Diesel inj pump pressure relief valve

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kapilamuni

Active Member
Posts
550
Hi,
Can some one explain this to me,pls?
I came to know that it controlls the inj pump internal pressure n failure of this will create timing adv/retard issues. We could be blaming the wrong item part like timing chains,solonoid etc. May be thats why some got hot start iussues even after replacing the timing chains. Just expect professional /expert views.

Regds
 
kapilamuni said:
Hi,
Can some one explain this to me,pls?
I came to know that it controlls the inj pump internal pressure n failure of this will create timing adv/retard issues. We could be blaming the wrong item part like timing chains,solonoid etc. May be thats why some got hot start iussues even after replacing the timing chains. Just expect professional /expert views.

Regds
Click to expand...

Only on the mechanical VE pump not on the EDC one fitted to your car.
 
I read about this on a VAG forum which discussed VW Passat with a VP37 pump.
I was thinking that all VP37 s are EDC types.
Btw, the timing solenoid of our cars just open/close an orifice so that pressurized fuel acts on or not on the timing mechanism against spring pressure. So the fuel pressure is key element here not the solenoid. Fuel pressure is a related to roational speed of the inj pump I assume. So, what controls the pump internal pressure? Our pump too has a valve next to fuel inlet connection. What functions does it control?
Also, with a hot engine, original design does not provide any advance as against hot start fix. So, it could be the pump internal pressure that plays havoc when the engine is hot. Thats why some people experience hot start issues even after changing the timing chains. Pls comment.
 
kapilamuni said:
I read about this on a VAG forum which discussed VW Passat with a VP37 pump.
I was thinking that all VP37 s are EDC types.
Btw, the timing solenoid of our cars just open/close an orifice so that pressurized fuel acts on or not on the timing mechanism against spring pressure. So the fuel pressure is key element here not the solenoid. Fuel pressure is a related to roational speed of the inj pump I assume. So, what controls the pump internal pressure? Our pump too has a valve next to fuel inlet connection. What functions does it control?
Also, with a hot engine, original design does not provide any advance as against hot start fix. So, it could be the pump internal pressure that plays havoc when the engine is hot. Thats why some people experience hot start issues even after changing the timing chains. Pls comment.
Click to expand...


Here have a read. http://www.dieselbookmarks.com/bombers/VEPump.pdf
 
Very little or zero. But starts building it when cranking. Injection timing solenoid still needs internal pressure to advance timing. I have a mate that assembled pump in wrong order, so it had zero pressure with engine running(unbelievable it was running!), but was unable to reach more than 90 km/h and lots of smoke.
:D
 
N2O said:
Very little or zero. But starts building it when cranking. Injection timing solenoid still needs internal pressure to advance timing. I have a mate that assembled pump in wrong order, so it had zero pressure with engine running(unbelievable it was running!), but was unable to reach more than 90 km/h and lots of smoke.
:D
Click to expand...

He ballsed up the pressure relief valve then?
 
Fitted vane pump cover 180 deg out covering inlet or outlet hole.
Still have no idea how it was getting fuel to injectors running only on in tank lift pump.
:D
 
N2O said:
Very little or zero. But starts building it when cranking. Injection timing solenoid still needs internal pressure to advance timing. I have a mate that assembled pump in wrong order, so it had zero pressure with engine running(unbelievable it was running!), but was unable to reach more than 90 km/h and lots of smoke.
:D
Click to expand...
when cold the engine starts in one or two turns. Is it enough to build the internal pressure so that coldstart timing advance activated? Or is thdir different mechanism to push timing advance other than the internal pressure?may be something electro mechanical.
 
kapilamuni said:
when cold the engine starts in one or two turns. Is it enough to build the internal pressure so that coldstart timing advance activated? Or is thdir different mechanism to push timing advance other than the internal pressure?may be something electro mechanical.
Click to expand...

There is no timing advance for starting other than that set as static. Fuel is increased for cold starts that is why the engine RPM is higher at cold start then drops back as engine warms. Get the static timing correct and have your injectors serviced.
 
quote;
There is no timing advance for starting other than that set as static.................
unquote.
That means if the chains are stretched which in turn retard timing then a cold engine will struggle to start.
Conversely, if an engine starts when cold in the normal manner, static timing is okay, and can assume that no
chain stretch.
If above is correct, then what exactly is the famous 'hot start fix' is trying to do by evoking a "cold start timing advance" in order to fool ECU into thionking that the engine is cold?
 
kapilamuni said:
quote;
There is no timing advance for starting other than that set as static.................
unquote.
That means if the chains are stretched which in turn retard timing then a cold engine will struggle to start.
Conversely, if an engine starts when cold in the normal manner, static timing is okay, and can assume that no
chain stretch.
If above is correct, then what exactly is the famous 'hot start fix' is trying to do by evoking a "cold start timing advance" in order to fool ECU into thionking that the engine is cold?
Click to expand...

No not exactly so. Extra fuel is provided for cold start as is pre combustion chamber heating and the lift pump is switched on with glow plugs.
There is no cold start advance. Hot fix tells the ECU the engine is cold, so the ECU provides extra fuel and allows glow plugs to work. Simple as that. Any chain stretch that retards static timing will also alter valve timing.
 
Okay. So extra fuel and glow plugs for cold start. Then for hot start only useful is the extra fuel supplied by hot start kit.
Now, if the car start on the button when cold, can I assume that no stretched chain?. Basically, hot or cold, timing advance is not required except static timing on the
dot, I guess.
 
kapilamuni said:
Okay. So extra fuel and glow plugs for cold start. Then for hot start only useful is the extra fuel supplied by hot start kit.
Now, if the car start on the button when cold, can I assume that no stretched chain?. Basically, hot or cold, timing advance is not required except static timing on the
dot, I guess.
Click to expand...
No. Cold start is assisted by extra fuel and pre combustion chamber heat. As it is with Hot start device fitted. Normal hot start is not, so incorrect static timing will effect that. As will tired injectors. Check your pump modulation, if it is a lot above 50% the chains have stretched and static needs setting.
 
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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