Diesel Hard to Start? Common Causes and What to Check

A diesel that cranks for a long time, starts only on the second try or will not start at all may have a fuel system problem, but not always. The pattern tells you a lot.

Hard to start when cold

Glow plugs are the first thing to check, particularly if the car is fine once it has warmed up. A weak battery also slows cranking, and a diesel needs good cranking speed to start. Worn injectors can make a cold start worse as well.

Hard to start when warm

Trouble starting a warm engine often points to low rail pressure. Injectors leaking back too much fuel can stop the system reaching the pressure it needs. A weak high-pressure pump can do the same thing. A sensor fault can also cause it, so read the fault codes first.

Cranks but will not start

Check the simple things first: fuel in the tank, the fuel filter, and air getting into the fuel lines. After that, a diagnostic check can show whether rail pressure is building. Without enough pressure the injectors will not fire, and the fault may be the pump, the injectors or a sensor.

Do not ignore metal in the fuel

If a high-pressure pump fails internally it can send metal through the fuel system. If that has happened, fitting a new pump on its own can lead to another failure, so the injectors and fuel lines need to be checked at the same time. Tell us if your pump has failed and we will go through what needs testing.

Seized glow plugs

Glow plugs can seize in the head, and a plug that breaks during removal makes the job much bigger. Our staff have the tools for removing seized glow plugs, so talk to us before forcing one out.

Testing and repair in Dublin 15

We test injectors and pumps on our test benches and recondition them where possible. Testing starts from €80, injector reconditioning from €140 and pump reconditioning from €250. Reconditioned parts have a 1-year, parts-only, unlimited mileage warranty.

Call 085 200 9922 or request a quote. Diesel Injector Repair, Unit 6, 1st Floor, Old Quarry Campus, Blanchardstown, Dublin 15, D15 HX03.