cold start relay

bmw performance · Post by **bmw performance** » Fri Sep 11, 2015 9:23 am

Where is the cold start relay on an 81 euro e12?

If the engine is cold no matter the temp out side it cranks and dies, cranks and dies. It does that about 5 times then will stay running barely and you have to let it warm up a little before you can go anywhere. Above 2000 it runs fine and after you let it warm up it runs fine.

You can get in it first thing in the morning and it will barely run until it warms up. You can drive it to work let it sit until lunch and it fires right up. Drive it to lunch let it sit until you get off and it will fire right up again. It is just when it sits say longer than 12 hours it give the problem.

Have replaced the afm, temp switch, cold start injector, air valve, and still have the problem. The only other part I know of is the cold start relay but can't find it. What do you guys think?

Mike W. · Post by **Mike W.** » Fri Sep 11, 2015 11:38 am

The cold start system is cold start, not cold run or warm up. It is only intended to operate while the car is cranking, as soon as you let off the starter it stops, if not before. So I don't think that's the problem. Since you mentioned it's a euro, how was it federalized? What ECU and AFM? Is there a Johnson box? What is the fuel pressure? Any vacuum leaks, how is the AFM adjusted? Correct injectors? Actually the very first thing I'd so is check for vacuum leaks, then adjust the AFM.

bmw performance · Post by **bmw performance** » Fri Sep 11, 2015 3:47 pm

Will see if I can find any leaks and report back.

RandyM · Post by **RandyM** » Thu Sep 24, 2015 9:13 am

To start, I don't have the depth of knowledge or years of experience of others but I do spend a fair amount of time "tinkering" and removing/cleaning/adjusting the little bits that make my ride run and perform better. Since your problem seems to be temp. dependent…
Try checking the operation and adjustment of the auxiliary air valve and its electrical connections.
Maybe vacuum leak that goes away as engine warms, metal expands?

The Cold start valve and its relay operation is easy to check, pull the valve and hold it in a container to receive gas while cranking. There a description of anticipated volume/time in the FAQ IIRC if it comes to that.

Good luck!

bmw performance · Post by **bmw performance** » Wed Dec 02, 2015 9:43 am

Finally got back around to working on the car again.

Found a leak in the hose running to the brake buster and fixed it. Thought that would fix it but did not.

It would not crank and I had to pull the plug to the AFM to get it to go into "limp home mode" to get it to crank. I changed out the AFM to the one that came on it originally and now it will idle but has a bad dead spot until above 3000. Drove it to the store and it would not crank at all. Finally got it cranked and drove it home. Thought it was a fuel issue so I pulled the fuel filter and checked it but clean. Put a new one on anyway and cranked it up. Still is not running right.

Thought about fuel pressure regulator but I don't think I have a spare. What do you guys think?

Mike W. · Post by **Mike W.** » Wed Dec 02, 2015 12:19 pm

Homemade fuel pressure tester can be made for under $10 with a water pressure gauge and a brass 5/16" barbed fitting all from a local hardware store. So that's one way of getting a handle on the FPR.

AFMs can generally be repaired, you have to reposition the wiper so it runs on a fresh section of the board.

Lastly do you mean it won't crank, meaning the starter doesn't engage or run, which is clearly an electrical/battery problem or it cranks but won't fire?

bmw performance · Post by **bmw performance** » Wed Dec 02, 2015 12:31 pm

It cranks over but will not start. Let me see if I can make a video.
https://www.youtube.com/watch?v=j7KC3gKDEjk

bmw performance · Post by **bmw performance** » Wed Dec 02, 2015 2:57 pm

Same car after it warmed up about 30 seconds. It is acting like it is dumping fuel in it and bogging it down.
https://www.youtube.com/watch?v=Styh5YgBou4

bmw performance · Post by **bmw performance** » Thu Dec 03, 2015 11:53 am

It is not the fuel pressure regulator as I changed it out.

Vintagemotorwerks · Post by **Vintagemotorwerks** » Thu Dec 03, 2015 11:59 am

I use to have that same problem too in my US spec E12. I swapped out the AFM for another and it fixed the problem. Your euro spec AFM could be damaged. Try to source another one.

bmw performance · Post by **bmw performance** » Thu Dec 03, 2015 1:38 pm

I think I found at least part of the issue the temp switch and timer switch wires were backwards. Will have to wait until it cools down completely to see it it still has the early morning starting issues. I have several AFM so swapping them around is not an issue.

Vintagemotorwerks · Post by **Vintagemotorwerks** » Sat Dec 05, 2015 12:38 am

Those two sensors will cause you headache if they don't work properly

RonDwyer · Post by **RonDwyer** » Sat Dec 05, 2015 7:07 pm

If the age of the hoses is unknown, do yourself a favor and replace all the hoses on the fuel injection, the injector seals and especially the hoses to the fuel injectors. Tighten the manifold bolts, better yet take it off and put on new gaskets. This is a Saturday afternoon project. Unless you start from a known baseline a phantom vacuum leak will continue to or eventually plague your quest to keep it running smooth.

bmw performance · Post by **bmw performance** » Sat Dec 05, 2015 7:44 pm

All the hoses and gaskets have 1400 miles on them. Reused the manifold to brake booster hose orginaly as the new stuff does not look the same as the orginal. The one way valve looks different also.

philipj · Post by **philipj** » Mon Dec 14, 2015 1:58 pm

I have a similar problem, and since someone has mentioned the AFM as a possible culprit, can someone please indicate how to adjust the AFM? How many turns on the bottom screw should I have for starting point?
If the screw is turned clockwise for instance, am I making the engine run richer? Thank you.

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cold start relay

cold start relay

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