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Matt
Matt, Mechanical Engineer
Category: Car
Satisfied Customers: 21362
Experience:  BEng hons Mech engineering, in auto industry 22 years
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I have a 2003 VW LT28 2.5TDI which has a cold starting

Resolved Question:

Hi, I have a 2003 VW LT28 2.5TDI which has a cold starting issue, I have changed the glow plugs and the relay looks ok, it will start after a pre-longed turnover (10 turns) the rest of the day it is fine, there is no fault codes on the VAGCOM software, can you help
Submitted: 1 year ago.
Category: Car
Expert:  Matt replied 1 year ago.
Hello
I'd check that you're getting full power to the glow-plugs, they pull a lot of current so take care when checking but see if the relay is clicking when the ignition is turned on first and also check the fuse if this is OK check to see if the engine earth strap is also OK.
You can test the glow-plugs with a multimeter by measuring the resistance across the plug ( between the power connection and the body) it should be around 4-8ohms if its tending to infinity / open circuit the plug is faulty or by using a clip on current clamp, either on the supply wire to glow plugs or onto engine earth, with glow plug light on you should see 15-20amps for each glow plug fitted, 4 cylinders would be approximately 60-80amps.
Also if its not injecting at all then check the connections to the crankshaft sensor, unplug it and check for corroded contacts and broken wiring, and consider fitting a new sensor - do the same for the cam position sensor
If the EGR valve is stuck open then this too can effect starting so try disconnecting it to see if this helps or changes anything
Could also be an injector leaking fuel back through the overspill pipe, so not getting enough fuel pressure to tell ECU to fire the injectors, this is trickier to find and you’ll need the garage to do a ‘run back’ test to identify which one is the issue
Lastly it’s also worth considering fitting a new fuel filter as if only slightly blocked this can lower fuel supply pressure and choke the main pump, the pump will be more sensitive to this when its cold as diesel thickens considerably with low temperatures.
Customer: replied 1 year ago.
Thanks for this, the relay is clicking and the fuse is ok on it, it is supplying power to each of the pins, I will check the amps at the glow plug side, I had replaced the engine earth strap so this should not be an issue, the fuel filter was changed with it's last service just under 9 months ago. It is an intermittent fault as I was out in the van today and it started from cold after 3 turns but can take as many as 10 turns to start.
Expert:  Matt replied 1 year ago.
thanks for the additional information
as its so intermittent I'd say its likely to be the crank sensor or a leaking injector
as crank sensors are cheap it may be an idea to replace this if its wiring checks out
Customer: replied 1 year ago.
Sorry for not making that clear at the start, I would say it is usually more difficult to start than not, it just seems to be the odd morning that it will fire up straight away.
Expert:  Matt replied 1 year ago.
hello this is also another sign of a failing sensor as temperature will effect parts as they expand and contract
Customer: replied 1 year ago.
Thanks for this, I will start with checking the loom and take it from that point. Due to the weather at the moment I have not had the chance to get under the bonnet, I was looking for directions as to likely causes, as I have already replaced the glow plugs, engine earth strap and checked the relay. I wasn't sure if it might be a injector issue, the vehicle has done 74,000 and as a paramedic we had the LT's and Sprinters doing over 300,000 with the same injectors so I was tending to rule this out. Is there a way to test the crankshaft sensor?
Expert:  Matt replied 1 year ago.
Hello
if its an early 2 wire sensor then yes you can measure resistance across both pins
it should be 200-300ohms
Matt, Mechanical Engineer
Category: Car
Satisfied Customers: 21362
Experience: BEng hons Mech engineering, in auto industry 22 years
Matt and other Car Specialists are ready to help you
Customer: replied 1 year ago.
Many thanks for the information once I get the van under cover I will work through your suggestions.Thanks again....Joe

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