M52b28 swap. No start after swap

[jwindbigler]

Car: 1993 BMW 325 5 speed
symptom: Cranks for days but does not fire

Story: Since the getrag syncros were going, I found a doner car. A 1998 328i. So instead of swapping just the transmission I swapped the engine too. I'm using all the obd1 electronics. DME, crank sensor, cam sensor, knock sensor, one of the temp sensors (since there wasn't a second hole for the other), and the vanos solenoid. Both engines ran and drove prior to the swap. I feel in missing something. Could 1/2/4 seem to be furring but 2/5/6 don't. It's acting like it's out of time. It will occasionally give a puff. But never fire up.

Im using all the obd1 stuff. The M50 manifold, throttle body, wire harness, using the OEM red label 413 DME. Both engines are vanos engines.

Ive got it at a shop and I'm trying to help him troubleshoot it, but we're kind of stumped. In theory it should fire. Any sort of assistance would be helpful. This is my first M52 engine swap.

Justin

[M3blitkrieg]

Using obdl injectors?

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I'm not a experienced guy with this swap so hopefully someone will chime in that does? Have you compared the flywheel tooth pattern for differences?

[jwindbigler]

I'm using the pink top 24 lb injectors that were on the doner car instead of the green top 19lb injectors that were original to the car. I haven't compared number of crank pulley teeth as I already sold the M50. But that thought did cross my mind. On the obd1 conversion thread it does not mention a need to swap crank pulleys.

[M3blitkrieg]

Check all the first steppers? Fuel, spark, act.

[jwindbigler]

Yup. It's firing 1,2,4 but not 2,5,6 for some reason. I did have a bad Bavarian autosport coil pack, and since swapped that out for an OEM one (temporarily). It's something electrical. Something that when doing the swap changed. Crank and cam sensor are working and sending signal to the DME. I'm really curious if that second temp sensor needs to be plugged in for the engine to fire. It doesn't make sense to me, but I'm curious about it

[Eric93se]

The cam sensor is different, different technology and I think dimensions as well. The crank sensor maybe be different as well. You have to find out how people put an OBD2 engine in an OBD1 car.

Also be aware that the fuel pump has to be upgraded, your old one will not feed the new motor sufficiently.

[jwindbigler]

Cam, crank, and knock sensors are OBD1. Switched them over. Also switched the vanos solenoid.

Now the fuel pump is interesting. You're saying that my M50 pump doesn't have enough capacity to start the M52?

[Eric93se]

At high RPM it will not provide enough fuel

[flyfishvt]

Stock fuel pump will be fine. Its the same pump that's in the S50

[jwindbigler]

So which is it? I'm looking to get it dyno tuned as well as soon as it runs. Possibly raising the rev limiter. Will I need an M52 pump then?

[M3blitkrieg]

Do you have the coil ground straps on the rear set of coils as well as the front? I would check the coil leads and then the dme for signal and voltage. Double check the grounds, plugs, engine ground strap.

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The original fuel pump should be fine. Unless its going bad but it has nothing to do with spark so what's it got to do with anything at this poinot? As long as it gives FP appropriately, its fine.

Edited for spelling.

[Richard81]

I'm using the pink top 24 lb injectors that were on the doner car instead of the green top 19lb injectors that were original to the car. I haven't compared number of crank pulley teeth as I already sold the M50. But that thought did cross my mind.

This is potentially one of the big issues here. A 24lb injector flows 26% more fuel per injector cycle compared to the 19lb one. That could overfuel the engine on a startup, enough to flood and not have a start. Actually no, its a 2.8 now so that should be fine.

But....you are starting your 2.8 engine with a 2.5 ecu. Timing may be an issue. You need to check this.

The car can start and run badly on 3 cylinders. So those should not be almost catching.

I take it you retained the M52 engine's 2.8 fuel pressure regulator. That will work with an M50's fuel pump.

Please ohm out the crank sensor. It shoudl read 540ohm +- 10%. It can go bust during major swaps. Basically other things can go bust during major work even if that work was done properly. Old stuff.

Check that you get continuity from the dme clamp to each of your ignition coils. Wires might have broken. Check continuity from the clamp to the crank sensor connector too. And if I were you, I would check for the injectors as well. Wiring can break and right now everything needs to be checked. Check the crank sensor's resistance through the clamp to simultaneously confirm the wiring's integrity, the crank sensor, and that these two are correctly connected to each other. Nothing should be misconnected.

Can you smell unburnt fuel in your tailpipe after you crank for some time without the engine catching? If you can't, then fuel is not being injected. Fuel pump, fuel pump relay, or crank sensor.

It might be a good idea to unplug your cam sensor for the time being. Reduce the variables involved.

Ohm out all your coils too. Resistance values are in the manual.

Basically go to town with a digital multimeter.

It might be a good idea to reoil your chambers in case all the oil has been washed off by flooding. Pull the fuse and crank a few times, or if need be remove the plugs or lift up the fuel rail and spray some wd40 through the injector ports, works well. Faster than removing the coils and plugs.

I'm sorry, lotsa ideas thrown out here, some might already be covered. Please organize them in a smooth way and check through everything. If both engines were confirmed running before the swap, then there's no reason why it shouldn't work now. Compression for M50 and M52 is the same.

p.s. You won't get the full potential of the new engine until you retune your ecu. A 2.5 ecu cannot max out a 2.8 engine. It would have been better to swap the M52's harness and 2.8 dme. They may sell off the shelf chips for this which you can use in your M50 ecu. Those DIY swap threads that you saw, you can post there and ask them if a chip is available. GL.

[jwindbigler]

Thank you for the ideas. I'm not sure how timing would be different. Don't they share a common timing system?
I plan on getting my 413 dyno tuned after it runs.

[carwiz008]

Yup. It's firing 1,2,4 but not 2,5,6 for some reason

So 2 is or isn't firing? And how are you checking?

[FiberFast]

So 2 is or isn't firing? And how are you checking?

Well there is the problem, its a 5 cylinder. its a typo, he thinks 3,5,6 aren't firing.
I hope you get to the bottom of this cause I am picking up a 325 with a non functioning half swapped m52b28... Inquiring minds would like to know.

[Richard81]

The cam sensor is different, different technology and I think dimensions as well. The crank sensor maybe be different as well. You have to find out how people put an OBD2 engine in an OBD1 car.

The non vanos and vanos M50 engines had different cam sensors. The nv was a normal cam sensor, the v was a hall-effect cam sensor. They literally worked differently and the "timing plate" attached to the camshaft is different as well. When you do a conversion from nv to vanos by changing cams and adding a vanos unit, this plate needs to be fixed there too.

There's a good chance that the M52 had the same hall effect sensor since it came on the later vanos M50. You can check that out later but for now best to leave it unplugged.

Also be aware that the fuel pump has to be upgraded, your old one will not feed the new motor sufficiently.

This is not an issue. Fuel pumps put out pressure at around 72psi. This is standard across the board no matter what car. Its the regulator that steps down the pressure for that particular engine / engine capacity. M52 should be 50psi-ish I guess. So as long as he's using the regulator from the M52 he's good with the M50's fuel pump.

[Richard81]

Thank you for the ideas. I'm not sure how timing would be different. Don't they share a common timing system?

I'm not sure its just a risk that's best ruled out. So i asked you to check that out.

And please check off all the other items on the list I suggested, then get back to this thread. Maybe do that before checking on timing. If timing was an issue, good chance one of the swap threads would have mentioned it. But check eventually.

The engine swap is a very complicated thing. It puts your head in a 'everything has to be complicated' space for awhile. So you might be looking for difficult problems to this no start. Its far more likely that its a very simple problem. A wire broke, the crank sensor was wrongly connected, crank sensor died, fuel pump regulator's gone, etcetra. So check off all that stuff on my list first. Will take you about half hour but after that you know these things are good for sure if they're good.

Until then we're just speculating which is a waste of time and does not fix anything.

p.s. Oh, and make sure the temp sensor that you're using is the brown tipped temp sendor for the dash gauge and not the is the blue tipped coolant temp sensor. Though the blue sensor is more important to the car, for the short term you need to monitor engine temps more easily. We can swap in the blue sensor after you've run the engine for abit and all's good. We'll need to think of a way to get the brown sensor to come online - you need a constant engine coolant temp readout.

[jwindbigler]

I've heard that turner motorsports makes an adapter plug that allows you to use the 4 pin OBD2 temp sensor. So I may run that instead.

Didnt get a Chance to get out to the car today. I'll start knocking off the little things.

Believe me, I'm pretty sure it's something stupid. Wasn't trying to over complicate things. I came on here to see if I missed a step. It appears that I have. It missed a step, but rather had something go out on me mid swap. I'll start troubleshooting the stuff above as soon as I can.

Thank you for the assist.

[FiberFast]

I've heard that turner motorsports makes an adapter plug that allows you to use the 4 pin OBD2 temp sensor. So I may run that instead.

Didnt get a Chance to get out to the car today. I'll start knocking off the little things.

Believe me, I'm pretty sure it's something stupid. Wasn't trying to over complicate things. I came on here to see if I missed a step. It appears that I have. It missed a step, but rather had something go out on me mid swap. I'll start troubleshooting the stuff above as soon as I can.

Thank you for the assist.

Curious if the obd2 injectors are a problem. It doesn't seem to me that they would be an issue unless they require more voltage or something.

[Richard81]

Curious if the obd2 injectors are a problem. It doesn't seem to me that they would be an issue unless they require more voltage or something.

Voltages are the same, just the size of the nozzle would be different. Its an on-off signal from the dme and when it is commanded on and how long it stays on depends on the fuel map built into the dme.

And i wondered about the bigger injectors too, then realized that the engine is a bigger engine compared to his old one so that should compensate for the extra fuel even during startup.

And finding it tough to go past a certain low rpm usually means fuel or air starvation. More likely fuel starvation because weak pumps can be inconsistent but blocked airboxes are consistent. But the airbox and air filter ought to be checked for thoroughness.

[FiberFast]

Voltages are the same, just the size of the nozzle would be different. Its an on-off signal from the dme and when it is commanded on and how long it stays on depends on the fuel map built into the dme.

And i wondered about the bigger injectors too, then realized that the engine is a bigger engine compared to his old one so that should compensate for the extra fuel even during startup.

And finding it tough to go past a certain low rpm usually means fuel or air starvation. More likely fuel starvation because weak pumps can be inconsistent but blocked airboxes are consistent. But the airbox and air filter ought to be checked for thoroughness.

Pumps are all the same.

[Richard81]

wah?

[ddtech]

Well there is the problem, its a 5 cylinder. its a typo, he thinks 3,5,6 aren't firing.
I hope you get to the bottom of this cause I am picking up a 325 with a non functioning half swapped m52b28... Inquiring minds would like to know.

I would also like to know too. I also have an engine where it's non-functioning - difference is that I don't know the internals. (Will start a thread on that though)

Btw: fuel pumps may be similar, but I wanted to know. So I checked the ETK at bmwfans.info and cross ref'd those numbers with pelican and they are not the same. Fuel delivery unit 16-14-1-182-842 (92-95, maybe 96) and 16-14-6-758-736 for post '95 and up (part number changed in 2001). I used my 94 M50 sedan and my 97 328is coupe for reference. M50TUB25 and M52B28 do not use the same fuel pump.

wah?

[FiberFast]

I would also like to know too. I also have an engine where it's non-functioning - difference is that I don't know the internals. (Will start a thread on that though)

Btw: fuel pumps may be similar, but I wanted to know. So I checked the ETK at bmwfans.info and cross ref'd those numbers with pelican and they are not the same. Fuel delivery unit 16-14-1-182-842 (92-95, maybe 96) and 16-14-6-758-736 for post '95 and up (part number changed in 2001). I used my 94 M50 sedan and my 97 328is coupe for reference. M50TUB25 and M52B28 do not use the same fuel pump.

I wonder if you can run the obd2 fuel pump with the obd1 dme? That's the real question. I'm pretty sure the 3.0l obd1 m3 used the same pump though, I looked those up several places and at least the bosch one were all the same.

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I wonder if the OP ever figured this out...

[Richard81]

Fuel pumps

- Different part numbers for fuel pumps does not necessarily mean different output pressures for the pumps.
- All fuel pumps are permanently switched on as long as the engine is running. There is no dynamic management by the dme. So different DMEs will not have any problems with different pumps.
- Fuel pumps put out substantially higher fuel pressure than the car needs. Usually 5 bars.
- Fuel rail pressure is stepped down and maintained by the fuel regulator which is set to a pressure only that particular engine and engine capacity requires. Usually between 2.5-3.5 bars. So a 320 and and 328 may have the same engine, but because the capacity is much higher for the 2.8, the regulator will typically be rated higher. Typically 0.5 bars higher.
- The pump's vastly higher fuel pressure is there to ensure enough pressure remains for the engine even after fuel is pushed past a tough fuel filter.
- So, as you can see, the fuel pump can put out 4 bars, or even 10 bars. It doesn't matter as the regulator will step it down to the right level for the engine. The pump just has to be strong enough to push past the fuel filter and have enough excess pressure for the regulator to step down.

Injectors

- Circuitry wise, all fuel injectors are the same. OBD2 injectors were not specially redesigned versions of the OBD1 ones. So it is meaningless to speak in terms of OBD versions. The only way to distinguish them is by the fuel flow ratings in pounds of fuel flowed per hour.
- The only difference is the #age, and that's only controlled by the size of the nozzles at its tip. So a 19# injector has tinier nozzles than a 24# ones. If the current stays on all the time, in one hour, the second injector will output 26% more gasoline than the first one.
- The current sent by the dme to the injectors to have it open, is like super low. That's because the solenoids the current has to energise are extremely tiny. They are the smallest solenoids in use anywhere in the car.
- A solenoid is an electromagnet. Remember that experiment in school where you wrapped wire around a small iron bar, flipped the switch and then the iron bar could pick up metal stuff ? I.e. move stuff ? Something similar happens in the injector. Either it uses its electromagnetism to pull open a gate. Or the whole thing moves open. Can't remember which.


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I hope that resolves all doubts about the injectors and pump situations.

In this case, the OP is using his old pump with his new engine. But it probably outputs the same pressure as the new pump so it doesn't matter. He is using the new higher rated injectors, but also with the new regulator, with his new higher capacity engine. Put it all together, shouldn't cause a no start issue here.