535i HAS HARD STARING ISSUE

[schnitzel#boy]

When I start my car ( 1985 535i ) it sounds like a German machine gun going off before it starts up, seems to take too long 4-5 cranks . Should start on 1 or 2 .

Car has :
- New battery
- Rebuilt injectors
- All new vacuum hoses
- New oil pressure switch
- New spark plugs
- New cap, rotor and coil
- New starter
- Alternator tested functioning OK
- New Bosch fuel pump relay

Can someone shed some insight on this issue ?

[waynet1]

4-5 cranks???
Something like this?
https://youtu.be/DArvPMlxHeQ

[demetk]

4-5 cranks???
Something like this?
https://youtu.be/DArvPMlxHeQ

It takes 2 cranks to build up fuel pressure if you have lost it all. So 4-5 cranks sounds good to me.

[schnitzel#boy]

Will work on changing out Fuel Filter, Fuel Pump and Fuel pressure regulator and 3-4 feet of Fuel hose down in that area that may be crusty. Will see how she runs after this

[Beemernut]

I parked my 535i out back of the shop for the winter and every time I go back there it seems to be giving me a hard stare. A tear comes to my eye and I say, "Not today, old friend."

[tn535i]

Will work on changing out Fuel Filter, Fuel Pump and Fuel pressure regulator and 3-4 feet of Fuel hose down in that area that may be crusty. Will see how she runs after this

If the problem as suggested above is fuel pressure bleeding down from either a poor check valve in the pump or the FPR... The above will fix that but lot of expense. Once upon a time BMW sold a chunk of hose with check valve for ~$10 that did the job but no more unfortunately. Replacing ALL the pressurized fuel lines on a 30 year old car is not a bad idea though.

[schnitzel#boy]

I replaced the Fuel pressure regulator this weekend and I noticed a slight improvement but when Hans comes up to temperature he start shaking the idle starts looping up and down. Waiting for ramps to get delivered so that I can change out the Bosch filter and fuel pump .

[tn535i]

Hans may need some more work as generally a fuel pump is either good (making pressure) or bad. The CTS (coolant temp sensor) is one of the few parts I would just throw at an old BMW since it has so much impact on mixture as it warms up. The O2 sensor is another one or simply try unplugging it to see if that helps (green wire that breaks out on engine side of glovebox firewall). What you describe almost sounds like extreme dithering from too rich mixture and the DME trying to lean it back out. Next up would be distributor cap, rotor & plugs depending on their age. Do you have any idea the age or condition of these?

Again, if getting into these things replacing the fuel lines with high quality 'high pressure fuel injection line" is a good idea. I've use USA made 5/16" but some would shudder if it doesn't say BMW on it.

I once had a car name Franz (after Klammer the skier) and in the back of my head this has been the name I would give my old 535 if I did that sort of thing Maybe they are brothers ?

[schnitzel#boy]

Yes , I did that too early on I replaced both the coolant temperature sensor and the temperature sending unit. I also cleaned the idle control valve and throttle body as well as replace the idle control sensor. I will try the O2 sensor as suggested to see what happens. The cap / rotor plugs and spark plugs were all replaced by previous owner. I was just trying to do my part prior to taking Hans over to the Beemer Clinic up in Hendersonville , NC the guys has over 28 years experience with older BMW so hopefully he can figure this out he has worked booked out ten days in advance so either late Dec or in the new year. I will post an up date when I do Fuel filter and Fuel pump

[tn535i]

Definitely see what it does if you unplug the O2 sensor. This is simple test. Sometimes an old O2 will flat line output and drive the DME to an extreme. I've read even water soaked ones can give bad readings. Either means the DME corrects for something that isn't real making the car run horrible. One reason newer cars have multiple O2 sensors is so they can better self check and ignore one that might be bad. My son's e46 has 3 or 4 I think.

Are you able to drive it. For example if you can get past about 3500 rpm in WOT where it goes open loop and ignores the O2 and find it runs great, that's a strong clue the O2 is fouling it up in closed loop.

[schnitzel#boy]

Yes the car runs great! pulls strong just idles like it has the shakes only when it reaches operating temperature . It actually idles pretty good when it is cold .

[tn535i]

It will ignore the O2 until it reaches temperature... seems like a lot of this suggests a bad O2 sensor.

It is pretty easy to test with a meter and you want to see it dither or swing between about 0.2 and 0.8 vDC. If it seems to stay at one extreme or the other it is probably bad but try blipping the throttle to see if it swings. If none of that produces any change in output it is most likely kaput.

However, maybe back up and double check vacuum leaks and such at idle. Quick check does lifting the dipstick or removing th eoil cap change anything.

[schnitzel#boy]

I ordered an O2 sensor as you suggested , great deal on EBay NOS for 25 bucks they have 1 left . I will return Bosch Fuel pump since I was barking up wrong tree . I will have the fuel filter changed put any how as part of preventative maintenance .

https://www.ebay.com/itm/BMW-OEM-Oxygen ... 2749.l2649

For this price you can go wrong will report back after I have it installed . Boy I hope this does the trick

[tn535i]

Let's hope that solves it but since you haven't tested much there is no guarantee. The O2 sensor is one thing that will wear out though and should eventually be changed. I'm tempted to grab one myself for that price.

[schnitzel#boy]

I managed to replace the O2 sensor last Sunday and took it out for a road test , once again when Hans comes up to operating temperature an I stop at a light he starts shacking and the idle keeps looping up and down . I will have to take him in for an appointment to have the specialist check into this annoying issue .

[schnitzel#boy]

Mystery solved - Car has an old alarm system that was installed way back in its day,. this causes a slow drain on the battery , thus the hard starting . Car started right up when I had to give it a boost. Solution rip out all the alarm stuff out or get a battery tender and wire it up . this will regulate and keep battery at optimal charge. I didn't suspect the battery because the previous owner told me that he just put in a brand new battery.

[tn535i]

Crazy stuff like this seems too common on these old cars and really no way for us on the other end of the internet to even guess.

Well it sounds like Hans has some new parts and probably a few e-spares and is happier now.

[schnitzel#boy]

Since I don't drive this car much I bought a battery tender ( automatic battery charger ) it took a day and a half to get the green light on that battery

[tn535i]

I have a Battery Tender Jr. that I casually rotate (maybe move every couple weeks) between the M6, e30 and my boat battery. It seems like it is always a day later before the light turns green even If I have started the car and let it run before connecting the charger. I think it's normal.

[schnitzel#boy]

Also add into the mix , a MAF box that is not calibrated with the idle control valve and becomes a recipe for disaster.