Main Relay Failure

[nicobaires]

Well, not sure if everyone has seen my previous posts so I'll sum it up for everyone.

Car used to hesitate and sputter after driving for a while. I would shut the car down, wait 5-10 minutes and would work great again until failing after 10-20 minutes.

After many trials on my own I brought it to a specialist who said the tank was rusted causing the issue. Took the car, failed again, he then said it was the fuel pump, which I had already changed prior to the tank. New fuel pump, said car was great blah blah blah, took the car home. On the way it started the symptoms again and completely died. Would crank but no fuel at all. Towed it home.

So I started messing with it today and jumped the main relay and the car fired right up. Could a bad main relay give me all these symptoms? It idles fine and everything but I'm afraid to drive it and get stuck again.

[FernandoBunster]

Many of our cars have ECU that are beginning to fail because of their age. Weak solder joints or failing capacitors are common causes of intermittent starting problems.

[CW6er]

Yes, checking the main relay is one of the first things to check:

Break down of components needed to get fuel to the engine:
Ignition Switch, OBC Relay, Main Relay, Fuel Pump Relay, Fuse 11, Intank/Main Pumps, - Fuel Injectors, Fuel Pressure Regulator, Speed Sensor, ECU, CTS, (No Vacuum leaks).

[nicobaires]

All relays were checked but I guess this one was on it's way out causing these symtoms every now and then.

The ECU was switched and the problem still persisted.

I'm hoping its the relay, we'll see

[CW6er]

Check out this thread on an intermittent main relay:

http://bigcoupe.com/phpBB2/viewtopic.php?t=5894&

[nicobaires]

Thanks for that link, that's me to a T!!!!
New relay here I come!

[CW6er]

Here is a cut & paste info on the relays:

(Updated 01/01/10)

The main relay is a 5 prong relay with 2 terminal 87's. The OEM's have 2 separate internal contacts with a pin 87 and 87b. In these, one terminal could test good and power the fuel pump relay and the injectors, but the other could be bad and not power the ECU. Many of the replacements just have the one internal contact and two pin outs, both labeled 87. Do not confuse the Main relay with the 5 prong Change-over relay (High-Beam, and Blower Select) with pins 87 and 87a (see below)

Main Relay, 5 prong, 4 choices:

OEM BMW (12 63 1 708 646 - 25x25mm case, Double Diode) - $33- Special order from the Dealer, Pelican or BavAuto (OEM $24 from SteveHaygood.com) These units have potting compound to seal the bottom (First one to the left in the photo below).

Audi-VW /Stribel (61361729004* - Larger white case, with ears, difficult to fit under rubber boot, Double Diode) Potted bottom like BMW OEM - $17.40 (AutoHaus) (White middle one in the photo below). (There is a $13.95 look-a-like at BavAuto & Pelican, but it does not have the potted, sealed bottom)

Bosch replacement (0 332 014 135 - 25x25mm case, Resistor) - $11.33 (AutoHaus) This unit is unsealed, like the other relays inside the fuse box and is the 25x25mm metal can that fits under the rubber boot. It would be protected in an M6 glove box. (Last one to the right in the photo below).

Hella (12631708646 - Black case, No ears, Double Diode) Don't know if unit is sealed or not - $13.08 AutoHaus (not shown)

There is also the Bosch (0 332 014 112) which will work in a pinch, but it does not have a suppression resistor/diode across the coil, so it will wear the ignition key contacts faster - $11 at AutoHaus. (This info may be wrong, AutoHaus shows this relay with a diode on terminal 86)

Fuel pump, O2 and other 4 prong Relays**:
( K1, K2, (K4- '83-'87), K5, K6, K7, K8, K9, and Start Relay. The OEM Green ones - 61 31 1 373 585/ended - 61 31 1 378 297, no longer seem to be available):
Bosch 0 332 014 406 - $9.95 (BavAuto) This is the 25x25mm metal can relay that fits under the rubber boot on the outside of the fuse box, and is the same size as the original green relays

There is also the cheaper ($7 AutoHaus), and easier to find Bosch 0 332 019 456 (Same size and style with ears as the White one below, but Orange case) that is a slightly larger case then the OEM Green ones, with several lugs sticking out that will just barley fit in the fuse box and work, but looks out of place with the other stock relays. This wouldn't be a problem under the dash in an M6.

High-Beam Headlamp (K3), and Blower Select relay:
5 prong change over relay (output changes between pins 87 and 87a as relay operates) - Bosch 0 332 204 401

The photo shows the same 3 Main relays, turned to show all of the sides:



______________________________
For a more comprehensive listing of the relays, and why the relays need suppression resistor/diodes, the BCG Tech library: http://www.normgrills.net/bcg/Electr...ectrical-47857

** Cross References (unverified) for the Bosch 0 332 014 406 = Valvar /230006; - Hella /4 RA 003 205 00; - Stribel /SR 9875; - Wehrle Kirchzarten /21 201 12 V
* (This number at Pelican brings up a BMW Mototronic 5 prong for the e34 5 Series and a list of 3 Series it is used in, but I don't believe it is potted, $18.25).
______________________________

[nicobaires]

Chris,

I took this pic from the other website, I have the relay that is shown on the left. From what I have read, some say they are interchangeable and some say they are not.
The part number is Bosch 0332014133.
Although mine has a different schematic on the side of it. The numbers read:
86 87 87 on top and below the diagram the numbers read 85 30

Any experience?

sorry, can't upload the pic for some reason but here is the link, pic is in the middle of page.

http://bigcoupe.com/phpBB2/viewtopic...=5528&start=30

Thank you!

Weird, the one that was on my car isn't even listed on there, maybe it's really old.

[CW6er]

Are you talking about this photo?

The one on the left is the wrong relay, it even says so in the text. It is a change-over relay, i.e. it switches output back and forth between terminals 87 and 87a and the car definitely won't start with it.

But you say yours has a different schematic on the side? Then it is not the same relay. I guess I'm not following?

[nicobaires]

Yes that picture.

Mine has the same schematic as the one on the left but with different numbers.
On the top of that one it says 85 87 87 and mine says 86 87 87 and on the bottom of that one it says 86 30 i believe and on mine it sas 85 30

[CW6er]

Yup, it's the wrong one, if that has been in the car as the main relay, it is guaranteed not to start!

The only difference you point out from yours and the photo are the terminals 85/86 are swapped which are simply the 2 ends of the solenoid coil and it doesn't matter which way the current travels through the coil. It is the output from 30 to both 87's (or to 87/87b), simultaneously, like the diagram on the one to the right, that matters.

[nicobaires]

My car did run fine though at one point in time with the wrong relay in. I guess thats why it failed.

I was able to get a relay from a friend that looks like the one autohaus sells but it's old. Anyway I installed it and the car started up, it took a couple of cranks but got it going.

I let it idle for a while then shut it down and put the old relay in and it started as well. I didn't drive it though.

If the car has been running would it have enough gas to start up once I switched and put the old relay back in to start it, is that the reason the old one worked?

[Tnarkowicz]

Also check your distributor cap/rotor.

I had intermittent problems a few years ago. If car was left idle for over a week, it would start, run, but die after about 5 minutes. Happened about 5 times, almost at exactly same spot on way to work!

Mechanic changed TDC sensors, air flow meter and tried another few things. Cost me a fortune and did not fix the problem.

Ended up being a very fried rotor cap and dizzy cap!!!

Tony

'86 635

[nicobaires]

I haven't received the new relay yet but I put the spare one a friend had. I shook the relay and it seems like there's something loose inside it but i put it on and took the car for a ride. It rode great for about a mile then the hesitation and sputtering started again. i got home and it idled like crap. I turned it off, disconnected the relay and used jumpers to start the car back up to see what it would do. It still idled like crap so this leads me to believe that it might not be the relay?

It's definitely something to do with the temp of the car. When the car is cold it's great but once it warms up, it dies

[CW6er]

The O2 sensor doesn't kick in until it warms up, try unplugging it and see if that help? Have you checked the CTS?

[nicobaires]

Supposedly the shop checked all sensors and the O2 is less than a year old but I will check that again this weekend.

I'll look at the CTS again for any breaks in the lines also.

It has to be something temp related and electrical. When the car is cold it runs awesome, smooth as ever, no misses , hesitations, nothing.

In the winter it ran great which is weird because the car would run at normal temp. but the cold winter air did somethignt o it to make it run ok.

Now Yesterday it was around 90 degrees and it only took about half a mile to start with the symptoms again. WTF???

[Taylor Marshall]

I wonder what would happen to a car's driveability if the AFM thermistor went bad ?

I have never heard of this happening but it is there for a reason and causes the DME to adjust the AFR depending on the temp (re density) of the ambient air being sucked past it. I'm just not sure how dramatic its effect is though. Anyone know ?

I am suspicious of your CTS too...the sensor itself and not just the wiring. How did your techie check it ? At 3 or 4 different temp gradients ? I would check it myself.
And finally, I agree that a funky cap n rotor will cause all sorts of bad craziness. It is my opinion that anyone buying one of these cars should replace them unless they have definitive proof that the PO did relatively recently. Just good prophylactic maintenance.

[nicobaires]

I am not sure how they checked my CTS but they are a very reputable BMW shop that only works on BMW's. ALthough their diagnosis was to replace the fuel tank and main fuel pump. Now they want to change the in tank fuel pump but I'm 100 percent sure it's not that.

So i'm leary of bringing my car back to them.

[nicobaires]

Well today I took the fuel return line off and jumped the fuel pump relay. Very little fuel came out. I jumped the relay for about 10 seconds and i got about 2 teaspoons of gas out of the fuel pressure regulator.

Could a bad fpr cause all the symptoms I've been having??

[CW6er]

Put a pressure gauge on the inlet line (at the rear of the fuel rail, next to the firewall) and see if the fuel pump is putting out.

[nicobaires]

Chris,

I was beginning to wonder why my car wouldn't start up when I got the new main relay. I double checked and I think they sent me the wrong one.
Here's the pics, I checked with your list and it's not on there.

[CW6er]

The list is not all inclusive, the diagram in your photo looks like it should work fine. This looks like one to add to the list.

I just looked it up and AutoHaus shows it as superseding the Bosch 0 332 014 135 that is on the list, they have this note:

"Due to Bosch supercession, replacement units may now have black plastic housing, version 0 332 019 109, instead of this metal version."

https://www.autohausaz.com/search/pr...32%20019%20109

[cadeaudr]

I was wondering if you ever figured out your relay issue. I have an '81 633csi and I'm trying to replace the main relay. It is a silver 4 prong relay that is mounted to the front of the car in front of the fuse box. It is 12v 70 amps. I cant seem to find it anywhere. I can only seem to find a 5 prong relay.

[CW6er]

I was wondering if you ever figured out your relay issue. I have an '81 633csi and I'm trying to replace the main relay. It is a silver 4 prong relay that is mounted to the front of the car in front of the fuse box. It is 12v 70 amps. I cant seem to find it anywhere. I can only seem to find a 5 prong relay.

That's not the Main relay. IIRC your '81 has the Fuel injection Combination Relay, nothing like the ones discussed in this post. If you have a Motronic system, you have the 5 prong Relay as discussed here, or if you have the L-Jet you have the Combo Relay. You can buy them new from AutoHaus, but they are expensive. Here is how to fix it :

http://www.firstfives.org/faq/ljet/combo_fix.html


An overview of links about the L-Jet and Combo relay, with a link to a PDF of an L-Jet wiring diagram:
http://www.firstfives.org/faq/ljet/ljetronic.html

I don't believe our cars ever had a 70 amp relay, it sounds like it might be an aftermarket relay? Has someone swapped the headlights for more powerful ones? Or maybe Fog lights?

[bigray122]

Ordered a new main relay and should arrive in the next day or so. I cannot find the picture where this relay is located? I thought I saved it. I have an E34...any help?