E21 randomly shut off while driving, cant start it back up

[Mailxpur]

Hi everyone im new to this forum and i have had my 1983 320i for about a year now. The car has been running fantastic for the last year with the occasional tough cold start but nothing major and ive always stayed on top of maintenance.

I was driving home from work just last week when the car suddenly shut off with no indication of anything going wrong. The car stumbled for about 2 seconds then all power from the motor stopped. I was able to tow my car home to take a better look, I immediately thought it might be an issue with the fuel system (Jetronic system) as it seemed like it was a sudden fuel cut.

Things i have tested or done.
-Tested the spark plugs and they are all producing spark
-checked the air filter and its brand new
-checked the fuse box and replaced the main fuse with a another fuse i had in the car. The new one and old one were clicking when the ignition was put to auxiliary.
- the high pressure fuel pump does seem to be producing pressure and supplying the fuel distributor but i don't have a pressure tester so i have no way to verify the pressure.
- I took the airflow meter and the fuel distributor out and cleaned everything as best i could also i checked all the screen filters including the warm up valve filter and everything looked brand new. The diaphragm in the distributor had no signs of wear at all too.

I know there are a thousand different testes i can preform to find the issue but im relatively new to the M10 motor and i don't know all the tips and tricks. Anyone's impute would be greatly appreciated and thanks for reading through this

[yatisr]

Have a look at the ignition control unit. This failed on my 323i (Bosch K- Jetronic six cylinder) causing the engine to immediately shut down and refuse to start. All was well once it was replaced.

Yatis

[Mailxpur]

Thank you Yatisr! definitely the same symptoms but obviously i have the 4 cylinder, i will take a look anyways of course. Do you know where the unit is located?

[yatisr]

On the 6-cylinder cars it is located just behind the left front strut. I assume the same for the US specification 320i.

Yatis

[jbartiromo]

I had a similar issue not starting when engine at temp and shut off then attempting a quick restart (like at a gas station or being released after a traffic infraction warning stop - lol). I wired a push and hold on button switch to the cold start injector. Press and hold while cranking when "heat stroke" starves the Jetronic system. Never been sitting an hour waiting for cool down again.

[Jeroen]

Speaking of cooling down reminds me of an issue we've experienced a few times here, but that is only applicable to the 323i (and other fuel injected cars that have the dual exhaust system fitted afterwards): the fuel pump is fitted just above the right rear wheel. With the 323i, the right rear muffler and piping runs right underneath and heats up the fuel pump assembly. As long as you're driving and generating some air to pass through you'll be fine.

But when pushing real hard on a hot day, or when you hit traffic, the exhaust further heats up the fuel pump assembly. What we've deducted is that the fuel starts to boil inside the pump and that results in the fact the fuel supply seizes. We had several occasions during our Alps trips (pushing hard on a hot day) and when we hit road works, several cars would stall and not start anymore, or be hard to start shortly after shutting down.

Usually spraying some water on the pump or allowing some cooling down time would suffice. In one case the issue was very persistent but that was on a Hartge car with longer mufflers, coming even closer to the pump (on most other cars it would just be piping right under the pump at a slightly larger distance). In case of the Hartge a metal heat shield was fitted around the fuel pump which solved the problem indefinitely.

Something else: several recent experiences show that the current series of Bosch fuel pumps are absolutely rubbish and within months or a few years lead to an unstable fuel supply. You car starts to have the weirdest issues and random power loss and the last thing you'd suspect is that fuel pump you replaced just a short while ago... but the pump then is about to fail completely.

[nic65]

per la 323 un bollettino tecnico di Bosch prevedeva lo inserimento della ventola dopo lo spegnimento a caldo per raffreddare il vano motore ed evitare fenomeno di vapour lock