Bad fuel, hot jug and climbing CHT

Briar Rabbit

Briar Rabbit

Line Up and Wait
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626
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Albion, Nebraska
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Rob
I was flying to Davenport Ia yesterday. The Centurion has 35 hours on a 0 time Continental io520. When we installed the new engine also installed a JPI 900 engine monitor. The original egt is still hooked up and functioning. With a new engine I had been watching the cht’s as the engine was breaking in and was familiar with where it had transitioned from and to. At 1 1/2 hours into the flight a routine scan of the gauges showed #3 cylinder egt had rapidly jumped from 1380 to 1520 and the cht on that cylinder was climbing. Cht on #3 had been 366 and was at 400 and slowly continuing to climb. Now about 405 in another minute. The other 5 cylinders perfectly normal - 1&2 around 340, 4 about 362, 5&6 around 350-355. EGT on the other 5 cylinders also normal between 1340 to 1380 or so. The factory egt had not moved, no indication of a problem. Figured I had a problem with the fuel system for that jug. At the time I was running 15.5 gph per the JPI unit. First I hit the high speed booster pump to see if that made a change - no difference, turned it back off. Then I increased the fuel flow to 16.5 gph and opened the cowl flaps half way. The cht dropped to 390 and egt back to 1460. We were close to Davenport, about 40 minutes continued on and monitored.

I talked to the local A&P at KDVN and explained I expected a problem with the #3 injector. The next morning he pulled 1 & 5 injectors and compared the flow. Sure enough the #3 was partially plugged. He cleaned the #3 and problem solved.

So I am pretty impressed with having the JPI 900 engine monitor. There was no other indication from the original engine instruments we had a problem. I don’t know how long the jug would hold up with continuous operation at 400+ cht in cruise, and probably would have been higher during an extended climb-out, but doubt if it would have been 1,900 hours. I feel the JPI monitor was a darn good investment! Would not have been alerted to this anomaly without it, at least not that timely and with a minimal $50 fix.
 
Engine monitors are wonderful. The RVs are pretty tightly cowled, so we have to pay special attention to the CHTs, especially on hot days.
 
Wow, good info. I don't have the fancy-schmancy 900, but I DO like having the JPI-700 I have. Gives me good info on the fly, so to speak.
 
I think he meant bad in the sense that the cylinder wasn't getting enough. Unless there's some sort of filtration system in his injector spider that routes all bad fuel to one cylinder.
 
SoCal RV Flyer said:
Engine monitors are wonderful.
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That they are! Arguably the most important thing on your plane is the engine. Having real time monitoring is priceless. The Cirrus and my usual Archer was booked this past weekend when I had family in town, so I rented a new (okay, 2006, but only about 2,000 hrs) Archer at the club to take my brother up.. and felt so "naked" without having any real engine monitoring other than an EGT gauge and the standard oil temp / press gauges
 
I had a similar experience on a flight a few years back, one cyl jumped up much hotter than the rest. As I was just climbing out of the home field, I nosed over, reduced power, kept the cowl flaps open and RTB. Mechanic found that cyl injector to be clogged. Engine monitor good!
 
Briar Rabbit said:
Fuel was contaminated, something in the fuel partially plugged the injector. Airport where the fuel was purchased owned up that they have been having problems plugging their filter at the 100LL pump.
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Which airport?
 
Briar Rabbit said:
Fuel was contaminated, something in the fuel partially plugged the injector. Airport where the fuel was purchased owned up that they have been having problems plugging their filter at the 100LL pump.
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It takes a much bigger piece to partially block an injector than any of the three filters in the airplane would pass. There's the fine screen in the fuel strainer. Downstream there's a finer one in the fuel servo. Then there's a fine last-chance filter in the fuel manifold ("spider"). The thing that blocked the injector was likely some bit of crud that got into the manifold outlet or injector line during overhaul.
 
Ok technically correct, partially plugged should be rephrased to atomization disrupted. The contaminant was not large enough to affect gage measurable gph coming out of the nozzle but did affect the atomization pattern enough that it did not burn evenly and created higher EGT. May not have passed thru the screens but not sure that I totally agree with Dan that it can not happen. We are talking about a contaminant the size of the head of a sharp pin that may be so small to not be visible and maybe or probably less than 5 microns? It is possible too that it was in the line for 35 tach hours and just broke loose and moved to the injector. The A&P did see a fuel quantity difference from the #3&5 injector flow. And it is not disputed that there was a fuel issue at the airport, KBVN. So however you want to phrase it or consider the source of the contaminant the key point I am offering is the engine monitor was a darn good investment!
 
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Maybe saved your wallet, and your bacon! Good testimonial.
 
Here is an update to the fuel / fouled injector issue.

On the next flight and about 2 1/2 hours more engine time we had another engine roughness for a brief moment and now cylinder #4 started to heat up rapidly. Previously it was #3. The fuel was from the other tank but still from the same airport (BVN) and fill date. This time the increase in temp was not adequately controlled by increasing mixture and opening the cowl flaps. Fortunately we were descending and only about 10 miles from the home airport. Once again the original factory gauges gave no indication of a problem but the JPI 900 monitor lit up the engine warning light.

We pulled injector #4 and just looking thru the injector could see a contaminant inside prior to flushing the injector. We also pulled the screen located in the nose gear wheel well and found it to have contaminants stuck to it. The airplane was 10 hours out of annual, this screen was checked at annual and previously free of debris. I discussed with a factory Continental engine technician and was told that fibrous contaminants can migrate thru the screens and cause injector problems so I elected to have the entire system cleaned. From the tanks there is a quick drain at the bottom of each wing tank, there are two more sumps with quick drains in the belly of a Centurion. There is the drain with the pull knob by the oil dip stick. Then the fuel goes to the afore mentioned screen in the nose gear wheel well. This is followed up by a screen in the fuel injection system throttle body and finally a screen in the manifold valve or spider that sits on top of the engine case. A contaminant from a fuel tank has to pass thru all of this to reach and affect an injector.

We found this debris in the belly sumps and the nose gear screen. One of the POA members did not think the contaminants could get past this screen but the Continental tech assured me it can and I thought you might find this enlarged picture interesting:
upload_2018-6-1_17-1-0.jpeg
This is the second screen in the system and out of the throttle body. There are no cloth, paper or fibrous filters in a Centurion fuel system.

An A&P is not supposed to open up and clean the screen in the spider so it is enroute to Continental for cleaning.

The airport where the fuel was purchased denies any responsibility. We have never had a problem previously with fuel contamination. New engine ran perfectly for 35 hours prior to this fuel fill. Their response was to take an airport tank fuel sample, but I contend that a small sample is probably not adequate to find the issue. We had purchased over 75 gallons and the contaminant total would probably cover the bottom of a thimble. The airport tank is an underground tank installed in 1999 and the sample was taken from the pump.

Sounds like I am stuck for the maintenance charges but hopefully preventing engine damages or a power failure. I have been told there have been some power anomalies in the local 172 and attributed to carburetor ice by student pilots but no one knows for sure. I have expressed my concern to the airport management and hoping no one else has issues. Not planning to purchase anymore fuel there in the near future!
 
Report the potential contamination issue to the fuel company they buy fuel from. Probably won’t get your mx paid for but just might save someone else’s butt. Fuel contamination is nothing to be taken lightly
 
Tarheelpilot said:
Report the potential contamination issue to the fuel company they buy fuel from. Probably won’t get your mx paid for but just might save someone else’s butt. Fuel contamination is nothing to be taken lightly
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They know. Also had two conversations with FSDO.

Any ideas from the picture what the contaminant is from? I still believe I know where the airport source is but not sure what it is.
 
Dan Thomas said:
It takes a much bigger piece to partially block an injector than any of the three filters in the airplane would pass. There's the fine screen in the fuel strainer. Downstream there's a finer one in the fuel servo. Then there's a fine last-chance filter in the fuel manifold ("spider"). The thing that blocked the injector was likely some bit of crud that got into the manifold outlet or injector line during overhaul.
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Agreed.
OP, did your mechanic say what was clogging the injector? Or did he simply blow it out with a blow gun and screw it back in? :)
It is good practice to carefully remove the debris and inspect it (along with the injector nozzle). Injector flow rate should be checked too.
Inspection of the debris often provides clues as to the source of the contamination.
 
BigBadLou said:
Agreed.
OP, did your mechanic say what was clogging the injector? Or did he simply blow it out with a blow gun and screw it back in? :)
It is good practice to carefully remove the debris and inspect it (along with the injector nozzle). Injector flow rate should be checked too.
Inspection of the debris often provides clues as to the source of the contamination.
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Both times the affected injectors were removed. I was not present the first time. And both times the partial obstruction was removed with carburetor cleaner or CRC spray can. As stated previously the second time it was visually noticeable that it was reducing the ID of the injector. But still very small. Based on the additional flow required to return the cylinder to the previous egt temperature I estimated the size of the contaminant to be in the range of 3 to 4 microns. I am sure the math I used is questionable but at least a rough idea as to size. The second contaminant was larger but still one would think it would just flow on thru the injector? But they did not. I believe the ID of the injector to be about 50 microns? The contaminant was not caught during flushing from the injector. You do not fish in the injector with any element as you can damage the injector, has to be flushed. Also it is important to torque the injector when replacing it, on this engine 55 to 60 inch pounds. The jpi 900 confirmed the injector was performing back to original specs after installation.

Again the Continental factory engineer confirmed a filament material can work its way thru all the screens and get to an injector. Please click on this enlarged filter picture and compare the filament contamination size to the size of the openings in the screen from the middle screen(fuel servo). It is obvious these filaments are smaller in diameter than the screen openings. This same material was found on the surface of the first screen and some were removed from one of the belly sumps.
upload_2018-6-3_10-50-15.jpeg
Thanks for sharing your thoughts.
 
I would think the ID of an injector nozzle would be on the order of about 2000 microns (~.080 inch) to get the necessary fuel flow. Does anyone know?

A string-like thing in the ID would affect the fuel distribution enough to do what the OP describes though.
 
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