Very Strange Starting Problem

[Madmaximus]

Hi Guys

I have a Very Strange Starting Problem.

When My car is Cold it will start 100% every time.

When it is Hot (Normal Running temp) will start every time

If I Drive it and leave it for more then 30 min so the car has cooled a bit and the Temp gauge is in the middle of Hot and Cold it will not start until its Cold again?

Anyone had a Similar Issue or know of a problem like this?

Car : Bmw 518i 1982

Please Help :ty:

 

[Luis Malhou]

Looks like the temp sensor might be a bit confused and over fueling.

There is temp sensors on the water housing on the front of the motor, normally 2 or three sensors. One is the sensor for the gauge, the other one goes to the ECU telling the temp of the motor. In the morning it will tell the ecu to provide more fuel for cold starting and when the motor is up to temp it will deactivate. Yours might be activating all the time, you should however be getting bad fuel consumption. Two things could be happening that allow the car to start when fully hot. When you stop the extra fuel has enough time to vapourize in the chambers so the car is not flooded and can start, however if the car stands for awhile the fuel might again condense or the coldstart activates at a higher temp because of the sensor signal causing the flooding of the engine and causing it not too start.

Also just check if their is spark at the point when its not fully cold and if the plugs are wet with fuel.

I can't recall but if you unplug the sensor it reverts to a zero figure removing the cold start feature, try unplugging the wire of the sensor when it doesn't want to start and see if it starts then, if it does then definitely the sensor.

I will ask a friend who is in the know and see what he says too..

 

[Madmaximus]

Looks like the temp sensor might be a bit confused and over fueling.

There is temp sensors on the water housing on the front of the motor, normally 2 or three sensors. One is the sensor for the gauge, the other one goes to the ECU telling the temp of the motor. In the morning it will tell the ecu to provide more fuel for cold starting and when the motor is up to temp it will deactivate. Yours might be activating all the time, you should however be getting bad fuel consumption. Two things could be happening that allow the car to start when fully hot. When you stop the extra fuel has enough time to vapourize in the chambers so the car is not flooded and can start, however if the car stands for awhile the fuel might again condense or the coldstart activates at a higher temp because of the sensor signal causing the flooding of the engine and causing it not too start.

Also just check if their is spark at the point when its not fully cold and if the plugs are wet with fuel.

I can't recall but if you unplug the sensor it reverts to a zero figure removing the cold start feature, try unplugging the wire of the sensor when it doesn't want to start and see if it starts then, if it does then definitely the sensor.

I will ask a friend who is in the know and see what he says too..

Thanks you for the reply :ty:

I have tried Pulling the sensors and plugging in again with no luck, I am Almost sure my car does not have an ECU, but i could be wrong what I can tell you is that when its not Fully Cold yet and not starting there is No Spark at all, Someone also suggested it could be the Fuel Relay?

Thanks for the help

 

[Deren]

Hi

I am assuming your car is fuel injected? if so it could be a leaking fuel injector maybe have that checked out as well:coolShake:

 

[Luis Malhou]

No spark could lead us in the right direction. If its Injection it will have an ecu. Its a small crude early computer box but it will be there.

I dont want to rule out a leaking injector, however one injector could lead to hard starting when hot and even when cold, but car should still start on 3cyl. If more than one injector is leaking then its a different story.

If your in JHB I can suggest you go past Paul Cassons place, it helps if you have the physical car in front of you to investigate the fault.

Ye is in Wynberg / Kew 0117862992, try him after 10am.

GL

 

[Madmaximus]

Thanks Again Guys

Unfortunately I'm in Port Elizabeth

Ill have to take it to my local Mech and see if he can find the fault, I know its going to be one of those trial and error jobs. :thumbdo:

 

[Solo Man]

I remember many years ago i had a 1985 E28 535i with much the same problem. My mechanic told me to disconnect the cold start sensor which was some place below the inlet manifold iirc. That was on the six cylinder car, so not sure if that could be your problem (i think Luis was talking about the same thing). In our climate it did not make matter if it was disconnected.