Surge under low boost/ Air locking the fuel system question!

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Surge under low boost/ Air locking the fuel system question!

Postby kzink » Tue Jan 26, 2016 7:56 am

Ok guys... have some questions about whats going on with the old goat... for starters, it is a 93 d250, 5 speed. truck has the typical pump mods, denny t st. II, 3200 gov. 1/8" timing bump, 6x0.13 injectors, low pressure piston lift pump, hx35 w/ wicked wheel and ceramic button clutch. Under low boost driving down the road, when trying to accelerate and build power under a low RPM, the engine has a shutter until it starts building boost. If im not trying to accelerate hard, it normally doesn't do this, but when you lay into it hard, it happens almost every time. Any suggestions on resolving this issue??

Second question: Air locked the fuel system twice last night... Contacted Eric with the hungry diesel and he said that this could be caused by letting off the throttle too quickly. Now the question is, besides doing a p pump swap to get rid of the ve, is there a way to possibly eliminate this or is it strictly going to have to be a driving style change?
93 D250 ex. cab 2wd. Denny T St. II, 3200 gov, 6x.013 SAC, Hx35 W/wicked wheel, HVLP Lift pump, Valair Ceramic Button
kzink
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Re: Surge under low boost/ Air locking the fuel system question!

Postby CumminsPower59 » Thu Jan 28, 2016 11:20 am

How low of RPM are you seeing the surging?

You can let off the throttle fairly fast and not air lock the fuel system, but it takes a little bit of practice to find that sweet spot where you can let off quickly, but not air lock it. I happened to air lock mine on the way to work this morning (first time ever)...but I put it back in gear, let out the clutch and I had enough road speed to spin it over fast enough to fire, and in about one second it was back to life.
Ike

91 W350 SRW, 3.07's, NV4500, 370's, THD LPPP, Super HX40, 2nd gen IC swap, BHAF, Isspro's, 2" lift, 285's on 3rd gen 17"'s.
04 VW Jetta Wagon TDI 5speed
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Re: Surge under low boost/ Air locking the fuel system question!

Postby Agentorange » Mon Feb 15, 2016 11:43 pm

I'm having the same issue while surging at low rpms in my 91 non ic d250 5 speed. I'll accelerate normally and it will pick up more power then back off a bit. I'm going to replace the fuel filter. Would this be lift pump issue or injectors? Lift pumps are cheap so I might just replace it because I don't really know the history of my truck. I can find a good set of 5x .012 for a decent price if it comes down to the injectors being bad.
Agentorange
fuel screw!!!!
 
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Re: Surge under low boost/ Air locking the fuel system question!

Postby spencerdiesel » Tue Feb 16, 2016 6:13 am

Any time you have a diaghram lift pump and more fueling than stock, I would reccomend getting a LPPLP.

I'd get a piston pump anyway just for reliability reasons.
1992 W250, 5 speed, 4.10, Ext. cab Ext. bed, 12.5k winch, 75 gal. fuel tank

H1C/18

Fuel: THD 6x10 VCO sticks, THD 12 psi piston pump, THD fuel pin, 366 spring, fuel screw 2 turns in, timing to the head/ >1/4”
Muffler delete

Minimum 60% WMO full time since Sep. 2018
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Re: Surge under low boost/ Air locking the fuel system question!

Postby Agentorange » Tue Feb 16, 2016 1:06 pm

THe hungry diesel has them but do I just need the pump or the whole kit?
Agentorange
fuel screw!!!!
 
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Re: Surge under low boost/ Air locking the fuel system question!

Postby spencerdiesel » Tue Feb 16, 2016 4:43 pm

I got the kit, would do it again in a heartbeat. I'd reccomend the kit because it has the new line, and I couldn't get the old line off the diaghram pump without destroying it.
1992 W250, 5 speed, 4.10, Ext. cab Ext. bed, 12.5k winch, 75 gal. fuel tank

H1C/18

Fuel: THD 6x10 VCO sticks, THD 12 psi piston pump, THD fuel pin, 366 spring, fuel screw 2 turns in, timing to the head/ >1/4”
Muffler delete

Minimum 60% WMO full time since Sep. 2018
spencerdiesel
14mm rotor
 
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Joined: Tue Oct 27, 2015 4:02 pm
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Re: Surge under low boost/ Air locking the fuel system question!

Postby DMan1198 » Tue Feb 16, 2016 6:53 pm

Even though it isn't really necessary I really like my raptor 100 pulling from a sump, and going into a dual filter setup that's all 1/2" line to the pump. It primes the whole system very quickly with no effort.
Ducati- professional nap taker, and thread derailer extraordinaire
Brownie: 80 dodge heavy half. Ghost cummins under the hood, and some sinister plans
The Roo Hunter: 93 w250, lifted, 2 whistle machines, and a bunch of other go fast goodies, uhh..... not there yet
Jaeger: 12 ram 3500. Lifted, exhausted, and fed an excessive quantity of air
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