BMW Forums : BimmerForums banner
1 - 20 of 24 Posts

·
Registered
Joined
·
65 Posts
Discussion Starter · #1 ·
Hey everyone I recently bought a 525tds 135k miles in clock m51 engine I have hot starting problem

Car starts and runs fine from cold pump in tank runs OK I cleaned tank and pump and gauze fuel pump relay is OK fuses all OK no fault codes associated to fuelling I originally thought it was fuel delivery issue

Mate of mine in bmw reckons the crank sensor is at fault when I had it up on live data it was also v slow to register the rpm to the dde so it is possible

I hope the pump is not goosed as I seen on other forums they can get worn out

I want to ask yeir thoughts on what ye think it might be

I've crank sensor on the way and and new fuel filter egr appears clean and manifold I have yet to unplug the maf sensor to check n see if it's causing this problem I also inspected engine earth straps for fray or damage

My mate in bmw reckons crank sensor is the problem as its resistance gets messed with as it heats up with the engine he has done dozens if them on both diesel and petrol models resolving starting issues but what do you guys think?
 

·
Registered
Joined
·
65 Posts
Discussion Starter · #3 ·
Very possible it is the crank sensor.
When i had that problem i got a fueling related code and turned out to be leaking injectors x2.
Thanks Alan for the input yeah I have no fuel related codes had an old code for charge pressure sensor or the boost sensor as it was missing but that has since been replaced n cleared so I've no codes in the dde also I pulled the crank sensor to measure its resistance

Spec is 1300ohms plus or minus 10ohms

The value I got was 1260 which is off a lil maybe also why the cranking is also prolonged from cold too
 

·
Registered
Joined
·
842 Posts
This was a common issue on the TDS engine. I had one and it had a long crank when warm before it would start but great from cold. This was also a well documented issue on the Range Rover with the same power plant. I fitted a relay which activated every time the ignition switched on for about thirty seconds which activated the in tank pump and put on the glow plugs and this sorted it 100%. I will try and find a link to a thread if I can. I also had a 325tds and it did exactly the same too.
cheers
jim
 

·
Registered
Joined
·
842 Posts
Found this on eBay which is what I fitted and as I said it transformed the way it started when hot.

cheers
jim
 

·
Registered
Joined
·
65 Posts
Discussion Starter · #6 ·
This was a common issue on the TDS engine. I had one and it had a long crank when warm before it would start but great from cold. This was also a well documented issue on the Range Rover with the same power plant. I fitted a relay which activated every time the ignition switched on for about thirty seconds which activated the in tank pump and put on the glow plugs and this sorted it 100%. I will try and find a link to a thread if I can. I also had a 325tds and it did exactly the same too.
cheers
jim
Yeah if I unplugged the collant temp sensor would that not trick the car into thinking its cold then activating the plugs and every time I turn on ignition even when hot I still hear the in tank pump running
 

·
Registered
Joined
·
65 Posts
Discussion Starter · #7 ·
Found this on eBay which is what I fitted and as I said it transformed the way it started when hot.

cheers
jim
Thanks Jim I will save that p38 kit and if the crank sensor does not resolve the hot start issue I will buy the kit n wire it in
 

·
Registered
Joined
·
842 Posts
If you disconnect the coolant sensor it will over fuel all the time like running on choke. This tricks the ecu for thirty seconds and then reverts back to normal signals so the fueling is not affected. I seem to remember it was real easy to fit as well.
cheers
Jim
 

·
Registered
Joined
·
65 Posts
Discussion Starter · #9 ·
Thanks Jim ill fit the crank sensor when it arrives n see how I go if it doesn't resolve it I may look at getting the kit that said I also seen videos of guys on the net loosening pump bults and adjusting the timing of the pump then tightening and restarting engine and kept repeating this procedure until the engine started hot the chains seemly stretch v small amounts w age and wear and the factory pump setting is no longer any good for correct amount of fuel to be injected on a warm start 😳
 

·
Registered
Joined
·
65 Posts
Discussion Starter · #10 ·
Just an update the p38 tds hot start fix I have just purchased for 20 quid from Poland tricks the dde and injection pump in the warm state into thinking uts cold it's not an ideal fix but for 20 quid and 15mins wiring uts not bad however I might just get one if my mates to time the pump with me he works in bmw and if timing the pump fails then I may look at getting a refurb done at my local diesel specialist or a refurbed unit I also forgot to note the fuel filter is probs due a change n I've one on the way so might help the situation

Tomorrow I will be changing
Thermal oil level sensor
Oil and filter
Air filter
Fuel filter
Fuel pump relay
Crank sensor

I have already cleaned the fuel tank and tested and cleaned the lift pump and fitted a new gauze to it
 

·
Registered
Joined
·
842 Posts
Good luck and I had this engine in my e39 and it had 367 thousand miles on it when I sold it and it still ran really strong on the original turbo and injector pump. Not the fastest engine out there but bulllet proof.
cheers
Jim
 

·
Registered
Joined
·
65 Posts
Discussion Starter · #13 ·
OK lads update on the tds m51 fitted new oil level sensor fuel air and oil filters new oil crank sensor and fuel pump relay problem still persists with the hot starting and cutting out when hot

The fuel filter is helping and the new gauze after the servicing and parts today I took it fir a spin going lovely through all gears and driving fine from cold once warmed up I was on the yard and put it into drive n everytime I did the revs dropped lower than the idle until she gradually cut out

I chatted a specialist today and an old skool mechanic he said the pump may need ignition idle setting and it adjustment so he will be coming out tomorrow to see if its doable and also to get his verdict on the overall health condition of the pump
 

·
Registered
Joined
·
65 Posts
Discussion Starter · #15 ·
There are seemly 4 screws on the pump that you loosen and you lightly tap or move the head off the pump towards or away from the driver and this seemly adjusts the pump the specialist said he will know by the sound of the engine whether its right or not hopefully this will solve the hot start problem I also need a new throttle position sensor potentiometer assy which I will order once I get the pump sorted
 

·
Registered
Joined
·
65 Posts
Discussion Starter · #16 ·
OK update guys as you can see from the image purple are the 3 lower torx screws 1/4 turn loosening and then orange arrow towards driver or gearbox is advancing or increasing the idle and green arrow is retarding or decreasing idle speed you have to get roughly 750rpms steady with 8mg/stroke I had launch beside me and was watching the parameters in live data while adjusting the pump this has certainly improved cold and hot starting scenarios these pumps can be also statically timed but you need to set engine to tdc on cylinder 1 and use locking kit but my timing seems OK relative to the engine a mate of mine said he can adjust the governor some way regardless of it being vp style pump I'm very pleased with the result car is pulling like a dream since the adjustment also.
Automotive tire Electrical wiring Motor vehicle Pattern Electrical supply
 

·
Registered
Joined
·
65 Posts
Discussion Starter · #17 ·
Also a disclaimer I am and consider myself a suitably qualified person to adjust these pumps so any adjustment is at your own risk but just be v gentle w the tapping as you can snap a crankshaft by doing this seemly

Also I ended up doing this on my own as my mate didn't show up
 

·
Registered
Joined
·
65 Posts
Discussion Starter · #19 ·
OK so guys I adjusted the timing of the pump I advanced it approx 1 to 2 mm and the engine ran much smoother and was fueling better however when the car was at operating temp and fully warned up I knocked it off and tried restarting car still would not restart cranking over and over no restart I loosened the bolts more and advanced the pump further again to the block and still would not restart so its looking to me like the fuel injection pump needs a refurb please note though the advancement of the timing considerably helped starting to 45 degrees c and running much quieter and smoother so for those of you struggling with p38 or m51 bmw hot starting try this as a last resort before going about refurbishment of the pump in some cases this will cure the hot start but unfortunately in mine the internals of the FIP are too worn and will not start hot so it's up to me now if I want to break the car for parts or get a refurb done on the pump I will keep you guys posted.
 
1 - 20 of 24 Posts
Top