difficult warm start

[bluebenz]

I read all the threads on R3V concening difficult starts.

Here is my problem. Car is a 1986 325E, completely stock, 76 000 miles. Timing belt, spark plugs, plug wires, dis cap, rotor, coil, fuel filters, battery, some fuel lines all replaced within a year. Both fuel pumps are original but not noisy.

Car runs perfect, idles smoothly. Hot start is perfect (less than 1 sec of cranking, cold start is good (less than 3-4 sec of cranking) but warm start (if car sat for an hour) is difficult, sometimes 4-5 attempts of 6-7 sec cranking. Once car is started, it runs perfect, idles smoothly, accelerates well. I changed cool temp sensor because it was cheap and easy but problem persists. If I had other symptoms it would be easier but the hard warm start is my only problem.

Any ideas where to look?

Thanks for your help

[packratbimmer]

Have the injectors been cleaned? They could be dripping.

I'm throwing it out because cleaning my injectors (325i) helped on all aspects of starting.

[jlevie]

The injectors, fuel rail pressure on a warm start, and the cold start system are all suspects at this point.

[bluebenz]

Have the injectors been cleaned? They could be dripping.

I'm throwing it out because cleaning my injectors (325i) helped on all aspects of starting.

They haven't been cleaned or tested. But wouldn't leaky injectors also cause other symptoms?

[bluebenz]

The injectors, fuel rail pressure on a warm start, and the cold start system are all suspects at this point.

Thanks, it's definitely a fuel problem. I was also thinking a fuel pump problem but not sure why it would mostly affect warm start and not general driveability.

I'll need to have a step by step approach to solve this problem.

[jlevie]

If the injectors are leaking, they will flood the engine and that will be noticeable on a warm start. If the engine has cooled off enough and the cold start system is not quite working right you could have a problem that only shows up on a warm start.

[bluebenz]

CURED!!!!!!!!!!!

Hope I'm not too hasty to say it's cured, because it has been less than 24 hours, but it now starts instantly.

I am not good with a wrench, so I didn't do this the right way, I didn't follow an intelligent diagnostic aproach.

But to me, the car was acting like if it was starving fuel after it sat for an hour or so, but otherwise ran and idled perfect. So I assumed the car was loosing pressure in fuel lines after it sat, and I ordered a 3/8" inline fuel check valve, and got my mechanic to install it right after the main fuel pump. Took 15 minutes, and car now starts instantly!

Thanks for your help!

[jlevie]

That isn't a bad temporary fix, though a bad check valve in the pump should affect should and warm starts equally. Generally speaking, when the check valve fails, the pump won't last much longer.

I'm not convinced that you have really solved the problem and my strongest suspicion is that you have leaky injectors. Of, if an ETA, a problem with the cold start system.

[bluebenz]

That isn't a bad temporary fix, though a bad check valve in the pump should affect should and warm starts equally. Generally speaking, when the check valve fails, the pump won't last much longer.

I'm not convinced that you have really solved the problem and my strongest suspicion is that you have leaky injectors. Of, if an ETA, a problem with the cold start system.

It is an ETA. But you raised doubts in my mind, so I went outside and started the car again, it really starts instantly now, a huge difference.

My theory is the following: Before, when the car was hot it started well because there was still fuel in fuel rail, it started OK (but not perfect) when cold because of the cold start injector, and was hard to start after sat for two hours (not stone cold) because the gas drained back to tank. Does that make sense?

Again, thank you for your help!