REFLECTOR: Fuel Pressure Reads zero or low/intermittent -- SOLVED

[Jay Yu]

Not sure if this is useful info but welcome any/all comments.

I just came back from a test flight. I saw fuel pressure at 7~8 psi in
flight and ~6 psi on the ground. I did NOT buy a new sensor. What I did was
I reinstalled the sensor at the bottom of the engine in the path of fresh
air flow from my lower cowl intake air scoop (The sensor used to be on
firewall about 4" away from exhaust pipe but covered with reflective heat
shield).

Another thing I noticed is that I now get ~170 degree oil temperature with
2500RPM/24"MP. This is 50 degrees lower than what I had before. The
difference is that I used to install oil temp probe on a tee in between oil
bypass group and old style fuel pump and now I installed it in the plug
where the "stronger" spring is installed. I did see that the oil temp
increased to more 190 degree while taxiing back to hangar after landed.

The third thing is that I got ~5" vacuum at 2500 rpm. Apparently the
direction change of the vacuum pump did not screw up.

Jay Yu
Velocity RGE
N86YU

-----Original Message-----
From: reflector-admin@tvbf.org [mailto:reflector-admin@tvbf.org]On
Behalf Of Ronnie Brown
Sent: Wednesday, May 07, 2003 7:54 PM
To: reflector@tvbf.org
Subject: Re: REFLECTOR:FW: Fuel Pressure Reads zero or low/intermittent


That's not too good.  If it had been parked for 5-10 years, MAYBE!!  I'd say
JPI needs to provide higher quality sensors.

On the other hand, let me put in a good word for NAVAID.  I bought my Navaid
autopilot three years ago (too soon), but in any event, I just started
flying my Velocity last month.  I have 29 hours flown and got around to
trouble shooting the fact that the Navaid would not lock onto GPS course,
but would track a heading.  I called Navaid and he said he would ship me a
new GPS Coupler to fix the problem.  No hassle!!!  NOW THAT IS CUSTOMER
SERVICE!!!

Ronnie

----- Original Message -----
From: "Jay Yu" <jayyu@arczip.com>
To: <reflector@tvbf.org>
Sent: Wednesday, May 07, 2003 7:54 PM
Subject: REFLECTOR:FW: Fuel Pressure Reads zero or low/intermittent


> FYI.
>
> (I can't believe this! Mine was sitting since last August.)
>
> -----Original Message-----
> From: JPI Tech Support [mailto:jpitech@pacbell.net]
> Sent: Wednesday, May 07, 2003 11:30 AM
> To: Jay Yu
> Subject: Re: Fuel Pressure Reads zero or low/intermittent
>
>
> This is a follow-up from our phone conversation of earlier this morning.
We
> have reviewed you request and still think that replacing the Fuel Pressure
> sensor is the best resolution. The Part number of the Fuel Pressure sensor
> is 3060-17 and sells for $100.00 plus shipping.
>
> The main issue is in the sensor where you have a wiper are that after
> sitting for a pro-longed period will create an indentation in the pickup
in
> the sensor and would only read at lower temperature (or pressure), then
when
> the engine gets warmer, the wiper arm in the sensor would get stuck in
this
> depression and would not read higher. Another thing is to be certain not
to
> hard mount the sensor. It must be mounted on a flexible tube about six (6)
> inches in length (AEROQUIP 303 line) to protect the sensor from engine
> vibration which can damage the sensor's wiper arm and sending unit.
>
> Lastly, to check the instrument you simply disconnect the harness wire and
> the instrument head should read a high reading caused by an open circuit,
> then connect the wires and the reading on the instrument will read lower
due
> to the short.
>
> We hope this helps.
>
> Regards,
>
> JPI Product Support
>
>
> ----- Original Message -----
> From: "Jay Yu" <jayyu@arczip.com>
> To: <jpitech@pacbell.net>
> Cc: <jay.yu@bankofamerica.com>
> Sent: Tuesday, May 06, 2003 9:10 PM
> Subject: Fuel Pressure Reads zero or low/intermittent
>
>
> > Hi,
> >
> > I have a SlimLine fuel pressure instrument. Recently I saw 0 pressure
> right
> > after engine runup (before take off). It seems that when the engine is
> cold,
> > the reading is ok. Also when I removed the cowls, the reading was ok
too.
> > This seems to suggest that when the engine compartment is warm/hot. I
have
> a
> > reading problem. Does this make sense?
> >
> > This evening I measured the resistence between the two wires on the
> > connector on the instrument side. I noticed that when there was no fuel
> > pressure, the reading was 7.5 Ohms. When I turned on electric boost
pump,
> > the reading was 29.8 Ohms (I can normally get about 5 - 6 psi when the
> > electric boost pump is on). I also plugged the fuel pressure connector
to
> > oil pressure instrument. I noticed that the reading was 0 when there was
> no
> > fuel pressure and the reading was 15 psi when I turned on electric boost
> > pump.
> >
> > Based on these observations, can you tell if my fuel pressure instrument
> is
> > bad or the fuel pressure sender is bad? If it's the fuel pressure
sender,
> > could it be the temperature in engine compartment causing this problem?
> Also
> > can you give me some technical specification on the fuel pressure sender
> > such as the relationship between resistence and psi? On your web site I
> saw
> > the correlation between oil pressure and resistence such as 0 Ohm for 0
> psi,
> > 89 Ohms for 50 psi and 630 psi for open circuit.
> >
> > Thanks,
> >
> > Jinquan Yu
> >
> >
>
>
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