DME relay plug (socket) with a burned wire

[xxxJohnBoyxxx]

I always thought the relay in the DME compartment was the unloader relay. It is active during start since all interior lights, radio, a/c and such are off during the cranking process, as soon as the car starts the main central relay is active to run all accessories and lights.

Guess I learned something new today

John S

[alika808]

Originally Posted by Shellback

reason mine fried: I accidently swapped relays.
I removed the SAP relay and installed a Fuel pump relay. Never again!

+ 1 here, Sometime ago, I bought a car so cheap, 1998 318ti/$400.00/80,000 miles because the owner's mechanic cannot figure out what to do next after the car won't start. I found out their mechanic installed a wrong relay into the SAP and fried the brown wire (ground) inside the wire harness bundle. I repaired the brown wire and replaced the camshaft sensor. By the way, their mechanic try to troubleshoot the fuel pump and replaced the SAP relay instead. To make my story short, turn around and sold the car 4 times the total expenses and purchase price. Lesson learn, make sure the relay is the specification and the same part number.

[ilokano]

After analyzing the schematic diagram the DME relay PIN 86 and 30 should be hot at all time (12 V) coming from the power distribution, and when switch on, The DME PIN 27 sends a signal to PIN 85 of the DME relay to bridge PIN 30 and 87 then sends a 12V to fuel pump relay PIN 86 . While the switch is still on, DME PIN 63 gives a signal to fuel pump relay PIN 85 to bridge PIN 30 and 87 and sends a 12 V to fuse #18 15A to run the fuel pump motor. With this schematic diagram I don't see the camshaft sensor connected going to the fuel pump relay but only gets 12 V from the DME relay but unless the camshaft sensor gives a signal to the DME to let PIN 63 sends a signal going to the PIN 63 of the fuel pump relay. Anyway I'll try to change my camshaft sensor to to see how it does.

[ilokano]

As I check in my relays It seems that there is no signal received on my DME relay coming from pin 27 to PIn 85. Could it be the crankshaft sensor that activates the PIN 27. But looking again at the schematic, the crankshaft sensor gets 12V on DME relay PIN 85.
Here are the list that gets power on the DME relay PIN 87:
1) fuel injection valves of cylinder 1 to 4
2) Evap emission valve
3) intake resonance change over valve
4) idle speed control valve
5) camshaft sensor
6) hot film air mass meter
7) carbon canister valve
8) fuel change over
9) secondary air pump valve
10) secondary air pump relay- PIN 86
11) fuel pump relay-PIN 86

[alika808]

Originally Posted by ilokano

With this schematic diagram I don't see the camshaft sensor connected going to the fuel pump relay but only gets 12 V from the DME relay but unless the camshaft sensor gives a signal to the DME to let PIN 63 sends a signal going to the PIN 63 of the fuel pump relay. Anyway I'll try to change my camshaft sensor to to see how it does.

Yes, the camshaft gives signal to the DME and do the rest.

[alika808]

Make sure all your relays are good. You can manually check the serviceability of the relay in applying power and hear the clicking sound or continuity present when power applied. I recommend to replace the crankshaft sensor. I think you check by ohms with multimeter with at least 500 ohms but it's that accurate. The most accurate is use the oscilloscope by checking the wave signal while starting the car. I know it's pain in the butt to replace it. It's located near the starter and you don't have visual to do it. Just use your imagination.

[alika808]

If the crankshaft sensor won't the solve problem then I am leaning to check the DME (ECU).

Here are the most common symptoms of a bad ECU
1. Check Engine Light stays on after resetting
2. Car was jump started on reverse polarity
3. Engine turning off for no reason
4. Water Damage or Fire Damage on the ECU
5. Apparent loss of spark
6. Apparent loss of injection pulse or fuel pump
7. If your alternator overcharged the battery
8. Intermittent starting problems
9. Overheating ECU
10. ECU has Broken Pins
11. Loss of communication between the ECU and the Scanner
12. A control module memory checksum error

Many other symptoms may occur that can drastically lead to an ECU failure such as:
1. Erratic idle
2. Stalling
3. Poor running condition
4. Excessive fuel usage

[ilokano]

I'm little bit confused, what should I replace ? Is it the camshaft or the crankshaft sensors?

[alika808]

Crankshaft

[ilokano]

Went to a BMW dealer to order the part and just have to wait till it arrive.BMW is poor in its design, it's too hard to get to the crankshaft sensor coz it's sitting below the starter and have to remove a lot of parts to get to it while older model is just by the crankshaft pulley. Don't have any idea why they relocated it. While waiting for the part I might just change the water pump, thermostat, oil filter housing gasket, timing chain gasket, cylinder head cover gasket and the crankshaft seal, I see oil leaking.

[alika808]

You have to remove it from under the car.

[ilokano]

Installed the crankcase sensor and no luck still don't run but it looks like it wanted to run.I checked for the cylinder compression and found out that 3 cylinders has no compression at all so, I took the head out and to my surprise the head bolts are torque 22 ft. Lbs , the valves leaks and has a warp head (learned my lesson to check for spark, gas and compression before anything else). I've just did the head shaved (DIY), the valves to make sure it sits properly and still waiting for the valve seal to arrive. Will keep updated when installed ( hope this time it runs)

[ilokano]

After putting all back together and tried to start it, "holla" the car runs and idles smoothly. I want to thank everyone especially alika808 on giving me help and I will also be giving advice to the best of my knowledge. The next project will be changing the rear subframe. (Total expenses on this project is less than $300) again thank y'all