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

Wed, 14 May 2003 16:49:58 -0600

You probably want to adjust that down to 4.5", unless you have stock in 
a vacume driven instrument company.

Scott

Jay Yu wrote:
> 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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