E30 wont start

[Kocka]

Hello,

2 weeks ago I bought my first e30 and I love it . It was in drivable condition and everything, but now it won't start.

I checked the fuel pump (connected it to the battery) and it is working. I also blowed pressurized air through the fuel filter. I used multimeter to check if 12V are going to the fuel pump and its not. If I use jumper wire on the relay socket (where relay sits) I get 12V on the fuel pump connectors. If I put back the relay nothing (0V or close to 0 on the pump and no clicking on the relay itself). I checked the relay on a battery and it is working-klicking. Also the relay socket gets 12V if I turn on the key.
Can bad crank position sensor cause relay not to work properly (cut the power to the pump)?

[arrisbmw]

firstly . our cars only run the pump when the engine is cranking. NO PRE PRIMING LIKE A Modern Car.
in answwr to your Q yes . if the crank sensor is knackered , it wont tell the ECU ENGINE TURNING , therefore no pump.

have you check the main relay dme ... that send power to the fuel pump relay . and injectors and icv

you can temporary bridge the relys . but i cant remember how you need a wiring diagram to work it out.

look on here wiki for more info

if you remove the back seats , you should be able to hear the pump running while someones carnks the engine.

have you check for a spark at all 4 plugs ?

3 rrasons car wont start air , fuel or spark period

[arrisbmw]

if your cps is knackered , you wont have a spark . another test your rev counter should flicker when you crank engine , proving impulses are coming from it
and check your rotor for tracking . ( black marks or cracks ) needs to be removed to check properly.

[Kocka]

Ok i will take another look on the rev counter when i get home. I remember before even if i turn the key to 2nd position the pump could be heard. Its sn older car so the pump is at the rear left wheel. And engine was replaced with m42b18
Under the back seat is this. I dont think it a pump. I think its a guage for the odometer fuel level

This is the pump and the filter

[arrisbmw]

your car has 2 pumps. 1 in the tank and one under the car .

the pump in the tank has rubber hoses coming from it. as in first photo.

the sender only has wires to it.

https://www.r3vlimited.com/board/showth ... &p=4072478 this might help

look at the diagram . main pump is in the tank check out colour wires .

auxiliary pump is, in line , outside under car . iirc the pre face lift car had an extra pump. up 1987 approx

[arrisbmw]

As you can see in the wiring diagram the pin 30 on fuel pump relay is live .
but the power to the coil inside the relay is made live from the dme relay . then the f.p relay is controlled by the ecu . to ground it and make the circuit.
so both the dme relay and the f/p relay must be good for the circuit to complete. plus the control from the ecu finally switched the f/p relay on, throu fuse 11. confused yet ?

[Kocka]

As you can see in the wiring diagram the pin 30 on fuel pump relay is live .
but the power to the coil inside the relay is made live from the dme relay . then the f.p relay is controlled by the ecu . to ground it and make the circuit.
so both the dme relay and the f/p relay must be good for the circuit to complete. plus the control from the ecu finally switched the f/p relay on, throu fuse 11. confused yet ?

Nahh it's totally understandable. I will replace/check all 3 relays under the windshield and check the CPS and the fusible link. I dont have fuse 11 in the box, but I saw another fuse outside the box and I tested it if its connected to the fuel pump relay and it is. So thats my fuel pump fuse. Fuse is 30A but it should be 7.5A right? Is it possible that so much current flew through the fuse (because external fuel pump was whining before it stopped working and the negative screw (-) didnt have cap/protector on it and it was all coroded and on the top of the fuel pump relay pins that lets current to the pump was little blackish ) and that led to shorting out the fusible link or the main relay? But if the main relay failed, I shouldn't have 12V on the fuel pump relay when I turn the key to 2nd position right? I suspect the CPS is bad because its all covered in gunk and the wire is realy hard . I measured the pin 1 and 2 od the CPS and its showing arround 500 ohms. I will clean the magnet side of the cps and try again.

You said ecu turns the relay on throu fuse 11. I think fuse 11 just lets the power from the relay to the pump. Multimeter makes a beep sound if i connect one side of the fuse and a relay.

[arrisbmw]

You said ecu turns the relay on throu fuse 11. I think fuse 11 just lets the power from the relay to the pump. Multimeter makes a beep sound if i connect one side of the fuse and a relay.

yes your right .


I shouldn't have 12V on the fuel pump relay when I turn the key to 2nd position right
YES BUT pin 30 0n fp relay is live from battery
(not going throu dme main relay ) look at wiring diagram

pin 86 on f/p relays comes from the dme relay.

when you say 3 relays there are only 2 in this circuit ..... main relay ( dme ) and the f/p relay .

i.,m not sure what size fuse you should have . 15 amp i think but check in your handbook or google it or wiki om here , it not 30 amp.

[arrisbmw]

if you got corrosion on the wires that could well be your issue.

I think 500 - 550 is correct for cps . but does not prove its working .

[Kocka]

if you got corrosion on the wires that could well be your issue.

I think 500 - 550 is correct for cps . but does not prove its working .

And it was. The car is running again .
I've cleaned the terminals on the fuel pump and connector and installed everything back on the car. I've jumped-started the fuel pump relay and I was surprised it didn't kick in. After couple of seconds it started working but it shut off fast. So I folowed the power wires to the back seat. Ground wire that goes on the chassis was corroded and grounding point wasn't good so I cleaned the surfaces and bolted it back. Positive wire was also coroded where 2 wires join. I've cut that out and reconnect the wire, changed 30A fuse to 15A and started the car.

But now my rev counter doesn't work everything else works on the vdo odometer. I will google it and try to fix it...

[Oseanosea]

Nice work! Thank you for explaining your troubleshooting results. Grounding issues are a common cause, but aren’t always easy to track down.

[arrisbmw]

glad you got it sorted. its often the basic things that are the problem . but not easy to find.
and you have learn more about how your car works. on the electrics

[Contours]

I had to relocate fuel pump fuse 11 outside of the fusebox as well as the wire burned out under the fusebox. Maybe the same happened to your car. A strange occurrence and the fuse itself didn't blow either. It is a 7.5 amp fuse for the fuel pump circuit.

[Kocka]

So I'm gonna replace auxiliary pump + fuel filter and I saw there are more types of these pumps (pressure specs: 0.1 0.2 and 3.0 bar). I checked the oem e30 318is m42b18, it has 3.0 bar main pump so I'm going with 3.0 bar auxiliary pump. I tried to find main pump for my tank online but cant find one (all I found is facelift pump with removable level sender unit) . If you look at my pump in the 4th post there is no removable part of the pump. I checked realoem and bmwfans for the pump but it looks different then my pump... can someone point me in right direction for main fuel pump... I checked the output on my main fuel pump connectors if I remmeber correctly one pin had 12V, second had some small voltage (probably for level sender unit) and 3rd is probably ground I forgot...

[martauto]

Nice work! Thank you for explaining your troubleshooting results. Grounding issues are a common cause, but aren’t always easy to track down.

What he said

Mart.

[Joe26]

Hi I'm new to the e30s and i have the same problem but i can't figure out how to get access to the wires where they connect to the internal fuel pump as its not working, i need to check for connection as i jumped my external fuel pump and it worked and i even checked my relay and fuse which are both good so the only thing is the wireing. I removed the fuel level 'cap' that is situated under the rear seat but can't see how i can get access to the inner pump and wire terminals. Any help? Thankyou in advance!

[Brianmoooore]

Welcome to the E30 zone.
Not all E30s with an external fuel pump have an auxiliary pump in the tank. If there are only three wires going to the unit under the RH access cover in the seat base, then you don't have two pumps, Five wires means you do have two pumps.
It would be better if you start a new thread of your own in this forum as it can get VERY confusing when others piggyback their problems onto an existing thread.

[Joe26]

When i removed the cap i only found the fuel level gauge but there are fuel pipes like the previous picture but i cant find where the wireing is. I only can see the leveller wires. My question is where i can trace the +ve wire that goes to the external pump. Thankyou in advance for your help!

[Brianmoooore]

The two pipes are feed to the external pump and fuel return pipe from the fuel pressure regulator.
Wire to the external pump is green/purple and runs down the front left corner of the cabin, back the LH sill, onto the rear seat pan, and then down underneath the car.

[Joe26]

Ok thankyou that helps alot. I have an m10b16 carburated not fuel injection but it doesn't have a fuel regulator. Is that normal or i need to fit one ? (Attached is a picture of the cap) Thankyou in advance!

[Joe26]

Hi, i found the wires but i had no luck with power. Ground is good but there is no 12v coming in from the green wire. I checked fuse number 11 and no power aswell but the relay has all 4 from 5 12v so the relay is good. Any knowledge why is this ? And fuse is new.

[Brianmoooore]

You'll spend a long time looking for the electrical supply to the fuel pump on a 316, because it doesn't have an electrically powered fuel pump.
The only fuel pump is mechanically driven by the camshaft, and is mounted on the cylinder head.

[Joe26]

But It has the eletrical pump fitted to the LH side under the tank and found the eletrical wires going to ut but just no power. Currently it is running on the camshaft pump but wanted to convert it to an electric pump and it has everything just bo power to the fuse.

[Brianmoooore]

I've owned a couple of 316s and neither of them had an electric fuel pump, nor is there any electric pump for this model listed anywhere in the ETK. if any of the electric pumps used on E30s were to be fitted, the pressure they develop would overwhelm the float needle valve in the carb., and fuel would spill over the engine. Carb. engines that use an electric fuel pump use ones that develop a very low pressure.
The wiring (green/purple) used for an electric pump is present on late 316s (at least), all the way from the engine loom plug, via the fuseholder in the fusebox, to the socket on the RH side of the rear seat pan, but is unused.
The position occupied by the fuel pump on models with an external high pressure pump, is used for the fuel filter on later six cylinder models, or left empty on the four cylinder cars.
Cars with electric fuel pumps are required to have some kind of safety cut off system if the engine isn't running or the car has been subjected to an impact. BMWs only activate the fuel pump when the engine crankshaft is rotating, but some other makes use an inertia switch instead. Since your engine uses a pump driven off of the camshaft, it meets the criteria of only pumping when the crankshaft is rotating.

[Joe26]

Thanks alot for your help!