93 Bmw 318i crank but no start help

[Slomochino]

Hello everyone I'm new to the forums. I had just purchased my first bmw a few days ago and when i first bought it, it ran well when i had bought it so I took the car to get smogged. I was told the car had failed and was suggested by the technician that I should change oil and spark plugs and wires. I do what he says and changed the oil,spark plugs and spark plug wires. However when i went to turn the car on, the car would crank but wouldn't start. The car has an m42 motor so it has individual coil packs so I assumed the coils went to the cylinder they were pointing too (however I looked at previous posts and they said a different firing but I'm confused about that, we also checked if the fuel relay would activated when turning and it did. We also checked to see if the fuel pump activated didn't hear the fuel pump making a noise. This was our first thought was that the fuel pump when bad. I have no idea what else to check. Can someone lend a hand?

[ed323i]

Yeah, coils and cylinders should be in the same order, aligned. Should be good.

What you want to check is if you have a spark. Remove one spark cable, and plug an old spark plug in it. Then make the spark plug touch a good ground point on the engine (bare metal).. See if it sparks.

If it sparks, you know the DME, DME relay and probably most injection electronics under the hood get power and are working. Also the DME gets a signal from the crankshaft position sensor.

If it doesn't spark, check if the coil pack receives +12V. Disconnect the big coil pack connector, and, with ignition on, try to find +12V on one of the pins. Use a multimeter (buy one if needed) and connect one of the leads to a coil pack connector pin (wiring harness side) and the other lead to a known good ground point, like one of the 3 bolts on the shock tower.

If you find +12V, then DME is working, DME activates DME relay (which is working) and all electronics under the hood get power. But somehow the DME can't find a proper RPM signal from the crankshaft sensor. Then it won't spark, won't inject, and won't activate the fuel pump relay. Probable cause is the crank position sensor (or wiring)..

This should get you started. Good luck!

P.S. Forgot to mention: Do not shock yourself while testing for spark. You won't die, but you won't like it either. Use something insulated to protect yourself (for example rubber gloves, or some insulated tool/clamp)

[Slomochino]

Yeah, coils and cylinders should be in the same order, aligned. Should be good.

What you want to check is if you have a spark. Remove one spark cable, and plug an old spark plug in it. Then make the spark plug touch a good ground point on the engine (bare metal).. See if it sparks.

If it sparks, you know the DME, DME relay and probably most injection electronics under the hood get power and are working. Also the DME gets a signal from the crankshaft position sensor.

If it doesn't spark, check if the coil pack receives +12V. Disconnect the big coil pack connector, and, with ignition on, try to find +12V on one of the pins. Use a multimeter (buy one if needed) and connect one of the leads to a coil pack connector pin (wiring harness side) and the other lead to a known good ground point, like one of the 3 bolts on the shock tower.

If you find +12V, then DME is working, DME activates DME relay (which is working) and all electronics under the hood get power. But somehow the DME can't find a proper RPM signal from the crankshaft sensor. Then it won't spark, won't inject, and won't activate the fuel pump relay. Probable cause is the crank position sensor (or wiring)..

This should get you started. Good luck!

P.S. Forgot to mention: Do not shock yourself while testing for spark. You won't die, but you won't like it either. Use something insulated to protect yourself (for example rubber gloves, or some insulated tool/clamp)

I did the spark plug test and all 4 were firing. So it could be the crank position sensor?

[ed323i]

No, the crank position sensor should be fine, otherwise the DME wouldn't know when to fire the coils..

So, you're very probably looking at a problem with the fuel supply. It can be either:
* Fuel pressure regulator bad
* Fuel pump bad (or fuel filter completely clogged)
* Fuel pump relay bad
* Bad fuel pump fuse (number 18 if I remember correctly)
* Wiring to/from fuel pump - fuel pump relay bad

When you crank the car, you should hear/feel the fuel pump relay "click".. If it does, then see if the fuel pump receives +12V (it's under the rear seats). Measure with multimeter to see if it receives +12V and if you can hear/feel it spin if it does. You can also bench-test the fuel pump relay. Search on youtube how to do that.

If that's all okay, then it's best to check the fuel pressure in the fuel rail. You probably need a T-piece that you connect to the fuel rail inlet (not outlet, which has no pressure), and then connect a fuel pressure gauge to it. Then crank it (or just supply +12V to the fuel pump). Not sure about the 4-cylinder pressure but probably should be 2.8 bar at idle and 3.5 bar at WOT.. Or perhaps 0.5 bar less (both values).. If there is not enough pressure then either the fuel pump is bad (or perhaps fuel filter clogged) or the fuel pressure regulator is bad.

Good luck!

P.S. You can also spray some starter fluid in the intake boot, while WOT and cranking. Then it should combust. Then you know 100% sure it's a fuel supply problem.

[Slomochino]

No, the crank position sensor should be fine, otherwise the DME wouldn't know when to fire the coils..

So, you're very probably looking at a problem with the fuel supply. It can be either:
* Fuel pressure regulator bad
* Fuel pump bad (or fuel filter completely clogged)
* Fuel pump relay bad
* Bad fuel pump fuse (number 18 if I remember correctly)
* Wiring to/from fuel pump - fuel pump relay bad

When you crank the car, you should hear/feel the fuel pump relay "click".. If it does, then see if the fuel pump receives +12V (it's under the rear seats). Measure with multimeter to see if it receives +12V and if you can hear/feel it spin if it does. You can also bench-test the fuel pump relay. Search on youtube how to do that.

If that's all okay, then it's best to check the fuel pressure in the fuel rail. You probably need a T-piece that you connect to the fuel rail inlet (not outlet, which has no pressure), and then connect a fuel pressure gauge to it. Then crank it (or just supply +12V to the fuel pump). Not sure about the 4-cylinder pressure but probably should be 2.8 bar at idle and 3.5 bar at WOT.. Or perhaps 0.5 bar less (both values).. If there is not enough pressure then either the fuel pump is bad (or perhaps fuel filter clogged) or the fuel pressure regulator is bad.

Good luck!

P.S. You can also spray some starter fluid in the intake boot, while WOT and cranking. Then it should combust. Then you know 100% sure it's a fuel supply problem.

Thanks for the advice.The relay clicks and the fuse is still good. Whats weird is the car almost turned over when we hit the gas tank. We tried the method with spraying fluid in the intake( We actually used carb cleaner but it should be the same) but it sounded like a hose popped and the car still didnt turn over. I ordered a new fuel filter and fuel pump so i hope its that.