OBD-I s52, has spark and fuel, but won't start

[sushipower]

Do you have the earth strap that is located underneath the engine cover?

http://www.realoem.com/bmw/showparts...08&hg=11&fg=15

[JGood]

Do you have the earth strap that is located underneath the engine cover?

http://www.realoem.com/bmw/showparts...08&hg=11&fg=15

There's 2 coil pack ground wires, the ground wire coming out of the front of the fuel injection harness, the main engine ground to the chassis, and several grounds near the DME. All have been triple checked.

[atldohc]

Not saying this is the cause, bc it sounds unlikely to me as well, but check your valve timing. All you have to do is pull your valve cover and see if the two squares on the cams near the firewall are level after lining up the crank pulley mark to the one on the timing cover (tdc). You can find more info on how tos on this on the pelican, dr vanos, and beisan systems websites. Again probably not the cause, but it's good to eliminate possibilities

[JGood]

Not saying this is the cause, bc it sounds unlikely to me as well, but check your valve timing. All you have to do is pull your valve cover and see if the two squares on the cams near the firewall are level after lining up the crank pulley mark to the one on the timing cover (tdc). You can find more info on how tos on this on the pelican, dr vanos, and beisan systems websites. Again probably not the cause, but it's good to eliminate possibilities

Since the motor hasn't been touched since it last ran, it would be impossible for it to change. It's not something that can "slip".

Also, if the squares on the cams are level, your engine is nowhere near timed right. The top side of those squares are not what is used for timing. They are not parallel when the engine is timed correctly, as the angles of the "squares" on the cams are not 90 degrees, they are more of a parallelogram. The side of the squares are used for timing (perpendicular to the head surface), and you need the cam block tools to check this.


Example:

[jrdeamicis]

So your getting spark? And fuel? Well that just leaves ... Air!

Give it a solid O2 sensor and unplug the MAF. Reverse and repeat.


So you converted it to run OBD1? using an OBD2 Intake or OBD1?

When you say back firing its backfiring into the intake?

[JGood]

So your getting spark? And fuel? Well that just leaves ... Air!

Give it a solid O2 sensor and unplug the MAF. Reverse and repeat.

Already tried a different MAF, and tried leaving it unplugged altogether. No way an O2 will prevent it from starting. Hell, my car ran better without the O2.

[jrdeamicis]

I am not saying that the O2 will prevent it from starting, but you need to know what helps and what doesn't.

You have 2 parts of a 3 part equation.

What harmonic balancer are you using? Stock OBD1 Crank position sensor?


So you are using the 17.5 Injectors?
OBD1 Fuel Rail?

And the intake question of course?

[Good & Tight]

You guys are over thinking, the engine ran before and was untouched. My engine had the same exact symptoms, back firing and all and it was the main relay.
Not sure if it was mentioned, fuel feed line connected to the front of the rail right.

[atldohc]

Ok anybody reading should disregard my last post then. I did use the holding tools when I replaced my vanos seals and from what I remembered the ends were squared, and I also noticed a little play in the sides of the holding tool, but I may have been mistaken. Anyways I would suspect the harness/wiring if it's the only thing that changed. You may need to bust out some wiring diagrams. Also never tried this on the s52, but on many cars you can simply spray carb cleaner with injectors disconnected through a vac hose and the car will run fine. I've done this on A car before that had fuel pumping out the feed line yet wouldn't start, in the end needing a new fuel pump. I can't recall if you tested the pressure or volume yet.

[JGood]

What harmonic balancer are you using? Stock OBD1 Crank position sensor?


So you are using the 17.5 Injectors?
OBD1 Fuel Rail?

And the intake question of course?

The same parts that were on the car when it ran fine. Nothing was touched.

[Danny]

I think G&T may be onto something

[JGood]

You guys are over thinking, the engine ran before and was untouched. My engine had the same exact symptoms, back firing and all and it was the main relay.
Not sure if it was mentioned, fuel feed line connected to the front of the rail right.

Yes, feed to the front. Tried it the other way just for the hell of it.

With the return line unhooked, I'm getting fuel spraying out while cranking. That means the rail is pressurizing and the regulator is letting the excess out, so it's functioning.

I am very interested in the main relay though. I will try that ASAP.

[jahnaboi]

Mixed fuel lines (spark plugs still get wet that way) or mixed up relays/bad relays. Its one of those two.

[JGood]

Swapped relays, no go. As stated multiple times, fuel lines are hooked up correctly, and I swapped them and tried it anyway, still no go.

We're going to do a compression test next.

[samiam3356]

Fuel filter, pump?

Could have worked before and somehow take a shit at the same time, I guess. Seems like everyone is throwing darts I just wanted to throw some to.