olypopper wrote:
Brumbles88 wrote:
Thanks for the input. The solenoid checked out.
Decided to check out the flow from the injector returns. Turns out injector 4 is just dumping fuel.
This injector was a
when I started this project maybe I damaged it in the process of removing.
Does this make sense as the cause of low rail pressure (400psi)?
Gonna order a new one from oregon fuel injectors. Hopefully that's the fix.
So #4 is just bypassing fuel or is it going elsewhere?
Again, lessons learned from my experience. Assuming the CP3 is pumping fuel, its only going to 1 of 4 places.
1) Thru the common rail and being dumped back to the tank - check by pulling the low pressure return hose off the end of the rail (or fuel return block). Anything during crank? Directly out of the CP3 and back to the tank (never making it up to the rail).
2) Being dumped by the injectors and returned thru the low pressure (small diameter rubber hose connected to the top of each injector) injector return. Easiest way to check this is to pull 1 (or all individually) of the return fittings off the top of the injector itself. Special trick - don't pull the retaining spring off the injector. Just push it all the way in and seat it against the injector body. The tangs holding the return fitting in place will release and you can pop the fitting off. No risk of losing one of those retaining springs. There is a thread with pics showing this method. Also, while you are doing this check, look carefully at the top of each injector while someone cranks the engine. If you have a stuck/failed injector odds are you will see bubbles of air coming up thru the fuel in the top of the injector. That is combustion chamber pressure (air) being forced up and out thru the top of the injector. There is no guarantee this will occur with a bad injector - as I painfully learned. In my case the injector was smashed in such as manner that it allowed fuel to dump into the cylinder, but the injector needle was crammed up inside the injector body sealing off the air escape path.
3) This one is tougher to check and to verify. Its really tough getting access to the quick release fitting on the low pressure return off the CP3 itself. And the other end (where it attaches to the fuel block) is heat shrunk on and not meant to be removed. But, if you have already eliminated fuel coming into the fuel block from the common rail return and/or injector return, you can just pull the rubber hose of the bottom of the fuel block and see what's coming out. If there is fuel coming out it has to be coming from the CP3. Now again, this test is nearly worthless as I painfully learned. The problem with this test is the CP3 ALWAYS dumps some amount of fuel back to the tank, even when everything is operating properly. With a lift pump installed the amount the CP3 bypasses and dumps back to the tank is even greater. I know of no means to quantify the amount that would be considered 'normal' being bypassed by the CP3. And that's what caused me to continue to think/probe the CP3 as the culprit in my no start. Ended up changing the MPROP & CP3 only to find out it was operating normally.
4) So finally- the only other path the fuel can take is out thru the injectors. The only absolute test for this that I know of is to pull the injectors and look at them for signs of fuel. Since you are not building enough rail pressure to 'fire' the injectors, normally operating injectors will have dry tips. Failed/sticking injectors will have wet/fuel covered tips. But once you have them out (and it can be a chore as you know), I would have all 4 tested. Mine cost me $30 each. Cheap insurance.
Once last clue/test for #4 that would drive me (now - in retrospect) to pull the injectors long before I suspected a bad CP3. While someone is cranking the engine, look at the exhaust pipe. Are there puffs of grayish smoke that smells really strong (burns your eyes) coming out? If so, that is unburned fuel being forced out thru the exhaust from a sticking/leaking injector.
GL
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