No Start after fuel injector rebuild

[gespinal0301]

Quick summary of what I've done. My car kept throwing a lean code so I started to dig in to things. I checked for vacuum leaks and there were none, I realized the code would go away if I give the car some throttle so I figured it was something fuel related. Went ahead and tested fuel pressure and it was right around 40-45 psi at idle and would rise if given throttle (taken after fuel filter). I went ahead and replaced the fuel filter cause I was already there and started to dig down to my injectors to see if they were firing correctly.

So I removed the airbox and upper intake manifold where I found that the fuel injector connector clips were missing and the connector wasn't fully seated. I figured might as well just rebuild the injectors since I'm here and remove 30ish years of carbon and grease build up. While i was lifting the fuel rail out the injector wiring box snapped in half and I had new fuel injector connectors laying around so I went ahead and soldered the new connectors in.

I removed the rail and injectors. Disassembled my fuel injectors, made a fuel injector pulser circuit with a 555 timer, opamp and fet to cycle them while I dropped them into an ultrasonic cleaner at work for about 15-20 minutes. I put new orings, spacers and baskets into them. Also, since I had the fuel rail out I went ahead and ordered a new FPR. One thing I didn't notice until now is that the FPR is 3.5 bar instead of the standard 3.0 bar and I'm not really sure if this would affect the fuel system greatly.

After everything was installed back into the car I left the car sitting in the ignition position to build a little pressure and started cranking. I would crank in bursts of about 5 secs over a course of a minute and the car still wouldn't start. I think that would be enough time to pressurize the system in order to get it to fire not 100% sure though.

So I removed the manifold and checked to see if each injector is getting power and they are. The fuel rail had fuel in it, but it didn't really burst out so I'm thinking that I didn't let the pressure build for long enough which I'm hoping is the case.

Any other ideas to see if maybe I'm just overlooking something?

[PshlosE30]

Although i have years to fool arround with an M42,on M50,there is a brown ground wire that coming out of injectors box...If you dont ground it on block,the injectors will not fire! happen to me one time and i spent 3 hours of searching WTF was happening,also happened to other r3v members as well :P. As for letting pressure to build up,it will be build it in 2-3 secs even during cranking... the easiest thing to do is just unbolt the rail from manifold and while it is wired on car,put it on a tower or paper and crank 2-3 times to see if the injectors are spraying... Also are you sure that you connect the fuel hoses at right order? If u connect them backwards,it will not build pressure...

[bmwman91]

The M42 is set up differently. There is a 12V wire going in (from the main relay), along with 2 wires which go to the Motronic. Those two wires are switched to ground by the Motronic to fire the injectors.

A 3.5BAR FPR is not likely to break anything, but it will make you run rich for a bit until the O2 sensor can adjust the fuel trims. The Bosch 3BAR FPR is sold out nation-wide it seems, leaving the overpriced Genuine BMW one as the other option. Rock Auto sells some other OE branded ones which would probably work fine.

When you say that you had to solder on new connectors, what exactly did you end up doing? The terminals are/were crimped onto the original wires.

Anyway, if you don't see fuel being injected from any of the injectors then I would bet on either an electrical issue, or maybe something got reassembled backwards into all of the injectors.

[gespinal0301]

I don’t think I have the fuel lines mixed up the return is the one that connects to the leftmost port, the fuel line itself has a curve in it as well. Since the bracket bolts up to the lower intake manifold I don’t think I mixed them up. If someone has a pic to share please do just to make sure I’m okay.

I cut the original injector harness from the back of the oe connectors stripped back the wire and soldered in the new connectors. Before I put heat shrink over the joint I tested for continuity between the pin of the new connector and joint to make sure the connection was solid.

When I took it apart I did notice a kink in the fuel supply line. I might throw it back together tonight and try firing it to make sure I didn’t just move it into a bad spot when I put the upper manifold on.

[gespinal0301]

So still no start. I decided to try to see if I had continuity between the ECU connector and the fuel injector connectors.

Using this diagram I found online (pin 1 being in the bottom right) I probed the 3rd position from the bottom right to see if I had continuity between injector 2-4 and did the same for pin 32 (injectors 1 & 3). What I found is injectors 2-4 are on pin 32 and injectors 1-3 are on pin 3. I'm assuming by switching them they should fire in the correct order, but please correct me if I'm wrong.


Also, how do I embed images in my posts???

[varg]

Make sure the pump is running and you're getting fuel by disconnecting the return and putting it in a jug. If you're getting fuel make sure the injectors are firing, either pull the rail and crank with the injectors spraying out into the air or build yourself an injector test light with an LED and a resistor. If no injector pulses, check for power on C191 at the pin described in the etm. With the injectors firing, it should start, whether the pairs are reversed or not.

[gespinal0301]

rigged some led's into each connector since this was the easiest first step and they are pulsing. I'm going to check for fuel tomorrow and report back. When I did take it apart last time there was fuel in the rail though.

[gespinal0301]

Tested fuel pressure on crank and its around 40-45PSI on supply side before the rail. Last thing to check would be for spark which I'll test later on today then.

[gespinal0301]

I have spark as well. I'll post videos of everything Im testing, but maybe my fuel injectors aren't firing??

[bmwman91]

Man, this is an odd one. Yeah, I think checking the obvious (fuel injectors actually injecting) makes sense. I can't help but think it is somehow related to the rewiring of the injector harness box since that's sort of the only "odd" event in all of this. Granted, you were running lean prior to that, so maybe the mid-current driver IC in the Motronic took a dump. I don't think I have ever seen a failed one, but it isn't like I work with them for a living. Anyway, report back after testing that the injectors inject fuel when assembled on the car and I guess we will go from there!

[gespinal0301]

Honestly that thought is haunting me if I messed up the re-wire haha I don't know why I didn't think of this, but I can have a friend send me the injectors and wiring from the spare motor I have if I can't figure this out myself or if the injectors/wiring is bad. I'll post a video of the connectors (with LED's) firing as well as the fuel pressure on the supply side before I test the injectors themselves to see if there is something weird that I'm not catching.

On another note if it is an issue with an IC on the ECU would the parts be obsolete by now or are there equivalent replacements? Asking just in case I need to make a digi-key order in the future. This may actual give me the motivation I need to finish my MS3X project that I've had for way too long now!

[bmwman91]

The ICs are custom Bosch parts and I have never seen a reputable source for them. Used E30 M42 Motronic units come up on eBay for $50-80 pretty often.

[gespinal0301]

Here are the videos before I try putting the injectors into bottles. Just want to make sure I'm not missing something obvious. Sorry about the crappy angles but holding my phone and starting the car aren't the easiest things to do haha

One of the links will show the spark and the other fuel injection/pressure.

https://www.dropbox.com/s/cu69dv46wz..._3134.MOV?dl=0

https://www.dropbox.com/s/y9gln3xa2wpjpfn/IMG_3152.MOV?dl=0

[gespinal0301]

Forgot to update this, but I found out that only 1 out 4 injectors was actually spraying any fuel. I tried given them a light whack to loosen them up but nothing is coming through. Im having a friend send a set of spares and them throwing them in

[bmwman91]

Yeah, I just had this happen to me as well...all 4 injectors stuck shut. I had mine cleaned and flow benched 3-4 months ago, and then they sat until last week as I waited for parts and whatnot for my engine rebuild+reinstall. I got it all together, went to start it and...nothing. Cranking and cranking, no combustion. After checking every single sensor and connection, fuel pressure and verifying that the ignition coils were firing, I finally decided to pull the intake and injectors to test them. Sure enough, no clicking to be heard when pulsing them with 12V. Whacking them on the bench and giving them an ultrasonic bath of alcohol also did not help. I sort of needed to bump up to higher flowing injectors anyway, so I exchanged them with Sssquid Tuning (who cleaned them the first time). The fresh ones make a nice firm click when pulsed with 12V, so they went right into the car and once I burn the updated tune I'll (HOPEFULLY) be up and running.

I never would have thought that fuel injectors would be prone to getting stuck closed, but as I have looked around more online, it sounds really common. Basically, letting them sit dry for any significant amount of time carries a good chance of sticking them. If they are totally clean and dry, one theory is that atmospheric moisture causes a very very thin layer of rust to form, which sticks the needle to the port. If there is residual cleaner or lubricant in them, it can oxidize and get a bit varnishy. The solenoid in them is not super strong, so a small source of stiction seems to be all it takes to render them non-operational.