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Matt
Matt, Mechanical Engineer
Category: Car
Satisfied Customers: 21110
Experience:  BEng hons Mech engineering, in auto industry 22 years
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I have a 54 reg passat tdi with an intermitant starting fault

Resolved Question:

i have a 54 reg passat tdi with an intermitant starting fault it will not start if the pre heater light doesnt light up ever time it can go for weeks and not do it and then it may do it two or three times in the same day or week and then not do again for weeks or even months
Submitted: 1 year ago.
Category: Car
Expert:  Matt replied 1 year ago.
HelloI'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.If the plugs haven't been changed in the last 20K then they may have to be replaced.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
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Customer: replied 1 year ago.

hi mat i dont think you understand the problem i can start up probalby 50 times first turn of the key then the next time it wont fire up if the pre heat light as not lit up even if the engine is hot so i have to wait till it will light up then it will start up 1st time if it is an heater plug or fuse why is the fault so randam

Expert:  Matt replied 1 year ago.
Hello thanks for the extra informationSo I'd say its likely to be a poor earth connection possibly on the block that's having problems as the engine heats up and the joint expands also the resistance of the main earth lead will get worse as its all gets hot so check the tightness and cleanliness of the main earth connection and do the same for the glow plug connections too and also measure the resistance of the main earth wire between engine and battery earth
Customer: replied 1 year ago.

hi mat i will get these checked on wedsday when it goes in to gararge again but i would have thought these would have been by vw on the last 2 visits when they couldnt find any thing i will let you know next thursday regards roy

Expert:  Matt replied 1 year ago.
understood Roy
Customer: replied 1 year ago.

hi i cant rate your aswer as i said till after thursday but the garage says the answer you gave me are just general things that would be checked anyway in the course of fault finding and needs an auto electrician to check a lot deeper will let you know the outcome regards roy

Expert:  Matt replied 1 year ago.
understood Roy
Expert:  Matt replied 1 year ago.
Hi

how did you get on Roy?
Customer: replied 1 year ago.

hi mat you answer was no use at all after about a good hour or more the auto electrician couldnt find any thing at all with the wiring the imobiliser but after a lot of phoning around managed to possibley trace it to a little known about relay awaiting new relay to arrive had to order one regards roy

Expert:  Matt replied 1 year ago.
understoodthanks for letting me know
Matt, Mechanical Engineer
Category: Car
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Experience: BEng hons Mech engineering, in auto industry 22 years
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