C240 fuel pump problem

[stephentanks1]

Has anyone had a fuel pump cause poor starting on a C240.Mine sometimes takes a long time to start,sounding like a carb engine trying to start without the choke working.It has been on a Bosch diagnostic machine and the result was no electrical fault found.The specialist seems to think its the fuel pump non return valve.Any ideas please.

 

[bigasotonuk]

Hi,
You could try the fuel pressure regulator which is vacum operated i think, disconnect air pipe and see if it makes any difference.
When it starts does it seem like its flooded misfiring intially and clearing in a few seconds,
if so you could have leaking injectors but when starting from cold 'should' be ok.

 

[television]

Also do check that there is no air in the return system,that can cause poor starting

 

[television]

Also do check that there is no air in the return system,that can cause poor starting

 

[stephentanks1]

Thanks to both of you.Can you tell me where the pressure regulator is.There is a vacuum unit top front of engine.Connected or not or manually operated it makes no difference,and the diaphram in the unit is ok,it holds vacuum.

 

[BlackC55]

Get the fuel pressure checked. You wil then know if it is fuel related.

 

[Glenn Smith]

Get the fuel pressure checked. You wil then know if it is fuel related.

Agree, hook up a fuel pressure gauge and run the engine, if it's in spec turn off and check the fuel pressure is maintained, leave overnight and watch the fuel pressure as you try to start, if it takes a long time to fire, but does so as the fuel pressure builds, and runs fine once started it could well be the fuel pump valve,or other source of leak.my old 944 was like this when left for a few hours, not helped by having no prime on the pump as you switched on, if i bridged the relay just a few seconds then started it was fine.

 

[steve kane]

Our C250 (N Reg) had Air in the fuel system which gave these symptoms, I changed the Fuel Line O Rings which worked okay for a while but then one of the Injector Valves started to leak a small amount of fuel when cold (which took up when hot) and the result was more Air in the System, you can actually see the Air Bubbles coursing through the Plastic Fuel Lines with the engine running. I now have imported the Special Socket which people are more than welcome to borrow for a small donation (to me!!) that is required to remove the Injector Valves for you want to change the O Rings on these, its quite an easy job.
Steve.

 

[Ellsy Tanners]

Hello,
I have known on occasions on this engine for there to be water that gets into the fuel system and sits in the fuel rail. This can cause poor starting and sometimes missfiring. its not alot of water but a little bit makes a big differnce to the running.
Its just an idea, might not be your problem

 

[stephentanks1]

Hello everyone.This is the solution to my starting problem.It was number 1 fuel injector leaking.It cost £405.00 to put right including diagnosis,which is not too bad for a main dealer.

 

[steve kane]

When you say No1 Injector Leaking I assume that either fuel was pouring out of the union that connects the Fuel Pipe to the Injector? (I guess unlikely as this would be immediately obvious and fairly smelly with a warm engine) or did you have the same problem as I did? a very slight fuel leak from under the locking plate where the Metal Fuel Pipe of No1 Cylinder connects to the Injector Valve/Pump? I am guessing its the latter and that your Starting Problem was Air being drawn back into the fuel system as the engine cools, part of the problem with finding the fault lies in the fact that the leak of fuel is really at its worst when the engine is cold, the leak taking up as the seals warm up. Strangely my Leak was also on No1 Injector Valve, and so far I have only replaced that seal, but as I now have the special socket and some seals I think I really ought to replace the others just in case that also let me down.
Steve.