Possible injection system problem

[nomocom]

Originally Posted by Bubblehead

Don at AFP said in an email to me that the flow transducer should be between the servo and the flow divider. I think I will temporarily remove it from the system until we get the engine running right.

Verify and fix the obvious- the 13 psi fuel pressure.

The shotgun approach to trouble shooting can be expensive and unfulfilling....ask me how I know

IMHO, don't waste time futzing with the flow transducer unless you reinstall it immediately. For now, maybe look inside to verify it is clean, but don't pull it and not have the data it offers. It is a valuable diagnostic tool, and all I think anyone can say about location is the transducers are more stable and accurate between the servo and flow divider- however there are probably thousands installed before the servo working just fine.

The fuel system behavior sounds to me like air in the system. If the pumps can't get a full charge of liquid, they aren't going to achieve target fuel pressure. Seems unlikely both are going bad at the same time, more likely both are fuel starved at the same time (assuming your gauge is correct at 13 psi). I'd look for upstream restrictions, loose fittings, fuel selector seals..... that type of thing, something that would let air into the system.

[Bubblehead]

I've been troubleshooting this logically for about 2-1/2 years. The problem persists despite finding and fixing issues like cracked intake tubes, defective intake tube o-rings, and ignition wire insulation worn off in 2 spots.

My bottom line now is I am tired of being a test pilot. I will re-qualify the injection system and the ignition systems so that I eliminate them as either the primary or as contributing factors in the problem.

AFP has bench tested the servo and it is in spec although bushings are pretty worn. It is now in line for rebuilding. The hose between the servo and the fuel divider is old and Airflow Performance is making a new one.

The Magnetos are on their way to Ly-con in Visalia (as suggested by Don at AFP) for a "stress test". They were rebuilt 3 years/300 hours ago but depending on what Ly-con finds they may get rebuilt again.

I will eliminate non-essential components from the fuel system (flow transducer) and the intake system (alternate induction air flapper) to eliminate any contribution they make to the problem.

I will measure what I can (compression checks out fine) correct what I suspect (bad fuel pump, although I admit a mechanical gauge would have been a smart check.)

The hoses from the firewall to the servo are only two years old but we are pulling them off and inspecting them, and will replace them if they look like they are obstructing fuel flow.

We're going to check the fuel tank vents again to make sure air flows through them at an acceptable rate, although I don't know what rate that is! I will probably go blow in someone else's vent tube with the fuel cap off and get a feel for what good is then compare it to my airplane.

I know this is going to cost me some $s but I am sick of flying with a knot in my stomach. We're going to fix this! I appreciate everyone's suggestions. It has been very helpful!

[NickAir]

John,
from what I know of, the common fixes with your issue have already been posted. Many are watching this thread, including myself. Wish I could help more. Since you did not know the hours/years on your spider it is good preventitive maintenance to rebuild it along with the other things of same.

You will have a nice rebuilt fuel system soon. Hopefully the culprit part will be identified when re-installed and tested.

Thanks for posting your issue and especially your progress. Your issue will help many be more knowledgeable on this issue. I have seen A&P's have much frustration with this same issue. Your thread brings out possible issues involved.

[Bubblehead]

Thanks for the words of encouragement. They have helped me look forward in a more positive manner. I'll keep posting what is discovered along the way. Hopefully it will be of value to others.

[nomocom]

It sounds like you'll have a bird you can feel confident in when you are done. That's key. Just don't forget the elephant in the room, that 13 psi indicated fuel pressure. There are a few of us wondering about that- expecting you should see 25 psi there or so.

[Bubblehead]

nomocom - that one looms large with me too. I wish I had taken a reading with an analog gauge to verify the pressure before pulling the servo and fuel pump. When everything is installed we will use an analog gauge to verify pressure.

The low pressure with some under-cowl heat plus a small obstruction in a hose or the fuel flow transducer could be causing vapor which would make it go lean. OAT was about 50F when I had the problem so it would not seem to be likely, however all possibilities must be explored at this time.

Fuel pressure seems the most likely though.

[Ant CB]

It's hard to enjoy yourself when you fly behind an engine you are not 100% confident in.

Have you had any more luck with your troubleshooting?

Cheers,

[RV10inOz]

You are in Texas .....Walt is in Texas

Threaten him with greenbacks.

Strip everything and while you are at it look at the cam etc and then put all the ancillaries back on.

[Bubblehead]

Walt and I know each other well. He's done my static system checks and W&B and prop balancing and I trust him a lot. I will brainstorm with him about the problem.

The Fuel Injection system is now overhauled and on it's way back to Enid. The mags are at Ly-Con for testing and I hope to hear something yet this week from them.

[Walt]

John,
I'll probably be over to Hicks this weekend for the RV-1, I'd be glad to come over and brain storm with you.

We need to get this fixed