Megane Scenic July 1998 1.9DTi Starting problems

martinswales · Unread post by **martinswales** » 13 Jun 2003, 04:15

My scenic starts first time EVERY time so long as in REGULAR use. If left lying idle for three days or more starting is extremely difficult. Engine turns over just fine. It is as if there is no fuel to ignite.Will start EVENTUALLY. Once started then no problem until left idle for several days again.
Glow plugs changed - no improvement. Battery changed - no improvement!
Has anyone experienced this or have any ideas as to what the fault may be? I'd be grateful for help as my Renault dealer is charging me a fortune for changing uneccessary items and clearly has no clue what to do next!

Dave Burns · Unread post by **Dave Burns** » 13 Jun 2003, 04:42

Classic symptom of a slow air leak and typical of a Bosch equiped engine, so does it have a Bosch pump, and if it does, try operating the manual priming pump for about 30 secs when you next have trouble, if it starts ok after doing that then it confirms air ingress as the problem.
If it does the first place to look is at the leakoff pipes between the injectors, and on to the pump return line, don't forget to examine the blanking cap on the last injector return nipple.
These push fit rubber pipes go hard and brittle and simply crack.
If all looks well there you need to go over the entire fuel delivery and return system starting with the pipes and filters in the engine bay.
Dave

martinswales · Unread post by **martinswales** » 14 Jun 2003, 01:49

Thank you for this Dave. I'm not a DIY mechanic but i will get the deale to check out your suggestions thoroughly. I shall let you know how it goes.

martinswales · Unread post by **martinswales** » 17 Jun 2003, 03:25

Dave, have left vehicle stand for a few days to test for air leak as suggested. Is the manual priming pump a black rubber bulb by any chance? If so, do I just repeatedly squeeze it for about 30 secs before trying to start the vehicle? I'm grateful for your assistance. Thanks.
Martin

Dave Burns · Unread post by **Dave Burns** » 17 Jun 2003, 03:35

Yes Martin thats it, if its a Bosch pump the rubber bulb should firm up after about a dozen or so squeezes, depending on how much air (if any) is in the pump.
When the bulb goes firm and can't easily be squeezed, that should mean any air has been expelled.
Have the ingition switched on during pumping.
Dave

martinswales · Unread post by **martinswales** » 21 Jun 2003, 16:07

Dave, you are an absolute gem! You were spot on with this diagnosis. I left the car standing or a whole week to be absoutely sure the "problem" would manifest as it has been over the last four months. I did exactly as you said - it took about 40 pumps to get the bulb hard. The car started first time! I am thrilled. Thank you, thank you, thank you

) Now all I have to do is tackle the renault dealer who misdiagnosed this twice ( glowplugs and battery)and cost me a fortune in the process. I cannot tell you just how grateful I am to you for this. I really was on the point of giving up on the car altogether.
Now I am going to push my luck. The same garage 10 days ago changed my cambelt because of another issue - (it needed doing soon anyway) and since then my heater has only been partially warming up. Any clue as to what these idiots may have done to cause this?
Martin.

David Goddard · Unread post by **David Goddard** » 22 Jun 2003, 04:56

When they changed the timing belt, did they also change the water pump? If so, they may not have bled all the air out of the system. The feed to the heater matrix is usually quite high and may have an air lock. I don't know the Scenic engine layout, but would expect there to be a bleed screw on one of the heater hoses.
However, if the Scenic is anything like my wife's 306, the radiator cap my be lower than the heater. Hence it is not easy to entirely fill the system. On the 306, a temporary arrangement using a Fairy Liquid bottle has to be used to increase the "height" of the coolant in order to get all the air out of the circuit. Oh, the joys of sloping front cars with very low radiators!

martinswales · Unread post by **martinswales** » 22 Jun 2003, 05:53

Hmmmmm. Thanks for that very prompt reply. Coolant levels seem fine but I shall check it out.
Cheers.

Dave Burns · Unread post by **Dave Burns** » 22 Jun 2003, 06:20

Not sure about the heater problem but it does sound as though they have had the water out for some reason, and not put it back correctly leaving an air lock.
Back to the starting issue, I think you will find the air is getting in somewhere in the return line, this will almost drain the pump dry and make starting near impossible.
If it was getting in on the supply side the pump wouldn't be drained empty, and the car should still start but would only run for about 10 seconds or so depending on how close to the pump the leak was.
Dave