Fuel pressure gauge pegged-M20J

[wingsaircharter]

I have a M20J with a fuel pressure gauge pegged on wide open. Master on or off doesn't matter. Initially, it would peg pretty quickly when the electric pump was on and always when in flight. I replaced the pressure switch under the cowl for about $100 and that didn't do anything so  I am thinking its the gauge especially when it is full time pegged. The JPI shows that everything is normal as far as flows. The gauge is part of the multi-gauge cluster and each individual gauge has the two small black screws on the lower part. Does anyone know if anyone overhauls these? 

[y2kiah]

Mine is the same way. Both my old one and my new one, actually. You might want to consider leaving it alone.

When I told my shop (a good MSC) about the last one being pegged constantly, I was told the gauge was "shot". After the shop messed with it and did whatever it was they did, it never worked again, so it went from being pegged to the right, to being pegged to the left and marked "inop". I don't know about you but I will take pegged to the right over pegged to the left any day. I then went on the hunt for the right gauge that would match my particular cluster from my particular serial number range. After spending about 1.5 AMU and 6 months on this project, I ended up with a "new to me" gauge that is still always pegged to the right. Well... every now and then it blips down into the mid range.

What serial# is your J? I have an extra cluster laying around and if it happens to match the one you need, I will send it to you to try it out. I know how frustrating it can be to locate these. If it works out, you can pay me for the gauge and keep it, if not you can send it back.

Edit: I should clarify, master on/off and engine running/not running does show a difference on mine. If yours is really pegged to the right at all times, you have a different problem and it is truly inop.

[PT20J]

You might check the wiring

[larrynimmo]

Before you do anything…take the cowling off and check the …

1. Grounding wire to the transducer

2.  Wire leaving transducer and going back to the gage

in the case of my plane, wires snapped independent of each other about 2 months apart

[Guest]

It makes it easier for people to help you if you provide more information, your serial number, a picture of the gauge etc.  Many of us are good, but not psychic.

Clarence

[wingsaircharter]

18 hours ago, y2kiah said:

Mine is the same way. Both my old one and my new one, actually. You might want to consider leaving it alone.

When I told my shop (a good MSC) about the last one being pegged constantly, I was told the gauge was "shot". After the shop messed with it and did whatever it was they did, it never worked again, so it went from being pegged to the right, to being pegged to the left and marked "inop". I don't know about you but I will take pegged to the right over pegged to the left any day. I then went on the hunt for the right gauge that would match my particular cluster from my particular serial number range. After spending about 1.5 AMU and 6 months on this project, I ended up with a "new to me" gauge that is still always pegged to the right. Well... every now and then it blips down into the mid range.

What serial# is your J? I have an extra cluster laying around and if it happens to match the one you need, I will send it to you to try it out. I know how frustrating it can be to locate these. If it works out, you can pay me for the gauge and keep it, if not you can send it back.

Edit: I should clarify, master on/off and engine running/not running does show a difference on mine. If yours is really pegged to the right at all times, you have a different problem and it is truly inop.

24-0557.  Thanks for the reply. It is pegged full right sitting quietly in the hangar.

[wingsaircharter]

24-0557 There you go Clarence. 

[201er]

@jetdriven was sure it was a broken gauge or transducer but it turned out to be a busted wire on mine.

[PT20J]

From the description in the Service Manual, here is how I would troubleshoot it:

1. Ground the wire at the sender. If this makes the gauge read zero, it is the sender.

2. Ground the wire on the back of the cluster. I this makes it read zero, it is the wiring between the gauge and the sender.

3. If neither make it read zero it would be the gauge or a broken wire inside the cluster.

Skip

 

[wingsaircharter]

OK. The full pegged situation ended up being a broken wire. With that fixed, it does seem to respond more normally when turning the master off (below 0psi) and when pump is on (about 20 psi). The issue now is that when the master is off and the pump is off and the mixture in full rich and the engine is NOT running, the gauge still indicates about 4psi.  Is there an adjustment to zero the gauge when it is at a known zero pressure?

[Yetti]

some of them have an adjustment at the base of the needle.   You'd have to pull the cluster to access it. I would go with kentucky windage.