Diesel inj pump pressure relief valve

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kapilamuni said:
My car shows 93% timing modulation. We had a lengthy post on that and finally got yr advise to do the chains.
Do not misunderstand I,m just trying to learn something here, in general on EDC.
Going back to our discussion, if a car starts on the dot when cold we can assume the static timing has no issues and also glow cct and extrar fuel is there.( no timing advance required or provided). Hence, no stretched chains , right?

If the same car has hot starting issue, can we say it is the chains? Do stretched chains has its effect multified with a hot engine?Starting when hot with the 'hot start kit', cold scenario is created and the car starts. So, if the hot start issue is due to strtched chains which retarded timing, how come its cured just by the cold start scenario.? My point is that cold start scenario does not include any timing advance, as explaind by you previously, so it could not provide any timing advance when evoked with a hot engine. So if the hot start issue is due to retarded timing( due to stretched chains or any other), cold start scenario can,t help it though practically it helps.

Regd s
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NO, you are not listening are you. If the timing device is using 93% of it's available scale at idle to correct the point of injection. Then the static timing is retarded. Simple as that. Unless someone has made a complete balls up of doing static timing at some point, the bottom chain at least has stretched to cause that. The null point of the timing device with correct static is 50%. If the percentage was below 50% at idle, the timing device would be correcting over advanced static, if it is over 50% at idle, it is correcting retarded static. As i said a long time ago, get your static set correctly, get your injectors serviced. I would check the chains for peace of mind before the bottom one breaks and puts you in deep shit. When i did my chains the bottom one was worn but nothing like as bad as the cam chain which had serious toothache. I can only advise i cannot do the job for you.
 
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wammers said:
NO, you are not listening are you. If the timing device is using 93% of it's available scale at idle to correct the point of injection. Then the static timing is retarded. Simple as that. Unless someone has made a complete balls up of doing static timing at some point, the bottom chain a least has stretched to cause that. The null point of the timing device with correct static is 50%. If the percentage was below 50% at idle, the timing device would be correcting over advanced static, if it is over 50% at idle, it is correcting retarded static. As i said a long time ago, get your static set correctly, get your injectors serviced. I would check the chains for peace of mind before the bottom one breaks and puts you in deep shit. When i did my chains the bottom one was worn but nothing like as bad as the cam chain which had serious toothache. I can only advise i cannot do the job for you.
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You could if you fancied an all expenses paid holiday in Columbo.;):D:D
 
tomcat59alan said:
You could if you fancied an all expenses paid holiday in Columbo.;):D:D
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Good idea but I cant afford it at this time. May be later.

Shall we for a moment forget the issues my car has and look at the hot start issue.
If the chains are stretched , hot or cold the effect will remain. My point is if hot start issue is due to sctretched chains retarding timing then such effect would continue to remain when the engine is cold. That means static timing is out when engine hot or cold. So, an engine with stretched chain will not be started on the button even when cold.

That's why hot start issues continue to remain even after changing chains, in certain cases reported.
 
The maps in the ECU are different depending on whether the car is hot or cold. The cold map is more forgiving in all sorts of ways. The hot start fix can hide lots of niggly small problems. Over 90% modulation sounds like chain stretch or pump isn't right. Can you or someone test the pump on a bench somewhere?
 
Starting map can be modified to eliminate some of the hot starting problems. However it will not start when it's not cranking fast enough, no matter what you do.
 
Yes, some have solved the hot start issue with a new starter motor with new battery.
What exactly is the internal pressure of inj pump when the engine is not running?
 
So the internal pump is capable of building presdur so quickly within half turn of engine starting the car within one turn?
 
kapilamuni said:
So the internal pump is capable of building presdur so quickly within half turn of engine starting the car within one turn?
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I have told you before you are barking up the wrong tree. Did you not read and understand the link i posted for you? The injection pump does not need internal fuel pressure to inject fuel at startup, it just needs the presence of fuel. You are mixing up internal fuel pressure with injection pressure. Fuel is constantly bled off back to the tank through a restriction vent, a very short time after the engine stops all internal pressure will bleed off. Land rover tried to cure bad hot starting by having the lift pump running on cranking after 1999. Before that is only ran with glow plugs and when engine was running. Get your static timing done and get your injectors serviced. If your injector pump is tired incorrect static will do nothing to help you. An hot start unit will.
 
At the begining I explained that I want to learn the EDC process. I read the pdf in yr link, thanks.
I did not know that pump internal pressure and injection pressure are two things. I guess the timing advance is from internal pressure. Mind explaining me the functions of internal pressure ?
Would there be air inside the pump after the engine stops and fuel seeps back to the tank?if so it needs bleeding and so that pre 99 cars will take longer to start when hot.

Btw, can someone with above 1999 MY car can confirm they do not face the hot start issue as LR arranged the intank pump to run when cranking.
 
kapilamuni said:
At the begining I explained that I want to learn the EDC process. I read the pdf in yr link, thanks.
I did not know that pump internal pressure and injection pressure are two things. I guess the timing advance is from internal pressure. Mind explaining me the functions of internal pressure ?
Would there be air inside the pump after the engine stops and fuel seeps back to the tank?if so it needs bleeding and so that pre 99 cars will take longer to start when hot.

Btw, can someone with above 1999 MY car can confirm they do not face the hot start issue as LR arranged the intank pump to run when cranking.
Click to expand...

All that is explained in the link i posted. Which describes the pump function for both mechanical and EDC pumps. I will say again, if with your engine up to temperature and at idle, and your modulation is 90 odd %, your static timing is incorrect. This will NOT effect cold starting because extra fuel is provided by the ECU for this purpose and heater plugs are active. But it WILL effect hot starts, were no extra fuel is provided and there is no heater plug activation. With correct static timing the injection process has already begun when the piston reaches TDC. If the static is retarded it does not start until the piston is on it's way back down. Slow cranking will also effect hot starting specially if static is incorrect.
 
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