isx12 cm2250 fuel pressure only builds if injector harness is disconnected
01-01-2021, (Subject: isx12 cm2250 fuel pressure only builds if injector harness is disconnected ) 
Post: #12
RE: isx12 cm2250 fuel pressure only builds if injector harness is disconnected
Just my own thoughts on it so far ... just taking some guesses and speculating ...

Having +5v all the time on the injector harness means nothing whatsoever to me. For all anyone knows, the ecm may be using the ground circuit to fire the injector, or perhaps a high voltage like on the ISX engines (ref: http://rawze.com/forums/showthread.php?t...73#pid9973 ) ... and the +5v on it at all times might be normal. Even in the o-scope pic I took in the references post, you can see that there is about +5v on the injector between pulse cycles when it is not firing.


Does it actually have low fuel pressure during cranking?... Quickserv should tell you what the minimum allowed is in the troubleshooting tree. Is the fuel pressure actually below this point?... and if so, what is the ecm reporting and what does Quickserv say is the minimum for that engine ser#??

Also, if the injectors were actually being held wide open in a constant state by the ecm .... as soon as you cranked it, the engine would go into runaway. - I think you might be barking up the wrong tree, just saying.

(If fuel pressure is lower than what Quickserv says it is supposed to be minimum )...
Sounds to me like your fuel pump itself may have a snapped/sheered shaft, or some normally pressurized circuit, check-valve, the fuel actuator, etc.. is not letting it build proper pressure while it is trying to fire off.

- You also mentioned you have an active code for the fuel pressure actuator.... you need to solve that while your at it.

You said you flashed it back to factory programming ... I can only assume you installed the right one according to Quickserv and the engine ser# ... With the correct factory program installed, is there any alarms for engine shutdown? ... Is it stuck in an Anti-theft state? .... What is the fuel pressure during cranking? ... does it crank over slower than normal? .. Any restrictions in the air or fuel system?... Collapsed filter? etc.?

You said it had a delete done to it ... Anyone remove the down pipe off the back of the turbo to see if the exhaust has internally collapsed because some moron did not hollow out the cans correctly? ... Anyone check the turbo to see if it is locked up at 100% closed? .. blocked up exhaust or intake can cause one not to run more than a few moments at a time too.

Anyone pressurize the fuel tanks to 10 PSI, checked for leaks, and verified the systen was not sucking air anywhere?


A lot of things can cause an engine not to run. It is anyone's guess when they are not standing right there in front of it looking at it.

Quickserv is your friend. It has all the fuel system diagrams, no-start procedures and checks.


User's Signature: ->: What I post is just my own thoughts and Opinions! --- I AM Full Of S__T!.
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RE: isx12 cm2250 fuel pressure only builds if injector harness is disconnected - Rawze - 01-01-2021



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