No Start - Cranking - No Fuel - No Spark

[nc6carlover]

I know there are other posts on this as I have read them and printed them out to use but I'm still at a loss.

1985 e24 Manual trans.
Car is stored. Start car every week or other week for about a year now. Will drive up and down street occasionally. All has been fine until a week ago. This is where I am:
Battery fully charged, approx 13volts
there is Power to fuel pump relay - tested
there is Power to main relay - tested
there is No power to #11 fuse - tested at fuse box. Fuse is good.
there is No power to either fuel pump
Power is going to coil - tested
No spark from coil to spark plugs or distributor cap
Fuel injectors are receiving power around 11.7 volts
Did a jump on fuel pump relay, car still did not start (before attaching jump, no volts at #11fuse(fuel delivery), after attaching jumper was getting around .04 volts at fuse outlet)
Have switched different relays to fuel pump outlet, no change.


Q: What prevents power from going to fuse #11? Based on diagram, at run/start the fuel pump relay gets power and sends it to rest of fuel delivery system.
Could it be the switch? Even if its reference sensors they would not prevent power from running thru the system?
I have read other posts here and printed them for use but I'm still at a loss. Any advice?
Lets start there and I will check based on comments and give feed back. Thanks.

[Brucey]

from memory this sounds like it might be a fault with the OBC immobiliser relay; this disables the fuel pump if it goes faulty (and yes, they do go faulty).

cheers

[nc6carlover]

Thanks Brucey. I will research the immobilizer in OBC.

[BenM635i]

My OBC immobiliser started playing up so I had to resolve, PM me if you need to know more.

[nc6carlover]

Update:

Based on posting on other website I did the following:
Tested speed and reference sensors. On both sensors this what I found:
Pins 1 and 2 = 1026 ohms
Pins 2 and 3 = no value
Pins 1 and 3 = no value

The info stated I should have a value from 850 to 1064 ohms for Pin 1 and 2. Looks like im good there.
Pins 1 and 3 along with Pins 2 and 3 I should have a minimum value of 100,000 ohms. Looks like that is not the case.

Could this mean that both sensors are bad? Please advise. Thanks.

[Brucey]

it looks like

a) your sensors are good and

b) that you don't quite understand how to use a DVM.

BTW you should be absolutely certain that you reconnect the sensors properly; if you inadvertently exchange the positions the car won't go.

FWIW you could randomly check every single part on the car until you found a fault of some kind but it would take ages..... BTW there is not much point in mentioning fuse numbers and diagrams unless you say which diagram you are referring to; Fuse allocations can vary on E24

The best thing to do is approach the problem logically; for the car to go you need

- sparks
- fuel pressure
- some injector function

Since Motronic effectively has two separate fuel injection systems on a cold start (being main injectors fired by the ECU and cold start injector (CSI) fired by an analogue system during cranking) then if the car doesn't even splutter when you crank, this is usually symptomatic of

- no sparks

or

- no fuel pressure

It is very easy to test for sparks during cranking, using a spare spark plug connected to the king lead.

If you have CSI function (and fuel pressure) then the inlet manifold will absolutely stink of fuel after a failed cold start; the CSI should emit about 20cc of fuel per second during cranking. Whip the induction boot off after a failed start and look for the strong fuel smell.

You can confirm good sparks on cranking by squirting easy-start (or just raw fuel) into the induction system; whilst cranking you should get some spluttering.

If you have no sparks, then you start testing sensors etc.

cheers

[BenM635i]

Mine would randomly fail to start / spark.. few days later would be ok.

If your immobiliser acts up you may get no spark despite having power at the coil.

[nc6carlover]

Based on the things I have tested so far I can say that I have no spark.
I have no smell of fuel nor do I have any power going to the fuel pumps to cause them to run.
Fuel injectors are getting power.
Coil is receiving power.
I will re-test those again and let you know what I find.
As far as fuses go, on my e24 fuse #11(per BMW e24 troubleshooting manual 1985 and 1986) in the fuse box is specifically noted as being for fuel delivery system. When I test the fuse there is no power going to that fuse location from the fuel pump relay.
I checked the relay and its getting power. The relay seems good as well. I used the jumper that is recommended and got nothing.
It will crank thats all.
I do not smell fuel at any point in this process but I will go back thru it.

In my view, something is preventing spark from the coil and power from the fuel pump relay to the fuel deliver fuse thus to the fuel pumps. If I can figure that out I will solve the problem.
Lastly, I agree I am not great with a DVM but I'm learning.
Thanks everyone.

[EmperorNero]

Update:

Based on posting on other website I did the following:
Tested speed and reference sensors. On both sensors this what I found:
Pins 1 and 2 = 1026 ohms
Pins 2 and 3 = no value
Pins 1 and 3 = no value

The info stated I should have a value from 850 to 1064 ohms for Pin 1 and 2. Looks like im good there.
Pins 1 and 3 along with Pins 2 and 3 I should have a minimum value of 100,000 ohms. Looks like that is not the case.

Could this mean that both sensors are bad? Please advise. Thanks.

no value means that there's either extremely high or infinite ohms. the sensors are fine.

[daz635]

If the injectors have power that would indicate that the OBC and the main relay are Ok passing power

if the coil has power at teminal 15 this indicates that the ignition switch wiring is ok

If you jumper the fuel pump relay 30 to 87 does the fuel pump run. Ensure you have the correct relay as the fuel pump relay and the oxygen sensor relay are exactly the same and BMW had a habit of moving them to different spots. Socket 30 is hot all the time so jumpering it with 87 should cause the fuel pumps to run.

The motronic unit is responsible for opening and closing the fuel pump relay as required as you can see from the diagram attached ( fuel pump only operates when starting or running). if you have tested the speed and reference sensors which it looks like you have I would be looking at the wire from the starter to the motronic unit. This wire is black and yellow and sends a start signal to the motronic unit. Without this signal the fuel pump will not operate and no timing control signal will go to the coil as the motonic unit does not know that the car is trying to start.

Main Relay 635.JPG (155.44 KiB) Viewed 7064 times

Fuel Pump 635.JPG (166.22 KiB) Viewed 7064 times

[Brucey]

the 'start signal' (Bk/Yl wire which goes to pin 4 for the ECU) also appears at the diagnostic socket (Pin #11, see p101 of 1985 ETM). The most common fault with this is that the connection of this wire (to the starter motor where the signal is derived) goes bad.

The ETM (p115) is misleading in that it looks as if there is just one wire going to the starter motor pull-in coil, but IME they usually have two wires; one to power the pull/hold-in coil and a second skinny one (piggybacked to the first) to 'sense' that the signal goes to +12V during cranking. It is this wire which often just falls off.

cheers

[nc6carlover]

Thank you to everyone that is trying to help. Here's what I've done since seeing some of the posts:
Went back and re-checked that I had a spark. I connected a spark tester and witness the light in the tester to confirm I had spark.
When I used the jumper in the fuel pump socket (if correct term), I noticed I had voltage at the connector to the in-tank fuel pump. (with the fuse in I did not have power at this pump).
I then checked the external pump to see If I had voltage. It did not but I realized that it would only get voltage at start. I was alone so I could not confirm. I did come back with some help and tested for voltage as the car cranked and had no power at pump.
With that I decided I would disconnect the pump and connect an external power source to make the pump come on thus indicating the pump was functional. I tested the wires I was using to connect to the pump and they showed 12v so i am sure the appropriate amount of voltage was provided to run the pump. The pump was silent, not a sound, nothing.
With this I'm hoping that this is the real source of my problem. I also know that if there is a reason this does not indicate a faulty pump, someone here will point it out and why.
I look forward to hearing thoughts on this latest finding. Thanks again everyone.

[Brucey]

if you have volts at one fuel pump and not the other, it most likely means that the wiring (at the back of the car) is faulty, since they are fed by the same wire and should both run at the same time.

cheers

[oilcooler]

i'd like to know how this issue was resolved.

my 84 635 euro also has no spark and no fuel pressure, random dying, and also random starts...no fun. i know it's not the ECU, fuel and main relays, fuel pump, distributor cap and rotor. i checked the small gauge black/yellow wire that runs from/to the starter that supposedly connects to the ECU pin #4. so my next step is to dig into the OBC immobiliser relay box, but i need to know the location of the OBC relay box.

what other OBC immobiliser relays are compatible with my 84 635?