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Anybody have a good fix on JFS auto shutdown immediately after throttle is placed to idle … (after 60 sec. motor or even the old way of starting the puppies) this normally happens when the weather starts to get cold. JFS will normally (99.5% of the time) start the motor (220) on the second attempt and the book says this is OK. On one particular jet we changed “all” the components and still did it? Did the DESSC thing … no faults, do,da,do,da.doo? Changed JFS on that jet and worked good lasted long time!!! There has to be cheaper solution, even though changing the JFS is easy.

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Sounds like it was just a bad JFS...maybe the clutch was going bad since you said it would quit after going over the horn.

This time of year is a bear with the colder temps. I recently started having problems with the JFS on my plane too. I pump up the accumulators every morning to 3,000 (they're usually at around 2,400-2,500 after cold soaking overnight). First attempt at Start 2 spins up nice, but then just fizzles out without ignition. Grab a T Handle or mule to recharge and fires up like a champ on 2nd attempt. Like you said...book says it's okay. My arms don't think it's okay because I'm tired of pumping! Smile

DESSC tripped a flag and said fuel or ignition problem. Well duh! I think it says that for every problem. I spent the day Wednesday troubleshooting first by changing flow nozzel, ignitor, and slaved in a new ESS controller. Fired up strong first try...although the JFS could have still been primed from the previous start. Hooked up the DESSC again and had a slower start after about two hours later. Found my old ESS controller and tried that...yeah, it was still bad. Overtemp start cutoff. Decided the DESSC was porked and ordered/installed a brand new ESS controller and had the best start of the day.

With the 4 day weekend I'll be curious Monday to see if it's good to go since my bird is scheduled 2 a days all week. Cheers

Yup, if it wasn’t for the 1-minute motor prior to throttle engage we all would be some buffed crew dawgs right now! I looked at the schematics and I think it’s fuel delivery as well.
However there is “one” fuel nozzle out of two we can change on the line. I’m not convinced on the JFS fuel control, tried changing them and same problem. Clutch servo fixed one just before it started to warm up, however she had her first shut down recently during cool A.M. temps. (Almost 10 months later) I knew that didn’t fix her. Clutch servo is good fix when you chug-along but you’d think you see something on the downloaded graph that invaded one of the auto shut down parameters? I think the second fuel delivery nozzle is “coked” up causing a very un-uniformed fuel delivery pattern, which in turn flames the puppy out?

All I know is after Changing the JFS on my puppy she is so smooth during the idle transition that I wouldn’t even know the crew put the throttle in Idle unless he tells me what he is going to do.

Thoughts?

Elite 1K Joined: Apr 26, 2004 Posts: 1197 Status: Offline

It's been a long time for me but doesn't the max fuel valve kick in then? If so it might be bad.

Two Cents

Purplehaze wrote:

It's been a long time for me but doesn't the max fuel valve kick in then? If so it might be bad.

Two Cents

Yes sir that was an option, Since you have to pull the JFS to change the valves we normally change all 3 if we suspect that is the Prob, and that has been done. Also the 3 valves are not "GI Proof" so if you hook up the cannon plugs wrong ... you'r in a world of $@^& if you do that

Well, I've seen people "over" T/S the JFS and it takes weeks to figure out what's wrong. It's more often than not come down to changing the JFS. While normally I like to start with simple things, more and more often it's almost easier to just change the JFS or ESS controller and be done with it. Laughing

I almost miss air starts on the F-4 when my JFS is fussin'.

has anyone ever heard of "tying off" the fuel bias valves (changing their logic with the dessc) to prevent overtemps during the winter time?

Hey VarkVet you at viper or falcon?

Newbie Joined: Dec 02, 2006 Posts: 2 Status: Offline

cchief16 wrote:

has anyone ever heard of "tying off" the fuel bias valves (changing their logic with the dessc) to prevent overtemps during the winter time?

I'm working a jet with bad Bias Valve Logic. JFS works like a champ with the DESSC in. The DESSC downloads no faults but notes that if a ESS controller was installed it would have shutdown to a false overtemped. With the ESS in and bias disco'd the jet starts like a champ.

We changed the Fuel control in hopes of getting lower EGT's per the DESSC(may help) It only lowered our EGT when going over the horn by 20deg. The shitty part is they won't order a DESSC to fly in the jet because they say it's a temp fix.

I may just change the JFS and see what happens. The current JFS has 600+ starts.

A DESSC as a temp fix eh? My unit is finalizing getting full time DESSCs for all our jets since it's supposed to be easier and quicker to TS.

Of course the DESSC I had in my plane for about 3 months went Tango Uniform and a new ESS controller fixed it.

Elite 1K Joined: Apr 26, 2004 Posts: 1197 Status: Offline

We flew with DESSC at Spang as a temp fix until we needed them for T/S.

Hey Varkvet did that plane just come from hill depot? It sounds like you have the same problem we had at Edwards when we got a jet back from Hill depot. Check your jfs bottles air pressure thats what we found out the pressure was to high.

Purplehaze wrote:

We flew with DESSC at Spang as a temp fix until we needed them for T/S.

We still do this

IDCrewDawg wrote:

Purplehaze wrote:

We flew with DESSC at Spang as a temp fix until we needed them for T/S.

We still do this

Cancel "one" F22 or F35 order and we could put a DESSC in every non DESSC (USA jet) plus have money left over for a laptop for each F-16 with programs and cables for CAMS, EDNA, Sundstrand, EDU downloads, etc .

Laptop and Wireless router for CAMS on the line ... "PRICELESS"

[quote="VarkVet]
Laptop and Wireless router for CAMS on the line ... "PRICELESS"[/quote]

Actually, this scheme (or a variation of it) was tried at MacDill AFB in 1991-1992. Blue section (62d) actually had CAMS terminals in the line trucks from which they could supposedly document maintenance, order parts, etc.

They couldn't get it to work. My guess would be that with the advance in wireless technology since then, it would probably work pretty well now.

My personal take on it was that it was a good idea. There is a lot of "dead time" on the launch truck waiting for stuff to happen, and this would sure have helped a lot. CAMS documentation has always been a problem; inevitably, it is usually done at the end of the shift, where everyone is so dogged out from the workday that they aren't going to go into great detail in CAMS. What most don't understand is that the more detail you put into your CAMS documentation the better; even if they do understand that, where do you find the time to do that? Personnel cuts have already decimated our flightline force, and they want to cut them even further. Funny thing is the cuts are coming from people who wouldn't know an F-16 if you hit them with one, and whose idea of a bad day is one where the laser printer needs a toner cartridge, and they actually have to get out from behind their desk to get one.

Best Regards,

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JFS auto shut down