M20 Long crank / fuel pump and pressure questions

[jimsbim]

My 1991 325 IX developed a long crank condition over the winter.
After sitting overnight, it would crank sometimes for 8-10 seconds on first try - no start, then start quickly on second crank. Restarts throughout the day would generally be quick on first crank. After reading numerous posts, I decided to check for residual fuel pressure in the line to the fuel rail. I pulled the line this morning (cold engine after sitting overnight), absolutely no fuel sprayed out - essentially dry line. Reinstalled the line, cranked for 8-10 seconds, no start. Cranked again, car starts. Shut it down, pulled the fuel line again - viola - big spray of fuel, lots of pressure.

So, it appears the check valve in the fuel pump is bad. I've considered trying the inexpensive inline check valve route, but would feel more confident to just go ahead and replace the fuel pump.

Here is another thing that puzzles me. As a temporary fix to the initial long crank problem, many posts suggest turning the key to position one for several seconds to pressurize the system before cranking. When I turn the key to position one, I expected to hear the fuel pump energize. Mine does not. Is this normal? When cranking and the car starts, it is clearly running (buzzing.)

Any thoughts, help, suggestions appreciated. thanks Jim

[digger]

jump the fuel pump relay manually and see if priming the pump for about 3 seconds before starting helps the long crank. the bentley will tell you how to do this iirc

what injectors are you using?

[jimsbim]

Using stock injectors. I will try jumping and priming the pump / line, and expect it to minimize the cranking and solve the problem. But, still thought the pump should energize when the key is turned to position one - (before position two energizes the starter motor...

[101]

^^ nope. Common misconception.

On our cars the fuel pump only turns on when the crank sensor sees the engine turning over. There is no "priming" function like on most modern cars.

[digger]

mine didnt prime until was cranking either and i thought it was a fuel pressure bleedoff that caused my hardstart when engine was warm (trying to start it 15min after it had stopped made it crank alot), mine was an injector issue of sorts

[jimsbim]

101-Wrencher, thanks for the confirmation re the pump being non-self priming! It all makes sense to me now, and confirms that I will replace the fuel pump. Thanks again.

[Ether-D]

Hmmm, my fuel pump runs for about a half second when I turn the key to the "run" position. All of my e30's have. Good luck.