Here's that part number for the check valve kit.
http://www.bimmernut.com/%7Ebillr/im...checkvalve.jpg
Quote:
Originally Posted by Martin in Bellevue
There is a retrofit in line check valve to be placed between the pump(tank) & filter. The check valve in the pump assembly wears & allows the line to bleed down overnight.
I don't have the part number handy, but Pat@BMA knows the item. It is cheap enough to try first.
The check valve problem is primarily a hot start problem and if you
had it you'd know it... its more than a couple of seconds, more like between 7 and 10 seconds...
Quote:
Originally Posted by JonE
Does anyone know how long of a "crank" starts to become a concern? Are we talking more than a couple seconds, ten seconds? or what? Both of my BMW's take a couple seconds or so to fire up, cold.
To elaborate a little more, on older carburated cars vapor lock used to
occur because fuel would boil in the fuel line between the gas tank and the engine because of the low pressure of the fuel and the heat absorbed by the line from the exhaust and other sources. One of the reasons that the fuel pump was placed in the gas tank on most injected cars is that this way the entire fuel line from the tank to the engine is under pressure , typically 35 to 45 pounds. By raising the pressure in the lines it raised the boiling point of the gasoline quite a bit, helping to prevent vapor lock from occuring in the fuel line. The check valves job is to ensure that the fuel lines always have fuel under pressure right up to the injectors. If you have a bad check valve then the pressure will drain back to the fuel tank and the fuel in the lines will mostly likely boil at some point close to the engine causing a vapor lock condition, which requires more cranking of the engine to get fuel to the injectors to overcome this. So the fuel pump was actually moved to the tank for a good reason.
QUOTE=Bill R.]had it you'd know it... its more than a couple of seconds, more like between 7 and 10 seconds...[/QUOTE]
Don't get me wrong Jon, it still affects cold start, its just much
more noticable on hot start, but leaking injectors or a bad fuel pressure regulator will definitely affect cold start too.. Knowing Callen, i'm fairly certain that the plugs have been changed and typically a vacum leak wouldn't affect cold start much. The temp sensors and the engine computer determine how much fuel to inject on the initial cranking when cold, if it had a vacum leak it might run poorly immediately after starting but when starting I don't think its taken into acount on a cold start.
Quote:
Originally Posted by JonE
So Callen, is this a cold start problem only? Either way, it sounds as though checking that fuel pressure might be worthwhile, and, like Jeff said plugs and vacuum leaks.
All that said I would still try the check valve kit first , since its cheap and easy
Quote:
Originally Posted by Bill R.
more noticable on hot start, but leaking injectors or a bad fuel pressure regulator will definitely affect cold start too.. Knowing Callen, i'm fairly certain that the plugs have been changed and typically a vacum leak wouldn't affect cold start much. The temp sensors and the engine computer determine how much fuel to inject on the initial cranking when cold, if it had a vacum leak it might run poorly immediately after starting but when starting I don't think its taken into acount on a cold start.