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Bob Brock
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Posted Thursday, October 20, 2016 @ 04:32 PM  

Greetings:
Hard engine starting was really getting to be a problem and not much fun. When I wanted to fly my RF-4D, it would often take me countless hand props and starting fluid to get it running. Then when it was running, the engine seemed to run fine. Timing and power all checked out fine. The choke was confirmed to work fine and at idle I could over choke a warm engine and get it to stop running.
When I picked up N7725 some years ago it had not flown for a decade, yet it was easy to start... like on the third of forth blade after a few with choke on. Then I completely rebuilt the airplane and Collin Gyenes was rebuilt my engine. He also had the mag completely reconditioned with new ignition components (Tempest AB-473-D). The old harness was checked and the ends were cut to allow Bosch shielded spark plug connectors that Eugenio had given me so auto plugs could be used. Again, when it was running everything was fine except for some static on my Becker radio that got so bad I often just tuned it off. I tried different wiring and different antenna systems... the best seems to be the non base plane antenna from Aircraft Spruce that looks like a 40 inch strip of 1 inch wide plastic strip made for non metal aircraft. I rebuilt the carb using a kit Eugenio gave me and confirmed it was perfect by using a second extra carb that Collin loaned me.
To limit the spark plug noise I purchased a set of machined spark plug covers from Great Planes Engines (a source of good VW aircraft engine parts). Great Planes staff recommended smaller spark plug gap (.0015) and the use of non-resister plugs. New plugs and gap, still ignition noise and hard to start. So I purchased an engine primer from Great Planes and installed a primer line in the intake manifold near the head on one side. It seemed to help and I could at times get it started without the use of starting fluid. Yet I never knew when the engine would become temperamental and not start. Collin did not like me using starting fluid because it striped the oil off parts that needed lubrication. Collin even loaned me the mag off his engine which was a great help to have something siting side by side that I know worked for him.
Earlier this year I decided that I had to get to the bottom of the problem and removed the engine. Back to basics. Collin did a valve job on one side (might have been too much starting fluid, I don't know) and I took the mag to another highly rated mag shop (just in case the first expert got it something wrong like the impulse pins. Mag was perfect but he told me to try a new harness. What a joke… I spend hours on the phone with all the ignition harness people in the US. I would give them the mag model number and even the serial number and they would ask for the engine. Of course they had never heard of a Rectimo 4AR 1200, so none of them were of any assistance. Yet the Bendix mag was common and used in many aircraft so I simply asked my FBO if he had an ignition harness for a Centennial O-200 engine (knowing that Rene would have kept things simple and did not have the mag or harness built specifically for this airplane) and he sold me one of his Slick harnesses so I would not have to purchase two. “But, it is a Slick and I have a Bendix.” I told him. “No worries, they are all the same,” he said. True! Had to be careful to keep the firing order straight since the spark pug numbers on the harness were for a two mag engine that turned in a different direction. I added a primer line to the other side of the engine before reinstalling the engine.
Nothing changed with respect to starting and static. Engine was still hard to start and it was very frustrating. What more is there to do?? So I asked Collin if he could return my original spark plugs now that I had aviation harness type connectors. He gave me the plugs back (thanks for keeping everything Collin) and my problems went away when I put in the original resister plugs including the ignition noise in the radio. At lease they seem to have gone away but I will not be convinced until I start it about 100 times.
Yesterday I pulled N7725 out of the hanger. It had been a cold night but not winter with temp drop to below 40 degrees F. It was about 50 degree F when I attempted to start the engine. Two shots of prime, about 10 blades with choke half out, then, switch on and it started on the first blade. I flew to our glider port about 15 mins away, landed and talked with the people there for about ˝ hours. Engine start was again on the first blade… this time just turned it over about 5 blades at half choke, then switch on. How nice it that? I will continue to try to start the engine as the weather gets colder to confirm that the fix is real.
Frankly I do not know why the original resistance spark plugs make such a difference, but they do.

Donald
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Posted Friday, October 21, 2016 @ 04:15 AM  

Interesting stuff Bob. So if I read that right you're back with aviation plugs. Which ones?

I too have fiddled with my ignition components over the years. I've experimented with auto plug caps and plugs but, like you, resorted to an aviation harness.
I've tried NGK auto plugs with the Great Plains spark plug adaptors and yep, they work but presently I'm running Champion REL37B plugs as it's the only 14mm thread aviation plug out there with the reach, but they're very expensive and unaccountably I'm not wild about Champion plugs.

I'm sure you already know but the NGK FAQ web page has this to say about resistor plugs: "NGK strongly recommends using resistor spark plugs … in any vehicle that has other on-board electronic systems such as engine-management computers, two-way radios, GPS systems, depth finders or whenever recommended by the manufacturer.

In fact, using a non-resistor plug in certain applications can actually cause the engine to suffer undesirable side effects such as an erratic idle, high-rpm misfire, engine run-on, power drop off at certain rpm levels and abnormal combustion." (My Bold.)

Bob Brock
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Posted Friday, October 21, 2016 @ 04:06 PM  

Hi Donald...
Sorry you give me too much credit. I did not drill deep into the NGK data for plugs and applications (B7HS) but rather relied on the engine experts from Great Planes, et. al. I did indeed verify that the NGK plugs were gaped correctly and they did indeed spark at the right moment. My experience with spark plugs is limited to other aircraft so the cost factor was known, but it seemed that a plug should work or not work. They worked just fine when the engine was running, it was just very hard to start. How simple is a spark plug?

I was simply trying to prove each component knowing that somewhere I was going to find a solution to the hard starting or go crazy in the process. Turns out the plugs were about the last thing I considered since the expert recommendations were so strong. I even started the engine without a carb to verify the primer operation.

I will check the actual plug model number but I think they are Champion REL37B. The best price I have found is $45.00 each from Wag Aero.

Donald
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Posted Friday, October 21, 2016 @ 04:56 PM  

Hi Bob,

I've poked about in the online spark plug data in the past and, as mentioned earlier, have fiddled with the things in my engine but I'm no expert.

I have tried Bosch auto plugs but had two fail on me, once on climbout and once crossing the mountains here in Scotland, mere hills to you Rocky Mountain guys. Then a friend who runs his own Auto shop recommended NGK as having the best temperature tolerance, hence reliability and I'm pretty sure those B7HS are what I tried. However I was getting wild tacho swings on the Westach which picks up from the 'P' lead so I switched back to the Champion REL37B. I have tried to find an alternative aviation plug but there just seems to be no alternative at 14mm thread with 1/2" reach so I'm sure that's what you must be running too. (Plug Trivia, the REL37B was made for a Franklin engine.)

However, with that NGK advice I highlighted in my last post I'm going to get hold of a set of NGK BR7HS, the 'R' in the code telling that it's a resistor plug, and see how they perform. They cost not much at all so no big deal to give them a try.

Bob Brock
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Posted Saturday, November 5, 2016 @ 12:47 PM  

More on spark plugs... I checked and have two different brands of spark plugs. Two of my plugs are ACSR-47P fine wire spark plugs. I don't know if these were in my engine or if there were plugs Collin had from another engine, but they seem to work just great. I don't know if it really matters that I have two different brands and types of plug. Yesterday I started it twice... same procedure, two shots of prime and choke for ten blades, then switch on and it fired on the first pull. Nice. Thus I have about 30 starts without a problem since my first post. It really makes flying so much better.
Donald
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Posted Sunday, November 6, 2016 @ 07:16 AM  

Good for you Bob. I presume, though you don't say, that all 4 of your plugs are now ACSR-47P, another 'Resistor' plug from that code.
Not a plug I'd ever heard of and google doesn't turn up much, so it seems it might be obsolete. Perhaps you can refute that with a supplier.
Markku
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Posted Monday, November 7, 2016 @ 09:48 AM  

Hi Bob
When I visited you and tried to start your engine, I was surprised that it didn't start. My plane and our club plane have aviation plugs, might be just that REL37B, and we have got no problems with starting
Bob Grimstead
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Posted Tuesday, November 15, 2016 @ 03:02 AM  

That is very interesting Bob,

I have to say that I have been running auto plugs for six years and about 250 hours without any problems at all except some slight background radio interference.

After using NGK B6HS for a few years, simply for experimentation and because the NGKs were getting a bit old, I changed to Bosch W8ACs. I have not had any difficulty starting with either type of plug in ambient temperatures from +5°C to +40°C.

Nowadays I do use a primer tapped into the air filter housing and squirting directly into the carburettor venturi rather than the old choke, because it reduces the number of priming or 'sucking-in' turns of the propeller to two or three rather than the eight or ten I needed with a choke.

I apologise that this is at variance with your experience Bob, but I thought I had better mention it in the interests of giving a full picture.

Incidentally, one problem I did experience was of one of the automotive, copper-core HT leads pulling out of the Champion spark plug cap a couple of times where the threaded spike in the plug cap screws into the HT lead core. Cutting an inch off the HT lead and starting anew seemed to solve that problem.

Something else I should mention is that I use a mix of Avgas and motor fuel (mogas) in my Fourniers. Very approximately it is usually about one unit of avgas to five of mogas, although it varies widely and can often be all of one or all of the other. I add avgas to the mogas to get some tetra-ethyl lead into the combustion chambers because my compression ratios are about 8.5 to 1, which is too high for modern motor fuels of 91/95/97 RON.

A beneficial side-effect of this for starting is that mogas is much more volatile (evaporates more easily) than avgas which particularly aids starting. Also you may not be aware that, while the formula for avgas is constant all year around, mogas changes from season to season, being much more volatile in winter to aid cold starting, but less volatile in summer to reduce the chance of vapour locks, so it is important always to use fresh mogas from the current season.

Yours, Bob

[Edit by Bob Grimstead on Tuesday, November 15, 2016 @ 03:11 AM]

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Flying and displaying Fournier RF4Ds VH-HDO and G-AWGN, building replica RF6B G-RFGB and custodian of RF6B prototype F-BPXV

Bob Grimstead
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Posted Tuesday, November 15, 2016 @ 03:18 AM  

More sparking plug trivia...

I believe that the Champion REL37B plugs are also used on de Havilland Gipsy engines -- Tiger Moths etc.

--------------------
Flying and displaying Fournier RF4Ds VH-HDO and G-AWGN, building replica RF6B G-RFGB and custodian of RF6B prototype F-BPXV

Bob Brock
Master Sergeant

Gender: Male
Location: Portland, Oregon
Registered: Mar 2009
Status: Offline
Posts: 156

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Posted Tuesday, December 6, 2016 @ 08:39 PM  

Cold hard starts... no more!
OK, I wanted to verify that the fix was in, and I am happy to report my RF-4 sits in an unheated hanger with the temp falling below freezing... ice and snow on the ground, but it still starts right up. Even surprises me often on the first pull with switch on, after about 10 blades choke and prime. The little primer from Great Planes is a really nice addition at a very low cost. I am sure there are a number of ways to install the primer and lines, but I know mine works great. (I did try to start with just choke a few times and gave up) Anyway, problem solved.
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