E34 sohc question........

[Valvebounce 2]

So I took leave of my sences, and against my better judgement, (And the wishes of my heavily pregnant mrs) I just bought an E34.

I bought it off a mate, kinda to do him a favour, and kinda because my current daily is giving me a sore back. (I'm getting too old for daily-ing a car with coil overs etc)

So I bought this car, and it doesn't even run.

My mate had been screwing it, and the motor ate some rocker arms/dropped some cylinders. Cam was badly worn. Bought a donor vehicle, (With an alleged rebuilt motor) and swapped the donk over. All the sensors, injectors etc etc off the original engine were reused. The car had run, (although not on 6) so we're assuming that all those parts worked.

now with the new engine, the car is yet to fire. I've been reading through three workshop manuals that my mate downloaded, printed, and threw in with the car. So I have a bunch of things to test.

But since it was the thick end of two and a half years since the OG motor came out, the "where" that some bits are meant to go are a bit murky.

Main questions are,

Pulse generator Plug. Where does this plug into? There is a loose plug on it's own which it can fit, and then there are two more plugs which it can also fit up underneath the manifold. (One nearer the front of the engine, and one a little farther back) Obviously if that's not plugged into the right hole it aint never gonna go.

Pulse sensor on the number 6 spark plug lead. This has the same flavour of plug as the pulse generator. So it too fits the lone loose plug on a wire, and the two other plugs which are part of the loom up under the manifold.

So if one of you fine E34 anorak's could kindly steer me in the right dierection regarding these two plugs, I can begin wading into some fault finding proper.

Also, on the fuel rail, which is the fuel supply line, and which is the return?

Kind regards,

Bart.

[kiwi535 538]

the e34 came with many motors

[Eagle 1662]

Sounds like the M30. Get the E34 Bentley manual if you dont know what you are doing.

http://www.bimmerfest.com/forums/showthread.php?t=658075

[_ethrty-Andy_ 2132]

a SOHC E34 can be an

M40

M30

M20

(or an M70 hehe)

[Valvebounce 2]

Sorry guys.

It's a 2.5 sohc.

I'm pretty new with the bavarian money wasters.

Does someone have a car they can look at to tell me where they go? Also what route the pulse generator wire is supposed to take?

[_ethrty-Andy_ 2132]

Sorry guys.

It's a 2.5 sohc.

I'm pretty new with the bavarian money wasters.

Does someone have a car they can look at to tell me where they go? Also what route the pulse generator wire is supposed to take?

ok so you have an 88 or 89, maybe 1990 525i with an M20B25 engine.

M20 is the series of engine, B means Benzine (Petrol), 25 is the displacement expresed in deciliters.

That engine is also used in quite a few other BMWs, the E34 was the last chassis to use it before they moved to the M50 engine.

Anyways..... the crank position sensor as its more commonly known over here bolts onto the block above the timing wheel on the front of the engine (in your year engine), and then the lead follows the timing case up and clips in near the thermostat, you will see two plugs. One is for the CPS, the other is for the spark sensor off lead 6. From memory, you cant get them around the worng way due to the design of the plug.

The CPS sensor should show ~540Ohms +/- 5-10%, test it with a multimeter, they are a fairly common fail point due to thier location, particularly when the sump gaskets havent been changed etc. Once you know it is in spec, check for spark, if you are getting spark, then the CPS is working correctly, as is the DME (ECU in BMW speak).

The M20 is overall a pretty basic engine, there isnt much to them, all the emissions crap on later model cars wasnt invented yet, and they still have the good old distrubutor spark system etc.

Hope this helps.

Would also strongly advise you put your location in your profile as well so we know where you are, and can tailor help to your location where necessary etc.

[Valvebounce 2]

Right,

Yeah it's a '88 NZ new manual E34. With the M20B25 engine. There are no plugs near the T/stat housing.

The plug on both the Spark plug thingee (What is the proper name for that BTW?) and the crank sensor are the same. Like I say there is one random (female) plug alone which lies somewhere above the alternator. and two more which are part of the loom which attaches to the underside of the inlet.

I took a bunch of pics today with my work phone. And I see this forum allows pics to be attached.

I'm pretty retarded with computers etc, so I'll have a go at putting some up.

[hotwire 352]

The third plug you speak of is probably the oil level sensor plug. The sensor is in the top of the sump under/by the alternator.

The other two under the inlet are the spark sensor (lead 6) & crank angle sensor. From memory they will interchange so can be connected incorrectly. Check for spark, if none - reverse the connections & recheck.

Fuel line - return is the one coming from the pressure regulator on the rail. Supply is obviously the other.

[Valvebounce 2]

Thanks Grant!

Yeah I'm getting the oil level sensor warning on the dash too. Actually I think the sensor on the drivers side got damaged while the motor was out, so I'm going to swap it out for the one off the original engine which is still sitting on my mates driveway, leaching oil. While searching the www I found another bmw site where some anorak said that oil sender warnings wouldn't prevent it from starting.

I've tried those two plugs both ways around, and no spark has been seen. Thats why I need to know which way around they're supposed to go. Following the fault fiding flow chart is a waste of time unless evevrything else is right 1st. I was hoping that someone who owns one would take a look at theirs and give me a definitive answer.

Then I'll sort the oil sender issue too.

All the fault finding in the world aint worth a pinch of the proverbial if it's put together wrong...........

[hotwire 352]

Which oil warning is coming on? The oil pressure light (red light in dash) is controlled by the pressure sensor on rhs bottom of block.

The oil level w/light is in the check control panel - along with coolant, washers,lights etc.

Neither will stop the engine starting/running.

No spark either way around will mean something else - crank sensor, engine harness wiring connections - eg power to the ign coil?

Are you saying there is no spark out of the coil lead or the plug leads?

[Valvebounce 2]

There's no power at the coil. And no spark coming out the plug wire for number one. (I'm not sure if I've tried the wire out of the secondary side of the coil yet)

I've been digesting the fault finding in a haynes manual, (I haven't begun wading through the Bently one yet) but I need to know where everything goes 1st)

Oil level I think.

Edited December 4, 2014 by Valvebounce

[hotwire 352]

If there is no power to the ign coil - therein is a/the problem. You will definitely have no spark output anywhere. Nor will it be crank sensor at fault. The coil supply is a straight ign feed, can't recall the exact route from source to coil offhand though. Check engine harness plug C101 - the plug connecting engine harness to car.

[Valvebounce 2]

you make an excellent point there Grant. Thanks.

Somewhere the previous owners brother printed off a list of things to check for no power at coil. Check circuit between +ve low tension wire, and some terminal at the ecu. (I don't actually know where they put that piece of paper, but I'm sure it will turn up)

I've asked elsewhere on the WWW where the plugs belong too.

It's hard when someone has been there before and muddled things up.

[hotwire 352]

Have just checked my wiring info. Ign supply (green wire) comes straight from ign switch, through a couple of connectors & to the coil, that in turn loops back to the DME. Check that circuit. It does seem an unlikely circuit to fail though. Make sure you are not confusing yourself here in thinking there is no power on this circuit.

The other plugs have nothing to do with this power supply. There really is not much to get wrong - apart from those two plugs.

[will 169]

The first thing you need to fix is the power supply to the coil. Most of the time the lack of supply is caused by someone cutting into this supply wire and installing an alarm/immobiliser, mostly in the area behind the glovebox.

To determine the exact problem, you need to start at the ignition switch. Remove the cover and test that there is +12v at the thick red wire. If there is no supply, you will have to trace the supply back to the battery to find where it has failed. (There is a fused link in the thinner of the 2 battery wires just after the battery terminal. It is covered in heat shrink so is not obvious. If it blows, it affects supply to most components, including the ignition switch.)

(It should be noted that it is best to use a 5w/21w bulb when testing for power as it will only glow brightly if the supply is good. A multimeter will show voltage even if the supply amperage is poor, i.e. through a corroded joint, so you will think you have a supply whereas, the minute you load it up, it will fail. Using a bulb eliminates this possibility.) I have an e30 front indicator unit I use which has long wires and and an assortment of connectors like croc clips for the wire ends to connect onto whatever I am testing.

If you have +12v at the red wire, turn the ignition on and test for +12v at the thick green wire. If there is no supply to the green wire, your ignition switch is faulty. If you have +12v at the green wire, go to the X20 plug in the engine bay, undo it, and test for +12v at pin 7 on the body loom side.

If you do not have +12v at pin 7, you need to find where the green wire has been cut between the ignition switch and X20. Dig around under the steering column and behind the glove box and look for an alarm/immobiliser unit. If you find one, cut it out of the car and re-establish the circuits that have been cut. Otherwise, run a new wire between the ign switch and X20.

If there is +12v at pin 7, and nothing at pin15 of the coil, either try to find where the break is in the engine loom, or just run a new wire from X20 pin 7 to pin15 on the coil.

Once you have ign power to the coil, switch the ignition off, disconnect the battery, and then disconnect the plug from the MCU (ecu) to test which plug goes to the engine speed sensor (CPS) and which to the cylinder ID sensor. on the no6 spark plug lead.

View of MCU plug.

Using a multimeter or other continuity tester, put one probe into pin 47 of the MCU plug and then test the pins of the 2 plugs till you find continuity. That plug will need to be connected to the engine speed sensor (CPS), the other to the cylinder ID sensor.

Reconnect the MCU plug, then the battery and try to start the car. Hopefully it will...

If not, we will need to go down another path of testing to find out what else is fubar..

[kiwi535 538]

even more basic,is there a rotor in the dizzie,and what is its condition?

[will 169]

rotor will not help if there is no power to the coil... kinda like having tyres but no rims

[hotwire 352]

All well put Will. I probably should have gone into the explanation in more detail. You did it for me instead. Immobiliser in the ign circuit sounds the obvious scenario, assuming there is infact no power to the coil. The switch sounds ok bearing in mind he has ign lights

[Valvebounce 2]

Thanks Will! Great info there.

The car does have an old Alpine alarm. There are no remotes, so I assume it's long defunct.

I did put "alpine alarm" into google. And some of the search results were for E34 BMW's. So could have been factory fitted?

some said it was prefered to interupt the spark (and maybe injectors?) feed as a crank disabled car could still be tow started. People did say it was a mofo of a job to remove the whole alarm. One guy said he removed a "bushell" of wire. Another guy said it was a drum full.

I did try the "factory alarm deactivate" preceedure. But no change to speak of.

definately some good stuff to try there.

But it's all kinda moot when I don't even know if the engine is connected to the car correctly or not.

All input is greatly appreciated guys!

[hotwire 352]

Well Bart, Just check the ign supply as prescribed by us. Easy enough to do.

I seriously doubt it would have a factory fitted Alpine alarm. That the case & being aftermarket fitted - follow as to where the alarm module wiring integrates to the vehicle wiring. The immobilisation circuit/s can be connected to any circuit anywhere - every installer has a different interpretation of installing, and some better than others at doing so - disguising wiring & connections etc.

Assuming as you say is correct (no power to the coil) the only bearing the engine could have in the equation is the engine harness - vehicle plug (green ign wire passes through it). If there is no power at that plug - the problem is back in the vehicle.

That being the case, I would be highly suspicious of the alarm circuit interrupting the said ign wire. This the case though, it would have to be in the circuit after where the rest of the ign feeds are tapped into.

Above statement assuming you have all other ign functions/warning lights etc???

Also assuming you "definitely" have no power supply at the coil - checked with a test light as Will alludes to???

[Valvebounce 2]

I checked the +ve terminal of the low tension side of the coil with a meter, and there was no voltage shown, even when cranking.

Yes I have all dashlights etc, as it's got the oil level sensor warning flashing up on the dash. However I was at my mates house who I bought the car from for a BBQ last night, and the old motor still has an oil level sensor with a plug that matches the "spare" plug I have floating around. So that's one mystery solved.

I'll have to try what Will has offered up, and see what I can find. Since it will run sans the spark plug lead sensor, if I can get juice to the coil, (and if the injectors are working there's only two ways the CPS can go.

I think part of me was hoping that it was something as simple as plugs being wrong, and that a stupidly easy fix was starring me in the face.

Cars huh, who'd want to spanner them for fun?

[Valvebounce 2]

So I just re read and digested the how to posted by Will again. (Takes me a few goes for stuff to sink in sometimes)

I'm not able to test between pin 47 and the two plugs as I can't see the plugs. They're facing down, up under the manifold. And I can only just feel that they're there. Can I be a PITA and ask what the X20 plug looks like/where I might find it?

[will 169]

It should be at the passenger rear of the engine bay next to the fuse box. It is a large round male/female plug. Being a M20 motor it will be a 20 pin unit, not the 25 pin unit used with the M50/M52 motors. Pin numbers are on each half of the unit.

[Valvebounce 2]

Cheers again dude!

Damn your avatar is hard case too.

[will 169]

It's a selfie...