Starting issue

[6670charger]

92 525i Touring, 2.5 M50 engine/manual trans, about 167K miles:

Just developed a starting issue with my 525i Touring yesterday. Seems all of a sudden she occasionally wants to start hard, instead of firing right up like normal. She'll occasionally crank and hiccup a bit first time, then fire right over the second attempt; starts normally the rest of the time. Been doing a little reading on the site, and sounds like the most probable causes are either fuel pump or CPS. Can anyone think of anything else I might look for?

Also been having a pretty consistent issue with brief, uneven acceleration for a few minutes after it's been sitting for several hours. She'll run like a champ for about a minute right after startup, then seems to sort of bog down for a few minutes, and runs/accelerates unevenly. Seems to occur during intermediate warmup, and then cures itself once she's warmed up.

Thanks.

[Tiger]

It does sounds like fuel pump, CPS or MAF. Put a fuel pressure gauge on it and see if it meets spec.

[genphreak]

The first culprit is an air leak into the intake somewhere. Do you know all the places to look on an M50? Also, a number of other things can be found when problems get to this stage- connectors, pipes, temp senders, FPR, injectors, plugs. You need to check them all (and certainly not just the CPS and FP); you may well find they several are not quite right and more than one are really bad...

[jeffheron]

IMO, you need to clean up the oil and plugs there is also a possibility of fuel is not properly injecting.

[6670charger]

Well, found out what the problem is. I had a pinhole in the return line above the tailpipe near the diff. Took it in to the shop today to see if I could cut out the bad part and splice in some decent line with some 8x13 gas hose and clamps. While pounding on one of the fasteners for the line retainers, the pinhole opened up into a nice eight-inch long gash and was spewing fuel all over the place. All it would have taken was a good bump somewhere while I was driving and I would have had fuel spraying all over the exhaust pipe. Then, while trying to cut off the end of the return line, I found that it was also rusted through above the diff itself. Got it free from the retainer near the filter and was beginning to make a cut there so I could put my rubber connector piece in, and the whole works pulled down out of the tank. It was rusted off up there too!! ARGH!!!! Now I have to drop the tank to finish bending the new line so I know where it all connects. Problem is, I ran out of time and I can't get back to it again until next weekend, so looks like I'm bike riding this week. Better than walking I guess.