E34/535 No start

[Rus]

Since the issue seems to be related to cold temperatures and doesn't manifest itself on a hot engine, it is probably not fuel-related. In my case, when fuel pressure bled off, the engine would start after maybe 4 or 5 seconds of cranking. Basically long enough for the pump to pressurize the system. This would also happen on a hot engine.

It may be worth a try to pull out the spark plugs and check the gaps, condition and color. It is not unheard of in colder climates for cars to not start with worn plugs (Russia comes to mind :-p ). In cold weather, having good spark to ignite the fuel mixture is pretty important. Also, it may be a failing crankshaft position sensor. Generally, they'll just outright not work when they fail, but I've heard of instances where they caused issues before causing a no-start. For the longest time my CPS was causing a hesitation when pulling away from a stop on a cold engine in the morning (diagnosed the CPS after it crapped out completely and was replaced). The new CPS has eliminated the hesitation, made the car catch much faster on start up and smoothed out the idle. If you have a multimeter, check the CPS as per the Bentley manual. Do it hot and cold to check for differences.

Also, if you want to double-check the fuel pressure issue, jump the pump relay and run it for a few seconds before cranking the car. If it starts faster, then its fuel.

Hope this helps

[DABLACK]

Could be the fuel pump or the fuel pump relay

does anyone have the part # for the fuel pump relay

[ahlem]

I'd try turning the ignition from off to fully energized but not far enough to crank several times at about 3 second intervals then try to start the car. I believe the fuel pump kicks in for about 2 seconds then shuts down. If you do it a couple times, you build fuel pressure. If it starts right up once you do this you have verified that the relay works OK and something is letting down fuel pressure when it sits. You can have a helper do the on-off manuever while you listen in the trunk for the two second fuel pump run. Cheap and painless check.

[DABLACK]

I'd try turning the ignition from off to fully energized but not far enough to crank several times at about 3 second intervals then try to start the car. I believe the fuel pump kicks in for about 2 seconds then shuts down. If you do it a couple times, you build fuel pressure. If it starts right up once you do this you have verified that the relay works OK and something is letting down fuel pressure when it sits. You can have a helper do the on-off manuever while you listen in the trunk for the two second fuel pump run. Cheap and painless check.

This is the technique I used when it was getting hard to start on very cold days after a while(turn the key 2 or 3 times to get pressure and it would start) then i installed the check valve and regulator and like i said now nuttin doin it wont start

[DABLACK]

This is the technique I used when it was getting hard to start on very cold days after a while(turn the key 2 or 3 times to get pressure and it would start) then i installed the check valve and regulator and like i said now nuttin doin it wont start

Well boys, I talked to my bro who was a Bimmer & Volvo tech he suggested all the same things you guys did but last night he said "as a shot in the dark I should pinch off the retun hose at the regulator and try to start it" i did this this morning and VOILA after a sputter and choke the son ova b**** started.
Any thoughts gentleman...now im wondering if im missing somthing. I read an earlier post that he installed the check valve as well and he didnt get his e34 going until 1-3 days later and hasn't looked back...but that still seemed odd
am i being too skeptical.....

[Rus]

Your FPR must be faulty and letting fuel through at all times. The way it should work is this:
Engine off - no vacuum - FPR valve closed and fuel retained in the injector rail.
Engine on at idle - high vacuum - FPR valve open, some fuel returned to tank
Engine under throttle - low or no vacuum - FPR valve partially open or closed, less or no fuel returned to tank.

If you pinched off the return line and the car started up, then the FPR is open all the time and when you tried to start it before, the pump couldn't build enough pressure in the system.

[DABLACK]

Your FPR must be faulty and letting fuel through at all times. The way it should work is this:
Engine off - no vacuum - FPR valve closed and fuel retained in the injector rail.
Engine on at idle - high vacuum - FPR valve open, some fuel returned to tank
Engine under throttle - low or no vacuum - FPR valve partially open or closed, less or no fuel returned to tank.

If you pinched off the return line and the car started up, then the FPR is open all the time and when you tried to start it before, the pump couldn't build enough pressure in the system.

FPR....i hoping you mean fuel pressure regulator...(im out of the loop with some terminology so I need to learn up on fancy code names)...I got a new one on 2 days ago just in case...while I was eliminating some things after check valve, like relay's etc i got it pronto as my brother and you guys suggested and after that it still didnt wanna give until the ol pinch off technique
so I wanna make sure im not assuming the problem is solved and screw myself

and again thanks Rus and the rest of ya'll guys...ive been a long time reader here and picked up some no ALOT of help and tips and the main reason is all of the people here are just the best!!!!!!

[Rus]

Yes, FPR means fuel pressure regulator. If your car is starting up when you pinch the return line, something isn't right with the FPR. It should be doing the pinching, not you. You may have gotten a brand new faulty FPR. Stranger things have happened :-p I'm not sure if there's a way to test the FPR outside of making sure that it holds vacuum. You gotta realize that its up against about 60 psi of pressure and the smallest imperfection in the valve inside of it may cause it to leak. You could pull the little return line off of the FPR and then jump the fuel pump relay terminals to operate the pump to bring the system pressure up. Watch for fuel to come through the FPR. It shouldn't be siphoning fuel through when the engine is off. Be sure to use a rag to catch any fuel that comes out. Wouldn't want to spray the engine with gasoline.

[DABLACK]

Yes, FPR means fuel pressure regulator. If your car is starting up when you pinch the return line, something isn't right with the FPR. It should be doing the pinching, not you. You may have gotten a brand new faulty FPR. Stranger things have happened :-p I'm not sure if there's a way to test the FPR outside of making sure that it holds vacuum. You gotta realize that its up against about 60 psi of pressure and the smallest imperfection in the valve inside of it may cause it to leak. You could pull the little return line off of the FPR and then jump the fuel pump relay terminals to operate the pump to bring the system pressure up. Watch for fuel to come through the FPR. It shouldn't be siphoning fuel through when the engine is off. Be sure to use a rag to catch any fuel that comes out. Wouldn't want to spray the engine with gasoline.

I have started it successfully 3 times now without a hiccup since this morning....the real test will come tomorrow morning after 16-18 hrs of sitting overnight in the cold

[DABLACK]

I have started it successfully 3 times now without a hiccup since this morning....the real test will come tomorrow morning after 16-18 hrs of sitting overnight in the cold

Started like a charm this morning..I guess its fixed for now.... next job is spark plugs and looking at new/rebuilt injectors. Keeping an eye on some intresting posts for injectors...