Random Long Start

[AutoXinE30]

So I'm going NA M/S in the next few weeks so I can learn it before I go full turbo but I've developed a random long start that is beginning to become more frequent.

I can crank the key for a few seconds and it'll start and die or I can crank it and give it some gas and it'll start rough for a second and then run on it's own power. Doesn't see to make a huge difference whether the car is cold or warm or if the weather is cold or warm. Sometimes I can come out to to the car and it'll crank right away. Sometimes if I turn the key on without cranking it and leave it there for a few seconds and then crank it'll start right away.

My first thought would have been FPR and it's just not holding pressure after the car is switched off but, I figured I'd ask to see if there was something more common.

Thanks

[jlevie]

The most common cause of starting problems is intake leaks. Have a smoke test run on the intake and fix the leaks it reveals. If the problem is still present after eliminating intake leaks you could have a bad FPR or failing fuel pump. Other possibilities exist, but that is the order you should take in solving the problem.

[AutoXinE30]

So smoke test first, then check fuel.

Outta curiosity if it is an intake gasket leak why would it be intermittent?

[jlevie]

In the presence of intake leaks even small changes in engine or ambient temperature can have a big affect on starting. Hence the suggestion to eliminate intake leaks first. There are a number of placed on the engine that can result in intake leaks and the best way to check all of those possibilities is a smoke test.

[AutoXinE30]

Negative on smoke test. Although I did find the IAC valve had a small crack in the hose, replaced that with an uncracked one. The metal tube that goes into the throttle body was very loose. I put a small amount of RTV on the side that goes into the TB when I put the uncracked hose on. Idles better and feels different on the road but still has the long start.

Guess it's fuel pressure time.


What kind of fuel pressure should the stock motor have at idle? and what should it hold while it sits? And I assume that the fuel line leaving the fuel pressure regulator is the return line and the one underneath is the feed line correct?

[jlevie]

Rail pressure for an M20B25 is 3.0bar and for an M20B27 2.5bar

[gw ix]

Fuel pump or ECU relay?

[hotballs]

99% FPR issue.

[AutoXinE30]

I did not buy a fuel pressure gauge yet but I do have a vacuume tester and I don't know why I didn't think of this before but if the FPR is leaking out then I should be able to pump the FPR up from the vacuume line and it shouldn't loose vacuume pressure right?

Like if I pumped it to 20in/hg it shouldn't bleed off right?

There was a fuel fume smell in the vacuume line to the FPR from the intake mani, unsure if that is normal. I have not actually hooked the pump up yet though.

BTW this is an M20B25 (89 325i) since I haven't actually clarified that yet, sorry.

[AutoXinE30]

Took the pump out to test the car, pumped to 15in/hg and turned the key, immediate crank. Popped off the line to plug back into the intake mani and a small bit of fuel dribbled out...

Guess thats problem solved.

<-- Dummy.

[AutoXinE30]

Just a follow up for any future seraches...

Purchased a brand new FPR wed and installed it. We've had temp ranges from 80 in the day time to 57 degrees just last night. In the last 4 days not one single long start nor do I need to blip the throttle to get it running.

It does have a slight miss every so often but that will be something to figure out in the near future. Starts and idles like a dream now.

[87-325ic]

strange. i have had a intermittent hard/long start lately too, my fuel stuff is all pretty new.. so i guess i should check intake leaks better. time for a smoke test.