S52 OBD1 Conversion Complete...here's what I learned.

[95s52]

I apologize for such a broad question, but this place seems to have the knowledge and experience to assist my needs. I have done some research, but it looks like nobody has attmpted this.

Basically, I'm doing the opposite frrom what the OP did. I'll try to make it as simple as possible. I have an s50 that I am trying to throw into a 92 325is. I have the original 325is harness, but it's a non vanos. I also have a full s52 harness. I was wondering if there is a way I can use the two to make one I can use on the s50. Also, can I use my m50 ecu and then order a TMS chip and state that its for an s50 or do I need to get a 95m esu? Is it worth the hastle or should I bite the bullet and go out and get an approporite harness and an ecu. I would hate to spend the money and later learn I had all the parts needed to put this thing together.

Thanks

[ScotcH]

Your car is not OBD2, so using the s52 harness makes no sense. You need to buy an OBD1 vanos harness ... anything else and you're just asking for a lot of work and ass pain. Not worth it.

For the DME you need a 413 red label or a 506. The TMS chip will work with either (they are basically the same DME).

[G60 CAB]

Quick question. Since the OBDI crankshaft sensor is on the timing cover...is there a mount for it on the OBDII timing cover?

[///M3///M5]

Yes

[vinnymac]

Quick question. Since the OBDI crankshaft sensor is on the timing cover...is there a mount for it on the OBDII timing cover?

Yes, the casting are the same with the major difference being the coolant pipe. The OBD1 crankshaft position sensor will bolt on to either timing cover.

[Don Nguyen]

So I am about to do this as well, for one of my cars (actually going to be using the parts off of one car to convert the other to obd1 ).

So from what I have gathered from this thread, there have been some revisions of various things, from the original post made by vinny.

1. Valve Cover - The OBD2 valve cover does not have provisions for routing the coil pack connectors because the OBD2 cables enter from the passenger side and the OBD1 cables enter from the driver side. This is where you need to decide which route to go. You can keep your OBD2 valve cover, which allows you to keep your OBD2 coil packs or you can use an OBD1 valve cover which will require OBD1 coil packs. Either way is fine since both coil versions plug into the OBD1 harness. I choose to keep my OBD2 valve cover and will modify it slightly with a Dremel to route the wiring.

1. Modifying the valve cover is ok, to make provisions for the spark plug harness/wires.

2. Vanos Solenoid - The OBD2 Vanos solenoid wire connector is shorter than the OBD1 solenoid so you will either need to use an OBD1 solenoid, or keep your OBD2 solenoid and extend the cabling with BMW part # 12-52-2-274-971 to the engine harness. The BMW part is a transmission harness used to connect the engine harness to the back up light switch but it's perfect for the Vanos solenoid since the connectors are the same.

2. You don't need to get the vanos solenoid harness extensions.

3. Coolant Pipe - The main coolant pipe from the timing cover (back side of the t-stat housing) is different between OBD1 and OBD2. OBD2 cars use a metal pipe that is fixed in the timing case cover with plumbers sealant. OBD1 cars use a rubber hose that connects to an aluminum neck that protrudes from the timing case cover. You can either use an OBD1 timing cover ($100) or get a coolant pipe adapter ($20) from Bimmerworld, AA, or Turner Motorsport. The coolant adapter fits into the OBD2 timing case cover and is secured with JB Weld. This allows you to pipe clamp the OBD1 coolant hose.

3. Not too sure what the concensus was on this, as far as the coolant pipe goes.

4. Intake Manifold – This is where the “performance gain” from an OBD1 conversion comes from. The M50 intake manifold flows better than the OBD2 (M52/S52) intake manifold. You must use this manifold for the conversion. The OBD1 manifold will have a air temp sensor and vacuum port for the fuel pressure regulator on the underside closest to the firewall. The M50 intake manifold will bolt right up to an M52/S52 cylinder head without modification.

5. Throttle Body – You can use your OBD2 throttle body but you will need an adapter for the gasket seal. The OBD1 throttle body has a flat mating surface that clamps to a gasket on the OBD1 intake manifold. The OBD2 throttle body is the opposite and has a gasket in the throttle body that clamps to a flat mating surface on the OBD2 intake manifold. You can solve this problem two ways. You can get an adapter plate ($20) that sits between the OBD2 throttle body and OBD1 manifold, which provides a mating surface for both gaskets. The other option is a get an extended gasket ($15) that allows you to clamp the OBD2 throttle body directly to the OBD1 intake manifold. Of course, you can always use an OBD1 throttle body and not use any adapters.

4/5. Did the M50 manifold conversion on my car a long time ago, so I don't have worry about any of this.

6. Coolant Temp Sender – OBD2 management uses a single coolant temp sender on the cylinder head under the intake runner for cylinder #1. The OBD1 setup uses two temp senders on the cylinder head under intake runners #1 and #2. You can splice the main engine harness wiring together and use the OBD2 plug connector from your old wiring harness to connect to your single OBD2 temp sender. Another option, which is much cleaner, is to use the coolant temp sender wiring adapter ($50) from Turner Motorsport that is completely plug and play.

6. Just use the plug and play harness from TMS or tap it yourself.

7. Crank Position Sensor – The OBD2 crank position sensor is located on the engine block in front of the starter motor. The OBD1 crank position sensor is located on the timing cover and mounts on a circular tab with a 6mm allen bolt. You must use an OBD1 crank position sensor. Just leave the OBD2 sensor in place to plug the hole.

7. Use crank position sensor from OBD1 car, simple enough.

8. Fuel Lines – The fuel delivery setup is significantly different between OBD2 and OBD1. The OBD2 fuel rail has both fuel lines attaching in the rear near the firewall and the fuel pressure regulator is located forward of the fuel filter under the driver side of the car. The OBD1 fuel rail has the supply line on the front of the rail and the return line on the back of the rail near the fire wall. In addition, the OBD1 fuel pressure regulator is on the fuel rail itself next to the return line. You must use the OBD1 fuel rail for the conversion, which will require modification to the fuel lines. You will need to remove the OBD2 fuel pressure regulator from the undercarriage of the car and route new 8mm fuel lines to the OBD1 fuel rail. There is a pair of hard lines mounted to the chassis between the OBD2 fuel filter and engine bay. Simply bridge the gap left by the removal of the OBD2 fuel pressure regulator with new fuel line and connect the feed from the fuel filter to the front of the OBD1 fuel rail and the return line from the back of the fuel rail to the return line under the car. You will also need to connect the OBD1 fuel pressure regulator vacuum line to the one-way valve on the bottom of the OBD1 intake manifold. The connection is on the back corner of the manifold closest to the firewall.

8. Fuel lines do not need to be modified, OBD2 fuel rail can be used in the OBD1 conversion.

9. PCV – The OBD2 crank case vent is setup up differently than the OBD1 vent. There are several options to address this issue. If you are using the OBD2 valve cover, you can keep your OBD2 PCV setup and figure out a way to mount the breather valve (cone shaped plastic valve with round breather on top) under the intake manifold. If you are using the OBD1 valve cover, you should use the OBD1 breather valve that clips on to the crankcase vent port. The OBD1 valve has a vacuum line that connects to the plug that joins the ICV to the intake manifold and a large oil drain line that runs to the dipstick. The last option is a hook up a hose to the crankcase vent and run a breather catch can. I picked up a small length of 1” rubber hose and connected it to my OBD2 valve cover and hooked up the other end to the OBD1 breather valve and use a barbed connector to join the oil drain line to my dipstick.

9. I don't understand what needs to be done for the PCV. Isn't it fine as is, if you use the OBD2 manifold with the OBD2 PCV?

10. Idle Control Valve – the OBD1 and OBD2 ICVs are the same. You can reuse your OBD2 ICV. You will need to get the connector and hose for the ICV to intake manifold connection and the hose that connects the ICV to the throttle boot vacuum port.

10. I believe the ICV thing was taken care of in the original M50 manifold
conversion that I did a while back already.

11. Fuel Tank Breather – You can reuse your OBD2 fuel tank breather valve. You will need to get a couple fittings to connect the vacuum hose to the vacuum port on the throttle boot. I went to the hardware store and picked up 3/8” and 5/8” barb fittings and rigged something up to connect to the throttle body vacuum port.

11. Seems straight forward enough.

12. Oxygen Sensors and Secondary Air Pump – Only OBD2 systems have secondary air pumps. This emission control system is completely removed during the conversion. In addition, you get rid of your two precat OBD2 O2 sensors in the OBD2 exhaust headers and the two postcat OBD2 O2 sensors in the catalytic convertor so do not forget to get plugs for the ports. You’ll need an M18 bolt for the plugs. Any auto parts store should have them. FYI, the Toyota LandCruiser oil pan drain bolt is M18. OBD1 management only uses one precat OBD1 oxygen sensor.

12. The o2 sensors and secondary air pump no longer exist on my car, since it is FI.

13. Oil Pan & Dipstick – I kept hearing you needed an OBD1 oil pan and dipstick for the conversion. This is entirely false. You can use your OBD2 oil pan and dipstick without any issues or modification.

13. No need to modify the oil pan dip stick.

14. EWS – there is a lot of variability in which E36s have it and which ones do not. I used an ECU from a non-EWS vehicle but I still had some ignition issues after the conversion. There is an easy modification to the main engine harness to avoid any issues with EWS. You have to take the protective rubber boot off the connector to the ECU and cut wire #66. It should be solid green but it can also be black/violet according to the Bentley wiring diagrams. Just cut the wire and dress both ends with some electrical tape.

14. Just cut the #66 (green) wire to solve the EWS issue, during the conversion.

[clovold]

Quick edit - Before you read the rest of this I want to say that I got it going. It turns out that even with a 506 ECU you still need to cut the EWS wire!! Why did it start at all with EWS interfering? I have NO idea.

Hey all, this thread has been a great help in getting me through the conversion on my '98 M3, but I'm stuck with a car that is VERY hard to start. It takes 4 or 5 tries on the starter of 5 seconds or so each to get it fired up. It sputs and spits like a flooded engine and then finally roaors to life. Once running it idles solid and runs very smoothly (and with great power). It's hard to start whether the engine is warm or cold. I bought brand new fuel injectors (24 lb), knock sensors, cam sensor, crank sensor, plugs, and euro hfm. I have a 506 ecu with a Turner/conforti chip specific to my setup. After trying to start it for a while I pulled the plugs and they were all wet. I checked the resistence of the air and coolant temp sensors at the ECU and they were 2000-2100 ohms, which sounds about right for the temp it was at. Fuel pressure during cranking is 3.5 bar and drops to 3.0 bar once the engine is idling. I even swapped in a known-good ecu with a similar chip and it acts the same. This car was starting and running fine before the conversion.

I didn't cut the EWS wire because I had a 506 ECU. If this was a EWS issue it wouldn't start at all, right? I also did not make any changes to the wiring plug from the wiring harness to the chasis, but it soundls like I might need to for the CEL, but not really anything else.

What would happen if I had the knock sensors reversed? I never checked which was which because I thought it didn't really matter.

Lastly, to the above thread, yes that all seems right. For the PCV valve the only real change is that you need to tap into the hose from the ICV to the intake manifold and run a hose form there into the open hole on the PCV that used to connect to the intake manifold. That should already have been done in an M50 manifold conversion, though. And DO leave the hard coolant line in place. It makes it a little trickier to run some of the hoses, but it's much nicer and cheaper (no new hose or coolant pipe adapter needed). By not swapping it out I never had to open the cooling system on my car during the conversion.

[eye145]

Knock sensors should only come into play when engine is running and pinging is picked up. At that point the engine retards timing to help keep from detonating.
Knock sensor at ecu plug are: pin 70 cyl 1-3, pin 69 cyl 4-6.
Pull the boots back on knock sensor plugs and look at the wires, there is blue tape on cyl 4-6 and red or yellow tape on cyl 1-3 plug, but it is best to just check with a multi-meter to be sure.

[dhinez]

I'm doing the conversion into my 96 328i. I have the red labeled dme and harness from a 94 325. I have no spark or fuel. Fuel pump tested fine when I did the jumper test. I cut the EWS wire at pin 7 at the main round connector and pin 66 at the dme connector. I did notice the idle air control has a humming as if it has power with the key off. Please help. How do I test the crank sensor?

[joon]

First off, let me say this thread helped me a lot when I was doing my conversion last year

If you're doing this conversion, I highly recommend biting the bullet and getting all brand new sensors. You can't use any of the OBD-II sensors except the IAT and TPS.. if they are still good sell them to the OBD-II guys. The sensors you should get new are :
1. Crank sensor
2. Cam position sensor
3. O2 sensor
4. Knock sensor (2 pieces)

This will save you a lot of grief... When I did my conversion with used sensors, it wouldn't start and I was about to begin the whole troubleshooting cycle when I thought the hell with it... and went to get new sensors, it fired up right away and ran beautifully.

[clovold]

^ +1. Right on. Just bite the bullet; buy new sensors and be done with it

Oh, and check the ground wire coming out of the injector wiring rail. It must be grounded by the coil packs or you will be a no-go.

In my case EWS allowed fuel to flow, just no spark.

[cansis332i]

Where did the larger of the 2 hoses coming off of the PCV valve go to prior to your conversion? I am reassembling my 3.2 OBD1 motor and I have the larger hose marked as going to the dipstick and I thinks its correct. But others have said it is supposed to go to the T-Body boot. I am not running tractional control so I purchased the '95 M3 boot that has to holes in it. One hole is for the Idle Control Valve hose but I dont know what the second one is for. Does anyone know??

That is the confusing part. Some people post that the larger of the 2 hoses plugs into the second hole on the bottom of the boot, while other say it goes to the dipstick pipe. Trying to figure out which one is correct.

I second these concerns about the larger hose running from the PCV valve. I have a '94 325i, with an OBDI swapped '97 motor (M50 manifold), tranny, etc. The previous owner has this larger hose running from the PCV valve into the second hole in the throttle body boot. I recently replaced this boot, and I noticed that the old boot had a lot of buildup, which I'm guessing is from this line which is running from the PCV valve.

Do you guys recommend I plug this second hole in the throttle body boot, and rerun this hose into the dipstick tube? If it was supposed to run into the dipstick tube, it makes sense that it shouldn't be running into the throttle body boot, right?

My car has been running like poo lately. I just recently cleaned my ICV, so I'm thinking I have a vacuum leak somewhere. My car has also thrown a 1215 CEL code on occasion. A few times I have pulled over when almost all power would cut out and I moved some of these vacuum hoses around while the car was still (barely) idling, which seemed to help for awhile. I almost feel like tearing the intake manifold down and replacing all the hoses and gaskets... Anybody have ideas?

[dhinez]

Well, I did this again but this time with new sensors and I'm getting the same results. I cut the ews wire on both ends (dme and round connector). I also have a custom chip installed. The ICV has a small hum when the ignition is off and it stops when the ignition is on. I'm using a different ICV from when I first atempted this. I am now thinking bad DME? I have everything connected correct as far as I can see. Car cranks but doesn't atempt to start. I even tried to jump wire #8 (gray on X20 connector) to wire #1 (gray on the x6031 connector) to get my check engine light to work so I can diagnose my problem but that's a no go. HELP!!!!

[ELIBEEMER]

Dhinez:
There is black round terminal (From the harness)that plugs around the power terminal in front of the DME (from the DME) is that hooked up to Ground or to Power?

I made the mistake of hooking up mine to ground. Since it was black and round. my car wouldnt fire until i fixed this condition....

[dhinez]

Dhinez:
There is black round terminal (From the harness)that plugs around the power terminal in front of the DME (from the DME) is that hooked up to Ground or to Power?

I made the mistake of hooking up mine to ground. Since it was black and round. my car wouldnt fire until i fixed this condition....

Elibeemer,

Do you have pics of terminal at hand? there were two that were round and color coded black. One was closest to the diagnostic port and the other that was close to main power wire (real thick).

[warptkid]

I didn't touch the fpr on my conversion. I did have to make some slight modifications to the fuel rail mounting brackets to get to line up on the obd1 manifold, but that was it.

I have two wires dangling off my wiring harness, they are for the "running losses" thingy that is next to the Fuel pressure regulator & fuel filter... the wires are white/blue and brown and have no plug...

question: do I have to plug splice a plug onto the wires or can I just let them hang --- do I NEED the 'running losses' circuit???

[clovold]

The OBD1 wiring harness doesn't have a connection for that, and mine has been running fine with it disconnected.

[Eryan36]

I'm looking at doing this in my '95 M3, using the S50 (popped) as the donor motor. I assume this should be easy(ish), since the wiring harness is already in, and I'll have all the necessary sensors and such. Am I right in assuming this? In this case, is it pretty much pull my motor, pull the sensors, put them on the S52, swap the manifold, put the S52 in my car. Yes?

[Don Nguyen]

Yes.

[Eryan36]

Word.

[Dave V]

Digging up an old thread here.... I want to put a 2.5 M52 from an e39 in my e34 which is OBD1, just a couple of quick questions.

Can I use the OBD2 intake? I havnt got one from a 2.5 yet and don't think the one from my 2.0 will fit.

Will I need a chip?Im going to use the e34 525i ECU Im not aware of one thats made in europe, and our octane is different to the US.

[JimmieG]

I have done the s52 swap into a 92 non vanos changed the harness it was out of a auto. Got a euro hfm and tuner chip for 21.5 injectors & the hfm but the car would not fire up no injector pulse and no spark swapped the stock chip back into the red label 413 and it fired right up.The chip tuner sold me is the 41313009 I didnt think I would have any ews issues since the car is a 92 and the harness and red label dme are non ews.

Jimmie

I guess I will cut #66 etm shows it going to on board computer. I will call TMS also and get the skinny.

Jimmie

[JimmieG]

Well tuner sold me the wrong chip and they took care of it and overnighted the correct one got it in today and the car runs very strong. I have a air mass code. Bought a 3.5 hfm from a member here he said it was new but when I got it it was pretty dirty and had dirt on the inside also not a good sign.

Jimmie

[Tim95M3]

Here's one for you guys. I have a 5/94 M3 thats now totaled, and another "totaled" 7/97 that i'm putting my whole driveline in. The 97 was an automatic, and the 95 was a manual. Obviously the engine harnesses are completely different, where the 97 has 3 round connectors by the fusebox, and the 95 has only one. Currently the car will not crank. Wondering what kind of mods ill have to do to the 97 harness... I already cut the pin 66 green wire on the ECU. Im lost

[328iJunkie]

You have to rewire the console to make the car think its a manual. Think park safety switch.