Help 8v71 wont start

HB of CJ · February 26, 2016, 03:54:40 PM

Yep. later 71 series engines did not have that flapper? DDEC engines? That flapper can cause major problems. Years ago we burned the roofs off of three (3) very expensive homes due to a series of very unfortunate events starting with the first due engine accidentally having that pesky 8V71N flapper ... flap! Yikes!

Lin · February 26, 2016, 05:52:21 PM

If he does not have a flapper, then it is disqualified. If one is not sure whether they have one or not, this would be an excellent time to learn.

robertglines1 · February 26, 2016, 06:30:15 PM

Clarkesville is FT.Campbell=Should be some one in motor pool that could help. Do follow thru with solution as it may help someone else. Bob

bevans6 · February 27, 2016, 04:23:30 AM

Clifford, in 1980 MCI's had the flapper, and a special switch on the dash with a red air-craft style cover you had to lift to operate. Mine still has the switch...

Brian

luvrbus · February 27, 2016, 04:45:59 AM

I am just pulling Lin's chain Brian,I'll dig up the old service bulletin from DD on what year they wanted those removed. Fwiw 92 series had those in some applications.They were always a problem mostly because of maintenance issues

carneybus · February 27, 2016, 08:29:49 AM

so it started. it was the flapper. i hate and love that thing at the same time. shes running now.

thanks everyone.

TomC · February 27, 2016, 08:59:42 AM

When my 8V-71 was turbocharged by Don Fairchild, he removed the flapper since he changed the injectors to 7G75 which are spring loaded. This left a wire and switch not used on the dash that made for the perfect spot for my misters. Good Luck, TomC

luvrbus · February 27, 2016, 09:01:07 AM

Quote from: carneybus on February 27, 2016, 08:29:49 AM
so it started. it was the flapper. i hate and love that thing at the same time. shes running now.

thanks everyone.

I have the hate relationship only, those things are a problem the little seals and shaft gets ware and dirt is sucked into the engine then the latch gets ware and they self deploy all because lack of maintenance, they are a real PITA.I see a lot of those the owners solve the problem with zip ties and bailing wire

Lin · February 27, 2016, 12:09:10 PM

When I got our bus, he flapper did not work. After learning that is was supposed it work and could be very important, I searched out the wires and put a protected switch on the dash. I really should give it a test since I haven't tried it in quite a long time. Anyway, now that it's there, I question whether I would ever be brave enough to use it. If the engine had gone rogue, I would hope that I could shut it down by cutting off the fuel. Because of that nasty belt on the MCI, I keep a stick around for that purpose. I think that I could only get myself to hit that button if it was a desperate last resort.

solardude · February 27, 2016, 08:32:05 PM

QuoteIf the engine had gone rogue, I would hope that I could shut it down by cutting off the fuel.

It is my understanding that traditionally when a diesel goes "rogue" that it is because oil from a blown turbo? In which case shutting off the fuel would not solve the problem. Which brings us back to the flap, or some other means of starving the engine of combustion air.

Please correct me if I'm wrong.

Solardude.

Oonrahnjay · February 28, 2016, 04:39:29 AM

Quote from: solardude on February 27, 2016, 08:32:05 PM... the flap, or some other means of starving the engine of combustion air.

Please correct me if I'm wrong. Solardude.

Not a "correction", SD, but the flap/emergency-shut-off-valve IS the means of starving the engine of combustion air (at least in theory). Look at the archives and you'll read about times when people have had to deploy it and had results like the engine "swallowed" the entire valve (and continued to run away, of course) or the vacuum ruptured the blower seals, etc. When people talk about a love-hate relationship with the flap valve, they're not joking.

bevans6 · February 28, 2016, 04:44:49 AM

You are correct in that one cause of engine run-away is from a serious oil leak upstream of the intake. On these DD two strokes the worrisome issue to Detroit was a sticking injector holding the rack open, causing not an oil run-away but a "stuck throttle" situation which in a bus could be a serious safety issue. They put the kill switch on the dash under a big red safety cover (MCI's at least) so the driver could kill the engine. Don't forget that if an injector sticks open the rack is no longer under control of the governor and so it can really overspeed and cause a lot of damage. Later in the game (sometime after 1980 I guess) they redesigned the control rack tube fingers from a fixed design to a spring-loaded design so that one stuck injector could not hold the rest of the injectors open. At that point they wanted the air flap gone because it was no longer needed for stuck injectors and because to would self-deploy and cause problems. Mine did it twice, causing a no-start only, but if it had done it at speed on a hill I would have been some upset!

Brian

TomC · February 28, 2016, 07:54:12 AM

Besides killing a run away engine, the flapper valve is a good one for use when parking the bus for a long time un attended. The flapper can be an effective theft protection. Good Luck, TomC

MB LeMirage · February 28, 2016, 03:57:14 PM

My 1980 Prevost still has one as well and the red flip up cover over the toggle. Right beside the steering wheel.
Ryan.

Iceni John · February 28, 2016, 04:29:47 PM

I've thought about adding something to stop a runaway engine (mine's blessed/cursed with electronica), and I have an additional toggle switch for directly turning on my Jakes manually - someone suggested that it may be enough to stop a runaway, but it just growls the engine down at idle without actually stalling it. I think a CO2 injection system could be effective: it won't harm anything else, unlike a flapper's collateral damage. Has anyone here got a CO2 setup for this purpose? Is this a silly idea, or is it something worth thinking about?

John