Start- Idle- Off: WHY?

[gidgaf]

I get in my 1986 528E, and start it up. It idles for maybe 5 seconds, shuts off. It will start again in 2 or 3 minutes, otherwise it just cranks and cranks. But it shuts right off again. I checked the fuses, swapped the relays, banged the ICV valve, unplugged the cold start valve- all the same.
I searched and read, read and searched- nada.
Anybody have a simple clue besides swapping ECUs and nuking from orbit?

[300+K540i]

Does your car have a camshaft sensor? Mine's a newer model 540i but had the same characteristics until I changed it...

[gidgaf]

*Me again. It was the fuel pump relay. Dagnapple Frazzit!
* "Didn't you check that already, fool?" They ask. Yes I did. The horn relay and the high beam relay also both worked last week. Maybe from jumping my broinlaw's car? Me not know. But all three didn't work this morning; well the horn relay worked but there was a big lag there. Sheer doggedness- just going thru all the connections and relay sockets with my multimeter. There really was voltage coming into the relay socket when the key is on and the car started and after it died yet again. WTF ?!?! I took my reset tool (paperclip) and shorted #30 and #87 clips, started her up and after a few seconds of rough idle it ran again. She Lives! The date on that relay is "12/85", btw, so I think it was almost due anyway.
* Autozone lists the relay for $55. Oreilly wants $84 for the offishul BMW relay, and $9.50 for the horn relay. Pep Boys wants $15 for the horn relay- and the same for a horn installation kit that includes a Bosch 30 amp relay with an assortment of connections, wires and a big button. I'm trying to figure a reason for putting one of those big buttons on my PC.

[witeshark]

gidgaf : enough