Fuel Pressure Gage Pegged

[JCD]

1978 M20J 201

Looking for some advise. Just to be clear let me get some background on this. I noticed on sevral flights that while in different phase of flight the fuel pressure would slowly increase past redline. Turning on the auxiliary had no effect. It would then work its way back down to nominal question pressure.

 

 I went to fly the plane this morning for a breakfast flight and went to start it as normal. When I turned on the electric fuel pump it came onto 14 psi and then when I turned it off it settled back to just about 5 psi prior to start.  I then started the aircraft with the boost pump off.  As soon as the engine started I watched it for a second  as the fuel pressure pegged past redline and then shut the aircraft off  

I appreciate your insight  

 

[N201MKTurbo]

The mechanical fuel pump regulates pressure by the force of the diaphragm spring. The engine lifts the diaphragm and the spring pushes back down. When the pressure is above the setpoint the spring simply doesn't push down because the fuel pressure on the diaphragm is higher then the spring pressure.

So the only way to increase the fuel pressure is to increase the spring pressure, sense that is impossible, something else must be pressurizing the back of the diaphragm. The only thing that I can think of is crankcase pressure. You may have a blocked crankcase vent.

[N201MKTurbo]

If it does this shortly after starting the engine. remove your oil filler cap and run up the engine and see if the fuel pressure is OK.

[INA201]

I recently had a similar problem where the pressure would register normal then would peg to the far right at times.  My mechanic said it was a connection to the sender or the gauge.  When the connection is loose it pegs to the right. He later determined that the fuel pressure sender was bad.  Nonetheless the sender was bad and $80 later with a new sender it now works great.  Hopefully yours is this simple as well.  Not to discount the fact that it could actually be a pressure issue that MK mentioned but to at least take this possibility into consideration.  

[JCD]

Well, The mechanic Though they found the cause.  Faulty gauge.  Sent it out for Re-work, not overhaul.  As no one can overhaul these 1978 gauges. (does anyone know of replacement or aftermarket gauges for a '78 M20J?).

They got the gauge back and it still does not work.  So now its the transducer, which they told me they tested with air pressure and and volt meter before sending the gauge out for re-work.  I guess the good news is that the fuel pump is fine and producing good pressure per their test.  More to follow.

[JCD]

On 3/6/2016 at 11:59 AM, INA201 said:

I recently had a similar problem where the pressure would register normal then would peg to the far right at times.  My mechanic said it was a connection to the sender or the gauge.  When the connection is loose it pegs to the right. He later determined that the fuel pressure sender was bad.  Nonetheless the sender was bad and $80 later with a new sender it now works great.  Hopefully yours is this simple as well.  Not to discount the fact that it could actually be a pressure issue that MK mentioned but to at least take this possibility into consideration.  

You said your sender was $80.  My Mechanic is quoting $300.  Do you know where they got yours?  How long ago did you have this done? Any info you can provide is greatly appreciated.

 

[INA201]

The part number ps-211-9000 at spruce matches the number on my bill so I think it is the same one.  I was charged $85 by my mechanic for the part.  Your problem sounds quite similar to mine.  You might want to double check thread size but I think 1/8 is accurate but I'm not positive.

[ALP]

My gauge would peg upon starting and stay there. Verified with regulated air pressure and a second gauge connected with a tee. Pressure climbed normally but as pressure was gradually decreased, the transducer would stick.

[JCD]

Well...My Saga continues....The new transducer had no effect so we are back to the faulty 1978 Fuel Pressure Gauge.  Does anyone know where you can buy a new or overhauled gauge for a '78 Mooney M20J 201? See picture attached

 

 

Edited March 23, 2016 by JCD

[mooniac15u]

The gauges on an early J are just measuring resistance through the sensor. IIRC, a short to ground will cause that gauge to deflect full scale to the right. You might want to check for a short in the wire between the transducer and the gauge. 

[Marauder]

Well...My Saga continues....The new transducer had no effect so we are back to the faulty 1978 Fuel Pressure Gauge.  Does anyone know where you can buy a new or overhauled gauge for a '78 Mooney M20J 201? See picture attached

 

 

Have you considered moving to another primary? I didn't have problems with mine but I was always concerned it was on borrowed time. A replacement gauge will probably cost you as much as going with another primary.

I went with the EI product.

Sent from my iPad using Tapatalk

[JCD]

On 3/24/2016 at 5:56 PM, Marauder said:

Have you considered moving to another primary? I didn't have problems with mine but I was always concerned it was on borrowed time. A replacement gauge will probably cost you as much as going with another primary.

I went with the EI product.

Sent from my iPad using Tapatalk

Absolutely would do this.  How much did you pay for the gauge and install?

 

[Marauder]

On 3/24/2016 at 5:56 PM, Marauder said: Have you considered moving to another primary? I didn't have problems with mine but I was always concerned it was on borrowed time. A replacement gauge will probably cost you as much as going with another primary.

I went with the EI product.

Sent from my iPad using Tapatalk

Absolutely would do this.  How much did you pay for the gauge and install?

 

Not sure how much they go for now. I bought mine in the 1990s and it was around $350. I did the install under supervision of an IA and it didn't take very long. Maybe a couple of hours.

I have the Electronics International FP-5L.

[ArtVandelay]

On March 24, 2016 at 8:56 PM, Marauder said:

Have you considered moving to another primary? I didn't have problems with mine but I was always concerned it was on borrowed time. A replacement gauge will probably cost you as much as going with another primary.

I went with the EI product.

Sent from my iPad using Tapatalk

I thought you had a JPI?  How do they share the various fuel sensors?

[Marauder]

On March 24, 2016 at 8:56 PM, Marauder said: Have you considered moving to another primary? I didn't have problems with mine but I was always concerned it was on borrowed time. A replacement gauge will probably cost you as much as going with another primary.

I went with the EI product.

Sent from my iPad using Tapatalk

I thought you had a JPI?  How do they share the various fuel sensors?

I can't remember whether it was fuel pressure or fuel flow or both, but apparently the transducers are compatible and can be shared. I think I have the FT-60 transducer for fuel flow. The pressure is always showing within a half pound on each. Sorry I don't have a picture of both at the same time showing the pressures. For fuel flow, since they each have a k factor, I can tweak both for total fuel used independently.

[JCD]

Well the Mechanic and I both gave up with a New Fuel Pressure gauge, New transducer and verified the wiring between both of them.  The fuel pressure reads 5 PSI high all the time now.  Even where there is no pressure on the system.  $1800 later and now I know it shows 5 PSI High. 

 

Time to get rid of the last of my 1978 instrument panel.  I have a JPI 830 (Secondary flight instrument) what is recommended to replace the Fuel Level in each tank, Fuel Pressure, Oil pressure,  Oil Temperature, and Cylinder Temperature without totally wrecking my instrument panel?

 

All ideas appreciated.

 

 

[JCD]

On March 26, 2016 at 10:07 AM, Marauder said:

I can't remember whether it was fuel pressure or fuel flow or both, but apparently the transducers are compatible and can be shared. I think I have the FT-60 transducer for fuel flow. The pressure is always showing within a half pound on each. Sorry I don't have a picture of both at the same time showing the pressures. For fuel flow, since they each have a k factor, I can tweak both for total fuel used independently.

Is this JPI EDM certified as a "PRIMARY" instrument to replace the existing Mooney Analog Instruments?  If so, do you have exact model number?

 

[Marauder]

On March 26, 2016 at 10:07 AM, Marauder said: I can't remember whether it was fuel pressure or fuel flow or both, but apparently the transducers are compatible and can be shared. I think I have the FT-60 transducer for fuel flow. The pressure is always showing within a half pound on each. Sorry I don't have a picture of both at the same time showing the pressures. For fuel flow, since they each have a k factor, I can tweak both for total fuel used independently.

Is this JPI EDM certified as a "PRIMARY" instrument to replace the existing Mooney Analog Instruments?  If so, do you have exact model number?

 

Yes. The JPI 900 and 930 ard both primary. I removed my analog gauges including the fuel gauges.

[JCD]

6 minutes ago, Marauder said:

Yes. The JPI 900 and 930 ard both primary. I removed my analog gauges including the fuel gauges.

Do you mind me asking what you paid for it plus installation?

[Marauder]

The unit was $3100 after the JPI rebate and I don't have a clue on the install since it was done with a whole bunch of other panel work. I do know he spent a fair amount of time getting the fuel levels correct due to float issues.

[ArtVandelay]

The unit was $3100 after the JPI rebate and I don't have a clue on the install since it was done with a whole bunch of other panel work. I do know he spent a fair amount of time getting the fuel levels correct due to float issues.

But you were upgrading from 830, was rebate on 830?

Since the 900 is the same footprint was 830, someday if JPI has an upgrade special I might do the same.

[JCD]

Just now, teejayevans said:

But you were upgrading from 830, was rebate on 830?

Since the 900 is the same footprint was 830, someday if JPI has an upgrade special I might do the same.

If its the same foot print that would be awesome! 

 

[Marauder]

Just now, teejayevans said: But you were upgrading from 830, was rebate on 830?

Since the 900 is the same footprint was 830, someday if JPI has an upgrade special I might do the same.

If its the same foot print that would be awesome! 

 

It is the same footprint. You also can reuse some of the 830 probes. That is what I did. I was able then to sell the 830 to offset some of the cost.

[JCD]

Just now, Marauder said:

It is the same footprint. You also can reuse some of the 830 probes. That is what I did. I was able then to sell the 830 to offset some of the cost.

What did you get for your 830?  What sensors did you sell with it?

 

[carusoam]

There is a supplier here with the latest digital fuel level sensors for the tanks.  They would go nicely with the JPI 900 series fuel level indicators.

Search on Cies.  The MS guy here is aka Fuellevel...

Best regards,

-a-