Fuel pressure

[S3flyer]

My fuel pressure has read lower than my normal the last couple flights. Symptoms:

• My normal cruise reading is in the 3.5 to 3.9 range
• Now reading 2.9/3.0 at 5000 RPM
• Went as low as 2.8 in a full power 3000' climb
• Pressure goes up when throttling back
• Pressure is around 3.3 at idle
• The readings are steady ( not bouncing around or drifting one way or the other)
• Gascolator is clean
• Engine is running well
• Switching on the aux fuel pump does not increase the pressure (my plane is a Sting) but it is working

Fuel pressure sender and/or connections? Is the sender the same VDO component as the oil pressure sender?

I'll be working on it this weekend but was looking for likely candidates to check first.

 

[Safety Officer]

Hi Dave,

 

It's a 98% chance it is your VDO pressure sender. These and other senders down in the low psi range can be terribly inaccurate and get out of whack by a few psi. They typically almost always start to read low when going bad and will read high with a poor ground. It is a VDO sender, but it isn't the same one as the oil pressure sender. The oil pressure works between 0-150 psi and the fuel pressure between 0-30 psi. The oil senders get off too, but you would never notice a few psi difference on that one.

You can try to clean your VDO sender and it works sometime and other times it just needs to be replaced. Turn the instruments on after it has sat all night and see if the fuel pressure reads without the engine on and cold. Many have some pressure on them that isn't in the actual system of .3 - 1.0 psi.

Pull the sender off. Get a can of carb cleaner spray with the little red 4" long nozzle. Hold it up to the hole in the sender (away from your face) and give it a quick 1 second squirt and then let the cleaner pee back out the sender orifice. Do this 4-5 times and put it back on the plane. If it works, which it does about half the time, then your good. If it didn't help toss the sender and get a new one. The new VDO sender is a 360-043.

 

http://www.egauges.c...sp?Sender=30PSI

 

Off to chase a squirrel. If you have any issues let me know and I'll help if I can.

 

p.s.

I don't chase old prehistoric squirrels. I like them fresh.

 

 

[S3flyer]

Well, it wasn't the VDO sender, partly because my configuration uses a Wetach 16psi 240ohm sender. Since I didn't have a replacement:

• Cleaned the connections
• Cleaned the sender
• Blew the fuel vent clean
• Cleaned the fuel cap O-ring and tightened the locking clip mechanism

This seems to have addressed the issue. I'll order a back up sender just to add to my collection of parts. Don't know if the Westach is better than VDO but it is about 4.5 years old and still working.

Anyone want to buy my unopened VDO sender for cost ($32.50) plus shipping (USPS flat rate)?

 

[Roger Lee]

Hi Dave,

 

I'll take it. I use them fairly regular. I'll send you an email.

 

 

 

Just for every ones info on the postal service flat rates. They are expensive unless you ship a lot of weight. Point in case from just 2 hours ago. I sent two sets of carbs out US mail. Each was boxed the same, except one was a priority flat rate box and one was my own brown box. They were the same size and within several ounces of each other. The flat rate was $15.45 the other was $9.35 and they were both priority. The lady at the counter said unless you ship something heavy then the other boxes of the same size and weight are usually cheaper.

 

For me from now on it is US mail and my own box.