Shutdown issue

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Shutdown issue

Postby Cumminsfever » Mon Jun 11, 2012 6:13 am

Do any of you guys have a shutdown issue after a flatout run, and chopping off the throttle? This is a known issue with vp44 trucks that have power box and bigger injectors. Wondering if any of you higher hp guys have this issue? I am specifically referring to VE pumped trucks.
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Re: Shutdown issue

Postby BC847 » Mon Jun 11, 2012 6:20 am

Yes.

It's my opinion that with side-stepping the throttle, obviously the fuel pressure in the injector goes down. I believe it's then that the still relatively high boost (turbo hasn't un-spooled) has the combustion pressures high enough that some of the combustion pressure is backing up into the injector effectively air-binding it. With that, the engine unwinds and is left missing on one or more cylinders (if you're lucky), if not completely shutting down. I have to pull over and burp the air from the injectors to make the engine run again.

Some of the so called geniuses on CompD feel it's an issue with the injection pump. I feel they are full of sthi.

At the end of the day, the best and quickest fix is to learn to roll off the throttle. Works just fine.
David

1993 12mm VE Fueled W250 CC, Green
12.67 @ 103.35
Your basic farm truck ;)
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Re: Shutdown issue

Postby Cumminsfever » Mon Jun 11, 2012 6:33 am

Thank you BC847! I am running into this issue on the 4bt, and had no clue it was an issue aside from the vp44 trucks. Figured I'd come here and ask the pro's!!
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Re: Shutdown issue

Postby cougar » Tue Jun 19, 2012 9:04 am

Just thinking out loud here so don't shoot me.
Fly weights
Governor spring
Manual fuel shut off
The governor spring balanced the centrifugal force on the fly weights maintaining the correct (or metered) amount of fuel for that RPM. When the fly weights and spring are in equilibrium, you have a fuel/defuel state happening to maintain RPM. When you take your foot off the throttle, you go into defuel mode, right? At full throttle, you are applying a lot of governor spring force to hold the flyweights in balance. Thing of what happens when you "side step" the throttle. It's going to slam the governor into defuel mode big time. Now think of how the manual shut off works. It manually pushes the governor through defuel into fuel dump. This may be what is happening when you side step the throttle after a full power run. Your putting the governor into cut off instead of defuel. That will allow air into the injectors, much like running out of fuel.
RIP 91.5 W250 5 speed. The great experiment.
92 W250 HD 47RH with Compushift. Upgraded H1C to 60/60/16, Scheid Lightning VE, 60# valve springs, DAP 7X.010 injectors, 4" DE exhaust.
01 2500 "the work truck".
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Re: Shutdown issue

Postby BC847 » Tue Jun 19, 2012 9:08 am

The question with that is where is that air coming from?
David

1993 12mm VE Fueled W250 CC, Green
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Re: Shutdown issue

Postby oldestof11 » Tue Jun 19, 2012 2:05 pm

Just one god over there David and even my patience with him is no more. :roll:

I still think a low case pressure from a full throttle situation to low case pressure fuel bypass to bring the rpm's down is causing pump cavitation from the rotor spinning fast.
Jon
93 D250~ Mismatch of cheap parts, trying to look fast going slow
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Re: Shutdown issue

Postby RCCUMMINS89 » Wed Jun 27, 2012 9:04 pm

I was having this issue last year but for some reason no longer have it?

But last year at the dyno I ran on a fella by the name of Lance from Seatlle (I'm sure we know who) explained it to me as a cavitation inside the pump from abruptly shutting off the flow.... "like shaking a pop".

The mroe I think about it I believe that is what is happening, like was said by oldestof11



Just dawned on my why, I was having it happen when I was letting off coming to a stop and pushing in the clutch. I have since learned not to push in the clutch. So I can't really cause it because the rpms slowly come down no matter what. On an automatic the rpms drop.
89 RC on shortened 92 diesel frame - NV4500 w/dual disc/4.10s on 37s. - Self built pump, "hot screw", lots of timing, True high volume low pressure lift pump, 62fmw/68/.7gated, 77lpm SAC Inj., Studs/O-rings,- 423/1220 Mustang - 11/16/2013 http://www.TheHungryDiesel.com full line dealer, if you don't see it please ask.
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Re: Shutdown issue

Postby BC847 » Wed Jun 27, 2012 9:16 pm

Cavitation is caused by reducing pressure on a liquid (in this case diesel) to the point the liquid vaporizes. With the resumption of a higher pressure, said vapor bubbles collapse back into a liquid. http://en.wikipedia.org/wiki/Cavitation

Suggested issues of cavitation in the IP does not explain air-binding of the injectors.


"Shutting off the flow" as in sidestepping the throttle, is brought about by dumping fuel contained in the head/rotor by the throttle-collar. This is a relief of pressure, not interrupting the flow of fuel into some part of the IP that may bring about cavitation.
David

1993 12mm VE Fueled W250 CC, Green
12.67 @ 103.35
Your basic farm truck ;)
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Re: Shutdown issue

Postby RCCUMMINS89 » Wed Jun 27, 2012 9:33 pm

I just sat here and typed about 20 different responses and realized that I had nothing intelligent to say. LOL
89 RC on shortened 92 diesel frame - NV4500 w/dual disc/4.10s on 37s. - Self built pump, "hot screw", lots of timing, True high volume low pressure lift pump, 62fmw/68/.7gated, 77lpm SAC Inj., Studs/O-rings,- 423/1220 Mustang - 11/16/2013 http://www.TheHungryDiesel.com full line dealer, if you don't see it please ask.
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Re: Shutdown issue

Postby PToombs » Thu Jun 28, 2012 5:36 pm

That never stops me! :mrgreen:
pete

Just enough power to break everything behind the crankshaft.
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Re: Shutdown issue

Postby Sutter1stgen » Fri Sep 14, 2012 8:46 pm

Bc, I've read your reasoning to this on other forums and now here. I can see where your coming from. It used to happen to me. Then I learned to roll off easy. I even rolled off of it on the dyno this weekend. Ever since I learned to roll off I've had yet to have a problem. And when I did have it happen, the usuall injector crack fixed it. I didn't have to prime the pump or anything else. Just a simple 2-3 second crank with 3 injectors cracked and shed fire.

Eric
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Re: Shutdown issue

Postby BC847 » Fri Sep 14, 2012 9:03 pm

Hey Eric,

With rolling off it, it's not a problem.

I can't do a proper heating of the tires out of the water-box. It's embarrassing having to burp the injectors at the line.

I've got this new IP on the truck and have been chicken to test the theory of it being old/worn IP related. When it has been a problem, I've typically just came from a thorough flogging and the turbos are glowing. Gonna burn the heap to the ground squirting furl all over the hot stuff.

This is why I won't get popped drive-drunking.
David

1993 12mm VE Fueled W250 CC, Green
12.67 @ 103.35
Your basic farm truck ;)
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Re: Shutdown issue

Postby Sutter1stgen » Sun Sep 16, 2012 8:52 am

Haha yeah I noticed it when I gave my bro inlaws jeep grand cherokee a stomping on the freeway. A chp was on the side and I sidestepped the throttle and coasted right on by the chipper with a stalled engine. Took the next exit in the bad side of sacremento and had to bleed the system. Well I've got some new problems now trying to tune theses new 6x16s I've a aquired. My pyro probe was misreading this whole time and I'm just sick to my stomach that I towed blind this whole time. Any advice with these squirters for tuning and lowering egts. Pm if you'd like to not clog this thread. Thanks.
Oops sorry, I need a few more posts to pm.
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Re: Shutdown issue

Postby dazedandconfused » Sun Sep 16, 2012 1:22 pm

PToombs wrote:That never stops me! :mrgreen:


Yeah we know that. :lol:
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Re: Shutdown issue

Postby DodgeFreak » Mon Sep 17, 2012 5:18 am

does it happen worse with bigger injectors???
92 D350 Cab and Chassis. Auto stock, wiring gremlins. 330k miles
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