s52 hard start...

[jakeb]

So twice today my recently swapped s52 took a little longer to start. Cranked for 5-8seconds and then shut the key off and tried again and it started right up. This was after driving the car all over and letting it sit for maybe 90 minutes. Car restarted later after driving, only being off for 5-10minutes. Then about 3 hours later it did the same thing. Drove a little bit and shut it off and it restarted fine....after a few minutes.

Any ideas? sounds like it is loosing fuel pressure when it is sitting. Or at least that is what i think. The fuel pump is fairly new.... Maybe a bad FPR?

obdI s52 in a 318is

[jakeb]

just went out and started it again...after 2 hours of it sitting. It started quicker but still did take a lot longer than normal. Also to add I replaced the fuel filter last summer and the pump this spring

[pedal2metal]

Leaking fuel injector.
To test, hook up a fuel pressure gauge. Run engine, shut off engine and immediately pinch off both fuel lines. And if the pressure drops you have a leaky fuel injector. If you find that you have a leaky fuel injector, remove the fuel rail w/ the injectors still attached, you'll have to plug 1 side of the rail then apply about 50-55 psi air pressure to the other side of the rail, then open and close all the injectors several times until all the excess fuel in the rail and injectors is eliminated (very important!). Once all the fuel is out of the rail/injectors, pressurize the rail w/ 50-55 psi air pressure and dip the injector tips into a tank of water and watch for bubbles. If one is leaking you'll be able to tell right away. a few bubbles is ok, but usually a leaky injector will spit out a substantial amount of bubbles in a short amount of time. Then replace the suspect injector and enjoy easy start-ups. And use good fuel (Shell, Cheveron) or use fuel sys cleaner regularly. Or just remove all your injectors and send 'em to this guy...http://www.witchhunter.com/

[jakeb]

thanks for the reply... I actually have a extra set of injectors so I could easily swap them out. The extras are actually from the engine and the ones in now were an extra set that were already off the fuel rail.

I will try that tomorrow, easy enough to do.

If I still have the problem I will use your test.

thanks

[pedal2metal]

Usually when you have a leaky injector, you can drive the car for a while, shut it off, and if you try and start it within an hour it will crank for a while because of the extra fuel in a particular cylinder. But if You let it sit over night the fuel will seep past the piston rings and into the crankcase and start right up with no delay. Which is REALLY bad for your conrod and main bearings. Good luck!

[slow e30]

if the cyl is full of fuel, take the sparkplug out and leave it out while you replace the injector. should be ready for a refire once all reinstalled.

[jakeb]

So if in the morning it starts up quickly then it helps confirm the leaky injector? If that is the case would it also be a good idea to change the oil? I havn't really driven it all that much, to work and back for the past 2 weeks. Not many trips where it has sat for a short period, all have been either minutes or many hours.

thanks again for the replies

[jakeb]

Well it did start quicker in the morning so I swapped out the injectors for another set I had. The ones that are in it now are the set that came with the engine....may have been sitting for 6 months. But anyway...started fairly quickly after I got them in. Seemed to have more power as well. Drove it around for a while. Then it sat for 3 hours and when I started it it was hard again. Took two tries to get it going... I bought some injector cleaner and drove it around with that in it. Could this other set also be leaky? or is it something else?


I have an extra fuel rail (obdII left overs) that I am going to use to test these other injectors I pulled out and see if they were leaking...... if so then I will pull the ones in the car and test as well and come up with a non leaking set. If not then......

[1990m3]

you have a different problem. My car does the exact same thing and I haven't been able to trouble shoot it.

Try this the next time you think it will hard start. Turn the key to the on position, let it sit for approx 3 seconds and then fire the motor. It sounds stupid, but it works for my motor just about everytime.

Cold motor starts perfectly, warm motor cranks over for a while. But, when I try the above method it works very well. I don't have any leaky injectors.

[jakeb]

what all have you tried?

could it be a bad Coolant temp sensor? This is not the same sensor I had when I had the m50 as I broke it when I took it out. This is out of a m42 I had in the garage...same part number though.

I will try your method next time I get a chance. I am also going to test the injectors I pulled out and see what I come up with.

[Jason89i]

check the resistance of the dme water temp sender at the c101. not the single pin temp sender (for the gauge) but the dual or 4 prong one for the dme. if it is not making contact, the dme reads 0ohms for resistance and assumes it is REALLY cold and over-fuels. this causes hard starts (especially when warm) and results in a rich running condition. i had a faulty connector at the sender and it was intermintant...hard to diagnose. wiggling the connector and it was ok, wiggle some more, it lost contact.

cheers, jason

[jakeb]

the dme coolant sensor does not come back to the c101....it should come back to the dme connector. I will have to find out what pins it comes back to.

A slight update... I checked to see if the injectors that I pulled out were leaking and they were not so I assume the ones in are not as well as the problem is the same.

I pulled the connector off the coolant sensor and am checking the resistance of it. This was with the car warm and it was around 450ohm. After about 15 minutes of it cooling down the resistance was going up. I will check it when it is cold.

I checked another sensor I have on another car, m42 in my 2002, and at dead cold it is reading just over 2000ohms.

Does anyone have a m50 sensor they can check the resistance of or is there a listing somewhere of the curve of it. Maybe a MS guy has the curve?

TIA

[Jason89i]

check the resistance of the dme water temp sender at the c101. .......

the dme coolant sensor does not come back to the c101....it should come back to the dme connector. .
TIA

DDUUUHHHH. sorry, my bad, brain freeze.
We had it hooked up to a gt-1 and could see the actual readout in real time. after some monkeying around, we found it.

sorry, dont have any ohm / temp graphs.

[jakeb]

well I found the pin out for the DME here, http://www.wedophones.com/Manuals/BM...g%20Manual.pdf
page 147 for future reference if anyone has this same question. My harness is from a 93 e34.

sensor goes from pin 78 to 44. I do get connectivity from the plug to those pins, also when plugged in to the sensor I am getting the same resistance reading as when reading it from the sensor itself.

As the car is cooling down the sensor is now reading around 1200ohm. So the sensor is reacting to the change in temperature.

One thing I have noticed is the sensor is not blue like it is on my m42 and from what I read the dme sensor is supposed to be blue also saw a picture of it on bavauto's site and it is a blue sensor and is the same from the 91 318is m42 to any of the m50 cars.

I am thinking of swapping the sensor from the m42 car over to the s52 and see if that changes anything.

Any other ideas for me to check out?

[jakeb]

Well I swapped the sensor out for another one that has always worked fine. I also checked the vacume lines at the bottom of the TB/elbow and at the brake booster as they were hard to get on when I put the engine in.

Took a little extra to start when I first started it this morning. Drove it for a half an hour it then sat and cooled down for just over an hour....and when I went to start it it was a hard start. Took a lot longer than normal. Drove the car home...made a quick 5 minute stop and it started fine when I came out.

So the problem is still there. I am thinking it sounds like it is loosing fuel pressure after sitting for awhile. Maybe after it sits all night and starts the dme knows the car is cold so is injecting more fuel so it start a little easier but it does still crank longer than it should be.

I am thinking the next time I know there will be a hard start....over an hour or so of sitting... I am going to try and prime the pump and see if that helps. What pins on the fuel pump relay do I need to jump to get the pump to run?

This is my DD and I would like it to start as it should..... any other things to check.

jake