AFP Fuel Flow during purge

I flushed then leak checked my fuel system The leak check involves running the boost pump with the purge valve in the ICO position, this should circulate fuel back via the purge return line. I was getting about 12 PSI pressure but little to no fuel flow reading. It would flicker from 0 to .1 I opened the throttle and this caused the flow to start to climb, I closed the throttle not wanting it to flood the engine I don't plan to start for few days.

The manual talks about the post installation check but I don't know what numbers I should be seeing as fare as pressure and fuel flow. Can anyone provide me some numbers I should see.

Cheers

Boost pump on you should have 25-30 PSI, with throttle and mixture full forward you should see about 4 GPH FF (approx. same FF with purge valve open or closed).

Should get 25-30 psi. Flow should vary with the throttle opening. Little flow at idle position, about 18 gph full throttle. Flow won't vary much with the purge valve open or shut.

Nope, wrong, others are correct. Flow with the purge at idle cut off is 1.6 at closed throttle to 4.5 at full throttle. Flow with purge in the run position is 2.5 at closed throttle to 5.0 at full throttle. Pressure is pretty steady at 26-27 psi.

prime or purge flow is 30psi and 4GPH...

Full throttle, Full rich engine priming or purge flow is around 30psi and 4GPH for me (engine OFF)... with the engine ON, flow full flow is around 21 GPH.

Don't trust your fuel flow or pressure readings until you verify them... you can easily pull a fuel line at the flow meter and measure the flow to verify the reading that you see from the fuel flow meter... if you really have good flow look into the set up in your Dynon settings.

Before the throttle body you should see flow in excess of your full throttle demand... easy to pull a line here and test flow by timing a gallon fill as well.

Since you are seeing measurements of low flow and low pressure you may have an actual obstruction of some kind... but I would look at actual flows first for a quick check to see if the problem is really in sensor setup.

Throtle and Mixture might be wrong

I will have to do this again. I just did the leak check with the Purge at ICO, it did not say anything about Throttle and mixture so I and left them at ICO except with I pushed up the throttle to try to get some indication of the flow.

I will re-accomplish this test to see what I get this time. The engine was run on the test stand so the stuff from the fuel control to the engine should be good the only thing I added was the flow sensor between the fuel control and the purge valve. I will also dig into the manual more maybe there is a more amplified section I can reference. I was just doing the last step on the post install which was a leak check at idle cut off on the Purge valve it did not say to do anything with the mixture and throttle.

I had good flow when flushing the lines with the boost pump (hose disconnected from the inlet to the engine pump, I ran 5 gals from one tank and 2 gal from the other into another gas can, 5 gal seemed like over kill. I did this before running fuel through the fuel control for the leak check. I was not going to disconnect the tiny nozzle lines since I know this engine ran well on the test stand. If felt that step was a post install step accomplished by the engine builder.

Keep sending me information. I will check this site on my phone from the hangar to see if more pointers are given.

Maybe there is some air and I have to flush some with the hose at the disconnected at the purge valve?

How to check EMS

[email protected] said:

F....
Since you are seeing measurements of low flow and low pressure you may have an actual obstruction of some kind... but I would look at actual flows first for a quick check to see if the problem is really in sensor setup.

Click to expand...

Steve my personal helper again. How do I confirm the EMS reading put on a hardware store pressure gauge inline with the hose? I assume the same for flow, I guess I can get a flow gauge from the home store? I never heard of a bad sensor out of the box that seems rare.

Since it is not forecast to rain I will try to trouble shoot this today, I don't like doing this stuff with the fuel in the hangar or the rain.

Cheers
Mike

Ah, with no airflow...

Hey Nemo:

I recall Don telling me that the purge valve allows about 1GPH to get by.

Why such a small amount? Well, it seems the fuel controller measures air 1st, and adjusts the flow to closely match the air. No air = no fuel.

You will be able to sidestep that small flow by setting FT and full rich, which is what the Purge Valve OPS manual page 4 says to do for a hot start.

The TCM type systems - I think there is one of this type available for the Lycs too - SilverHawk? - are completely different, and do not measure any air. These brain-dead systems can be identified by their requirement for a return line and a rotary pump, and operator intense mixture management.

On the upside, these TCM-type systems have no venturi, so they do give a bit more MP.

Carry on!
Mark

Fuel Flows

For a 360 Lycoming with Airflow Performance FI you should see 4-5 GPH throttle WOT mixture full rich purge valve in ICO. With the throttle it idle the flow should be 1-2 GPH. The purge valve allows you to bypass the flow back to a tank but the fuel flows at these settings will be whe same with the purge valve in ICO or rich. It only diverts the fuel to the engine in the rich position or returns the fuel in the ICO position. Using this valve is helpful as you don't have to worry about flooding the engine when doing these tests.

As far as operation goes, the Silverhawk and Airflow Performance fuel injection operate on the same principle. Both measure air flow to determine the fuel that is delivered to the engine. The TCM system is pretty basic. It delivers fuel based on engine RPM and throttle position. Not real smart, but it's simple.

Bottom line here is if you have a question about Airflow Performance products the simple solution is to call here and get the correct answer. This goes for any suppliers products.


Don

Half solved

Talked with Don and like Steve said first is to make sure my gauges are giving me good information. So I hooked up the gauge and sure enough I was getting 24-25 PSI. I reviewed the Dynon manual and realized I had not set the sensor type to 2 which is for injected engines. Now Dynon says 29.2 when my test gauge shows 24 I guess I will have to live with that unless Dynon tells me there is a new sensor will help. I will have to adjust my limit bands some so I don't get alarms all the time.

Now to figure out the fuel flow. I only show 1.2 gal per hour at WOT / full rich

I will confirm this in the Dynon setup the actually flow fuel for a minute and compare what I get!

User error is more than likely the cause here but I do have the FloScan sensor which it seems many don't like.

Cheers

Flow is good

I ran the pump for a minute into a measure cup and had almost 10 ounces in the cup that works out to 4.6 gph which is what my gauge should be reading. I have had this stuff in a box for two years are better what are the chances I can get a new fuel flow sensor from Dynon. Time to call I guess b

Cheers

Check the calibration setting on the fuel flow...

The fuel flow sensor reads around 68,000 pulses per gallon... (Red cube reference number from memory). The dynon has to be set up with the correct pulse count for a gallon... Since all that the sensor does is send pulses the computer needs to know what the pulses mean.

Solved

I tried a flow check right after the flow sender and still got 4.6 gph. Talked with Mike at Dynon and the only thing he thought was to remove the sender and see if some foreign object might be hanging up the impeller. When I re-installed I realized I had it reversed as far as in and out of the sender is concerned. Reattached correctly and now I get fuel flow of guess what 4.6 gph. User error once again, actually only partially.

My fuel pressure reads .6 when boost is off and 29.2 on, Mike had me check OHM between wire stud (with wire off) and the case and it is high. He thinks it might be a bad sensor. He trying to see if he can get me another to try so I don't have to buy a new one. Unfortunately they don't carry this type sender for fuel pressure anymore! At least he is making an effort to help me out! Going to go over things once more to make sure the pressure sender is not a user error issue.

I am glad to be the fool publicly so those after can just read the fix and not embarrass themselves.

Cheers