Need advice from experience for an M42 rebuild

[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]

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

[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.

[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]

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?

[JonsE30]

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

[Victell]

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

[roguetoaster]

You can take the injector rail assy out, place each injector in a bottle and crank once you disable the ignition system for safety. This will clearly show you any faults.

Are the injectors unknown or known working?

You can also clean injectors to some degree if it comes to that.

[JonsE30]

thanks for the advice guys. i got some free time while the kids were away. i unhooked the fuel lines and reversed them back. there was a little bit of pressure in the lines so i tried to keep a rag there from preventing it getting everywhere, but there was still some light splashing. i wiped off as much as i could then let it dry for a few hours.

i plugged the battery back then tried to start. it turned over but still didn't catch. i did the stomp code again and the 1216 tps sensor was cleared now, but now i got a 1252 which i researched is fuel injector #2 issue. one of the threads said it was due to no current/voltage going to that injector, but i tested it with the light tester and it was fine. does it mean the injector itself is bad or clogged? is this enough to prevent the car to start?

[JonsE30]

Thanks so much. I'll check that next!

[roguetoaster]

The hose that comes from the top of the tank to the fuel filter can be replaced if you just lower the tank.

You need to verify fuel supply at both sides of the fuel filter then at the connection to the rail. If you have it to the rail but not at the rail you have the supply and return lines crossed.

[JonsE30]

pulled each spark plugs and cranked while it was sitting on the intake manifold and all showed Sparks. when I pulled them they all look wet with oil probably from when I tried to prime the engine for the first time during the first cranks with no fuel. the fuel pressure regulator has the vacuum hose attached. more troubleshoot I've done: so I took the upper intake off and pulled fuel rail out. I bought a circuit tester light to check for power. I took off each injector off the rail expecting fuel to leak out but it was dry. I tested all 4 leads and they all have continuity. the fuel hose for the return line was the one leaking from the clamp so fuel was at the rail. i tried cranking without the injectors on to see if fuel would come out the 4 holes out of the rail but nothing came out. I am so confused. if there was fuel in the return hose, is it safe to assume the pump gets gas to the feed line through the rail and back to return line? I checked again under the car and the hose that connects to the back of the fuel filter up through a hole in the chassis then what looks to clamp to a hard line near the top of the tank is leaking. there is foam around that clamp and it's damp and soggy. do I need to drop the tank to replace this hose? I am so lost. can this leaking fuel hose be the cause of all the fuel supply issue at the rail and with the injectors?

[Victell]

A few things I would check:

- Make sure your fuel pressure regulator has the vacuum hose attached.
- Check to make sure you're getting spark
- Pull a couple spark plugs and make sure they are not wet with fuel, could be flooded.

[JonsE30]

Did more research and found out the fuel pump doesn't "hum" in there cars. I took off the upper intake and the left one on the black hard line was seeping fuel when it flexed a little bit so I clamped it down. But that tells me the fuel pump is working and getting to the rail. I got under the car and checked the lines again and it looks like there is cracking on the hose from the pump to the rear of the fuel filter. I pulled up the rear seat and checked the pump and lines there and no leaks but I'll need to fish out the bad hose and get a new one in there. Still no start so do you think it's the fuel pressure regulator, injectors, wiring harness, crank position sensor?

[JonsE30]

found out the main wiring harness was not fastened all the way down so the pins were not making contact with each other. i sorted that out and all the relays clicked and the i was able crank and pump the oil until the light went out. i then put back fuse 11 and fuel relay and tried starting it again. it did not start but now i found a little puddle of fuel under my car and it was coming from the fuel filter? could this be me mixing up the fuel lines that go into the fuel rail? UPDATE: I checked real OEM and my fuel lines are going to the right peg on the fuel rail. I tried it again and it only leaks as soon as the engine cranks. I didn't touch the fuel filter or pump during my rebuild, so I'm not sure if I messed up anything hooking up the lines under the hood?