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1996 E34 525 TDS Difficulty Starting Cold

8K views 6 replies 4 participants last post by  j0nr 
#1 ·
Hello,

I have a 1996 BMW E34 525TDS and it is starting to become difficult to start when cold. Cold as in properly cold, from over night.

The problem came around when we had a very cold spell (sub-zero temps over night). It seems to be temperature related, as when the temps aren't so low its not so hard to start.

To get it going most time I either have to crank it a lot, like 30 secs+ and it finally splutters into life in a big cloud or I have to turn the ignition on and off several times to let the glow plugs go on and off many times, trying to get some heat in there.

But it seems to be getting worse.

Could it be my glow plugs - How can I check them?

Could it be more serious - loss of compression?

Or maybe a fuel pump problem, i.e. the 'lift' pump in the fuel tank I have read causes a lot of issues like this, but I am not sure whether this is my case as once there is a bit of heat in there, it will start on the button.

Thanks in advance.

Jon Reynolds
 
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#2 ·
get your battery checked, just changed mine due to the same symtoms albiet on a e46 320d, trouble is although the battery may sound like it's turning the car over fine it's drawing the power away from things like glow plugs etc, try to start the car with jump leads from another car see if it fires faster, does it start ok when the car is warmer later in the day?
 
#3 ·
Hi steve,

The battery was replaced recently with a heavy duty one, so cranking/poor battery is not the problem I don't think.

As I said, once there is some heat in there (i.e. not freezing weather or just after a few minutes of running or even later that day after being up to temp and left to cool for hours) it starts on the button, no problem. Just seems to be when it is stone cold it takes ages to 'catch'.
 
#5 ·
Glow plugs are each wired separate so if one goes down it will not rob power from the others like some old Ford 1.8 diesels do.

Check how long the glow plug light stays on,this will vary due to outside temperature,so in summer it is on for less and winter stays on longer before going out.There is a temp sensor somewhere for this,possible an engine temp sensor.

The glow plug relay also powers the lift pump while the glow plugs are on.

So if you had 3 glow plugs out the engine would fire and then run rough on 3 cylinders until they got warm enough to fire.

A bad battery as in low amps but still showing full charge can be spotted by starting behaviour.If during use you find the car starts ok but seems to go 'whuumf ' and rev itself when started then this is an indication of low cranking speed due to low amps in the battery,the ecu dumps fuel in to raise the revs because the engine has 'only just caught and revs are low'.

The glow plugs can be checked with an ohm meter or just cycle them and touch them with your finger and get burnt on the ones that work and are hot,or the bodgers method which is to disconnect the six wires from the controller and touch a live on each one.Now one that works will take power and you will see a spark as the wires touch.

Lift pump.Now these get lazy but do not rule out an air leak letting fuel return to tank and lift pump not getting fuel to front of car in time before cranking for engine to start.

Keep the tank over half full and if it improves then 'lift pump 'o' ring is bad (easy fix).

The lift pump may be lazy,now park the car nose down on an incline and see if it starts ok.

Also the fuel filter may be blocked ?,if you run veg then expect the veg to thicken and cause problems which go away once the engine and fuel is warm.

It is not a compression problem it is either lack of fuel or lack of glow plugs.

Have a glance at the clear fuel pipe that goes from filter to injector pump first thing in the morning to see if any air in there.

I favour lift pump as the trouble or something along the fuel side of things,bad glow plugs will cause trouble but it should start quite easy but noisy with even a couple gone bad.
 
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