Disguised BMW E30 concept during testing, circa-1980

Grainy pic of a quite heavily disguised BMW E30 3-Series test-mule undergoing tests in Germany circa-1980. The square headlights and covered up Hoffmeister-kink lend an interesting look to this concept, but the roofline and rear-end give it away.

Ironically, it isnt a far cry away from BMWs latest 'Neue Klasse' design language, with the forthcoming 3 seriesredesign and new electric models.

 

BMW E30 / E28 Diagnostic Plug / Socket Pin Out Diagram

PIN:	WIRE SIZE:	WIRE COLOR:	APPLICATION:
1	1.5	Brown	Ground Distribution G101
4	0.5	Brown / Violet	Gauges / Warning Indicators,
			Coolant Temperature Sender
5	0.5	White / Green	Fuel Control,
			Injector Control Module (Fuel Rate)
7	0.5	White / Blue	Service Indicator,
			Service Interval Processor (Reset)
11	2.5	Black / Yellow	Start, Start Signal
12	0.75	Blue	Charge System, Alternator,
13	0.75	Black	Ignition, Ignition Coil
14	2.5	Red	Charge System, Alternator
15	1.5	Green / Yellow	Idle Speed Control,
			Idle Speed Control Unit

E30 318i [M40]: Massive air leak SOLVED - lower inlet-manifold gasket

I had checked and re-checked the idle control valve [ICV], the air-flow meter [AFM], ignition system, tested for the fuel pressure, performed tests on the DME [ECU] to make sure that was working and even laboriously tested the wiring loom for continuity, but still the engine idles terribly when cold. It ticks over lumpy, shakes the engine side to side and cuts out at will, even when power is applied. 

I checked the timing and all was good, under the rocker-cover showed no defective valves and the cam-shaft doesn't look all that worn. I guess the only thing left to check is the injectors... right?? Now hold on a minute I hear the E30 and M40 engine gurus cry, the symptoms you've described point towards an obvious massive air leak in the induction system! 

This is true and is also the very first thing I looked for and tested. Initially I performed the 'spray' test using a can of brake-cleaner (though 'Easy-start', carb-cleaner or electrical-cleaner work too, anything with alcohol content). This involves running the engine and spraying brake-cleaner around the intake-manifold, ICV, vacuum hoses, throttle-body etc. If unwanted air is being sucked in, say through a split hose, the brake-cleaner will be sucked in and combusted by the engine causing it to rev higher. If you are spraying in one particular place and the engine revs increase accordingly then you have found your air-leak. Thing is, I did this test over and over again and it showed nothing. 

I’ve heard that air can be sucked in past the injector bodies when the rubber sealing rings have degraded over time and that the lower intake-manifold is also a main culprit, but spraying round this area made no difference to the engine revs or affected the poor idle. I did a compression test and the readings were a bit low, but not enough to cause any issues.

At this point I decided it to bite the bullet and begin stripping things down. The removal of the lower intake-manifold is quite complicated because it involves removing the fuel-lines from the rail, which is why I put it off, but clearly if you want to fix something then you need to get your hands dirty so off came the fuel lines and away came the lower manifold to reveal.... well, as you can see from the photo, a virtually non existent gasket. Sigh. 

Cylinder 1 has a massive gap where the gasket is no longer there, so whenever there is a vacuum in the plenum it’s just filling up with fresh air even with the throttle-body shut and this explains why the ICV appears to be doing nothing and leads people to look there first. Whoever was refitting the manifold was obviously in a rush because the broken gasket has folded over on itself, causing the air gap to be even bigger. I guess they just tightened it hoping to make a seal, but alas no. Cylinder 2 is not much better with a noticeable gap and the rest of the gasket squashed flat. Cylinders 3 and 4 are better, but still paper thin. It looks like this may be the original gasket and the past 35 years have not been kind to it (or to me for that matter).

So... looks like I have found the culprit of the rough idle. Finally! New gasket is ordered, a snip at £6.88! Amazing how such a simple thing can cause such a severe problem and goes to show how sensitive these ‘analog’ ‘80s cars are to air metering issues!

E30 318i: Correct Temperature Sensor fitted (Brown Plug) + wiring/loom issue

The temperature gauge in the dash has not worked since I bought the E30, which was a little worrying on my 250 mile drive home, but the car does not overheat. Oh, it has some issues with the cooling-system, like the heater-matrix pipes fitted incorrectly and an air-lock at the back of the head, but hey it doesn't overheat. Still though, I thought it best to get the bottom of the faulty temp. gauge for peace of mind, particularly with summer coming / just about here.

The M40 has two separate temperature sensors that are independent from one another. The temperature gauge works from the 'Brown plug' sensor to the rear of the head [right in pic]. The forward sensor is the 'Blue plug' [left in pic] and that connects only the DME (ECU) to tell the car if the engine is cool or warm to help with cold-start procedures. A single sensor cannot be used for both purposes on these older engines as the resistance value ranges required for each function differ, the DME being a digital circuit and the temp. gauge still working in analog. [You can read more about this on the E30 Zone Wiki HERE].

MULTIMETER TESTING:

The temp. sensors can be easily tested with a multimeter set to 20k ohms resistance. 

The Blue plug is a two-pin sensor, so test across both terminals with the multimeter and you are looking for a reading of 4-4.5k ohms for a working sensor. This sensor and plug can be accessed easily without removing any parts from the engine.

The Brown plug though will require removal of the lower inlet-manifold to access the sensor for testing or replacing. This is a single pin sensor, so place one probe of the meter to the terminal and the other to a ground-point in the engine bay or against the block/head. Expect a reading of between 1k and 1.5k ohms for a working sensor. To test the Brown plug sensor without removing any parts from the engine, you can apply the multimeter to Pin 4 of the C101 connector (main wiring loom plug in engine bay) which is easy enough to get at, or at Pin 26 of the blue connector to the right side of the instrument binnacle, though the binnacle will need removing to do this.

WRONG SENSOR / CONFUSING WIRING LOOM:

All M40 engine wiring looms use a single pin temp. sensor on the brown plug that earths through the engine block and have only a single wire in use leading to it. Some looms, using components destined for other BMW models, are known to have a second wire leading to the Brown plug temp. sensor which is redundant on the M40 motor, though this is rare and seen more often on 6-cyl. M20 looms. My car has one such loom, however and I realise that this is what has caused confusion in the past and led to the wrong sensor in fact being fitted...

Upon inspection, the rear temp. sensor fitted to my E30 is black, not brown and has two terminals. The second pin means that the sensor body earths back to the loom and not through the block so, if the redundant earth wire in my loom is not connected to a ground-point then the sensor was open circuit. I guessed that someone had ordered a second Blue plug sensor by mistake and fitted that, but it turns out the part number doesn't match and the sensor is for a completely different model engine entirely. The reading from the multimeter was over 11k ohms, something like 7.5 times what it should be! That sensor was never going to work with the E30 temp. gauge circuit whether it was earthed or not.

I ordered the correct single-pin sensor with the brown base from mr-wiper on eBay, who also supplied my Bosch spark-plugs. It was only £7.69 delivered. My temp. gauge now works, but this may also be due in part to removal of an air-lock at the back of the head due to a heater-matrix problem so coolant is now flowing properly round the area of the sensor. 

A BIT MORE ON WIRING LOOMS:

Brown / Violet, brown being the main colour, denotes that the power source provided from the temp. gauge circuit is earthing through this wire and does not need to be a closed circuit back to the gauge. The other wire is either not wired in to the loom or goes to a body-earth anyway, so earthing the sensor through the block will make no difference. This colour coding is the same for all wires in all BMW looms, I would imagine most cars are the same.

E21 316: Update + MOT Pass

After my disastrous few weeks I managed to get hold of a Bilstein strut-insert and get it onto the car along with the longer springs, meaning it was finally back on the road and in an state worthy of the MOT test. I cautiously rolled down to the test-station on Saturday and am glad to say the E21 passed with flying colours!

Bilstein damper is strong, but will be a pain with the short springs.

This was a relief considering the slightly dodgy seat-frames I made bolted through the floor-pan, which stuck out like a sore thumb when it was up on the ramps, along with the scuff marks where I've grounded the underside, but with the car at a more standard height off the ground this didn't see to bother them and there was no problem with the chassis at all.

Oddly, the guy told me that the split-pins were missing from the castle-nuts on my steering track-rod ends and this would actually be a fail under normal circumstances, but they could see I'd been working on it and decided to give me the benefit of the doubt. This was true, I'd had them off swapping the springs and hadn't bothered to replace the split-pins as they would be coming straight off again to put the short springs back. That was decent of them to let it go, as it would have been beyond frustrating to lose another week to something so trivial and shows just what a pain the UK MOT test is.

Folded up and with a 1/4 inch thick layer of
pallet-wrap to send as a parcel.

Spending on the E21 has been a bit out of control since buying the E30 seats and it is still in desperate need of the wheel-arches finishing off. By this point, I'm past what I can recoup if I sell the car. I'm still using my E39 as my daily, the E21 has had no use for nearly a month with no MOT and finally, due to a planned move, it's looking like I will have to let her go anyway, unless I can find somewhere cheap enough to store it. I had hoped to have the arches skimmed off and painted by the guy who did the respray, but money is tight so I will be buying a rattle-can and doing the best I can with them.

Thankfully, I've managed to generate a bit of extra cash to pay for the strut-debacle [this post], by selling some bits on eBay, like a battered old set of alloys, an E36 nose-cone and other bits I had lying around, as well as the original beige passenger seat from the E21 - I think I have enough seats for the car now. I hope the seat arrives to the buyer OK, as I had to practically shrink-wrap it to be able to send it Parcelforce [£27], pictured, as the original method of courier was just over £60!

My spare set of E21 ash-trays is not selling on the other hand and is still on the site here - http://www.ebay.co.uk/itm/181235987123.

E21 316: More manifold gaskets for M10...

Stuck the new and much better quality exhaust-manifold gaskets on today from Euro Car Parts. They're thicker than the eBay ones and have steel rings round the inner rim like a head-gasket, should make a better seal. It's got rid of the cracking noise from that dodgy one on cyl. 4 [this post] and the engine sounds sweeter than ever.

Surprisingly the manifold nuts all came off as they should this time and left all eight studs in the head... weird, but it certainly made fitting the gaskets a lot easier.

E21 316: M10 Engine cured! - Culprit: manifold gasket...

After repeatedly timing the ignition perfectly to Z on the flywheel, [see this post], we decided there had to be something deftly wrong to be causing the loud noise and backfiring [in the vid below], rather than just the distributor being out of line.

The first hunch was the exhaust had broken while being twisted to get the cylinder-head out and was blowing like mad, but my initial inspections revealed no damage to the down-pipe or manifold and the four manifold gaskets looked all to be in position.

That is to say they LOOKED in position... Today, in the pouring rain, I got the car up on ramps to see what it was I'd missed and as soon as the torch flicked on I could see the answer at last - one of the exhaust-manifold gaskets had slipped off the stud and was only covering half the hole! Nightmare... Right at the back of the engine where we couldn't see and, ironically, the one for cylinder 4 that started all the trouble.

As you can see the gasket has been totally blown apart by the hot exhaust and has separated quite badly in the middle leaving only the metal. I checked the rest of the gaskets in my set for a spare, but can only find the same shape gasket with an oblong hole, perhaps for the E28, so tentatively decided to re-use the blasted one, correctly seated this time and caked in Holt's FireGum.

As soon as the engine fired up again it sounded like it used to. It's amazing the difference that gap in one single exhaust port made to the noise level. It was still idling low though and revving badly, so I grabbed the timing-light again to have another go, turning the distributor to line up Z on the flywheel - 25 degrees before TDC. Now the 30 year old M10 has really begun to purr once more. Awesome! Still some fettling to do on the carb. tuning, throttle/choke cables and checking to see if my damaged manifold-gasket is holding up, but at least she's back on the road after a tense month!

E21 316: M10 Distributor/Ignition Timing: Strobe Light Ahoy!

So my adventures into re-timing the spark-plugs continue with the purchase of a Gunson Xenon timing strobe-light! I went for the cheapest kit in Halfords, but it was still a slight pain at £45, considering it's in addition to a new dizzy-cap and rotor-arm, set of spark-plugs, compression-test kit, gasket-set, oil, coolant and a 30mm socket to turn the engine from the crank, but as I just can't seem to get the old M10 engine running happily I guess it's just as vital and at least we can use it to time in our old MGA engine this summer (hopefully).

Before I start to moan again about the intricacies of re-timing the distributor I should say that I know there is no need to remove it in order to get the cylinder-head off and the dizzy should really be left in place to save all this trouble, but the diaphragm on mine was blocking one of the head-bolts so that wasn't an option for me.

The timing light works by flashing every time your 1st-cylinder spark-plug fires. There is a timing-mark on the spinning crank-pulley or flywheel that passes a stationary mark on the block at the exact point the 1st spark-plug should be firing. When the flashing light from plug 1 is aimed at the spinning pulley it shows the timing-mark in a fixed position in relation to the stationary mark and allows you to gauge how how many degrees before or after the correct point the spark is. Clever stuff.

On the BMW M10 engine, there are two timing-marks on the flywheel, one for top dead-centre [TDC] and another, called Z, that corresponds to the right point before TDC that the 1st spark-plug should be firing. The marks are visible with the flashing light through a small oblong hole at the back of the crankcase. It's easy enough to find the hole, but seeing into it with the timing-light is a challenge in itself, let alone trying to adjust it or move the dizzy-cap and I ended up having to stand over it with my feet on the strut-tops to steady myself enough without leaning in from the side and crushing the wheel arches. There is another TDC timing-mark on the rearmost rim of the front crank-pulley, which is a lot easier to see with the timing-strobe from the n/s of the engine-bay, but the mark is tiny so when you do find it it's best to file a larger notch across the whole pulley - mine had this done already and it makes things a lot clearer.

It's best to first time your engine to Z on the flywheel, at 2200rpm, using 0 degrees of advance on the timing-light gun - just shine it into the oblong hole and rotate the distributor-cap until the large pointer is lined up with the silver ball, not the TDC line. Now check the front crank-pulley for reference by shining the light at it with 0 degrees advance. The groove for TDC should appear around 25 degrees before the stud on the engine-block. Rotate the dial on the timing gun slowly to 25 degrees and the groove should move in line with the pin. Simples.

Ignition timing isn't too much of a fine art, so as long as the rotor-arm contact is roughly on point no.1 on the dizzy with the engine at top dead-centre then it should fire right up and not need much adjustment to find Z. Mine was still making the god awful noise after repeatedly timing to Z, but this turned out to be a badly positioned exhaust-manifold gasket [in this post] so, obviously, check everything else isn't amiss before starting to mess with ignition timing.

E21 316: M10 Misfire Woes:

Went on a Maccies run with some work colleagues on New Year's Eve and I may have been pushing the old girl a bit hard, when a horrible clanging noise began from the engine and got worse quickly. Some of the guys at work suggested the first stop should be the rotor-arm and dizzy-cap so we managed to get some delivered through the parts dept. that afternoon, but it was still chugging on a mixture of cylinders and it limped home for me then refused to start again. When it eventually did the old M10 barely managed to fire 3 cylinders.

My list of diagnostic checks was:

Replaced distributor-cap and rotor-arm.

Tested all 4 plug-leads.

Replaced all 4 spark-plugs.

Removed, cleaned and rebuilt Weber carb.

Checked valve-clearances and confirmed all valves appear to be moving correctly, turning the engine by hand.

Finally diagnosed cylinder 4 as no firing.

Plug and lead tested again, this time sparking against the suspension turret.

Compression test revealed Cyl. 1 and 2 @ 150psi, 3 @ 45psi and 4 @ 25psi.


This all seems to point to a bust head-gasket between the 3 and 4 cylinders. It is unlikely the valves for 2 cylinders would have bent or suddenly need adjusting at the same time, so off with its head and lets look at that gasket.

*UPDATE: The head came off pretty quickly and revealed one seriously blown head-gasket right between the 3rd and 4th cylinders [detailed pics in this post]. Diagnosis spot on, but the culprit may be a slight warping at that end of the alloy-head - not very much at all, but still a worry considering it looks to have been skimmed before. Either way, the new head-gasket is on [I went for a full head set off eBay for £27.99, which includes the manifold gaskets etc.] and the car is running on all four cylinders again, though not as happily as it could be. I was forced to remove the distributor and seem to be having some issues with ignition timing since putting it back [in this post], and the carb. still hasn't been tuned properly since the rebuild, so a range of fettling awaits before I can drive it for the first time in 2013.

E21 Road/Track Nürburgring Challenge - PC Magazine