Another case for steel pistons (Crapy C.R injector failures)

Joesixpack

Joesixpack

Pull'n it.
Joined
Apr 4, 2008
Messages
4,118
First time I've pulled this.....if your not familiar with a C.R injector, if you blow the solenoid off, what you get is a injector stuck full open. (The high pressure section is fine.

Monotherms took it like a champ, (got it shut down quick so it didn't hydro lock on fuel)

Didn't even pull the injector, just swapped the solenoid with a spare injector.

Thats the last time I'll use a pressure box. Need more fuel, get some bigger holes.


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Happen'd to data log that run, mp8 about 45% and no higher than 26,300~

Have seen higher pressure in the past, and no rail relief either, thats going back as well.


However....

Studying the injector, high return circuit pressure is the culprit (aggravated by a pressure box)

Ball seat looked good, but I know I have high return, there is a check valve at the back of the head that is a pretty good restriction, and could let pressure build up in the head.
 
never mind I type to slow LOL if you don't mine me asking what setting were you running for pressure on the mp8 just pick mine up and would like to avoid that allready killed one motor from blowen injectors wash out all my bearing , p.s. have you dyno the steel piston beast?
 
bigorange said:
never mind I type to slow LOL if you don't mine me asking what setting were you running for pressure on the mp8 just pick mine up and would like to avoid that allready killed one motor from blowen injectors wash out all my bearing , p.s. have you dyno the steel piston beast?
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Every time I'm headed to the dyno I frag something else.....right now my turbine wheel on my primary is sick, (broken wastegate from my secondary pealed about 1/4 inch off)(Still makes 45 lbs boost) so I'm waiting on a replacement and will hit the rollers, on fuel, fuel water, fuel and a chit load of nawz.
 
doesn't always take a lot of pressure to do that. All you need is a messed up injector with a high return rate that overwhelms the return or a messed up return system as Bodie found. :D
 
That's my biggest fear with this thing now, with the steel pistons and billet rods, the only thing that is going to kill it, is dropping a valve or hydro locking it.

Lloyd's right though, I knew before my leakage was on the high side, and again.....IMO pressure is what helped that along.

Moma says excess rail pressure is the devil.....
 
How is the solenoid attached to the injector body? Is it a press fit or bolted on somehow? Is that an O-ring at the bottom of the solenoid where it connects to the body?
 
It has a oring, and is a crimp fit, parts in place and around the top lip is crimped in.
 
seems like kind of a rinky dink setup anyways.... Surprising they dont blow apart all the time!

Wouldnt you think that they would have designed them a little 'beefier'?
 
YkDave said:
seems like kind of a rinky dink setup anyways.... Surprising they dont blow apart all the time!

Wouldnt you think that they would have designed them a little 'beefier'?
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The worst part of the design is if it happen's the injector is FULL ON, like 100% duty cycle, never seen so much smoke in my life. Stopped traffic from both ways, must of thought I was on fire. LOL

Flux 5 on 100% duty cycle can flow some fuel I tell you.
 
lol, another good point, with a rinkydink setup like that, it would be nice if it was at least failsafe!

There goes $20 worth of fuel! LOL
 
I have blown 3 or 4 like that. Its not the overall pressure that pops them but the quick lift in throttle that will spike the return side especially if it still has the check valve at the back of the head. I have a straight through -6 fitting at the back of my head and have not popped one since then. I have popped one just revving it up in nuetral.
 
bdp said:
I have blown 3 or 4 like that. Its not the overall pressure that pops them but the quick lift in throttle that will spike the return side especially if it still has the check valve at the back of the head. I have a straight through -6 fitting at the back of my head and have not popped one since then. I have popped one just revving it up in nuetral.
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That "check valve" is there to keep the cp3(s) return from pressurizing the return side of the injectors.
 
I guess I should add then that I have a seperate return altogether for that fitting.

Even then not sure how it will cause pressure on a line that has an open end at the tank no matter how much the CP3 was dumping off.
 
bdp said:
I guess I should add then that I have a seperate return altogether for that fitting.

Even then not sure how it will cause pressure on a line that has an open end at the tank no matter how much the CP3 was dumping off.
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not sure, but you can check the thread that was here last week that Bodie had where they popped 6-7 injector solenoids from a hung up check valve.

Running a separate return makes since though.
 
Running a separate line as well, and pulled the check valve after the blow up, just finished a weekend pull so they did just get a ass kicking.

I'm going to track down the excess leakage and if they are all poached after 5k that will be the end of the rebuilds.
 
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