Hi All, My '88 325i cranks but would not start. Fuse #11 is good. I am investigating the fuel pump system, removed the fuel pump relay and measured the voltage between the socket coresponding to terminal 30 of the relay and ground - it is battery voltage. Then I measured the voltage between sockets corresponding to terminals 30 and 87 and I get nothing. I have tried with a fused jumper wire that has a toggle switch as well but the bulb in the switch does not light up and I can't hear any noises coming from the fuel pump (because there is no voltage present at the fuel pump, I've measured there as well). At this point I'm stuck, what should I do next? Is this a fault somewhere in the wiring and if so how can I debug this through the maze of wires? I would appreciate very much any suggestions/ideas, maybe I'm on the wrong track investigating this problem?
It is in the fuel tank - you have to remove the back seat in order to get access to it. However, the fuel pump relay is located in the engine compartment.
Pull the back seat and remove the cover over the fuel pump (passenger side). Remove the two pronged connector and put a test light across the terminal in the connector. Have someone turn the engine over. If the light comes on, buy a new fuel pump and enjoy driving your car. If not, post a reply here and we'll go from there. I'll guarantee your pump has died...
Is the check engine light on and if so, have you checked the codes? Silly question but...
Good
Good
Was this with the fual relay jumped or with the fuel relay in place? If the relay is jumped, try it with the relay in place. If it still gets fuel, this will rule out one possible ECU failure. The relay is grounded through the ECU. I remember you stating you checked the fuse so I won't go there. I am assuming you've tried to start the car since you've ensured you're getting fuel to the rail.
This clears the reference sensor (had that go out on me).
This could be an ECU failure. Did you had to jump start the car or anything severe electrical happen right before this problem surfaced? I haven't heard of jump starting killing an ECU but it's probably possible. I know it can knock out the ABS system. If you're worried about the timing belt, pull the front cover and check it. For the $30 or so it takes to replace it (and the tensioner pulley) I'd do it while you have the covers off. If the belt looks good and most importantly the timing marks line up, I wouldn't worry about the valves. I'm leaning more towards a fuel issue. You have fuel to the rail but the injectors may not be putting it into the cylinders.
I forget the details, but was the car running until recently or did you acquire the car in it's current condition?
The check engine light was never on while the engine was running (before it has started developing this no-start condition). Right now, since it does not start anymore the check engine light is useless I guess.
The fuel relay was in place while cranking the engine and getting fuel at the pressure regulator hose. Yes, fuse #11 is good.
I had to jump-start the car about 2 years ago and after that the On Board Computer (OBC) started displaying PPPP Km/h, PPPP l/100km etc instead of the actual values. I had read after the fact that I was supposed to remove some fuses before trying to jump-start the car...well...I guess I fried the OBC in that occasion. However, the car has had an erratically hard-to-start condition when engine warm mostly (and sometimes when engine cold, sporadically) since I had the car (and that's 2001). That jump-start apparently hasn't affected anything else for the next 2 years. This hard-to-start condition, one cold December 2004 morning, all of a sudden became a no-start condition and since then I wasn't able to start the car anymore - it just sat in my garage for the duration of the winter and now I'm trying to put the pieces together on what this problem could be.
I've answered above.
This past weekend I've checked the compression and these are the results: Cyl 1 2 3 4 5 6 Compression (psi) 140 140 140 135 130 100, 115,
120, 125
For cylinder #6 compression was 100 initially, then I've taken 3 more measurements and compression increased with each measurement as shown. The car has 192,000 km. Based on this I would say that the values indicate only worn piston rings and not damaged valves, right? And the engine should start even with lower compression on cyl #6. By the way, all the spark plugs were black and oily but I guess that's the result of endless crankings with no result in starting the engine.
So you suspect that the fuel injectors might be at fault? How can I test them? Do I need any special tools? Assuming one or two injectors might have become defective, shouldn't the car still at least start (and run roughly afterwards)?
Maybe, maybe not. Might be a code that helps diagnose the problem.
Ok, this is what I was trying to figure out.
Ok, the OBC just has to be reset but that's a different problem. We'll resolve that later...
Compression is good for the specified mileage and would run if all else was good. Clean the plugs real good (or better yet replace them) and try again. Dirty plugs will foul and not fire the fuel mixture causing a no start condition.
I don't suspect the injectors themselves being bad. As you pointed out, one or two being bad the car would still start. After you clean or replace the plugs, turn the engine over and then pull a plug to see if you're getting fuel in the cylinders. The ECU could still be at fault but I'm willing to bet it's something simpler. Check the codes to see if there's anything stored as the computer keeps the codes until it is cleared and surely there is at least one code present after all of the attempts to start the car. The fuel injection system relies on several sensors to provide data in order to deliver the proper amount of fuel. If you're getting fuel to the cylinders, it's probably too little or too much which is causing the problem. Could be a stuck or bad mass airflow sensor, stuck or bad idle control valve or several other things. All of the sensors in the system are monitored by the ECU and it will know if one has gone south.
First of all I want to thank you for your taking the time to answer my problems with valuable suggestions, I really appreciate it. I will try to get the codes, clean the plugs and everything else and then I'll post an update here within the next day or so.
I've replaced the spark plugs with brand new ones and...the first cranking I did, the car started for a split second and died right after. Subsequent tries yielded no more positive results, back to no-start condition. I removed 4 plugs and looked at them, they were smelling gas, but weren't wet, well maybe just an idea...I'm not sure what I should have seen, should they have been soaked? I'm thinking maybe the injectors are not opening because of lack of signal from the Motronic unit... I had no luck trying to getting the codes...the moment I switch the ignittion on, the check engine light starts blinking regularly (approx
1 blink/sec) and is unaffected by my pressing the gas pedal. I've tried pressing it to the floor 5 times within 5 seconds several times at different speeds and switching the ignittion off and on between tries. Nothing but the constant, uninterrupted blinking that does not tell me much. Any suggestions?
Yesterday, after weeks of investigation finally I was able to start the Bimmer! I think I've checked pretty much everything (except the timing belt which I was about to check this weekend) and I was kinda desperate because everything so far was checking ok. The last thing I checked was something I wasn't expecting much from, the idle air stabilizer valve. Took it out, submerged the half mechanical part of it into some carburator cleaner for the night, made sure the inner cylinder is moving freely (before cleaning it it wasn't moving that good), assembled it back and...the car started like a charm! I would not have believed that this idle part thing could have such an importance that the car would not start...I mean not even the computer could not compensate for the excess air...and the book didn't mention that this part could lead to no-start conditions...only idling problems... So after all, everything amounted to some cleaning...was that simple...but how many headaches! Thanks to everyone who helped me with their suggestions.
Before finishing, I would like to post another question: how do I reset the OBC so it doesn't display PPPP anymore? This started happening after jump-starting the car 2 years ago. I have disconnected the battery several times since then but it did not help reseting the OBC.
It should not have prevented it from starting if you feathered the gas pedal while starting. If it were stuck closed, the car wouldn't idle. Stuck open, it would idle but run lean. Doesn't matter as it fixed the problem. After rereading one of your last posts, I should have caught the IAC valve. Sorry about that.
Unplug the cable from the back of the OBC for a few days, this seems to clear out whatever residual electrical charge that keeps it from resetting.
Actually, that is incorrect. The IAC is *after* the AFM (Air Flow Meter) and is merely an air bypass around the main throttle plate.
This means the mixture will remain the same richness (or lean-ness) regardless of how open or closed the IAC valve is. So if it was stuck open it would just have a very high idle. Stuck closed would be low idle speed and stalling.
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