Bmw E34 520i 24v Compression issue???

[LazurE34]

Im currently working on my beautyfull rusty e34 520i which doesnt want to start anymore and am kind of clueless to why...

it all started with the DME getting wet with the rest of the relays... Relays and dme replaced (yes i had the dme opened and had been damaged)
Before with the damaged dme it couldn't open the injectors thus starving the engine, i ended up replacing it with a different one and fixed the fueling isue...

yet it still wont start and definitely has compression issues, and gets around 8-9bars on each cylinder (116 - 130psi) i will start a leakdown test as soon as i get to it! but should it not be enough to ignite the fuel?

Things that might be an issue:
The original DME was a siemens ms40.1 (Vanos) and replacement is a siemens ms40.0 (non vanos) (sparks and is getting fuel)
Sparkplug in cyl 2 had alot of oil on it and the rest where soaked in fuel
Can the timing be off by just a tooth?

[LazurE34]

Timing chain looks tight and neat... tried to start it with brake cleaner and backfired out of the intake could it be the hydraulic lifters not letting the valves close completely? the car has been sitting for quite some time... (almost 2 years) (bad fuel might be something too? )

[Layne]

130psi is extremely low, but it's still enough to run an engine. If they're all low but even, you're probably right about a timing chain issue.

The lifters cannot hold the valves open, but they may not be opening them all the way. Should still work though.

It's not easy to find information for the Siemens injection, and new parts are extremely expensive. You should probably consider swapping to the bosch injection from a 2.5l car. Or the whole engine if you can find it.

[ross1]

Timing chain looks tight and neat... tried to start it with brake cleaner and backfired out of the intake could it be the hydraulic lifters not letting the valves close completely? the car has been sitting for quite some time... (almost 2 years) (bad fuel might be something too? )

Read the label on the can of Brakleen please. Phosgene gas is a byproduct of it's combustion, phosgene is DEADLY.

Are you certain this engine will run on that DME? Sounds dicey.

I bought a car with an M50 that had been sitting a very long time. Apparently the lifters had all bled down so the valves weren't opening as they should. It cranked fast as if little compression or jumped timing. After cranking it a VERY long time it began to sputter and finally fired and made a bunch of lifter noise for a while. Was A-Okay after, albeit the starter took a mighty thrashing.

[B320i]

Think the issue is you've swapped the wrong DME in, a Non-VANOS DME may be wired differently thus causing the issues. Plus, without VANOS control, just makes things more complicated.

The poster above is 100% correct about price of parts for cars running a Siemens DME. Just as an example, for a Bosch 525i or 325i from 09/1993, the Knock Sensor is AU$77.13. Siemens? If you can find it from the OE, you're looking at AU$185 at the bare minimum. Cam and Crank sensors for the Siemens are closer to AU$300, and the Oxygen (Lambda) is over AU$300.
Bosch DME cars would be 1/2 or 1/3 the cost.

A Bosch DME is not a drop-in replacement. The wiring is all different. It would be better to find anything but a 520 and use the parts off of this vehicle. Or, if you want to persist with this car, source good secondhand parts, but better still, investigate this issue and do not 'throw parts' at the problem. You'll only end up bankrupt.

[Layne]

A Bosch DME is not a drop-in replacement. The wiring is all different.

Of course the engine wiring harness is different, but I'm assuming that either engine harness will plug right into either car. That may not be true, but engine swaps happen every day. It would be no different than reconfiguring an M30B35 harness to plug into an E28 for example. The engines are physically identical as far as I know, so all M50B25 sensors should go right onto an M50B20. But like I said, even better to swap out the whole engine.

[LazurE34]

Yeah, iknow... The m50b25 are very hard to come by and if you finally found one it would cost a fortune :/ (prices between 2500-3800$ for entire engine and 2200$ for only block and head + everything inside) those are very expensive engines in my country...

[Layne]

Yeah, iknow... The m50b25 are very hard to come by and if you finally found one it would cost a fortune :/ (prices between 2500-3800$ for entire engine and 2200$ for only block and head + everything inside) those are very expensive engines in my country...

Wow. Can you import from the US? They're like $300 here.

[LazurE34]

yes, but im kind of afraid of shipment and tax costs, since they just would shoot up in price after entering denmark... One of my friends payed 120$ for some headlights on ebay and the time it reached his house it ended up costing almost 500$ (Denmark really has some crazy tax problem, we even pay taxes on our taxes)

[XAlt]

yes, but im kind of afraid of shipment and tax costs, since they just would shoot up in price after entering denmark... One of my friends payed 120$ for some headlights on ebay and the time it reached his house it ended up costing almost 500$ (Denmark really has some crazy tax problem, we even pay taxes on our taxes)

I'd give it a shot, or try looking down south in Germany.

[LazurE34]

and even though throwing a 2.5l in my 2l, it wont pass the SYN (danish form of MOT every 2 years). since its highly forbidden to enhance engine output... Leaving it unroadworthy :/ i could try, since there is not much visual difference...

[LazurE34]

Thanks for the feedback so far... Back to the issue... It actually might be the DME not knowing when to spark or fuel and the vanoss getting the valves to open to early since nothing is controlling it, adding to the compression issue? is the camshaft position sensor different and/or giving it a different reading?? otherwise i will get the correct DME and try turning it again

Edit: didnt see B320is reply, sorry

[Layne]

Denmark really has some crazy tax problem, we even pay taxes on our taxes)

People always tell us Denmark is the happiest country in the world because your college and healthcare is free. I guess car parts aren't free.

- - - Updated - - -

Thanks for the feedback so far... Back to the issue... It actually might be the DME not knowing when to spark or fuel and the vanoss getting the valves to open to early since nothing is controlling it, adding to the compression issue? is the camshaft position sensor different and/or giving it a different reading?? otherwise i will get the correct DME and try turning it again

Edit: didnt see B320is reply, sorry

Most likely some of the DME pins are used for contradictory purposes. You can compare them if you can find wiring diagrams for the Siemens systems. I don't know where to find that though, I only know of diagrams for US models.

[LazurE34]

yeah... just having a car in general is expensive here... remember we pay 180% in taxes on top of cars... so if you want import a new car which costs 100.000$ you´re going to end up paying 280.000$... alot of people end up leasing cars instead or buying the smallest ones available...(vw up) and normal car parts have a more normal 25%tax

[B320i]

Make a note of all the part numbers on your original DME, post them here and search on eBay (etc) so as you can try out the correct DME and see if that works.

[LazurE34]

Already found one! just waiting for it to come with the mail
DME Numbers: Siemens 5WK9 002 MS40.1 (Part number 1738775.9)
Hoping it will fix the issue... Not as expensive as i expected... around 215$ used

[B320i]

When I bought my good spare, I paid US$135 for an MS40.1, 1703808 5WK9 002 DME.

Try and bargain the sellers downward in price if you can. And have a look on RealOEM to see if there are any DMEs that could be exchangeable. From memory, I think any MS40.1 can be swapped with any MS40.1, probably boils down to software revisions as product on the M50TU engines progressed.

[LazurE34]

Got the New dme installed, fired right up... yet, problems are not over... its running a very rough idle and crackles like crazy inside intake manifold... constantly changing between 200- 1500rpm... i know that the L shaped boot is cracked and havent checked the other vacuum hoses just yet... could it be a vacuum issue or something completely else? Been kind of bussy replacing fuel lines in the back, but just got it fired up
- Maikel

[XAlt]

Def sounds like a vacuum leak.

[B320i]

Idle on my 320i was all over creation once when I left the vacuum hose for the brake booster disconnected. Problem solved immediately when I reconnected it.

If you can't find any vacuum leak, just try disconnecting the MAF to see if that changes anything. If it does, you have a bad MAF. Could also be worth removing the ICV and cleaning it.

Mine has always had a personality after sitting a while and might splutter to life with ease and is a little rough at idle. Could simply be that yours needs a whip round the block to warm things up. Should at least help you figure out where the problems are.

[LazurE34]

Yeah... it was the u shaped piece under the manifold which had disconected and after idling for 30 min. She was purring like a kitten... thanks for the help