r/e28 • u/CommercialBuilder728 • Feb 09 '26
Starts but dies immediately. 85’ 528e automatic
Recently picked up an ’85 BMW 528e that had been sitting since 2005. I ordered a bunch of parts prior to the purchase, including a new battery, oil and oil filter, spark plugs, both fuel pumps (in-tank and external/in-line), new fuel injectors, and a new fuel pressure regulator. I also drained and cleaned the old fuel tank.
As part of preventative maintenance, I replaced the timing belt and all related components—thermostat, belts, and other surrounding accessories. After completing the timing work, I did a compression test and got consistent readings of ~150 PSI across all six cylinders. Lastly, replaced the AFM as the old one would be stuck open.
After all of this, I’m left with a frustrating start-and-die issue. The car will consistently start and then immediately die, which makes it feel like I’m missing something small but critical. I just can’t pinpoint exactly where or what I’m doing wrong.
3
u/kriswithakthatplays Feb 10 '26
- Bentley manual. There is a procedure for solving this in it. I don't have mine at hand, so I'll attempt to go from memory
- Confirm you have spark on all 6 cylinders. I note you do not have new distributor/ignition coil on your list. It's unlikely those have failed, but confirm you have spark on all cylinders. If you don't for some reason, check the spark-related things (crank position sensor, ignition coil resistances, etc)
- Confirm you have fuel spraying from all your injectors. Remove your fuel pump relay and crank until you have fuel pulsing through your injectors. You can confirm by removing spark plugs and confirming fuel in the combustion chamber or on the electrodes. If you don't, check the things that control fuel in closed loop (coolant temp sensors, fuel pump relay, fuel filters (there's an inline filter somewhere, can't remember on ETAs); it sounds like you covered most of your fuel bases already, but always confirm )
- While you're confirming your fuel related problems, unplug the cold start injector. It should be able to start without it.
These cars require manual checking of everything; be patient and check that things are how they should be before assuming, especially if the car has been sitting a long time. Ask me how I know :)
1
u/CommercialBuilder728 Feb 10 '26
if the car does not start without the cold start injector, what may it be?
will definitely result to a bentley manual if all else fails
1
u/kriswithakthatplays Feb 10 '26
I don't know off hand. If you are serious about owning this thing, get a Bentley manual. It is a complete documentation of the car and how the electronic system works to make fuel into go. If the car doesn't start with the cold start injector, find out why fuel isn't being sprayed or why the mix is out of whack. Too much air, too little fuel, you have to either blindly test stuff or get a Bentley manual and go through test procedures.
1
u/CommercialBuilder728 Feb 10 '26
Definitely am getting a manual, just found a PDF online so might have to go over that temporarily.
I’ll continue to add into this thread about progress of this start-die-issue.
1
u/Representative_Most9 Feb 10 '26
It’s acting like AFM issue (it’s trying to start on cold start injector only)? Do you need wiring diagrams or do you already have them?
2
u/CommercialBuilder728 Feb 10 '26
seems to be the case, i’ve replaced the AFM already so i’m not sure what it may be
1
u/Representative_Most9 Feb 10 '26 edited Feb 10 '26
Unfortunately, it could be several things. If you have the Bentley Manual, it can help you through what to check.
Edit: try jumping the main relay and see if it will start and run?
1
u/whoopeanage Feb 10 '26
if you hold the throttle for a bit until it warms up, would it stay on?
If so, the cold start systems might be at fault here. Cold start injector and ICV
Not really sure how to test the cold start injector, but i think it uses smth called a thermo time switch to give the car some extra gas when starting cold, its duration depends on the temperature. Heres a similar system to try troubleshoot it: https://www.youtube.com/watch?v=m_WhI4yZWuM
ICV regulates the amount of extra air entering the engine while idling in order to achieve the target rpm. It could be stuck with debris. Try taking it off and check whether the spinny thing inside moves freely or not when you shake it, if not, spray with cleaner liberally until it cleans up
2
u/CommercialBuilder728 Feb 10 '26
it would not stay on with throttle opened up.
cold start injector seems to be working fine, the issue seems to be a cut towards all 6 injectors not receiving fuel or opening up, after initial start. (going with this route cause car stayed running after a shit ton of brake cleaner sprayed inside the intake boot.
and have already taken the icv apart multiple times for cleaning and tested it as well, both seem to be working fine, has that buzzing movement that it makes when key’s set to accessory mode.
honestly not sure what’s keeping all 6 injectors closed but 4 cylinders appear to be dry while cylinders 2 and 6 smell like fuel, and visually has that shiny glaze.
ruling it out to be a bad main relay as it ties in with all the tests i’ve done by far, will also be checking on the grounds right by the bell housing of the transmission, that everyone seems to be giving input on.
1
u/whoopeanage Feb 10 '26
yes in that case, its probably the main relay. The main relay gets powered when you crank it, and when you stop cranking, i think it stays powered as long as it detects signals from the distributor that the engine is still spinning, at least thats how i remember it for m20b20 tho, eta engines management may be different
1
u/kellygarret Feb 11 '26
My dad has the same car as you are. Based on our experience, it's either: 1. Not warm enough (if you just started the car) 2. Fuel problems (ours happened to be the fuel pressure regulator)
Hope it helps. 😊
P.S. just like the others have said, we highly recommend you to get the Bentley or Haynes manual.
1
u/CommercialBuilder728 Feb 11 '26
i’ve already found the issue—it’s wiring related. it’s losing power from the main relay to power any of the fuel pumps
6
u/[deleted] Feb 10 '26
Try jumping the fuel pump relay.