Diesel hard to start · Autobedrijf Willemsbrug Rotterdam

Diesel hard to start in the cold? We find the cause

Is your diesel hard to start when it is cold? Or do you see white smoke after starting? Often the glow plugs, the glow plug relay or the battery are the cause. We test the parts and only replace what is needed, on vans and motorhomes too. You hear the price in advance.

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The short answer

If your diesel is hard to start when it is cold, the cause is usually the glow plugs, the glow plug relay, the battery or the fuel filter. Autobedrijf Willemsbrug at Boterdiep 11 in Rotterdam-IJsselmonde reads the fault codes, tests the glow plugs and tests the battery, on vans and motorhomes up to 3,500 kg too. You hear in advance what the repair costs, and we only replace what is needed, with your approval.

Jump to: symptoms · causes and solutions · frequently asked questions · directions

Do you recognise any of these symptoms?

You mostly notice a diesel that is hard to start on cold mornings. Look out for these signs:

  • The engine has to crank for a long time before it fires
  • You see white smoke from the exhaust in the first few minutes after starting
  • The engine runs rough or knocks after a cold start
  • The glow plug light flashes or stays on
  • The engine cranks slowly when you start it
  • The engine starts, but stalls again in freezing weather

With a cold diesel, wait until the glow plug light goes out before you start. Do not crank for too long in one go and do not use starting spray. Will the engine not start at all? Read what to do in a breakdown.

How a diesel starts

A diesel has no spark plugs that create a spark. The fuel ignites from the heat of the compressed air in the engine. When the engine is cold, that heat is not enough. That is why the engine has glow plugs.

The glow plugs get very hot in a few seconds. The glow plug relay powers them and controls how long they glow. They stay on for a while after starting, so the engine runs more smoothly.

If one of these parts is not working properly, the diesel is hard to start. A weak battery or a clogged fuel filter can also cause starting problems. That is why we test first, before we replace anything.

What we do when your diesel is hard to start

  • Read the engine fault codes
  • Test the glow plugs and replace them if needed
  • Check the glow plug relay
  • Test the battery, the starter motor and the alternator
  • Check the fuel filter and replace it if needed
  • Do a test start and run the engine until it is warm

Extra work is only done with your approval.

Diesel hard to start: symptom, cause and solution

This table shows which symptom often goes with which cause. We only know what is really going on once we have taken measurements.

Symptoms of a diesel that is hard to start, and possible causes
Symptom Possible cause What we do
Only starts after long cranking when cold, starts fine when warm One or more glow plugs or the glow plug relay Test the glow plugs and read the fault codes
White smoke and a rough-running engine after a cold start One or more glow plugs are not working Test the glow plugs and replace them if needed
Glow plug light flashes or stays on while driving A fault in the glow plug system or the engine Read the fault codes and test
The engine cranks slowly The battery is too weak Test the battery, starter motor and alternator
Also hard to start when the engine is warm Fuel system, air in the fuel lines, a sensor or the injectors Read the fault codes and check the fuel system
Starts and stalls again in severe frost Diesel thickened by the cold or a clogged fuel filter Check the fuel filter and replace it if needed
Motorhome or van hard to start after standing for a long time A weak battery or a fuel problem Test the battery and check the fuel system

Glow plugs and glow plug relay

You can recognise faulty glow plugs by hard starting in the cold, a rough-running engine and white smoke after starting. According to MVW Autotechniek, in mild weather you often get no warning on the dashboard, although the fault is stored. If all the glow plugs are the same age, it is often sensible to replace them all at once. Does the engine warning light come on, or does the engine also hesitate when it is warm? Then read more about an engine warning light and about a car that hesitates or stalls.

Battery and fuel

A diesel needs a lot of power in the cold. If the engine cranks slowly, the battery is often too weak. If you only hear a click, the starter motor may be the cause. In severe frost, diesel can thicken and clog the fuel filter. The engine then struggles to start or stalls again. Read more about the battery and about a car that will not start.

We work on all makes and models. You are also welcome with a van or motorhome up to 3,500 kg, such as a Volkswagen Crafter, a Mercedes-Benz Sprinter or a motorhome built on a Fiat Ducato.

Why we measure first

A diesel that is hard to start often gets a new battery or new glow plugs first, as a guess. If that is not the cause, the problem remains. That is why we first read the fault codes and test the glow plugs, the glow plug relay and the battery. After that you hear what is wrong, what it costs and how long it takes.

Our repairs come with a warranty. We tell you which warranty applies when we give you the quote. Call +31 10 479 00 00 for a check or a quote.

Frequently asked questions about a diesel that is hard to start

No need to click. All the answers are already open below.

Why is my diesel hard to start when it is cold?

A diesel has no spark plugs that create a spark. The fuel ignites from the heat produced when the air in the engine is compressed. When the engine is cold, glow plugs help get it warm enough. If they are not working properly, the diesel is hard to start. A weak battery, the fuel filter or air in the fuel lines can also be the cause. We find out which it is.

How do I know if my glow plugs are faulty?

Look out for these signs: the diesel is hard to start when it is cold, the engine runs rough or knocks after a cold start, or you see white smoke for a few minutes after starting. Sometimes the glow plug light starts flashing. Does the white smoke continue when the engine is warm, or is the coolant level dropping? Then stop driving and call us, because something else may be wrong. In mild weather you often get no warning, although the fault is stored in the car. We read it out and test the glow plugs.

Can I keep driving with a faulty glow plug?

Yes. With one faulty glow plug you can often still drive. The engine then starts a little worse and runs rougher after starting. If two or more are faulty, according to GarageGurus the engine is very hard to start, even when it is not cold. So have it checked soon, especially with winter coming.

Should all the glow plugs be replaced at the same time?

Yes. That is often sensible. If all the glow plugs are the same age, the next one often fails soon afterwards. According to MVW Autotechniek, many manufacturers therefore advise replacing them all at once. We test them first and discuss with you what is best.

What if a glow plug is seized or snaps?

After years, glow plugs can seize because of soot and rust. That is why we loosen them carefully, with the engine warm. If one does snap, it has to be drilled out. Sometimes the cylinder head has to come off. In that case we stop and first discuss the options with you.

How much does glow plug replacement cost?

That depends on the engine. On some engines the glow plugs are easy to reach, on others parts have to come off first. Call us with your registration number. Then you hear in advance what it costs and how long it takes. We only start once you approve. Our repairs come with a warranty. We tell you which warranty applies when we give you the quote.

Could it also be the battery?

Yes. If the engine cranks slowly, the battery is often too weak. A diesel needs a lot of power to start in the cold. According to the ANWB, the battery was the biggest cause of breakdowns in petrol and diesel cars in 2025. Read more about testing and replacing the battery and about a car that will not start.

My motorhome or van is hard to start after the winter. What now?

After standing for a long time, the battery is often weak. Charge it now and then, or have it tested. If the engine is still hard to start after that, have the glow plugs and the fuel system checked. We also help with motorhomes and vans up to 3,500 kg. A Volkswagen Crafter or Mercedes-Benz Sprinter up to 3,500 kg also fits on our lifts. Also read more about motorhome repair and van repair.

Diesel check in Rotterdam-IJsselmonde

You will find us at Boterdiep 11 (3077 AW) in Rotterdam-IJsselmonde, close to Stadion Feijenoord (De Kuip) and exit 24 Rotterdam-Feijenoord on the A16. The A15 is five minutes’ drive away. There is free parking outside if there is space. The Stadion Feijenoord tram stop (line 3) is close by.

We are also easy to reach from Barendrecht, Ridderkerk, Capelle aan den IJssel, Krimpen aan den IJssel, Hendrik-Ido-Ambacht and Zwijndrecht. Appointments are made by phone.

Plan your route to Boterdiep 11 or see our contact page.

Opening hours
Monday to Friday: 8.00 to 17.30
Saturday: 9.00 to 15.00
Sunday: closed
We are closed on Christmas Day, Boxing Day and New Year’s Day.

Is your diesel hard to start?

Call us during opening hours with your registration number. You drop the car off Monday to Friday between 8.00 and 8.30 am, or on Saturday at 9.00 am. You will hear the cost in advance and we only start once you agree.

Our score: 4.8 / 5 from 235 reviews. Read what our customers say (in Dutch).

Also see our pages about a car that will not start, car battery testing, starter motor replacement, an engine warning light, breakdowns, car diagnostics (in Dutch), motorhomes and vans.

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