running on half an engine - need help

[apbt_rescue]

Any advice is greatly appreciated as I am currently thumbing through a Bentley manual in hopes the answer will jump out and smack me in the face. Its a 325ix, all stock with a newly added 885 head off of a 325i. I just slapped on a new RPM sensor and it fired up, "sorta right". Except its obvious the engine is running on limited cylinders. I let it run for a couple of minutes hoping the new setup would smooth itself out, no dice, so I shut it down only to realize the exhaust manifold on cylinder's 1, 2, and 3 were dead cold.

Bentley - So the DME is responsible for independently controlling the first three injectors from the second three. Haven't run the electrical tests on the DME terminals responsible for the first three. I intend to, just looking for more advice.

What advice does anyone have on other possible culprits? Please, let me know if additional information is needed. I'm by no means an experienced mechanic, I just love learning on this E30.

[jlevie]

The injectors are organized as two banks of three. Bank 1 is composed of injectors 1, 3, & 5 and bank 2 is injectors 2, 4, & 6. On this car, you can't misconnect the injectors and mis up the banks. The injectors are fired sequentially, one bank at a time if the DME is seeing the cylinder ID signal from the #6 plug wire. Otherwise both banks will be fired at the same time.

The engine not firing on cylinders 1, 2, & 3 could be; bad injectors on those cylinders, bad ignition wires or plugs, or problems with the cam or valves on those cylinders.

[apbt_rescue]

the engine was gold before the head swap.. with the exception of lengthy start up, likely due to the failing rpm/timing sensor. i swapped the head because an exhaust valve snapped. thus the injectors should still be firing correctly (couldn't image the first three fail together).

jlevie: thanks for the input. always enjoy your input on other threads. cam/valve problems i like as a possible mechanical issue. i will look into the mechanical aspect tomorrow and compare to the original cam. i have two follow on question for you or others who feel liking giving input.

correct me if i am wrong here. i understand it as on the 1.1 motronic, the injectors are fired in two packs that are 1, 2, and 3 and then 4, 5, and 6. is this correct or have i misunderstood the motronic setup? on the same direction, i wil be sure to double check which cylinders are firing because maybe if 1,3, and 5 weren't that might still result in me thinking the first three were dead cold.

AH! i knew i had a second question brewing but its new years eve and the drinks are adding up. cognitive thinking is slowly disappearing.

[jlevie]

Motronic 1.1 & 1.3 use the same injector firing patterns, per the above post.

[apbt_rescue]

d@mn you jlevie for knowing too much about this engine just off the top of your head. shame on me for looking at the motronic fuel injector control sequence on the 85-87' and then immediately concluding it was the same on the later years. failing even to read on the adjacent page that 1, 3, and 5 are one set and 2, 4, and 6 are another.

update for anyone who cares: cylinders 1, 2, and 3 are confirmed to be just spinning in place. everything looks mechanically correct looking down at the cam and valve movement, and all cylinders are getting spark. i've played around with the injector harness connection in hopes something simple was the culprit. so i suppose ohm tests and voltage tests at the injectors are the next reasonable step? anyone have incite into why 1, 2, and 3 wouldn't be firing? can the injector harness have a short to those wires only?

[jlevie]

My best guess is that the harness or the injectors are the cause. But with no obvious cause, compression and leak down tests will tell if the new head is at fault.

[apbt_rescue]

just to update since i hate when the OP never provides feedback into what was actually wrong... turns out the first three injectors were just bad. nothing special or unique so this thread doesn't serve any unique purpose to provide insight other than what are potential reasons cylinders aren't firing. i actually had correct resistance across all injectors but those three were internally damaged or clogged for some reason. they worked when pulled and were never jet tested (or whatever the term is). i guess sitting for a few weeks wasn't good for them.