Is it possible . . . (?)

BC847

BC847

Member
Joined
May 14, 2006
Messages
851
. .. to have charge-air back into the injectors when getting off the throttle? Resulting in some of the injectors getting air in them and requiring "Burping"?

The typical example is at the top of a pass and getting off the throttle. I'm not side-stepping the throttle when letting off, I sorta roll out of it.
I'm fairly certain it's not a fuel supply issue.

My mess is a '93 12v with the VE (rotary) injection pump, 6x.016" EDMs and about 58psig boost.


What'cha reckon?
 
No, most likely pintle issues in a few injectors, not uncommon with the 6-hole VCO nozzle.
 
Same problem I have BC.

Will be installing new 4 hole 69 lpm competition series injectors from DDP in a couple days.

Hope this cures the issue.
 
Why do 24v engines with huge injectors also have this issue if you lift off the throttle too fast from WOT?
 
LReiff said:
Why do 24v engines with huge injectors also have this issue if you lift off the throttle too fast from WOT?
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I've had that problem a couple times on my 24v. That was just with S.0. pump though and 200 plus injectors. When I changed to monster pump and 240 plus injectors I never had the problem. Now I changed back to a different S.0. pump and some mach 6 injectors and had the problem happen again. Also curious why that would happen with S.0. pump but not monster pump? All my problems were from when I'm climbing hills at sand dunes or other places I may be offroading. I have to loosen up 2 or 3 injector lines and start cranking the truck over until i get fuel back flowing through lines then tighten them back up and back off playing around.
 
I have had this happen a few times also.. Sucks engine just dies and you have to bleed the injectors to get up and running again.

I just lift a little slower now..
 
I also have this problem, but on DTR chat the other night we were talking about it and Pulltilbroke said it was because of the transfer pump restriction inside the VE. The big injectors drain the case faster than the vane pump can re-fill it. Makes sense to me.
 
soggy said:
I also have this problem, but on DTR chat the other night we were talking about it and Pulltilbroke said it was because of the transfer pump restriction inside the VE. The big injectors drain the case faster than the vane pump can re-fill it. Makes sense to me.
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If that were the case, it'd get air in the injectors before completing the pass.

It's been my experience it's apparently related to side-stepping the throttle after a high RPM/boost blast. I can do it doing a stupid burn-out. As others have pointed out, rolling off the throttle can help a lot in reducing the issue. But I'd like to eliminate it altogether if it was a whacked mechanical thing.
 
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Ive never had this problem with combo's of: piston lift pump, A1000 setup, 12mm pumps, 14mm pumps, POD's, 6x.016, or 6x.018 VCO's.

Ill do some research this weekend and let you know what I can come up with.
 
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BC847 said:
If that were the case, it'd get air in the injectors before completing the pass.

It's been my experience it's apparently related to side-stepping the throttle after a high RPM/boost blast. I can do it doing a stupid burn-out. As others have pointed out, rolling off the throttle can help a lot in reducing the issue. But I'd like to eliminate it altogether if it was a whacked mechanical thing.
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That makes some sense, but it could be that when you snap off the pedal, the vane pump refills the case sending a big shot of air that was in the case into the lines/ injectors. I'm no expert, just throwing ideas out there.

JAyers93 said:
Ive never had this problem with combo's of: piston lift pump, A1000 setup, 12mm pumps, 14mm pumps, POD's, 6x.016, or 6x.018 VCO's.

Ill do some research this weekend and let you know what I can come up with.
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Cool, it is pretty annoying, hope you figure something out. Also, what are the odds of nearly all big injector VE and VP trucks having pintle problems??
 
I was under the assumption the topic was similiar to soot blowback, in a distributor type pump it is not uncommon to have air locking issues when lifting the throttle quickly.
 
soggy said:
That makes some sense, but it could be that when you snap off the pedal, the vane pump refills the case sending a big shot of air that was in the case into the lines/ injectors. I'm no expert, just throwing ideas out there.
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Where does the air come from? Isn't the fuel supply a sealed system?
 
I've had it happen before on my 24v, let out of the throttle and it died. Had to bleed the air out of the fuel lines
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My '93 used to do it , but that kinda of went away since I put the stock AFC foot back in.

The puller never did it, but had an A1000 supply. That motor is now in a '96 with a piston pump, and it still does not do it. The tranny is too weak to really load the motor though.
 
Smokem said:
I was under the assumption the topic was similiar to soot blowback, in a distributor type pump it is not uncommon to have air locking issues when lifting the throttle quickly.
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Why does this happen? Where does the air come from?

I also have an A1000 and run at 21 psi, still happens when I lift too quick.
 
It's do to excessive case pressure being discharged after the throttle is lifted. With a VE you will get smoke or what you call burp, with a VP44 the truck often dies. The return side is too restricted being the reason.
 
TheNatural31 said:
It's do to excessive case pressure being discharged after the throttle is lifted. With a VE you will get smoke or what you call burp, with a VP44 the truck often dies. The return side is too restricted being the reason.
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Is there any fix for that or anything you can do to help that? My brothers truck does it everytime if he doesn't ease off the throttle after WOT.
 
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