hard start [Archive] - Bimmerfest - BMW Forums

: hard start

03-30-2008, 06:05 PM
hey all, I have a 80 320i with a hard hot start issue. After the car is run 15 min or so under load and you shut it off and let it sit for 1/2 hour it just cranks and cranks for a while and then finally fires and runs rough then its okay. I checked for leakdown on the cold start valve and that seemed okay. any ideas?????? thanks

fireman steve
04-01-2008, 09:11 AM
I am new to these cars, but I would crawl under the rear end (passenger side) and check all of the fittings in the Fuel pump/filter/check valve cluster. A small leak there could make for a problem like you describe. Also, check the lines that lead into the injector pump (facing your radiator at the front of the motor) for any signs of seepage there. Good luck, let us know what you find out.

04-07-2008, 10:07 AM
thanks for the info fireman Steve, I checked all the conections at the fuel pump; all is well. I looked over the mechanical fuel injection no leaks.

I thought of checking the frequency valve ( fuel pressure regulator) but do not know of any methods of doing so.

Jonathan Payne
04-29-2008, 01:33 PM
There is a relay sitting alongside the fuse box under the hood whose job it is to recharge the fuel pressure after shut off. Sounds like that isn't working. J Payne

fireman steve
05-02-2008, 04:28 PM
*ugh* now mine has this problem too! Frick! :tsk:

fireman steve
05-02-2008, 10:59 PM
I checked on the fuel pump relay, and that isn't the issue. I can hear the pumps running for a moment after I turn the key off. I am going to kill the starter motor if I can't figure this out. :( I will tear into it on Sunday if I get a moment and see if there is an air leak in the fuel injection system. It seems to be starving for fuel. After 30-45 seconds of cranking, it will barely come to life and then run rough for a few moments. Then it is a great runner. What the heck??? :dunno:

fireman steve
05-06-2008, 04:28 PM
Here is my thinking... Tell me if this makes sense to y'all:

I have pulled all of my fuel injectors and brought them to my BMW service center to be cleaned. (new ones are about $50 each) I did this, because my motor was acting a lot like a flooded carbureted motor. So, I think I might have an injector or two that are sticking open a little and thus allowing fuel to drip after the motor is shut down. This would flood it, right? I cant find any other reason for the hard hot start, so I am hopeful that this solves the issue. I should have my injectors back Friday or Monday, so I will get back on here and let y'all know how it works out for my car. If this isn't the fix I need, I might go to the coil???

I am being a prolific poster on this issue because it seems to be a fairly common issue, but I have yet to see anyone post their solutions. I can't imagine that everyone with hard start issues is just dealing with the fact that they are burning up starter motors. If you have had this problem in the past, please don't be shy; let us know what your solution was.

Until next time motorists- :bigpimp:

fireman steve
05-09-2008, 08:07 AM
It's running, and starting, like a champ now. I think I got to the bottom of it. :thumbup:

fireman steve
05-11-2008, 11:30 AM
I stand corrected, still have a gremlin under my hood. :tsk:

fireman steve
05-13-2008, 06:56 PM
Just replaced the oxygen sensor, good chance that is the culprit. What a pain in the butt that job is if there is AC. The AC didn't work anyhow, so I took out the compressor. Easy job after that! :p

I'll keep y'all posted if that is the fix.

Is anyone following this, or am I just filling up space writing to myself???

05-30-2008, 06:52 AM
I had the same problem. I traced it down to the fuel accumulator. It is mounted next to the fuel filted. There is a diaphram inside the accumulator that developes a leak and allows the fuel pressure bleed off.

When the engins is shut off the fuel system should maintain a pressure of approximately 25psi. If the pressure bleeds off the heat from the engine vaoprizes the fuel and bingo you have a hot start problem.

There is a return line on the back of the accumulator that feeds back to the fuel tank. Remove the hose and activate the fuel pump. If the diaphram is leaking fuel will shoot out. Be careful, or you might have a fire.

There is also a check valve on the fuel pump that can cause problems. It only costs about $10 so replace it while your at it.

fireman steve
05-31-2008, 01:21 PM
Awesome! Thanks for the tips. I would not have thought to check those things. I will get right on it (them)!

I was beginning to think that no one actually replied in this forum but me. I appreciate you taking the time to share your experience. :thumbup: It is nice to have a support group for us grease monkey types...

06-01-2008, 07:05 AM
Let me know if it solves your problem. I also made a comment on your Vacuum hose question.