FI High Fuel Pressure

[roadrunner20]

I've check all the others threads on the topic with no solution.

Normal ops for 400hrs, fuel pressure reads ~16psi on my GRT EIS400 via a vdo fuel pressure sender.
A couple of weeks ago, on startup, my pressure was spiking ~50psi. Following the runup, it would settle back down to 16psi.
With the boost pump on would add +10 to the pressure.

This has been happening ever since but never in flight until this week.

I've cleaned my boost pump filter, snugged up fuel lines and intake.
Still have the issue.

I suspect it may be a bad sender & will get one next week.

Anyone else have any ideas that I might try this weekend in the event it's not the sender.
I hate to break down the engine-driven pump.
I figure I can at least wait for the sender as it's the least expensive and minimal maintenance.

[chaskuss]

Dan,
Sounds like either your transducer or the pressure relief valve inside the mechanical fuel pump. Can you borrow a mechanical gauge to temporarily substitute for the transducer? If so, that would tell the tale.
Charlie Kuss

[erich weaver]

Perhaps you have already seen this in the archives, but my fuel pressure reading spikes up every time I key the com mike - some kind of RF interference. Took me a long time to figure out that was the cause. Any chance you have the same issue?

erich

[roadrunner20]

Originally Posted by erich weaver

Perhaps you have already seen this in the archives, but my fuel pressure reading spikes up every time I key the com mike - some kind of RF interference. Took me a long time to figure out that was the cause. Any chance you have the same issue?

erich

I don't think so. It's been working well & reporting a stable reading all along.
I worked on it today & really suspect the vdo sender.

[roadrunner20]

Originally Posted by chaskuss

Dan,
Sounds like either your transducer or the pressure relief valve inside the mechanical fuel pump. Can you borrow a mechanical gauge to temporarily substitute for the transducer? If so, that would tell the tale.
Charlie Kuss

I worked on it today & really suspect the vdo sender.
I've also made sure the fuel vents were not clogged. It reports the same pressure on both tanks. I hope it's not the engine-driven fuel pump. That would be an expensive fix.

It's very erractic from 46-60psi. This is why I suspect the sender. Hope so.
I'll report the resolution once found.

Thanks for your input.

[mannanj]

Originally Posted by DanLandry

I worked on it today & really suspect the vdo sender.
I've also made sure the fuel vents were not clogged. It reports the same pressure on both tanks. I hope it's not the engine-driven fuel pump. That would be an expensive fix.

It's very erractic from 46-60psi. This is why I suspect the sender. Hope so.
I'll report the resolution once found.

Thanks for your input.

If you choose to replace the sender, I would recommend GRT's high dollar one($100.00+). It is a much higher quality sender. I've had no problems since I replaced mine. The VDO oil pressure sender is still ok. Talk to Sandy at GRT.

I replaced my VDO as it was showing a drop in pressure. VDO used to make quality products, not so sure anymore.

[roadrunner20]

Originally Posted by mannanj

If you choose to replace the sender, I would recommend GRT's high dollar one($100.00+). It is a much higher quality sender. I've had no problems since I replaced mine. The VDO oil pressure sender is still ok. Talk to Sandy at GRT.

I replaced my VDO as it was showing a drop in pressure. VDO used to make quality products, not so sure anymore.

Thanks Mannan,
I bought the prevous one from GRT for $35. It was probably the cheaper brand. I'll talk to Sandy she has always been very accomodating. I'm going to pull the sender off today. Maybe there's a bit of debris in the transducer manifold thats creating havoc.

[roadrunner20]

I found a small piece of debris in the transducer manifold.
All is well.

Other than planned maintenance and replacing the ryton sump, this was the first time I've taken out of service due to problematic issues.
It was good exercise in troubleshooting problems that present themselves.
I didn't enjoy the plane being down especially when the weather is so nice here in central Florida.

Thanks for everyones help.

[Bubblehead]

Dan - glad you found the problem. Just for the benefit of others reading the thread, I had a similar problem with oil pressure. It would spike up to 90 psi and then go back down a little later. I checked with GRT and they said to make sure there was a good ground to the case. So I checked - what had been a good ground had gotten gunked up and a little loose. Cleaned and tighted everything up and the problem went away.

[mannanj]

Originally Posted by DanLandry

I found a small piece of debris in the transducer manifold.
All is well.

Glad you found the problem.