warm startings a pain

Starts on the button first thing in the morning from cold.

Needs to turn over a bit when warm.

I know this could be accumalator or leaky injectors, anything else? I don't seem to have a fuel leak!

Peter.

Had this on the GTi, VERY embarrassing trying to start it from warm in front of everyone !!!!!
Turned out to be the Hall Sender, local auto electrician sussed it, repaired it and it's been perfect ever since. Mind you, at ?70 to repair it I should have got an exchange dizzy !!!!!!!

I haven't got a hall sender, cars too old for that kind of thing!

Peter.

I have same problem too Pete! From cold it always starts first time with no gas pedal. From hot, always needs to turn over longer and a bit of gas. Always starts, just not as efficient!

Might be worth trying a new checkvalve on the end of the fuel pump,as these can cause this problem even to the point where the car wont start at all when warm,the part number is 893 906 093. Not sure how much they are though

I had a new fuel pump fitted by a garage a few months ago. Is it likely the checkvalve would have been done then too?

How the thing runs once it has started can give you a clue as to the fault. If it runs perfectly straight off then it is probably a fuel pressure drop, if it hunts and then picks up after a few seconds it could be the injectors leaking fuel into the cylinders. Its well worth having a pressure gauge made up to do the tests yourself but be careful.

Haynes manual states "That the accumulator maintains residual pressure in the system for a short time to assist in Hot Starting" When cold the fifth injector provides a rich mixture to assist in starting . to me that means only one thing cold ok ! hot not !  possible cause the accumulator.

Trouble is the only way to see if your accumulator is faulty is to have the system pressure tested at all operating temperature or  renew it . The only stumbling block being the cost i think they are over ?130 from VW .

Chudd….

Hairy,im not sure if you get a check valve with new fuel pumps but you should be able to see if it looks new without taking the pump down.Thats the only trouble with these problems there is a few things it could be like Chudd said it could be accumulator,i once spent nearly two days on a friends car that wouldnt start from hot, changed everything under the bonnet with parts off of another car i had in the drive way that was running fine in the end i decided to change the check valve before taking the whole pump off and it sorted the problem so if ever i get that sort of problem again i know what ill be changing first    :wink:

volksacre
              all the pumps i have had have been sealed is this check valve only fitted to earlier cars or a certain type of pump ? I am talking Bosch pumps , can you take them to bits ?
  

Cheers Chudd…

The Check valve screws in at the front of the pump,its worth trying on of these before getting a new fuel pump. I dont know if you have seen this website but it tells you about it and many other things

Domain parking page

Top of the list in Haynes and Bentleys is a leaky 5th injector.

I think it just floods the engine, only supposed to work in cold.

Way to test is to unnbolt it, disconnect wires and bridge fuel pump relay for one minute.

No fuel should come out as long as it's electrically disconnected

Also mentions taking of the lead off the coil. Surely this isn't neccasary as I will have the ignition on but I won't be cranking the engine so it's not gonna start?

Anyone done fuel pump relay bridging experiments?

Anyways, seems like it would be easiest to test thermotime switch first. get engine nice and warm, disconnect leads to 5th injector and start the engine. If engine starts good then it's the thermotime switch. Could put a voltmeter across it but whats the point?

Gonna try thermotime switch on the way home from work.

Standby for results…

Peter.

Pete, it tells you about bridging the relay on that site for when you do pressure testing also it might be worth cheking the thermo time switch by unpluging the fifth inj, bridging the plug with a tester and turning your ignition on and just turn the key so it just cranks the engine and let go you should get voltage for 10 seconds that way youll know its definatly the time switch you do this when engine is cold to check it this way,but saying that this is what i did to my mates car that i mentioned earlier and i ended up going round in circles,i would of thought with the warm starting symptoms  that its going to be the back end of the fuel system ie accumulator,checkvalve. To save alot of time and money it would be worth getting the system pressure tested

I like the idea of the :

The Accumulator
The accumulator is the first of the components in the fuel system after the pump. This unit has an important role to fill in the operation of the Bosch K Jetronic system.
Its first job is to help smooth out any pulses in the flow of the fuel, this is achieved by passing the fuel through a series of baffles and into a chamber giving it slight capacitance and a much smother flow. Its other and possibly more important role is to maintain pressure within the system when the fuel pump has been switched off; this is achieved by the accumulator spring and diaphragm pushing against the fuel.
For the duration that the engine is running, the diaphragm will be against its stop within the spring's chamber. When the engine is stopped and all of the non-return valves close, the spring pressure against the diaphragm will maintain the residual or holding pressure and overcome any slight seepage.
Within the data books for this system, it is shown that the critical time for maintaining these pressures, is between 5 and 20 minutes. After a journey, when the engine is switched off, the under bonnet temperature increases causing the fuel in the lines to heat and it attempts to evaporate.
Maintaining the pressure eliminates this problem and ensures a clean start when the vehicle has been standing with a hot engine.

Info pasted from Domain parking page

I am learning every day thanks for the web link volksacre , Chudd…

This is why the check valve can also cause the warm starting problem due to wear and this is why i would change the checkvalve before the accumulator because its got to be cheaper.
Have a look at this site and scroll down to CHECKVALVE the sixth box up on the left

http://www.users.bigpond.com/INTERJECT/KSITEPLN.HTM

Disconnected Thermo time switch and…

it works!

Starts on the button when engine warm.

So, either I run a few more checks or I get a replacement thermotime switch.

Anyone got a part no. for the switch please?

The cost will decide how many more tests I do.

Peter.

Is it for the EG engine code if so then its 043 906 163A

Pete, when you say you diconnected the time switch and it started ok does that mean that the time switch was staying closed and chucking fuel in when the engine was warm

My accumulator is on the way out I think - well according to the local garage anyway. Cost had put me off looking at in any further for the time being!

does that mean that the time switch was staying closed and chucking fuel in when the engine was warm

I think so, thats what my books (Haynes, Bentleys and a Bosch one) list as the first reason for warm starting problems. It just floods the engine.

I guess it's listed first because it's cheapest and relatively easy to diagnose i.e, unplug it,

The next step off into accumalators, If it's the actual 5th fuel injector, leaky normal injectors etc which would be ???.

I haven't checked with a voltmeter whether voltage is still getting to the 5th injector which I might do before I buy a new switch.

I have read in Bentleys that it's possible to wire up the positive feed to 5th injector from the wrong terminal of the starter solenoid, which would give it permanent live, which would knacker up your mixture somewhat.

Peter.