Lazy fuelpump and starting problems

[Coutsi]

Hello,
I'm running 1.3.4 firmware on MS3Pro

Fuel Setup:
E85
Fuelab 1500hp pump with electronic fuel regulator
AN10 fuel lines with non-return valve in fuel filter
Fuelpressure compensation is activated for better startup
Fuelpump is turned on with relay controlled by MS3Pro

Symptoms:
When switching ignition on, fuel pump primes as it is intended, but if I don't crank engine just after pump starts to build pressure pump will shutdown and start again when cranking is continued. Problem is that fuel pressure takes little over 1sec to build and it drops before pump raises it. This leads to very long cranking or engine will start but dies because low fuel pressure.

Summary:
I have to crank my car just after pump starts its priming cycle if I want "clean" start.

In future development is there any plans to "open" fuelpump controllogic to avoid this situation?

This problem is hard to visualize on logs, but I can provide video comparison.

[papiogxl]

Sounds like you don't have a check valve inline. Fuelaboffers filters that have check valves integrated into them for this reason.

[jsmcortina]

In future development is there any plans to "open" fuelpump controllogic to avoid this situation?

As mentioned it sounds like your non-return isn't working. There aren't any plans to work around this.

James

[Coutsi]

Non-return is working as it is supposed to, it even holds pressure for few days.

I'm not sure if you understand physics behind this problem. We aren't talking about pressurized pneumatic system, where energy is stored in compressed gas and upon on release and depending on valve size pressure drops gradually. In fuel system you have pressurized liquid which can't be compressed and thus it doesn't store any energy (fuel lines expand a little bit, but that's obsolete) and when pressure is released through valve without any additional flow from pump, pressure drop is instantaneous and nothing really comes through injectors. For the same reasons every pneumatic tank is tested with water/liquid so that in case of rupture there won't be explosion.

I hope that you now understand the case I'm dealing with.

[wes kiser]

Got a log of the pressure trace during event? EVERY fuel system on the planet does some degree of what you describe, yet many of them crank quite quickly.

[Coutsi]

Sorry it took awhile to reply, but here is short log. From there you can see how the whole thing behaves.

For me adjustable priming time would solve my issue, now I just have to time my start about 1.5sec after pump has started to run.

[Coutsi]

Anyone had a time to check my logs?

[gui67]

I also use a Fuelab pump, PN41402. without a check-valve. What I have seen is that this pump needs some time to tart and build pressure
I have the opposite behaviour as yours:
If I turn the key to start immediately, it take a long time to start as there is no fuel going to the injector.
If I first put the ket on ign, let some time for the priming puls and then try to start it, it will start immediately. I use a very big priming pulse, maybe it does compensate the time for the FP to start and allows the engine to have enough fuel to start.

What I have seen, comparing my logs to yours is that your fuel pressure is very erratic. On my logs, it goes from 0bar to 3bar and then stays steady until I stop the car.
(I use a standard FPR) Could your problem not be linked to the electronic FPR?

There are some very strange things in your log:
at the beginning: why is the MAP at 31kPa with nearly 0RPM and varying TPS??? Or maybe the file I opened was corrupted???

[Coutsi]

I will look on to extending priming pulse for better start. I haven't verified fuel pressure sensor readings, so erratic pressure readings might be sensor related. I found one wiring failure related to electronic FPR which might have caused some erratic behavior. I will keep investigating on this matter when I get my engine back together.

[Coutsi]

My problem was almost fully resolved when I got Full sync working (36-2 + 1 cam tooth, I had wrong tooth settings and mega only got halfsync). Now I can start even when pump has stopped priming. This wouldn´t be that easy without check valve in my fuel line though.
On previous logs my fuel pressure readings have been erratic due to sensor problems, which I still haven´t figured out. I have 0-10bar sensor and my readings are nothing but right compared to my mechanical gauge...