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[Marks DTM Calib]

Morning guys,

Not bumping the thread but have an update....

I changed the inlets / fuel rail for a known good one yesterday. Hasn't changed the symptoms at all.

Now, the car is only struggling to start first thing in morning. If I cycle key a few times it gets itself going. Then after that it starts every time.

I'm wondering now if the check valve in the fuel pump has gone? Obviously fuel pump itself is working fine cos otherwise it wouldn't run lol but if check valve is bad and the built up fuel is returning to the tank.

Thoughts?

So the question you have to ask yourself is, check valve or no check valve.....where would the air be getting in to let the fuel run back to the tank.

Well, anywhere along the fuel line between tank and fuel rail? 

If, so I've double checked the two line connection to the fuel rail. I was under car yesterday and nowt wet at the fuel filter..... am I missing something obvious 

Ok, so if that was the case what do you think would be occurring with the pump running and the lines loaded with fuel at 3Bar of pressure 

Sorry for being cryptic, its a good learning exercise and trying to help you consider what the operating characteristics of the fuel line are 

[Webby the Bear]

Morning guys,

Not bumping the thread but have an update....

I changed the inlets / fuel rail for a known good one yesterday. Hasn't changed the symptoms at all.

Now, the car is only struggling to start first thing in morning. If I cycle key a few times it gets itself going. Then after that it starts every time.

I'm wondering now if the check valve in the fuel pump has gone? Obviously fuel pump itself is working fine cos otherwise it wouldn't run lol but if check valve is bad and the built up fuel is returning to the tank.

Thoughts?

So the question you have to ask yourself is, check valve or no check valve.....where would the air be getting in to let the fuel run back to the tank.

Well, anywhere along the fuel line between tank and fuel rail? 

If, so I've double checked the two line connection to the fuel rail. I was under car yesterday and nowt wet at the fuel filter..... am I missing something obvious 

Ok, so if that was the case what do you think would be occurring with the pump running and the lines loaded with fuel at 3Bar of pressure 

Sorry for being cryptic, its a good learning exercise and trying to help you consider what the operating characteristics of the fuel line are 

Not at all Mark. I like it! 

Well if that was the case it'd be pishing out somewhere......

[Marks DTM Calib]

Very good, so its a very reasonable inference that the fuel lines are fine and that fuel is not draining back to the tank 

If you really want to, you could pop the bonnet, remove the top from the fuel pump relay and press the contacts to run the pump for ten seconds or so prior to starting to rule the theory out.

[05omegav6]

Once the car is running, what happens when full throttle is applied for more than a quick burst?

[Webby the Bear]

Once the car is running, what happens when full throttle is applied for more than a quick burst?

Absolutely fine. Full throttle it's quick and goes through the rev range well.

However, just been out and noticed that at cold idle there's popping from the exhaust. Immediately goes away when throttle applied and runs smoothly and miss goes away. A quick spray of the breather bridge to TB reveals a bad vacuum leak... the engine almost stalled when I did this...........

[Webby the Bear]

Very good, so its a very reasonable inference that the fuel lines are fine and that fuel is not draining back to the tank 

If you really want to, you could pop the bonnet, remove the top from the fuel pump relay and press the contacts to run the pump for ten seconds or so prior to starting to rule the theory out.

Thanks Mark 

Re the post above.... I think it's a vac leak. It's leaking vacuum from breather bridge to TB and and the plenum to breather bridge (the circle thing that pushes in to the plenum). And I know vac leaks do affect cold starts.

[Marks DTM Calib]

Vacuum leaks affect anything relating to idling revs 

[Webby the Bear]

Vacuum leaks affect anything relating to idling revs 

Thanks for all your help mate. I'll get that fixed.

I did previously fit two new 'o' rings for breather bridge to TB but they don't seem to be sealing. Is there any home remedy other than filling the area with gasket maker? Would save me going to VX and being charged £5 for 2 of the smallest 'o' rings in history