Bimmerfest BMW banner

1 - 10 of 10 Posts

·
Registered
Joined
·
4 Posts
Discussion Starter #1
New to the forum and new to BMW's, too (but know my way around American and Japanese cars, pretty well).

Have a 1992 325is (w/ an automatic) that was running/starting fine. Parked it one day, came out two days later and it cranked slow and wouldn't fire. I figured the battery was too low (it was cold here) so I connected the battery to a charger and re-charged it. After it was charged, I hit the key and it cranked fine, but it wouldn't start.

Moved the car into the garage to address possible temperature issues. No change. Since that time I have (1) confirmed I have spark at cylinders 1, 2, and 3; (2) confirmed I have fuel pressure (about 45-50 psi); (3) confirmed I have 12v power to all fuel injectors; (4) confirmed the injectors are getting signals from the DME/ECU-thingy; (5) bypassed fuel pump relay; and (5) sprayed some starting fluid into the intake track between the throttle body and airbox. None of these tasks, or any combination of them, resulted in the engine starting. It just cranks and never feels like its trying to fire.

I'm not one to give up easily on cars, but I am starting to wonder if I've lost my mojo.

Any ideas or suggestions would be greatly appreciated.
 

·
Registered
Joined
·
12,726 Posts
Next thing I'd try is removing the throttle body end of the boot between it and the air box, opening the throttle wide open and spraying some starter fluid into the intake manifold. If you can have someone crank the engine over while doing it that would be even better.
The intake path from where you indicated you sprayed the starter fluid into the cylinders is pretty long and if it's really cold I doubt much of it got into the combustion chambers.
When you checked fuel pressure, did you use a T to connect in the fuel pressure gauge or did you just connect it direct the line coming to the fuel rail? When you saw the 45-50 psi did it peak when you first turned on the ignition and then bleed down right after that?

I'm suspecting you've got a crankshaft position sensor issue, and that's causing a no fuel problem.
In the starting process when you first turn on the key to the start position, the ECU turns on the fuel pump briefly, and then looks for a signal from the crank position sensor as the starter begins spinning the engine. If no signal from the CPS the ECU immediately turns the fuel pump back off. It's set up this way so that if the ECU senses the engine's stopped spinning (such as after a crash) it cuts off fuel to reduce the possibility of a fire. It will also cause a no start condition if the CPS is bad.
 

·
Registered
Joined
·
4 Posts
Discussion Starter #3
Hi DC,

Thanks for the suggestions! After I posted last night, I continued to search and found a thread that had your exact suggestion with the starting fluid and I tried it. Nothing. While I was puzzling on this, I had another thought.

With the throttle body exposed and held at WOT, I placed my hand over the throat and cranked the motor. No suction in the intake track. As I stated above, I'm new to BMW's, but I'm pretty sure the principle function of any internal combustion engine is to pump air. No air movement, no run. I can't see the valvetrain through the oil cap and I didn't see any obvious place I could inspect the cam/chain/gears/valvetrain operation so I will run a compression check on it tonight when I get home. I will also note, there are no odd noises coming from the engine when it cranks.

To answer your other questions (in case the mechanical issue doesn't pan out) I plugged a brass 'T' fitting into the fuel line off the fuel pump under the back seat. I pressurized the line by bypassing the relay and then clamped the line to verify if there was any pressure bleeding off in the system. It held pressure fine, only lost about 10 lbs in 20-ish minutes...

On the CPS comment, if I jump the fuel pump relay won't that take the CPS function out of the starting equation?
 

·
Registered
Joined
·
4 Posts
Discussion Starter #4
I ran a compression test this morning and it is not looking good. I only tested cylinders 1 - 4 and the results are 60, 90, 60, 30...

Is there a location on the engine that I can inspect valvetrain operation without pulling the valve cover? I am guessing the cams aren't turning and the valves are stuck at various positions creating the random pressure readings. Any suggestions out there?

I'm struggling to understand how this happened because the car was driven to where it died.
 

·
Registered
Joined
·
12,382 Posts
color me skeptical,....what is the battery voltage while cranking??

(12v is technically a dead battery, which is why i ask...)

next, given the symptoms, it is unlikely that *all* the cylinders lost compression, and slow cranking rpm will tend to give very low numbers.

if the battery is older than 4 years, get a new one, or hook a jump starter (not a portable jump box) and set to boost. this should charge the battery, or at least send enough juice to crank the engine to normal rpm speeds.

if that is not available, take the battery to get tested. get a new one if necessary and retest.


a wonky battery, even after being "charged" can give false readings leading to all sorts of wild speculative guesses which result in chasing your tail for hours or days on end.

ask me how i know....:angel:




df
 

·
Registered
Joined
·
12,726 Posts
This a long shot, but easy to do. Try pulling your vanos solenoid. If it sticks with the timing advanced it's a no start condition next time you try to fire the engine.
If you remove it that will allow the pressure to bleed off and you can check to see if it's stuck.
 

·
Registered
Joined
·
4 Posts
Discussion Starter #7
Thanks for the guidance on the situation, gentlemen.

When the battery went dead/cranked slow I charged it for a day, but it didn't feel like it took a charge very well so I pulled it and had it tested. The shop confirmed the battery was good (BTW...its two years old) but just needed a good charge on it. I went back and plugged it in and let it charge for a couple days. When I put it back in, it cranked the engine just fine. I have kept a maintenance charger on it since its been in the garage to make sure it is always topped off...

I'll continue to poke around a couple more days and see if I can narrow it down further. I will keep you posted.
 

·
Registered
Joined
·
17 Posts
Rehinger,
What method did you use to check for a spark on cylinders 1-3?
Also, did you check for fuel volume while doing the fuel pressure test?
 

·
Registered
Joined
·
4 Posts
I know this is a long time ago but did he ever find a resolution to the problem? I have a 95 m52b20 I've changed the CPS and still can't get it started.
 
1 - 10 of 10 Posts
Top