Author Topic: Weird Starting Problem (Read 7726 times)

bad_robot · « **on:** October 23, 2011, 03:15:03 AM »

E30 M40 1991 318i stopped and would not start.
Dash/service lights, head lights/high beam, fan did not come on
but low beam, wipers, indicators, break/interior lights and radio all worked.
I know the car is 21 years old and I am getting problems with exhaust (maybe a hole) and the idle.

New battery installed.
No change

Decided to move the fan, alternator and the engine a few degrees (by putting a screwdrive in the bolts holding the fan to the water pump and levering) -
guess what - dash/service lights come on and car starts.

Is there some location of a 'top dead centre' position (if I can call it that) which affects the location of something that needs to be moved slightly from the wrong (dead spot) position that the engine sat at when ignition was turned off?
NE1 have ne thoughts? Starter motor dead spot?

Had a similar problem with a Holden VH 1983 that needed a connection of positive to earth at the starter electrical connection point to move the starter or engine.

Geoff · « **Reply #1 on:** October 23, 2011, 08:26:01 AM »

Just my feeling from your description, more likely to be some sort of wiring issue, bad ground to the engine, corroded/loose harness plug, or on the back of the alternator, maybe. A bad spot on the starter doesnt act like that, when that happens all your lights work as normal, but when you hit the starter all you hear is a thud/click and all your lights go dim, but no start. Then it responds (the starter) positively to being whacked with a hammer, and politely allows you to go to the parts shop and get a new starter, if you are so inclined
Geoff

DesktopDave · « **Reply #2 on:** October 24, 2011, 09:36:19 AM »

+1 on Geoff's diagnosis...starter will work as usual BUT just spin or grind if there's a problem with the flywheel ring gear.

I'm betting it's a pretty simple electrical problem. How familiar are you with a multi-meter? They can save you a lot of time & expensive parts swapping, the little devils. I use mine so often I bought a cheap $5 one & left it in the trunk tool kit.

I'm not terrifically familiar with the M40, but I'll take a couple of guesses. I don't think rotating the motor made a difference, I'm figuring it was coincidental unless you twisted the motor enough to connect a damaged ground strap. If you're sure the motor is in adequate shape (no coolant leaks, oil in the sump, etc) I'd start testing the electrical system.

I'd be inclined to check the key switch, the inhibitor relays and the under-voltage relay. I'd also be sure the ground straps off the motor are in good shape. I'm not sure where they are on an RHD M40, but look for a beefy brown wire off the motor mounts/block/cylinder head connected to the chassis frame rails. Cracked insulation is OK, but a corroded cable must be replaced.

Did you hear any buzzing from the dash when trying to start the car? If so, your under-voltage relay is inhibiting the start circuit. Charge/test/repair the battery, find the short, etc... This system is designed to protect the electrical systems from less than 9VDC or so. Low voltage can damage electrical components in the car.

There are also a pair of relays (K5 & K7) that disconnect the car's electrical system when the starter motor is cranking, BMW calls them the unloader relays. Test them to be sure they're working.

bad_robot · « **Reply #3 on:** October 27, 2011, 08:34:22 PM »

Thanks for the advice from both.
No buzzing from dash as the battery was new perhaps.
Motor in adequate shape.
Ground straps ok. beefy brown wire ok.
The car is now starting ok.
I shall look at the key switch but the internal wiring was renewed about 30,000k ago.

Geoff · « **Reply #4 on:** October 28, 2011, 06:46:06 AM »

when problems go away on their own, its ok in a way but then you never know what the problem was until it does it again. And it probably will happen again, as even the mighty e-30 does not heal itself (for long)
Regards,
Geoff

bad_robot · « **Reply #5 on:** November 05, 2011, 08:42:21 PM »

Ur right Goeff
Car failed to start again - click
But, once again I moved the fly wheel a couple of inches and it started ok.
Really weird problem which has only happened 6 times since 2006 - must be the age of the car at 21 years. Only the same problem with a VH commodore caused me to also try a fly wheel movement here.- does not seem to be a electrical problem as such - maybe a bad position for some sensor.
Also move the car a couple of feet, if that and all is ok again. Twice in one day now.

Geoff · « **Reply #6 on:** November 06, 2011, 09:57:31 AM »

you must be having gremlins, I guess:eek: one of the hardest to figure out, until whatever it is manifests itself permanently, then you can usually track it down.. the crank position sensor would react to a movement of the flywheel, as I guess all others relating to the movement of the engine..theres one on one of the cams, not sure which one..even so, I think they would not effect the actual cranking of the motor, just its ability to start once it were cranking....so I'd concentrate on the cranking circuit, if I have a grasp of what your problem actually is..
G

bad_robot · « **Reply #7 on:** November 07, 2011, 05:53:13 PM »

tks G

I have a strange fuff fuff now as if there is a hole in the muffler but it comes from a muffler like section forward of the end of the coupe door and behind the o2 sensor. (is it a cat converter?)

Maybe the system treats a hole in the exhaust as an air hose leak and mucks up some other sensor like the sensor above the air filter.

Car runs ok at speed - plugs are white where they should be.

(I only get a starting problem sometimes [fixed by moving the car 20 cm or so] and the idle is a little fast - adjust the screw down too much and engine shudders too much and almost stops - then some sensor opens and revs increase just to drop off again - as the engine warms this problem gets better of course)

Geoff · « **Reply #8 on:** November 08, 2011, 06:03:09 AM »

yeah, its the cat right behind the o2 sensor, but right behind the cat is a resonator they like to rust out and leak too. I dont think a sensor will react to an exhaust leak, but the idle drop and then recovery sounds more like a vacuum leak to me. I dont think these issues are related to the non start thing, tho. In your shoes, I would, as time and money allows, track down the reason why your starter is iffy, then get a new exhaust system, or at least replace those parts which have a hole, then address the mess under the intake, which will usually take care of the vacuum and or coolant leaks associated with that system. If you are anything like me, you are only one lottery win away from solving all your problems..
Geoff

bad_robot · « **Reply #9 on:** November 09, 2011, 04:37:55 PM »

Tks G

Hole found at top of exhause pipe as it entered the rear muffler.
Shop indicated that there were no air leaks and the cat converter and front muffler were ok.
So rear pipe replaced with a little imaginery improvement(I think) in the idle - less noise mostlikes.

Starting problem still there and solonoid (?) click on start - move car 3 inches and car starts. HUH? But I can live with this until the starter fails proper like.
Mechanics at repair shop amazed at rev problem but are not BMW specialists and so had no possible solution to offer. Glad to see the end of me, methinks.

There is something (apart from the idle screw) that changes idle speed suddenly and I shall now search for that.
So ICV removed, cleaned and replaced. Oxy sensor changed about 15,000k ago, so these look ok. Plugs changed to new ones, too.

Ur right, starting and revs different issues.

and yes, i'm still waiting on that lotto win!!!

A quick jolt to the black box on top (behind) the air filter can alter the revs too.

Geoff · « **Reply #10 on:** November 10, 2011, 06:13:42 AM »

yeah, c'mon megamillions..woohoo!

your description of tapping on the black box ( MAF? ) changing the idle makes it almost a lock that there are vacuum leaks in the intake or emissions system. The box is attached to the intake air bellows, which can get cracks in it and leak. Also, there are hoses going to it from underneath that leak..all related to the well known "mess under the intake" which needs to be either restored to a stock but non leaking condition by replacing all hoses, or removed entirely, a process which is detailed and documented several times and a couple of different ways, in other threads. By the way, you are correct-those guys at the shop dont wanna be bothered..you need to find a place that speaks BMW, or at least has experienced mechanics that have seen it all and dont mind working on it..
Geoff

bad_robot · « **Reply #11 on:** November 13, 2011, 07:08:48 PM »

Tks G
I did more work on diagnostics - hoses ok but sprayed alcohol around and found a crack in the gasket somewhere in the front of the inlet mainfold - 21 years is just far too long and I cant count how many times the manifold has been removed and put back - solution replace gasket.

As for the starter, could be a spring in the solonoid failing to engage/disengage, methinks and it is getting worse, turning the motor a few degrees just hopeful luck - solution replace starter.

So, both are a bit too hard for me to do so back to the shop
(BMW literate mechs - they will get the job if they can verify the 2 problems from fifty paces)

Good clean little red coupe with no rust and $11,900 spent on it over last 8 years so another $750 is not that much.

Balkanac · « **Reply #12 on:** November 15, 2011, 12:47:11 AM »

Where in aus are you mate?

bad_robot · « **Reply #13 on:** November 15, 2011, 01:09:03 AM »

Near Nambour Qld

Geoff · « **Reply #14 on:** November 15, 2011, 10:47:49 AM »

yeah, I know what its like. I'm sure the shop will need to remove the intake once again to R&R starter, good time to do all the hoses under there and get rid of the potential leaks associated with them. I had to put mine in the shop too, for a head gasket. I would have liked to do it myself, but I need it done quickly and I totally jacked my back up at work, so...pay to play as the saying goes.
Geoff