Veetail88

Veetail88

Well Known Member
I ran my motor yesterday for the 2nd time and have a couple of problems. Sorry about the large pictures.

Problem 1, the motor isn't idling. When I start it, and with the throttle all the way back, it's running at 1700 RPM.

I have fuel injection by Precision. I believe the linkage is correct as the throttle lever appears to be against the stop.

I assume that turning down the idle adjustment screw will only increase RPM.

In addition, with only about an inch of throttle movement, the motor winds up to 2700 RPM. I was afraid to move it further.

o9tc.jpg


Problem 2. The mechanical fuel pump is not working correctly.

With the boost pump on, I show around 28 PSI and everything runs smoothly.

When I turn the boost pump off, the fuel pressure drops to around 2 or 3 psi and the motor isn't real happy about that.

I checked the model of the fuel pump and it is LW-15473, which is apparently the high pressure pump, so I didn't end up with a carb pump.

My red cube is between the electric pump and the mechanical pump, but others have said this isn't a problem.

Another has voiced a question that maybe the pump hasn't primed properly. The motor has a total of about 13 minutes run time on my 8.

I purchased it from Mattituck 3.5 years ago and haven't run it before. I assume this would have shown up on the test stand, but it's not like I can call them anymore. :(

Any help on these items would be appreciated.

Thanks

Oh, and yea, I'll torque that castle nut and get a cotter pin in it when I get out to the hanger next.

5sp.JPG
 
Are you sure it's idling at 1700 or is that just what your engine monitor is showing? Your engine monitor will have a setting you have to input that will make it read correctly. It's very likely that it's reading 1700, but actually idling at 850. If it misreads, it is usually by a factor of 2 or 4. Get an optical tachometer to confirm your EFIS setting. Hope this helps.
 
Sounds like it

Thanks Steve,

It sure sounds like it's running at 1700! Big difference from the sound a 360 makes at idle.

I have a digital tach I can borrow though and check it out.

In addition, I did have to configure my EFIS. On the first run it was above 3000 rpm the whole time! Setting it to 4 pulses seemed to work, per the AFS manual.
 
Well, engines don't run without air, so if you can see that the throttle plate is closed when the throttle is back, then either it is getting air from somewhere or it is the sensor factor. What was the manifold pressure for that engine speed?

Don't be too sure about Mattituck not taking your call. For what you paid, they can answer your questions. Most folks are nice like that.

On the fuel pressure. Does the engine stumble when the boost pump drops off? It may not not at idle conditions. It could be your mechanical pump, because many production dynos have pressurized fuel supply to the engine and that would just push right past the check valves in the engine pump, and they might not notice. Stuff happens.

Also, that throttle plate lever looks like the serrations are not seated either so check that before torquing, or risk part damage.
 
If the engine is really idling at 1700, you definitely have an induction leak somewhere. Guaranteed! When we ran engines in the test cell we positive fed the engine fuel system with about 2 psi of fuel pressure. So the pump on the engine would have run the engine in the test cell with a 2 psi positive feed. The fuel problem sounds like either a bad pump or some form of blockage to the inlet of the engine driven pump that the boost pump is able to overcome.
Tech support for the engine should be available from Continental Motors.
Good Luck,
Mahlon
 
BillL said:
Don't be too sure about Mattituck not taking your call. For what you paid, they can answer your questions. Most folks are nice like that.
Click to expand...

I believe he was referring to the the fact that Mattituck is no longer in business.
 
BobTurner said:
I believe he was referring to the the fact that Mattituck is no longer in business.
Click to expand...

Oops, pardon my ignorance,:eek: I just associated Mattituck with Continental and did not know the "brand" was retired along with the rebuild facility. But at least it looks like there is some support, not that I knew it though.
 
Could your Tach be counting double the RPM?

Are you sure you are able to hit 2700RPM? That is a HIGH RPM and you would have to have almost no prop load to hit it quickly, as you described.

Is your EFIS set up to count the RPM's correctly?
 
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Well...at 1700 rpm you would have be on the brakes pretty hard to stay still...850 rpm, not so much or at all need brakes.
 
RPM

I was there watching and it was running 1800 + for sure. The wheels were chocked & tied to VW beetle. It was at run up RPM,until fuel pressure would drop then it would approach something that was close to idle RPM but was on the verge of stopping, like one or two cylinders only, still firing. As soon as fuel pressure came up, back to 1800+ & running smooth. Ron
 
Couple of clarifications

Thanks for the guidance guys.

I am pretty sure the tach is reading right. The plane was tied to a car, but I think it would have been a handful to hold it still with the brakes. The motor makes a LOT of power! On the high end, it actually went to 1600 and inched up to maybe 1650. Constant speed prop, so the pitch was flat.

I'll take off the snorkel so I can see if the butterfly in the servo is actually closing all the way for starters, but I'm not really sure how to proceed on the fuel pump problem. I'll take off the lines and ensure nothing is stuck where I can see and I'll check out the fuel filter. I assume that since the fuel filter is upstream of the electric pump an obstruction there would be a problem even when the boost pump is on.

And yes, when the boost pump is off, the engine stumbles bad and wants to quit.

Any suggestions appreciated!
 
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And since you're here Ron,

Thanks again for your help yesterday! And the special delivery on the Skybolt! Much appreciated!
 
Picture

The picture you have here is the mixture arm, not the throttle. If that's what you are adjusting, that is your problem....
 
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A couple of thoughts on the physics. As someone said, the engine needs air and if the throttle plate is closed, the engine can't accelerate. The engine is a air pump and if the inlet is closed it can't pump. The engine also needs fuel so air coming from a leak won't meter fuel, so a leak that large is not likely with an engine that can run smoothly.

Regardless of timing, the engine can't accelerate with a closed throttle valve.

The other part of the formula is the load, and without a load on the engine (prop pitch too low), the engine has little load and so can accelerate easily. Note that if set properly, the prop should limit max engine RPM to engine limits (2700 RPM?)

So, if your tach is correct, at least one of the two is likely a problem.

Curious to see how this turns out.

Dan
 
It looks like the castellated nut holding the throttle arm is loose. Also, there is no cotter pin holding it in position.

Is it possible, then, that your throttle arm is slipping?
 
rv9av8tr said:
The picture you have here is the mixture arm, not the throttle. If that's what you are adjusting, that is your problem....
Click to expand...

Yes and no. There is an adjustable link on the throttle arm which adjusts mixture, but the main arm is certainly the throttle, and the idle stop/speed screw looks to be in contact (throttle blade closed).

I will agree that the arm itself does not appear to be locked to the shaft through the serrated coupling, as if the nut is not fully tightened.
 
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May have solved the high idle issue

Went out to the hanger to check to see if the butterfly was closing. Getting a better look and armed with a bit more knowledge from the VAF gang, I noticed that the throttle arm on the servo was not actually bottoming against the stop.

c74f.jpg



It doesn't seem like that would be enough throw to go from 700 to 1700 RPM, but I'm hoping it is. It's at least worth something. If needed, I see I can turn the idle adjust screw down as well if needed.

Better now.

06h3.jpg
 
Jesse,

Are you using a throttle quadrant??

If so that is your problem.
You need to drill hole about an inch up to compensate for the throw.

My .05
 
This illustrates one of the basic inspection points before operating/flying: ensure all engine controls hit the primary stops before the knob bottoms out.

The amount of gap shown on that idle speed screw could easily make 1700 RPM with no load. And if you managed to fly the thing like that, on downwind/final, you'd likely see even higher RPM than that. Heck, just a couple of twists of the vernier is the difference between 500 and 1500 RPM on my airplane.
 
It looks like you are onto a solution for the extra rpm at idle. If the mechanical pump was working at factory test (per Mahlon's 2 psi supply information) then you may easily have gotten some debris in a check valve.

Not sure what you should do, but if it was me, I would remove the pump and check for pumping action by hand. It may have to be dissembled to reach the check valves, maybe more hands on guys here can advise on that aspect. That is what I would do, but I will take apart almost anything. Especially if it does not work.

Hoses/lines are easily contaminated during the build process. If you remove the pump, blow out the lines/hoses while you're at it. Use a clean towel to see if anything is ejected.

Let us know what you find.
 
It's not completely clear from the picture but it almost looks like the teeth that allow adjustment between the arm and the injector unit weren't completely meshed together. Since you installed the cotter pin you've probably already adjusted these but it pays to look again - if those teeth aren't completely meshed it can end up slipping a tooth or two and you'll end up right back where you started.
 
gotta work through it.

Thanks for the extra ideas guys.

The fuel pump is actually plumbed correctly however and I'd realized when I posted the first picture that the castle nut was a little loose and there was no cotter pin.

On closer inspection last night, I checked it out, and while the nut was not tight, it wasn't loose enough to allow the teeth to slip. Torqued properly now and cotter pin installed.

It was definitely out of position though. I moved the arm so that when I pull the throttle back that the arm reaches the stop before the throttle quadrant runs out of throw. What I didn't check is to verify that the throttle quadrant can advance the injector arm to the full open stop as well. I'll check that soon, and if needed, I'll drill a new hole a bit further up on the quadrant arm to provide more throw from that end as suggested by some here.

I'll dig into the fuel pump this weekend. Anybody have a diagram of high pressure Lycoming fuel pump? I haven't been able to turn one up on the web.
 
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One problem down, one to go!

Had to fiddle around with the positioning of both ends of the throttle cable and the position of the throttle arm on the fuel servo, but finally got it set so we're up against the stops! It'll idle down to 650 RPM, but it's happier at around 750. Where should it actually be? Also had to adjust the idle mixture setting to smooth it out when it's running slow.

Regarding the mechanical fuel pump, it was working much better today, producing around 15 psi but the motor still isn't happy with that low pressure.

The motor did sit for about 3.5 years between test cell and now. Is it possible that the fuel in the pump just got gummed up and it's now working itself free? It seems like it.

I'll run the motor more tomorrow to test out the theory.
 
Good to hear that you are resolving the issues.

I probably don't need to say this, but just don't fly if that pump is not up to specification. Will you bet you life and/or plane that nothing it wrong? Probably not. :D

Although idle is 750 (ok- maybe 650) that after soon after landing and slowing down, Mike Seager taught me to get the engine idle back up to about 1000. It seems much smoother and easier on the airframe.
 
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Generally I'm at 1000 rpm when on the ground, but that's with the throttle cracked a little. You want the hard stop set much lower - like 600 or so. If the "hard stop" is set at 1000 RPM, you are going to float a loooong time when landing.
 
No, I won't be flying it this way. Plane isn't ready yet anyway. Lots of little details yet. Probably won't fly till spring. Just trying to get things sorted out.
 
Jesse,
Although the mechanical pumps do occasionally fail partially or completely, it is not likely on a new or freshly overhauled engine. AVGAS doesn't gum up quite like automotive fuel from what I understand. I would first check all fuel line connections between the boost pump and the servo. Check for tight B-nuts, cracked flares on hard lines, and debris between the flare on the hard line or the hose and the fitting. Also AL fittings can crack. Check the T-Fitting at the pump where you pull off your fuel pressure. There have also been issues with the red cubes leaking at the fittings. It is possible that the mechanical fuel pump is sucking air from one of the fittings at the red cube due to the way you have it plumbed. You might want to try temporarily removing the red cube from the system by bypassing it with a hose from the boost pump to the mechanical pump. Good luck.

Jerry Esquenazi
RV-8 N84JE
 
If the fuel pressure is highest at Idle speeds and declines as you try to increase engine power, it may be indicative of blockage in the plumbing to the pump. Maybe enough fuel to make higher pressure is getting through when the demand is less versus when you have a larger demand not enough can get through the blockage and thus the pressure drops. Just a thought.
Good Luck,
Mahlon
 
Just thought I'd update.

Yesterday I bypassed the red cube, checked the line from firewall to the spider and found no obstructions. It ran worse than the day before.

So, I undid what I did, then found the nut that tightens the inlet fitting on the fuel pump in place so it doesn't rotate was not tight. Tightened it thinking that MUST be it! It wasn't. :(

Fuel pressure with boost pump on is around 28 psi regardless of rpm, even at idle. Once I turn off the boost pump the pressure decays to about 15, again regardless of rpm, and the engine stumbles badly or dies.

It also puffs black smoke when it dies, and on 2 occasions the prop kicked backwards a turn or two at the end. Played around with the mixture with no satisfactory result at any point.

Strangely, with the engine running around 1800 rpm, smooth and strong, without touching a thing it will suddenly start running rough.

I'm starting to believe that the problem is simply the fuel pump is bad or something stuck in there.

I'm thinking of rigging up a small tank temporarily on top of the engine mount and feeding directly into the mechanical pump. This will isolate the problem at least to the fuel pump and injector system or a problem between the fuel pickup in the wing tank and the firewall.

If I find the fuel pump not working correctly, is there any danger in taking it apart myself to look for the problem? A new one isn't cheap so it would be nice to solve the problem this way, but on the other hand, I haven't been able to find a parts diagram. I'm assuming that SOP is to just chuck it and install new.
 
I'm sorry to hear that the trouble shooting hasn't worked out yet. I don't know much about the internal workings of the pump, however it appears to be a very simple device. You could remove it, take a look inside, and re-assemble. Having never worked on one and not having a manual I would feel more comfortable sending it off to QAA (Quality Aircraft Accessories) or something like that after taking it apart. Just be very careful re-installing the pump because apparently it is very easy to get the lever in the wrong position (it will go in in the wrong position) and bend some metal.

Jerry Esquenazi
RV-8 N84JE
 
Mounting Frustration

So my frustration is mounting.

My engine roughness continues. The fuel pump continues to only supply low pressure, it will not idle well and when running at higher speed, maybe 1800 RPM, boost pump on, it will be running very smoothly for a few seconds and then start coughing, belching and even backfiring even with the mixture full rich.

Even when running at that speed, turning off the boost pump causes the fuel pressure to drop to 16 psi, and by then the motor is dying.

Here are the steps I?ve taken.

I?ve gone over everything looking to find any induction leak. I found one of the intake tube o-rings to be installed, well, poorly to say the least.

kfpm.jpg


vzbw.jpg


dlm9.jpg



So I took it apart and put it back together squarely. Being sure that?s must have been what the problem was, pulled the airplane out of the hanger and ran it. Nope. Not that.:(

Not able to find any other induction leaks, I moved again to the fuel system.
I took the fuel line off at the firewall and ran a hose into a gas can to test the flow rate from the boost pump. Seemed pretty slow, so I looked in the wing tank as I?d only put in 5 gallons to begin with and couldn?t see fuel. So I assumed the level was so low I was probably sucking in air with the fuel. Put in another 5 gallons and tested the fuel flow through the boost pump.
The flow meter said about 14 gpm, but I measured the flow to be 1.25 gallons in only 2 minutes. I figure that has to be plenty to make the motor run, so I pulled it out of the hanger and ran it again. Nope. Not that.:(

So now I?m thinking the fuel pump HAS to be interrupting the fuel flow somehow. So I removed it and took it apart. Not much to those. All ports are open, all diaphragm gaskets in excellent condition as well as the check valves. Guess it should be as it?s probably got less than an hour of total run time on it.

So, I put it all back together, put it back on the airplane and took the airplane out of the hanger and ran it???? Not that either.:(

Anyone in the area have a high pressure pump I can swap out just to test to see if that?s the problem? I just can?t fathom that there is a problem with the pump as it?s so simple and everything seems to be in perfect working condition, visually.

So, I started thinking it?s spark. I have 2 P-Mags. Turning off either at 1700 RPM yields a 100 RPM drop. Seems high, but the motor reacts the same no matter which ignition I turn off. Checked the plug wires. All of them are on the correct plugs/connections to the P=Mags. The motor runs smoothly at higher rpms (before it starts coughing), so I assume the timing must be correct. Ideas about this?
During these runs, the number 4 CHT has been running higher than the rest. The motor is not cowled, so I assume that has something to do with it, but??.I swapped the injectors between 2 and 4 to check that. Injectors are clean and swapping them made no difference. :( I?m thinking P-Factor is keeping cooling air from blowing on that cylinder effectively.

One more observance, the #4 exhaust is discoloring much more than the others even though the EGT?s seem to be about the same. Possible valve problem?

fr8o.jpg



So, I?m at a loss. I have not done much with the fuel injector (Silverhawk) or the fuel spider as that stuff is daunting and I have NO experience with it. (normally I?m a bit fearless with mechanical things, but the fuel injection system seems scares me a bit)
Any more ideas?
 
Are the braided hoses in/out of the pump -6 or -4? It looks small in the picture. Have you been trying different mixtures on the run? Could it be way rich despite the fuel pressure indication?
 
All fuel lines are -6. Fuel pump is the correct high pressure unit. Not the one with the AD. And , yep, I've tried different mixture settings to no avail. When the engine starts to sputter the only thing that will keep it going is increasing throttle, which of course increases rpm, a lot.

Thanks guys.
 
It sure sounds like a bad fuel pump to me. I would buy another one, and if it turns out not to be the problem, at least you have a spare. It WILL quit eventually.
 
Based on some previous experience with the RSA series of servos and confirmed by the Precision manuals, the servo won't reliably work with inlet fuel pressures below 20PSI. The engine driven pump must supply at least 20 PSI or the servo won't meter fuel properly. If you want better details visit the Precision website at http://www.precisionairmotive.com/
and select the Silverhawk EX support. There are some excellent docs there. If you poke around the website you will find some training documents that explain how the system works.

Hope that helps.
 
Veetail88 said:
All fuel lines are -6. Fuel pump is the correct high pressure unit. Not the one with the AD. And , yep, I've tried different mixture settings to no avail. When the engine starts to sputter the only thing that will keep it going is increasing throttle, which of course increases rpm, a lot.

Thanks guys.
Click to expand...

Does the engine have a prop installed?
 
When you said 1.25 gallon in 2 min, that was free flow right? If you hook up a valve and run it, open or close it to maintain the psi you need, measure the volume. You need the volume at a certain psi. I vote for pump like mentioned above.
 
When I was a kid.

When I was a kid we used to bench over hall AC Delco fuel pumps. They had micarta valves then. They have nylon ones these days. WE just took a scribe and marked the side down the stack-up of the two chambers. Then took the screws out. If we did not find a diaphragm bad it was a valve broke or in many cases trash or a bad seating valve or valve spring. We just put a new kit in them and bench tested for flow and suction. I would never tell someone to do this to their aircraft pump, but it worked good on the same pump installed on many other engines. Now back to you airplane. Please check all you 3/8" pipes from the tank al the way to the pump. A bucket test flow of 1.2GPM is in the Ball park. But the part about the engine starting to stumble at 1800 sounds like it going lean even with the bust pump on. A flow restriction on the suction side will do this with either pump trying to supply fuel I don't know how many times I have had an engine run fair at low speed just to have it start starving when we pick the throttle up to half or better. just because of trash or a blockage between the tank and the pump.. Just a thought.... Yours as always R.E.A. III # 80888
 
Yeah Brett, that's free flow. And Robert, it also does not like to idle well either.

Starting it think I'm just going to have to buy another pump just to find out!

I will however go through all the suction tubing, again. It just doesn't make sense since I can get the gallon and a quarter through the boost pump.
 
The other thing to check is that the breather is free. One side of the diaphragm in the pump is vented thru a hole in the pump casting to the accessory case. If the engine breather is plugged the mechanical pump will quit pumping. I have done some experimentation around this in the past so I know it does happen.
 
Couple of random thoughts:

Rough running associated with black smoke is indicative of an overly rich mixture, not starvation.

Have you done a fuel flow check at the nozzles?

Why not bypass the mechanical pump entirely and get it running right on the boost pump alone? Thats the quickest way to rule out a mechanical pump causing "the" issue. You might have several things going on here - verify what you have before you start throwing parts at the problem.
 
Bob, I was not able to find a breather hole between the crank case and the top chamber of the mechanical pump, but I'm glad you posted that. That chamber had engine oil in it and I thought that was odd, but once I drained that oil out, inspected all the parts, reassembled and ran the engine again it had no effect. I thought maybe the oil in that chamber was damping the action of the diaphragm, but I was wrong. (don't tell anyone I ever admitted that ;-)

I still have not been able to locate a diagram of the pumps, but it's not a necessary now that I've had one apart. If I take it apart again I'll definetly look for that port.

Michael, thanks for the great thought. Just this morning on my drive in I was thinking that same thing! Need to isolate that pump so I can learn if I'm dealing with one problem or more. Problem is I might not have a chance to get to the hanger to try this before next weekend and I'm chomping at the bit to work on it.

Thanks again guys.
 
Your boost pump should be capable of delivering 30 gals/Hr, or about 1 gal in 60 seconds, and from either tank. If you're not getting the 30gals/hr, something is blocking the fuel flow....

Veetail88 said:
Not able to find any other induction leaks, I moved again to the fuel system.
I took the fuel line off at the firewall and ran a hose into a gas can to test the flow rate from the boost pump. Seemed pretty slow, so I looked in the wing tank as I?d only put in 5 gallons to begin with and couldn?t see fuel. So I assumed the level was so low I was probably sucking in air with the fuel. Put in another 5 gallons and tested the fuel flow through the boost pump.
The flow meter said about 14 gpm, but I measured the flow to be 1.25 gallons in only 2 minutes. I figure that has to be plenty to make the motor run, so I pulled it out of the hanger and ran it again. Nope. Not that.:(
Click to expand...
 
New facts help

If you fond oil running out of the breather port of the pump. That is an indicator that there is a problem. The diaphragm chambers should be dry, except for the fuel side. If you are getting engine oil coming out the weep hole. It is not correct. But the others are correct isolate the engine driven pump and see if it will run without it in the circuit, before you throw money at the pump. The engine driven pump may have the restriction in it or a simple fault like a valve stuck closed by a peace of drill shaving..Oil means not sealed off from the engine crankcase. You got a good one, but you can do it. Yours as always R.E.A. III # 80888
 
Oil wasn't running out of the breather port.

It was however present in the chamber depicted here. This isn't a really accurate detail as it's not the same pump at all, but it's close enough to get the point across. And it's upside down.:D

lc6l.jpg


There was unmistakably oil in this section, and I still don't think it should be there. I would assume there is an oil seal on the actuator shaft on the Lycoming pump similar to the one shown here.

Anyway. The plan of action will indeed be to bypass the mechanical pump and test it.......this weekend. Thanks
 
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