Warm start issue!

[jonathanyeah]

Hi,

I have had my 325i a little over a year. It has recently started being troublesome to start when warm.

It starts perfectly when cold but if i use it for a short trip and then try and start it again it will struggle and take 4-5 attempts to start, also chucking a load of raw fuel out of the exhaust.

A bit of googling tells me this is a fuel pressure issue.

Injectors seals leaking? (They are original and should prob be refurbished anyway)

Fuel pressure regulator?

The fuel pump was replaced not long ago.

Where should I start?

Many thanks

[Yeti]

it wont be the fuel reg as it regulates the fuel. i would say its either a firing problem so its misfiring and leaving fuel behind which then goes out of the exhaust. i bet you get black smoke or strong fuel smell from the exhaust.

or it could be the injectors them selves are clogged and are bleeding through when they warm up hence the hard starting and fuel out of the exhaust .

id say its either two of those things.

but before you go wasting money i would then compression test it when its warm to make sure there isn't a cylinder down as lack of compression would cause the misfire/over fueling etc too. you should get around 150 psi on each cylinder with no more that 20 psi difference between them ideally.

also get a fuel pressure gauge too to see what the pump is doing, when you rev the car the pressure should go up to 3.3 bar ish. on a 325 there set at 3 bar standard. ( i don't think its this but it wont hurt to check)

if all of that is ok. i would do what i have stated underneath.

i would make sure the spark plugs are fresh, the ht leads are good they should test out at about 5k ohms , the rotor arm and cap are cleaned on the metal contacts so the spark is at its strongest. as that should eliminate the possible misfire or weak combustion.

if there is still a issue i would look at getting good replacement injectors if not take your old ones and send them to injector tune to be ultrasonically cleaned. i changed my injectors in my 318 my god i didn't realise how bad the car was until i did that.

hope that helps

[Brianmoooore]

Leaking injectors. If they are original, as you say, then they are long overdue for a rebuild, and even if I'm wrong about them being the cause of your problems, the benefits will still be very worth having.
See 'injectortune' in our traders' forum.

[jonathanyeah]

Thank you.

Will start with the injectors as they probably need doing anyway!

[Cloggy Saint]

I had a similar problem and it turned out to be a small split in a fuel hose. Barely noticeable but enough to lose fuel pressure.

[jonathanyeah]

I have had several splits in hoses, a couple that were very bad but I have checked them over and not noticed anything. I have noticed them pretty quickly before just by the smell!

[Speedtouch]

I would check the blue temperature sensor is working properly as a first step:

http://www.e30zone.net/e30zonewiki/inde ... emp_Sensor

Then check the ignition parts are in good condition, also the fuel filter - they are often forgotten about for years on end, and clogged ones lead to this sort of thing.

[jonathanyeah]

Ordered a replacement blue plug anyway as only a tenner.

It runs perfectly once started, no smoke from exhaust, smooth acceleration etc

[Brianmoooore]

Blue temp. sensor 'failure', on a facelift M20, usually turns out to be corrosion in the plug and socket that connects the injector loom to the main engine loom.
If your problem was anything to do with this sensor, the car would not run properly when warm, so it's highly unlikely that replacing it will help, especially with a cheap sensor like you have found.
Test and diagnose is the way to go. Don't fall into the trap of randomly replacing parts in the hope the the fault will go away - this often leads to more faults and confusion.

[Brdjo]

Help yourself and first do the compression test and fuel pressure test..
Also remove the vacuum hose from FPR to see if fuel is coming out of FPR when rev up engine..

[jonathanyeah]

Update . . .

Fitted new injectors . . . . . . . . what a difference! Would recommend getting them refurbished to anyone!

However, didn't solve the problem.

Changed more fuel pipes as were all brittle and perished anyway.

Finally found the issue. Big split in the underside of the gallows section of the rubber intake boot.

Had inspected it previously in-situ but didn't notice it. Took it off for a proper look and found the split.

Very satisfying.

[Speedtouch]

Good to hear that, dude.