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  #1  
Old 06-22-2018, 08:57 AM
steve91t steve91t is offline
 
Join Date: Nov 2010
Location: Huntersville, NC
Posts: 138
Default RV7/io360 hot weather issue on the ground...

Hello all! My dad has owned his RV7 for 8 years now (had 300 ish hrs on it when we bought it) and we?ve had a hot weather issue from the start. The PO, the guy who built it, said that once in a while it needs the fuel pump when on the ground to help prevent vapor lock.

So it?s an IO360 with dual P mags.

During NC summers and on the ground, it runs great while warming up. But once warm, like after a flight, we have problems. Yesterday was a good example. A buddy of mine and I flew it to a grass field glider airport where I fly the tow plane. 10 minute flight in the morning, then it sat in the sun all day while I towed. At around 4 pm (over 100 degrees on the field), I jumped in with a friend to give him a ride. I did a cold start procedure and it fired right up. We took off and flew around for less than 10 minutes at 1500 ft and at about 20? and 2400 RPM. Came in and landed. Now I needed to do a quick turn around since one friend was getting out and the other was getting in. Hot starts with such a quick turn around are nearly impossible with this thing. So I decided to keep the engine running. I had it runnng at about 900 RPM and leaned out. Friend A jumped out and friend B climbed in. He was just about in when the engine started to die. It went from running smoothly then it sounded like I had pulled the mixture to off. That quick. I turned the fuel pump on, shoved the mixture in and added throttle. I just barely kept it alive. From there it was running like **** and there was nothing that I could do to make it happy. I told my buddy that we had to hurry up and go. I had to keep it at about 1300-1400 rpm just to keep it running. As soon as I added power for take off, it smooths right out and runs perfectly.

So we fly 30 minutes to get BBQ. Land and shut it down 45 minutes later I did a hot start, short taxi, and took off. It ran fine on the ground. Flew 30 minutes home, low pass, and landed. Taxing in, the engine was idling ok, but surging. Again, this has to do with the hot weather on the ground issue.

It just had an annual and the mechanic (familiar with RV?s) insulated the fuel lines to try to help his problem. But it made no difference. Everything I?ve read says that you might need the fuel pump to help with vapor lock until the cool fuel is pulled through the lines then you don?t need it. Our issue seems to be different. It?ll be idling just fine then all of a sudden it?s trying to quick and it won?t stop until you either take off or shut it down and let it cool. If it actually quits, it won?t restart until it cools.

Again, this is only an on the ground issue. Like vapor lock. But how could a 10 minute flight with just a few minutes of idling cause this? Something else is going on and we can?t figure out what. The problem seems to be getting worse.

I?m sorry this was so long, I wanted to give as much detail as possible.

Any help with be appreciated.

Steve
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  #2  
Old 06-22-2018, 09:04 AM
oaklandaviator oaklandaviator is offline
 
Join Date: Dec 2014
Location: Somerville, Tn and Little Rock, Ar
Posts: 116
Default Gascolator

Try blast cooling a shroud around both the mechanical fuel pump and gascolator, if you have one. I'd also consider removing the gascolator, as it's a perfect little oven for your fuel.
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  #3  
Old 06-22-2018, 10:08 AM
lr172 lr172 is offline
 
Join Date: Oct 2013
Location: Schaumburg, IL
Posts: 5,297
Default

This is a pretty common problem. Suggest you search and will find several ideas. I had most success with smaller injectors, stronger spring in spider and a fuel return system to provide cooler fuel before the servo.

Also suggest that you get your idle mixture dialed in. I like the method of adjusting to the lowest Map with the engine fully warm.

Larry
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  #4  
Old 06-22-2018, 11:07 AM
steve91t steve91t is offline
 
Join Date: Nov 2010
Location: Huntersville, NC
Posts: 138
Default

I’ll find out if a gascolator is installed.

We do agressively lean at idle.

The spider spring would be an easy thing to do. Not sure why that would make a difference, but it’s worth a shot. Any adverse effects of the spider spring?

Tell me more about this return line? So it’s cockpit controlled? You crack it open with the fuel pump on so it allows circulation of cool fuel? How big of a job is that to have it done?

Last edited by steve91t : 06-22-2018 at 11:52 AM.
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  #5  
Old 06-22-2018, 12:03 PM
airguy's Avatar
airguy airguy is offline
 
Join Date: Oct 2006
Location: Garden City, Tx
Posts: 5,145
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I'm running an IO360 with .024" injector orifices and a 4-pound spring in the fuel divider and it behaves perfectly well on 100LL and acceptably well on 91E10 in west Texas temps. I do not have a gascolator, nor an engine-driven fuel pump, and all my fuel lines are insulated with a double-layer of firesleeve.

The return valve you are asking about is the Airflow Performance purge valve, it's a simple three-way valve placed at the inlet to the fuel divider that, when activated, will isolate the fuel divider and reroute all the fuel to a return line back through the firewall and back to your fuel tank. The idea is that in the event of shutdown-heatsoak-hotstart routine, you would use this to precool the fuel system and remove the FWF heat in the fuel and fuel components prior to start. I have it installed in my 9A and hotstarts work beautifully with that. My hotstart procedure is as follows...

Throttle and mixture full forward.
Activate purge valve (cockpit control via cable).
Electric fuel pump on.
Wait 60+ seconds - during this time fuel is flowing from the tanks forward through the servo and the line to the purge valve and back to the tank, removing heat from those components that would cause fuel to boil.
Mixture to ICO, throttle closed plus a crack open
Deactivate the purge valve
Crank the engine and push mixture to mid-range as the engine catches. Every engine is different and it will take a while to figure out the sweet spot on yours, but with mine a hotstart is just as easy as a coldstart using this technique.
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Greg Niehues - SEL, IFR, Repairman Cert.
Garden City, TX VAF 2020 dues paid
N16GN flying 700 hrs and counting; IO360, SDS, WWRV200, Dynon HDX, 430W
Built an off-plan RV9A with too much fuel and too much HP. Should drop dead any minute now.
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  #6  
Old 06-22-2018, 12:38 PM
isosceles isosceles is offline
 
Join Date: Jan 2018
Location: Fremont
Posts: 59
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Quote:
Originally Posted by steve91t View Post
... It just had an annual and the mechanic (familiar with RV?s) insulated the fuel lines to try to help his problem.
Can you guys elaborate how that insulation is done? I have a similar problem and would like to try that trick. thanks
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  #7  
Old 06-22-2018, 12:41 PM
airguy's Avatar
airguy airguy is offline
 
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Location: Garden City, Tx
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Quote:
Originally Posted by isosceles View Post
Can you guys elaborate how that insulation is done? I have a similar problem and would like to try that trick. thanks
http://www.aircraftspruce.com/catalo...?clickkey=4118

buy this and install it over the existing lines with safety wire ties on the ends to hold it in place. If it's not convenient to remove the line to slide this over the hose, then buy a larger size and cut it lengthwise, wrap it around the line, and use safety wire every few inches to hold it in place.
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Greg Niehues - SEL, IFR, Repairman Cert.
Garden City, TX VAF 2020 dues paid
N16GN flying 700 hrs and counting; IO360, SDS, WWRV200, Dynon HDX, 430W
Built an off-plan RV9A with too much fuel and too much HP. Should drop dead any minute now.
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  #8  
Old 06-22-2018, 01:10 PM
steve91t steve91t is offline
 
Join Date: Nov 2010
Location: Huntersville, NC
Posts: 138
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Quote:
Originally Posted by isosceles View Post
Can you guys elaborate how that insulation is done? I have a similar problem and would like to try that trick. thanks
I?m not sure exactly what he did but I?ll tell you it didn?t make a bit of difference.

I just talked to him. He has another RV7 in his hanger with the bypass. He knows exactly what it is and how to install it.

So the plan is to remove the gascolator if it?s installed and install the bypass.

What?s funny is he also has an RV8 there without a bypass. He called the owner and asked if he has hot start issues. His answer was ?nope, because I know that whenever I shut it down, I?m there for at least 30 minutes!? I thought that was funny.
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  #9  
Old 06-23-2018, 06:52 AM
steve91t steve91t is offline
 
Join Date: Nov 2010
Location: Huntersville, NC
Posts: 138
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Can the bypass valve be cracked open on the ground with the engine running?
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  #10  
Old 06-23-2018, 04:18 PM
airguy's Avatar
airguy airguy is offline
 
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Location: Garden City, Tx
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Quote:
Originally Posted by steve91t View Post
Can the bypass valve be cracked open on the ground with the engine running?
No, it's meant to operate full-open or full-closed - and as soon as it's open to the bypass line, that goes all the way back to the tank so there's zero pressure left to open the fuel divider and all flow to the injector lines.

To do what you're thinking of would need one of the EFI solutions where fuel is delivered via electric pump all the way to the injector rail, with a bypass regulator at the far end of the rail that returns the excess fuel back to the tank. That design does truly keep cool fuel to the injectors all the time.
__________________
Greg Niehues - SEL, IFR, Repairman Cert.
Garden City, TX VAF 2020 dues paid
N16GN flying 700 hrs and counting; IO360, SDS, WWRV200, Dynon HDX, 430W
Built an off-plan RV9A with too much fuel and too much HP. Should drop dead any minute now.
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