Strange starting problem

[hlenoble]

My '90 535i has had a strange starting problem for the past month. The problem seems to happen only if the car sits for a week or so, not if it's driven daily.

The car starts when cold and runs fine. The first time it's turned off after that it doesn't want to start unless it sits for a while. In fact, it doesn't come close to starting for several minutes at least. When it finally does start it runs very rough for a little while, and then smooths out and runs fine. It will start normally after that one issue.

Cliff notes: Car starts fine cold, then is VERY difficult to start if tried again shortly after that. Example: I start the car, go stop and fill the tires with air, and the re-start is extremely difficult.

Thanks in advance for your help.

[hlenoble]

Could this be the check valve issue? It only seems to happen whenthe car is halfway warmed up, not fully warm, so the description doesn't completely match. Should I be looking at something electrical?

Thanks again in advance.

[Rus]

Your problem does not sound like fuel draining back to the tank. That would cause issues after the car sat for a while, not immediately after being shut off. It sounds like there is an electrical issue that manifests itself once something heats up. Check the relays for the fuel pump and the main relay. These are located in the passenger side control box under the hood alongside the ECU.

[Tiger]

Definitely the checkvalve issue as it is hot start problem. Easy fix with E39 repair kit.

[whiskychaser]

I'm with Rus on this one. Had identical symptoms on a Honda. Turned out to be dry joints on the fuel pump relay.

[Paul in NZ]

also check the dizzy cap and rotor...I had same problem,and rotor was shot and it was damp inside the dizzie

[genphreak]

A tip is not to start and stop cranking when it happens. Just keep cranking- after 20secs the M30B35 will fire.

The engine is flooding.

The check valve is the issue, and is a kit which is best sourced from bmaparts.com.

Fix the valve, else you will have to fix the starter and/or deal with flat batteries- it isn't good for any battery to crank an M30 for a long time. :) Nick