94 530i Won't Start (fuel pump relay suspected) HELP!

[piffdaddy]

My name is Ken, I am new to the forums here, although I have been behind the scenes reading all the great info on this site!



I went ahead and checked out in the bentley manual, tested the voltage of the connector that connects to the fuel pump, no voltage at all. (on position)
Checked the fuse it was fine.

I assume that it is the relay, my biggest problem at the moment is I don't know which one is the Fuel pump relay! the bentley manual shows a different picture then what I see in my e-box.
Says to refer to a sticker on the e-box, but there is no sticker on my car.

I just need to know on the 1994 BMW 530i, which one is the fuel pump relay?
Prior to the car dying, the car would stall out very often, but turn right back on.
The fuel level was always incorrect, showing a wrong level, then it didn't show a level at all (stayed on Empty). Right before the car stopped working all together, the fuel level seemed to actually be correct.
Then it died. I wonder if this has something to do with it.

Now I need to find which one is the fuel pump relay so I can buy a new one at the BMW dealer, because they need the part number in order to sell me one.
If anyone can help me I will be so grateful, because this car has been sitting too long, and I want to get this beast back on the road!

Thanks in advance!

[Critter7r]

When you're looking at the fuse box from the side of the car, there's a group of 5 relays arranged in a row of 3 over 2. It's either the middle on of the top row, or the right one of the bottom two. I'm pretty sure it's the bottom right one, but it might be that middle top row one.

[thejlevie]

In case you don't know, the fuel pump relay is controlled by the DME and only energized when the DME sees timing data from a rotating engine. So the check for power to the pump must be done while the engine is cranking over. No poer to the pump in that case will be due to; bad fuel pump relay/fuse, bad crank position sensor, no power to the DME, or a bad DME.

[bmwdirtracer]

+1. Key in on position does not guarantee power to fuel pump. Usually the pump kicks on for a few seconds at key on, then shuts off until cranking or running.

The fuel pump relay is less common a fault on your model than the older BMWs. More often on later E34's, the fuel pump itself is the problem, or the dme isn't ordering the car to start, most likely of all. Easier perhaps than tracing your relay, remove the engine cover, and locate the fuel rail, a shiny. 1" diameter squiggly metal tube running to both sides of the top of the engine in a "U" shape. Somewhere on top of this will be a schrader valve, just like the valve on a tire. After briefly cranking the car (2 seconds will do), turn off the key, get out, and press the little valve stem in the middle of the schrader valve. If fuel squirts out under high pressure, your fuel pump is working. This crude method doesn't guarantee your relay or fuel pump is good, but it does indicate that you need to go to the next step, and check for spark and injector pulse, to determine if the dme is even trying to start the car.

[piffdaddy]

If anyone has a picture, of where it is located, or a nice diagram, would be great.
I know it is hard to explain where a location is. I know that it is inthe box on the passenger side, from there, I am stuck. And I can't risk ruining the car, orsomething else by guessing.


Thanks for your answers, I am pretty sure that it is the relay, I know the sound the fuel pump makes in this car, even in the "on" position, and it is completely silent, i want to check the voltage again while cranking it, as sugested.
I want to buy the relay and just swap it, cant hurt for under 20 dollars.
I just need to know where it is, exactly.
I am pretty sure it is on the passenger side, in the "e-box"
I can't find the exact location in the bentley manual.

Thanks so much.

Thanks again

[bmwdirtracer]

Okay, had to get to work, here's your answer:

In the computer box, NOT the fuse box. From left to right, you will find: ECM(dme), then the trans control module (EGS), then three relays, then the ABS control module. The three relaus, top to bottom, are: ECM(dme) relay, fuel pump relay, and O2 sensor relay.

The fuel pump relay is the center one. Good luck.

Chris

[bmw slangen]

As bmwdirtracer said it is located in the the so called E-Box. Here is a picture of mine (BMW 535i -89) where you can see some of the stuff he correctly describes.

http://www.exx.se/maintenance/relays...s_box_text.jpg

Note I don't have the EGS (have a manual tranny) and my models (including many others) don't have a specific O2 heater relay, it re-uses the fuel pump relay (that is as soon as the fuel pump starts the O2 heater starts).






For a while ago I built by own fuel pump remote switch so I can operate the fuel pump manually. Used this when I started up the engine after a lot of things had been swapped (fuel filter, fuel injectors etc etc). If you prime the fuel system you don't have to crank for ages to get fuel pressure.

[piffdaddy]

slagen, and dirtracer:
Thank you both so much, this was a perfect answer, exactly what I have been looking for.
It was really cold and snowy today, so I didn't want to get to work today, but tomorrow I plan on getting to work.
I hope I am able to find a Relay for sale, the BMW Dealer Local said they had it, i had to pay a cab just for them to say they don't have it.
(waste of $80 for a cab).
Wish me luck!
I can't wait to get the beast on the road!


This car needs so much work, much more then the fuel pump relay.
I have to do some body work, (least of my worries)
My passenger seat has that common problem where it twists and then stops working.

The trans also has issues, my biggest problem, it slips when accelerating and jerks when it stops, "trans program" came on when I was trying to start the car (I really hope i didnt mess something up in the e-box when i was trying to put it back on after looking at it).
The trans problem started after getting a trans fluid change, I put in lucas trans fix, it helped, temporarily.
I HATE the fact there is no dipstick to check the fluid, because I dont have a lift, or a way to check it, for all I know, the mechanic that changed the fluid, may have not filled it all the way!

Thanks again to everyone with the suggestions, and advice.
I will keep everyone updated on the issue.

Hey Slagen,
You pictures were great, very very helpful.
I noticed u said that the new one is light green?
Is the new one(light green) a 5 prong relay?
As far as I know, the original fuelpump relay is 4 prong, the one they had a bmw was light green, but it was 5 prong?
He said I would have to break one of the prongs off to get it to work? i didn't like that idea AT ALL. So I said the hell with it, i will buy it online.
Now the only ones I see online are 5 prong ones. Is it true that I have to break it off? And is there a possibility to ruin the car by doing it like this?
Thanks

[thejlevie]

You don't have to break off one of the prongs. The socket will accept the relay as is and there isn't a wire in the "extra" position in the socket.

[bmw slangen]

Hey Slagen,
You pictures were great, very very helpful.
I noticed u said that the new one is light green?
Is the new one(light green) a 5 prong relay?
As far as I know, the original fuelpump relay is 4 prong, the one they had a bmw was light green, but it was 5 prong?
He said I would have to break one of the prongs off to get it to work? i didn't like that idea AT ALL. So I said the hell with it, i will buy it online.
Now the only ones I see online are 5 prong ones. Is it true that I have to break it off? And is there a possibility to ruin the car by doing it like this?
Thanks

Thanks! Yes, the original relay is 4 prong, see picture below. The info about colour of new fuel pump relay has been confirmed on another BMW forum (Swedish) - that's where I got the info. Never bought a new one myself though.

But breaking off a prone to get it working? Original BMW? Sounds ridiculous! I don't buy that!

You don't have to break off one of the prongs. The socket will accept the relay as is and there isn't a wire in the "extra" position in the socket.

True! Only four are connected - see picture below which shows the socket for the fuel pump relay from under.

[piffdaddy]

Perfect answer to my question!
Thank you so much again.
It was the coldest day of the year, so I didnt' want to do it today.
But I will let you guys know exactly how it goes when it is swapped.

And I am sure this forum will help many others, Ive seen this question asked many times, but never got a real answer.
Many people are going to be grateful for this