Got a problem that has left me in circles.
85 BMW 325e, manual. Won’t start. Previously had some driveability problems, sproadic brief stalling.
Using the key in ignition switch,starter spins the engine with no hint of a start.
IGN components all test to spec and during start attempt there is spark on all cylinders.
Fuel flow and pressure is within spec, both when FP relay is jumped and during start attempt.
Speed and reference sensors test good.
All inputs to dme have been tested, including power and grounds, and are good.
You need to see if the injectors are pulsing. This can be done with a NOID light or with a stethoscope/long handled screwdriver if you have someone to crank it over for you while you listen in. You should hear the injectors make a faint click each time they open.
Does the engine appear to crank over fast and easily? If so, maybe a timing belt has given up.
What Okay said, plus check for leaking injectors which will flood the engine and make starting difficult when hot…Engines with this problem usually start fine when they are cold, as in overnight cold…
All on car tests of injectors were ok, except I can’t check them while running of course. resistance is good and they are receiving the signal from the dme, appropriate voltage and “click” is present…
Engine cranks normally.
Engine won’t start cold or hot.
Compression is a good thought and I’ll check that, although the preceding intermittent behavior (which I believe may be connected) does not suggest that.
With good fuel pressure, pulsing injectors, ignition spark, and compression it should be doing something even if it won’t start. Cough, spit, backfire, something.
I agree; spray some carb cleaner into the intake and see if it runs for a second or two.
Haven’t been able to work on it lately. will get back to it.
Will check compression, but it seems unlikely that is the problem.
Will try priming as suggested.
I’m going to step through everything again. Could have missed something. (Obviously I’ve missed something.)
This car has electronic fuel injection, right? hmmm …
Checking compression and trying the old “starter spray into the intake manifold” trick is probably what I’d do next if I had this problem, given what you’ve already done.
A clogged exhaust system could produce this symptom. That’s worth a check too.
Edit: One other idea, one of the posts above reminded me of this. One time I had a VW Rabbit that wouldn’t start, and I couldn’t for the life of me figure out why. I tried everything in the book. Everything tested ok. It turned out to be simple, the engine was completely flooded w/gas. My prior testing of the fuel injection system had a side effect of spraying a lot of gas into the cylinders. The solution was to remove the spark plugs, crank the engine a few time to expel most of the gas, then let it sit overnight before re-installing the spark plugs.
Years ago I diagnosed a friends BMW of this vintage. It was a 5 series, forget the exact year.
Turned out the rubber hose between the MAF sensor and the throttle body was full of cracks,
so air entered the throttle without flowing past the MAF.
The computer didn’t see air going into the engine, therefore it delivered no fuel.
A wrap of duct tape on the hose made a temporary fix.
If the starter spray doesn’t get it to start and run briefly, like for a few seconds, I wonder if the engine is actually be cranked by the starter. Maybe what you are hearing is the starter motor turning, but it isn’t engaging with the flywheel and cranking the engine. Ask a helper to look at things in the engine compartment that should be rotating if the engine is cranking. Maybe they aren’t.
With a 30 year old vehicle like this, I agree with @circuitsmith’s comment on checking for cracked hoses, or any other way intake air can leak where it should not.
I do have some aging tubing and the intake boot that could fail soon. But I detect no air leaks at present.
Applied some carb cleaner to the intake as suggested but no glimmer of a start.
? I did a 1 cylinder, #1, recheck for spark(previously all leads showed spark), pulled plug wire and used a new plug grounded, which was good. Replaced the plug wire. Shortly afterward I was cranking the engine and it sounded like it attempted to fire, once or twice. ? Don’t know if there is any reasonable connection.
I really resist dx by replacement, but maybe it’s down to that.
Sheesh. Some people will take anything not chained down. I’ve been pretty theft free but after 9/11 someone stole my flag off the house.
I’ll second the air leak issue. My Riv had starting problems that I traced to a break in the intake hose. A little tape fixed it. Also, could you have a timing belt/chain issue if it hasn’t been mentioned?
Engine timing is on my radar, but to check it requires a little more disassembly.
The following is new since it stopped:
I renewed the plugs. The engine reluctantly started, sputtering through a few failed attempts. Continued to run with a miss. I could not locatize the miss to any one cylinder. I checked each cylinder by pulling each plug wire in sequence. None of them caused a change in the how the engine ran. And the exhaust is grey/black (not blue).
Since spraying fuel directly into the intake manifold didn’t produce a brief start, it sounds like some kind of an ignition system problem is the most likely culprit. If you decide to try the parts replacemet method, I’d start with all the spark plugs, the distributor cap, ignition rotor, and spark plug wires. It’s possible this is a cam or crank sensor problem too, but I’d still start w/the above.