Fuelling Issues

[billman]

Hi,

I encountered a problem where suddenly it seemes that it is very rich and VEMS tries to compensate with an EGO Corr of 85%.

At first I thought that it was the injectors. When i tried to take a closer look it came out to be (maybe) the vac line that goes to the ECU.

I repaired and changed the injectors. It seemed to cure the issue (I thought)!!!!

Old injectors 630ccm at 3 bar
New Injectors 1000ccm at 3 bar

Car FPR 3.8 bar.

I changed the Req fuel to 2.3 from 3.1 to compensate (and from Traditional to Simplified). It was almost fine even with it.
Today I start the car it it showed that it was too rich with these settings so I leaned everything out. I drive around and everything seems fine again. Then after 30min or so (38 celcius outside temp and 75 MAT) i stop and see that at idle I have Lambda 1 but an EGO corr of 85% (it was EGO Corr 100% 10 min ago).

I shut the car down and come back after 2 hour and start the car (MAT 65 Celcius) I start the car and while before I shut it off it was Lambda 1 with 85% EGO Corr it was Lambda 1 and Ego Corr 114% now!!!!

What the hell happens???

I change to my old map (when I only changed req fuel) and it was fine again.

How can it be? Any thoughts?

VEMS is Serial 1441. Lambda is also that old. I also thought about fuel pump (Bosch 044 3 years old and 20000km old). The pump is a bit louder lately but thought it is due to the extra heat around.

cheers

[GintsK]

My first thougts is about injector dead time. Are you sure about your values?

[billman]

I think!

Here is the map where I had to lean out in order to be OK. After it stood for a couple of hours then it was too lean with it.

http://vems.hu/vemstune/sharingcenter/reports.php?cmd=view&key=j6d8o3

This the initial map I had. When it showed too lean with the map above I used this and it was again ok.

As you can see the lambda still jumps a bit around but thats not the issue.

http://vems.hu/vemstune/sharingcenter/reports.php?cmd=view&key=Tha0jz

Note the car had similar issues with the old Siemens injectors and that is why I changed them.

[GintsK]

Then I suggest first to measure fuel pressure at those situations.

Gints

[billman]

As how is this possible? The FPR sits in the rail with a clip.

[GintsK]

Kinked return line rise the pressure, dirt/rust in FPR lower it!

Once restrictor factor comes to play pressure becomes flow and temperature dependent. Kinked line work as direct restrictor in-line, dust works as additional restrictor in-parallel with FPR.

[billman]

I will remove the FPR and fuel pump and check if there is rust, dirt. Then change filter and drive around.

[GintsK]

Check the pressure instead.

[Sprocket]

As how is this possible? The FPR sits in the rail with a clip.

Tee into and fit a pressure gauge in the fuel flow line from the pump to the fuel rail. The regulator is at the end of the fuel rail and everything before it is controlled to the set pressure of the regulator. Th return line is just that, there should be little or no pressure on this line.

[billman]

Can I use the pressure line near the fuel pump or it is not a good Idea? It is better to T into there as there is more space.

[gunni]

anywhere between the pump and regulator

[GintsK]

anywhere between the pump and regulator

I would say between filter and regulator. In case if filter restriction is reason.

[billman]

I had easy access between pump and filter right after the pump and I got 4.4-4,5 bar fuel pressure. The fuel pressure regulator is a 3.8 one. I will got my hands to a 4 bar FPR tomorrow and since it is easy to change them I will see if that changes something.

Blowed through the fuel lines the other day and they don't seem clogged or restrictive. I will also have a new fuel filter I can put on if the FPR doesn't make a difference.