Hey all, searched and couldn’t find exact help…I have an 325e, that I’m building for pikes Peak…aaaaand I kinda jumped the gun on wiring delete…then, I came here to see what I should keep, yup, ass backwards…anyway, deleted OBC, along with everything I felt " non-essential" Now I have a start/no start situation, assuming it’s the OBC, I need more detailed info on how to bypass it…ie, very specific wiring diagrams…ANY, help would be much appreciated…also, I have fuel pump set up on a switch panel…hopefully OK…and, the 3 wire plug coming out of the ECU, the green is to hot, I’ve got a black and a yellow I believe, important, and where do they go,…I’ve got a Bentley manual, but I am electrically challenged…build thread is on R3Vlimited in the track/autox section under Pikes Peak 2014. …thanks again.
Help, I "may" be an idiot.
That was chaos.
The OBC isn’t needed so it shouldn’t be necessary to figure out how to bypass it.
What does “start/no start” mean?
By ECU you probably mean the DME.
Something wrong with how the fuel pump electrical system was designed?
There isn’t that much wiring that is really necessary. Engine harness needs to have the basic stuff, some of the dash needs to work for the alternator and ABS to function, and the ignition switch wiring needs to work. That’s about it.
Take a look at the wiring on the engine side of the firewall forward of the passenger. If you screw that up the DME won’t get power.
Start/no start, sometimes it starts and will refire…sometimes no start for a couple days…yes, ECU=DME…wrong with the OE fuel system, nope, just got to cuttin’…I’m deleting the ABS , so that’s gone…I had the dash out for awhile before the major surgery…and she still ran…my google search for intermitent starting brought up OBC, main relay, CPS and DME …have not had time to check CPS or DME, relay is good…fuse box is gone but everything from DME main harness to engine is there…please be kind.
Check the three relays on the LF fender well. Then learn to read the wiring diagram to see which powers which!!
The “sometimes no start for a couple days” is darn odd. That can’t be a cut wire.
Starter doesn’t run or starter runs and car doesn’t “catch”?
Master and fuel pump relays could be intermittent. A ground, kill switch connection, the kill switch itself, or a batt connection could all be intermittent.
Cutting wire w/o knowing exactly what you’re removing is hazardous. Little dinky wires don’t weigh much. Removing whole harness is useful. Cutting individual wires less so.
Google jlevie e30 start and find Jim’s exhaustive doc on getting an e30 to start.
Thanks for replies…it does turnover, just no fire(spark), yeah, wishing I would not have cut as much, but, what’s done is done, so now just gotta figure it out.
I have seen your build thread on r3v, and I sort of went down the same route you did - but that was only because my car had been hacked up to begin with by the previous owner who had a local shop do the swap from eta to later i motor. Needless to say, the dash and OBC never worked when I got the car.
My plan of attack was to thin most everything out of the car that I could and get it to the bare essentials. If I were you, I would not even try to get the dash or anything not related to the FI/Engine/DME harness working, it can all be replaced easily since this will be a race car.
Just try to narrow in on getting the engine harness separated from the body harness (which sounds like you have already headed down that path.) Then I would try getting the essentials to the DME - which is a good ground and 12v. Then start working on making sure all the ground connections in the engine/FI harness are connected and solid. Then start checking the parts of the engine/FI harness that can wear out (relays, sensors/connectors…etc.)
I can’t remember on the eta’s but if your harness has a round connector for the injector harness, this is a common connection that can cause no start or intermittent start issues on 325i car’s. Sometimes, if the connector is in the stock bracket, it can separate just enough for the connection to be loose and you will get no power to the injector harness. At which point you can try removing the connector from the stock bracket (sometimes works), and/or clean the contacts with contact or electrical motor cleaner, and pack it with some dielectric grease.
Another issue could be the crank sensor/position wires. These get brittle with age, and the are a shielded wire, so if the ground/shielding gets brittle and cracks, you can have an intermittent signal to the ECU, which can cause a no start, or run and then die conditions.
Other possible areas: coil wires or even a crack in the board of the DME. Something to keep in mind, these cars are over 20 years old, and the electrical contacts/wires can get brittle with the constant temp changes in a car, so it’s not out of the question that a connection can be temperamental.
There is quite a few other things to check, but I would start with what has been suggested by others and work inward. So start with the Battery power to the ECU - make sure it’s good. Then start with the Fuel Pump - make sure it’s getting power and working. Then make sure power is getting to the coil with the ignition on, and then start moving through the system to verify everything is getting the voltage it should. The Bentley will be your guide, and if you do a search online, you can find the more thorough yearly electrical harness manual which shows the year specific “oddities” for the each engine.
Pull the fuel hose off of the rail and stick it in a bottle. Run the starter. If you get fuel, then that tells you that:
- Fuel pump is ok.
- FP relay is ok.
- DME getting power and ground.
- CPS is ok. I say again, CPS is ok.
If you want you can pull injector rail. Stick a piece of cardboard on top of the engine and put the rail on top with injectors pointing up. Run starter and you’ll see injectors spraying gas. Don’t blow yourself up.
If you do all that you’ve ruled out fuel so it has to be spark. Chase down Jim Levie’s doc and you’ll find good info on the electrical side of this.
First thing to check on the electrical side is the master relay. You can jump it by connecting the “outboard” socket hole to the “forward” socket hole. That is as opposed to the inboard socket hole and the rearward socket hole.
Sorry, but I don’t recall off the top of my head just how the DME signals the coil to fire. My guess is that the DME “delivers” ground instead of delivering 12V, but I don’t know for certain. Certainly by pulling a plug you should be able to see is spark. Since you’ve not screwed with your distributor, if the plug fires it should be firing hot as intended. If you screw with the rotor or distributor, there’s other ways to cause yourself problems.
Note that a common error is to mix up 2 engine harness connectors…the CPS and teh #6 plug wire sensor.