Need advice from experience for an M42 rebuild

[Victell]

Sometimes Ill use a couple sprays of starting fluid to see what happens.

[JonsE30]

do you spray starting fluid in the throttle body assembly when throttle is open?

[JonsE30]

some busy weekends lately but got a chance to try that test that roguetoaster and try to put water bottles under the fuel injectors and try to crank and see what happens. i tried cranking it for a bit and it didnt spray a lot of fuel out. i tried cranking again, then took out the water bottles and its like a few droplets. i put a dry rag and laid it like a blanket under all 4 injectors and cranked again and it's faint discoloration from fuel. like its not spraying, more like trickling? i still get code 1252 doing the stomp test.

does this mean my injectors are bad? the condition is unknown, i mean when i pulled them out almost 2 years ago when it still was running, then cleaned them before i put them back. could code 1252 mean a bad injector or is it like the wiring for the pulse trigger bad?

[bmwman91]

I believe that code 1252 is caused by an electrical fault where the Motronic detects that not enough current is drawn by the injector(s). The mid-current driver IC in the DME provides a feedback signal to the controller, and the ones for the injectors seem to need to detect at least 1A of current being sunk (IIRC) in order to signal proper function.

If all of the injectors are barely spraying any fuel, then there is virtually zero chance that this is a fault with the injectors themselves since they are not all going to fail at once. What voltage do you measure at these 3 locations, after putting the key into Accessory-2 position:
1) At the fuel pump across the power input terminals
2) At the injectors (if you pull the electrical rail and probe between ground and the terminals for the injectors)
3) At the power distribution block on the firewall. Not on the large lower part with the ~15mm wire, which is for the starter/alternator, but on the smaller lug above it where a ~5mm black wire connects. This is a separate wire run from the battery which is for the injection electronics.

If it all reads normal when just sitting in accessory power mode, then you could try #3 while a buddy tries to start the engine to see what it drops to. I am guessing that you are seeing a power brown-out in the injection circuit due to corrosion or fatigue on the ~5mm wire, about 15" forward from the battery where a 50A fusible link is installed on it. It is notorious for seeing failures at the crimp connections and causing really stupid, hard to resolve issues like this. That is, if you have an iS with the battery in the trunk...sedans with the battery under the hood didn't have it.

[JonsE30]

Thanks bmwman91 i will bust out the meter and check on these. i've come this far so i can't give up yet.

[JonsE30]

Update: she’s been sitting in the garage since our state was ordered to self quarantine at home. I put everything back together, charged the battery, installed it then tried to start her again. This time it caught and it sounded like it was choking. The first time there was a loud of loud clacking coming form the intake manifold area or maybe the valve cover. It eventually died. I remember reading that the sound could be the lifters because they need to be lubed up. We tried it again and this time it sounded really rough but it kept on trying to revive itself. I am scared that i f—ked up something during my assembly but I’m almost certain i double checked everything. I manually cranked it while on the engine stand to make see if the piston and valves had enough clearance and it didnt sound like this when i cranked it to pump the oil to the case. Here is a video, can anyone shed some light on this? It doesn’t look like there’s any holes blown through the case or head, no leaks, no white smoke coming from this exhaust. I’ve read it could be a rough idle from bad icv, fuel pump, chain tensioner, so many things. I pulled the valve cover and everything looks ok. The chain looks tensioned no loose bits that i can see in there. Also looked like steam or something burning off from the valve cover area.

https://youtu.be/CIm6fkZufWE

[bmwman91]

Based on the video, I would say that it sounds a lot like your timing is off by a tooth or two. That loud clacking / "diesel" sound is valves and pistons colliding. It's a distinctive sound that the M42 makes which brings back memories of late nights and frustration! However, you may very well be fine. I messed the timing up on an M42 back in 2006 in the same way and thought it was drained lifters, and even drove it around the block before figuring out the mistake. The engine made it another 7 years before dying to a failed timing chain sprocket, and it was 7 years of me beating the snot out of the thing. So, the M42's lash adjusting lifters do give it a surprising tolerance for what is usually an instant head rebuild. I mean, a valve could be bent, but it is not guaranteed. When I made the mistake, I also remember turning the engine with a wrench and not having it get stuck. But, I do recall thinking that it must have had really good compression since it got hard to turn every 180 degrees, which was just me forcing the pistons into the valves and (luckily) the lifters had enough travel to deal with it.

Anyway, assuming the timing is off, you need to verify that everything is properly aligned. After aligning the cams and crank at TDC did you turn the engine over by hand a few times and re-check it? If you just "set it and forget it" then things can easily not be at TDC once some tension is put into the chain and it is able to take a set in the sprockets. Usually it is not nearly enough to cause interference, and IIRC I was off by like 2 teeth when I had the issue, but it's also just good practice to double check after turning it.

Walk us through the procedure you used / use for setting the cams and crank to TDC.

Also, when you installed the timing chain tensioner piston, did you decompress it either before installation or by pushing on the tensioner guide rail after?

I hate recommending this, because "shit is about to get real" when it comes up, but I'd run a compression test after verifying the timing is set properly and running it up to normal operating temperature. I can't tell from the audio in the video if it sounds like a valve is bent, and it's usually sort of a low burbling noise as combustion products make it back up the intake, but the idle was stable enough that I'd give you 70% odds of being OK.

[JonsE30]

From what I recall, i lined up the split tooth of the crank pulley facing the timing case marker by the oil filter housing. When i installed the cams, cam lobes closest to the cam gears point towards each other, with that rear of the camshaft sitting flat. i had the cam gear arrows pointing up with respect to the angle of how it sits in the engine bay with that slant.

[JonsE30]

At this point, would it make any sense to redo the timing or did i just botch everything and the damage is already done and I am back to square one and gotta rebuild everything again?

[roguetoaster]

Recheck that you have the E marked cam on the intake side. Check for timing mark agreement with cam position. Verify TDC 1 with a dowel down a plug well when aligned on the marks. Check your plug wire order.

Don't freak out.

[JonsE30]

I’ll check on those items tomorrow. Thanks.

[bmwman91]

Recheck that you have the E marked cam on the intake side. Check for timing mark agreement with cam position. Verify TDC 1 with a dowel down a plug well when aligned on the marks. Check your plug wire order.

Don't freak out.

Yup, always good to verify that the piston is properly at the top with a sharpie and dowel!




I'd not use the oil filter housing arrow for much besides rough alignment. If you have any 8mm rods or long-ish M8 bolts, you can also set the crank to TDC with the hole in the block that grants you access to the lock hole in the flywheel (assuming you still have a stock M42 FW). Still, as Toaster said, the dowel method is reliable and I'd double check things that way no matter what.

I'd just check the physical timing first before making any other moves. If it is not too far off then you could be fine, even with interference occurring.

[JonsE30]

Sounds like a plan. I have a flywheel locking pin that i can use. And ill take some pics of the crank pulley and the cam gears and run it by here. Thanks guys!

[JonsE30]

So I hand cranked until I can get locking pin inserted: I checked the cam gear markers and they look like this:the one on the right maybe should be pointing a tooth more to the left? Cams look like this:

[roguetoaster]

You want to aim for centered in the cam windows and flat relative to each other across the back of the cam squares.

Perhaps I have been doing a no-no, but I've had good luck setting the chain in place, ever so slightly backing off the cam bolts and rotating the cam square with an adjustable wrench until flat, then tightening the bolts.

Also, I ignore the cam gear arrows and just remember to keep the cam position sensor dowel indexed as stock (down and left IIRC when voewed from the front).