Engine revs slow to pick up

[timchapman]

I have an interesting problem with a Ford FSD 2.5l naturally aspirated diesel engine.

When I start the engine sometimes it will not rev when I push the throttle open. After about 20 or 30 seconds it then bursts into life and is good until the next time I start it. I first thought this might be a blocked filter but then it would never burst into life if it was.

This happened when the engine was brand new and after a few weeks it stopped. Now almost 10 years later it's happening again.

It doesn't happen every time.

I'm hoping there are some engine experts on the forum who may be able to give an insight.

 

[Stemar]

I'm no expert, but it sounds like a sticky governor. Opening the throttle on a diesel simply tells the governor to allow more revs and the governer tells the injectors to inject more fuel.

A cheap possible fix would be to use an engine flush at the next oil change. There is a small risk on older, slightly knackered engines of cleaning them too much 'cos it's only the gunge that's keeping worn oils seals and scraper rings working. I wouldn't expect this to apply to your donk, but...

 

[Ammonite]

worth checking the fuel leak back pipes. If you have a slight leak here the engine won't fire on all cylinders after its been left for a while and the revs won't pick up until the fuel flow gets going again. Just a thought as that was what was happening on my Beta 20hp. Replaced a split leak back tube and problem fixed.

 

[Modulation]

A long shot but my Yanmar 2gm 20 did that when 3 months old and again 3 years later. On both occasions changing the air filter sorted the problem. Don't ask why a 3 month old filter fhould be defective............................