Occasional no-start condition - 92 535i

[Bill in MA]

The ol' girl has been acting up a bit recently. Probably 30% of the time I go to start the car and it cranks fine but never catches, doesn't even try. If I release the key then try again, the car usually starts right up, although it will occasionally run a bit rough. Depressing the throttle slightly also seems to remedy the situation. Seems to do it hot or cold.

I've recently replaced all ignition components (Wires, coil, plugs, cap and rotor) and injectors, fuel pressure regulator, filter etc.. as part of normal maintenance or upgrades I did with the turbo installation. Coolant temp sender is new.

Any ideas? Is this a reference sensor issue? I checked the resistences and they are within spec. FYI - This car does have traction control (EML)

Thanks

Bill

[Mobius]

If it runs fine otherwise - maybe it's this? http://www.bmwe34.net/E34main/Trouble/535ihot_start.asp

[shogun]

as Mobius already says.
Try the following: before you start the engine, switch ignition to position 2 and wait a few seconds. With they key in this posiition the fuel pump starts running for about 4 seconds and will switch off again if the engine is not started. This ensures that the required fuel pressure is there when engine is started.
In case that helps, you can be sure that the check valve is defect. Costs only a few $ and is easy to change and installation is on top of the fuel tank. If the original check valve from BMW is not available take one from the aftermarket which holds about 3 bar.

[Bill R.]

main relay and the fuel pump relay, if these relays have corrosion on the connections or if they have some arcing on the contact points then sometimes the first time you turn the key the pump relay won't make good contact and won't energize the pump...so that you could crank indefinitely and it wouldn't start but as soon as you shut it off and try again the next time the points make contact and it starts...So i would inspect those two relays first off and see what the points look like on them.. If they check out ok then i would look at the check valve next, then i would double check the crank position sensor for tightness and make sure that the gap was correct (1mm).







as Mobius already says.
Try the following: before you start the engine, switch ignition to position 2 and wait a few seconds. With they key in this posiition the fuel pump starts running for about 4 seconds and will switch off again if the engine is not started. This ensures that the required fuel pressure is there when engine is started.
In case that helps, you can be sure that the check valve is defect. Costs only a few $ and is easy to change and installation is on top of the fuel tank. If the original check valve from BMW is not available take one from the aftermarket which holds about 3 bar.