Hard to Start

[tbone5]

I have a '96 318ti and have been experiencing what seems to be a cold start issue. I have, out of basic necessity, recently replaced the starter and changed oil & filter, fuel filter, air filter, and plugs. However, even with the new starter and basic maintenance, the car cranks for a couple of seconds before turning over for the first drive each day. Once the car has been driven each day, it will start up on the first crank. What might be my problem?

[CirrusSR22]

Sounds like fuel pressure "bleed-down". The system holds a certain amount of fuel pressure in the lines after shutdown to make the next start quick. Overnight, the fuel pressure can bleed off either through an injector or back into the fuel tank. There some sort of check valve, I believe integrated with the fuel pump, which is supposed to prevent it from flowing back to the tank.

Next time try this simple test. Turn your ignition to "ON" (not start) which will activate the fuel pump. Leave it there for about 5 seconds, then shut the ignition off. Turn the key back to "ON" and leave it there for about 5 seconds again. Repeat the process 3 or 4 times. Then shut the key off and start it as normal.

This cycling of the key runs the fuel pump a bunch and thus primes the fuel lines again which should make the car start instantly. If this test works, your car is bleeding down fuel pressure somewhere. It's really not harmful to have it like this, just a bit of an annoyance. The only issue that could arise is that if a fuel injector leaks it could wash some residual oil off the cylinder walls, theoretically increasing cylinder bore wear.

Give it a shot! If nothing else it'll help narrow down your problem.

My car used to do this often. I've got in the habit of just turning the key to ON and leaving it there for about 5 seconds before I turn it to start. This allows the fuel pressure to build and equalize (?) maybe a bad term..... I have noticed on the times my car does crank for a few seconds it's always been after I've quickly spun the ignition cylinder all the way to start. I don't think the car has had a chance to build enough fuel pressure.

[tbone5]

That makes a lot of sense. I will try it in the morning and post an update. Thanks for the detailed explanation.

[tbone5]

Your suggestion seemed to help a little, but not entirely. Might I have a more significant bleed or leak somewhere? Someone suggested it maybe a bad "cold start valve".

[b.u.ti-ful]

Are you sure the plugs are correct and the wires are on good?

[tbone5]

I just changed the plugs with the NGKs that are called for. I just recently purchased the car and am not sure of the condition of the wires. Due to the cost and trying to avoid random parts replacement, I have not installed new wires. Would faulty wires cause this problem only on a cold start?

[b.u.ti-ful]

Here is what the Haynes manual says for hard cold start:

Battery discharged
Battery connections
Dirty air filter
Spark plug gaps wrong
Low compression
Fuel injection fault
Ignition system fault.

[tbone5]

Thanks-I'll check out the items listed. Do you happen to know where I get verify the gap settings for my NGK BKR 6 EK plugs?

[b.u.ti-ful]

http://ngk.com/results_app.asp?AAIA=1011452

[tbone5]

Thanks again.

[b.u.ti-ful]

Have you been able to make the car start up easier?