Is it normal for the fuel pressure to drop completely to zero every time I turn off tthe sled? I woulda expected it to hold pressure. I'm checking it through the shraeder valve fitting on the sending uniit.

 

[TurboMatt]

First off...

Sled runs or does not run??

Is this a Pressure test gauge...or did you wire up a fuel pressure gauge for permanent install?

If it goes to zero after you kill the engine, but it still runs with the gauge hooked up and NO external leaks....

Possibilities:

Pintle stuck open in one or both injectors.

Check valve in fuel pump not functioning.

Outlet hose from pump to PFA cracked and leaking inside of tank.

Defective Pressure regulator in PFA head.

Leaking O-ring(s) on Pressure regulator. (leaks inside of the tank...you would not see it)

Are you turbo'd on this sled?... If so, does it have an external pressure regulator?

Sled runs, It just seems to take more pulls than it should to start, whether its cold or not. It always takes 2 pulls when its hot and it it dead cold it sometimes takes 10 pulls.
This is a turbo sled, but its a Silber so no it doesn't have an external regulator.
I replaced my fuel pump over the summer(thats really the only thing I changed over summer with the fuel system) thats when the issue arose. I used the Walbro F20000286 from this website: http://autoperformanceengineering.com/html/fppumps.html
At his point I'm almost kind of leaning towards the fuel pump because thats the only component I replaced and now the issue surfaced. But it obviously could be something else as well. I didn't have my injectors cleaned over summer(I Know I probably should have).
What does PFA stand for? Anyone have any ideas where I should start first?

 

[mountainhorse]

Pull your pump from the tank and inspect the hose from the pump to the PFA (Pump Flange Assembly)

Also check the nipple for this hose on the PUMP (outlet side)... often, very often actually, the nipple is cracked during installation.... what kind of hose clamps did you use on this... regular worm drive hose clamps will be prone to leaking on this type of install...

 

[TurboMatt]

Pull your pump from the tank and inspect the hose from the pump to the PFA (Pump Flange Assembly)

Also check the nipple for this hose on the PUMP (outlet side)... often, very often actually, the nipple is cracked during installation.... what kind of hose clamps did you use on this... regular worm drive hose clamps will be prone to leaking on this type of install...

I used the fuel injection clamps on the hose. I will pull the pump and check things out.

thanks

 

[Merlin]

Matt,

Depending on where the schrader valve for the pressure gauge is actually plumbed into on the PFE(on the pressure line coming from the pump or on the return line feeding the pressure regulator) you may be able to install a set of hose pinch off pliers on either the pressure or return fuel hoses to determine whether the check valve in the fuel pump or the pressure regulating valve are faulty but that would still leave the injectors in question..............

FWIW, I think the best bet in order to troubleshoot the problem cost effectively would be to borrow a fuel injection test kit..........Then you can install shut off valves & a gauge on both the pressure & return lines in order to determine exactly where the fuel is bleeding off............On the other hand it sounds like you might have the problem narrowed down to the recently installed pump........


Good luck,


Glen

Sled runs, It just seems to take more pulls than it should to start, whether its cold or not. It always takes 2 pulls when its hot and it it dead cold it sometimes takes 10 pulls.
This is a turbo sled, but its a Silber so no it doesn't have an external regulator.
I replaced my fuel pump over the summer(thats really the only thing I changed over summer with the fuel system) thats when the issue arose. I used the Walbro F20000286 from this website: http://autoperformanceengineering.com/html/fppumps.html
At his point I'm almost kind of leaning towards the fuel pump because thats the only component I replaced and now the issue surfaced. But it obviously could be something else as well. I didn't have my injectors cleaned over summer(I Know I probably should have).
What does PFA stand for? Anyone have any ideas where I should start first?

 

[mountainhorse]

Good post Merlin.

As a heads up... don't pinch off the stock fuel lines to/from the filter engine or returns... They have a fairly ridgid Teflon (PTFE) tube liner to them... if you pinch it hard enough to block the fuel flow... you have a strong possibility of damaging the PTFE liner in the hose which could leak or burst later.

BTW... a good friend has one of those RR motors in his Vintage mahogany race boat... they are an amazing piece of equipment.







.

 

[Merlin]

Ooops, good catch!!!

Forget the hose pinch off pliers completely & use the appropriate adaptors from a fuel injection test kit for performing the leak testing.............

Good post Merlin.

As a heads up... don't pinch off the stock fuel lines to/from the filter engine or returns... They have a fairly ridgid Teflon (PTFE) tube liner to them... if you pinch it hard enough to block the fuel flow... you have a strong possibility of damaging the PTFE liner in the hose which could leak or burst later.

.

 

[mountainhorse]

Any word on this one???

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