injector pop?

chevota84 said:
If its the injectors, why don't p-pumps do it?
The problem is, rotary pumps do not pump air very well so when you drain the rotor on a hard pull they can't recover. P7100's don't have the same issue because they're a more positive pump and can work the air through.

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Both the VE and the P-pump are positive displacement pumps. The only difference there is one piston in the VE and 6 in the P-pump.
 
Smokem said:
12mm VE and 14mm VE, both fed with an Aeromotive A1000, never had the issue you describe. It concerns me that anyone would think that the cylinder pressure is greater than injection pressure, ever.
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It's my thought that when the spill-port is uncovered, the fuel in the H/R is bled-off back into the case instead of to the DVs and injectors. It's at that point when at full throttle, the fuel is cut, yet till the turbos unspool and the current compressed charge-air in the charge-air system(ducting, IC, etc) has not been reduced by consumption through the engine, that compressed charge-air in the cylinder perhaps may have enough pressure to lift the injectors needle off its seat and put a bubble in the injector.
 
BC847 said:
Both the VE and the P-pump are positive displacement pumps. The only difference there is one piston in the VE and 6 in the P-pump.
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Then why don't p-pumps do it?

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BC847 said:
that compressed charge-air in the cylinder perhaps may have enough pressure to lift the injectors needle off its seat and put a bubble in the injector.
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No, not perhaps, simply no. In every instance I have seen a larger low pressure pump used it fixed the issue. How could this be explained using your assumption?
 
Not to be a smart-tail, but how could rolling off the throttle eliminate the issue?
 
The limited amount of time I spent thinking about it led me to believe the sudden change in speed of the vane pump was causing cavitation.
 
Pondering that suggestion has me think the cavitation induced vaporous bubbles would collapse with the resumption of normal case pressure (assuming the case pressure dropped to begun with?).
Further, if the issue is a result of the vane-pump producing the bubbles, it seems to me that the vapor (?) would have to be of enough volume to empty out the high-pressure section of the case to starve the H/R enough to pass it through the entire DV and high-pressure lines to reach and effect the injectors. That's a LOT of vapor, especially if produced by cavitation at the vane-pump.

Just so it's been said, I do appreciate y'all taking the time to hash this with me. :clap:
 
Smokem said:
15BAR, really?
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217psi. I know it's not much, but hey could be. I'm trying to remember what I set the pop-pressure at the last time I messed with mine. It wasn't a whole lot lower that stock/OEM.
 
It wouldn't take much air in the pump to cause it to quit moving fuel. It wouldn't have to fill the lines.

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There is two things I know for certain;

1. It's not cylinder pressure reversion.
2. A higher flowing supply system resolved the issue in all instances I have seen.
 
chevota84 said:
It wouldn't take much air in the pump to cause it to quit moving fuel. It wouldn't have to fill the lines.

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Understood. But it's the air in the injectors that's preventing them from popping open.

- Where does that air come from?
 
Just for sport, is it possible worn/defective DVs could contribute to the issue?
 
No. Its the air in the pump preventing it from pushing fuel to the injectors. I've stuck new injectors in and cranked it over for a couple seconds without cracking lines and its running. If the pump is moving fuel it'll push the air through the injectors eventually but if there's air inside the rotor it will have a very hard time building up enough pressure to pop the injectors to clear itself. Also vane pumps don't pump air nearly as well as a piston pump ie, ve/VP and p7100.

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The little thingys screwed into the VE H/R that the high-pressure fuel lines connect to. They've got a little plunger that's shaped an awful lot like the DVs in the later IPs. Got a spring to hold them closed.

They aren't delivery-valves? Bottom/right. Just above the number two . .

3273ea8e.jpg
 
@ chevota84, I don't understand where that air you describe is coming from. I have no leaks in the fuel system that would allow air in.
 
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