Hesitating at full throttle ?

[marcjero]

P1010009 (5).JPG




Do you know the purpose of the hole ? I think the broken red part is a valve preventing the fuel leaving the pot when cornering for example.

[marcjero]

I did some maths. 60 kw injectors are rated to 147cc/min at 3.4 bar according to evilution site. We can consider a flow rate of about 170cc/min for higher fuel pressure. This means a total flow of 510 cc/min or 30 lph. The gss284 is rated at 65 lph at 4.9 bar. So even if injectors are stuck open fuel pressure shouldn't drop.

I found an interesting fuel pump model : http://www.deatschwerks.com/sites/www.deatschwerks.com/files/DATA/DW100%20Tech%20Sheet1.pdf

This baby is flowing about 50% more than the gss284. The performance at 70-80 psi is good. Works with ethanol too. And power consumption is very low maybe lower than the Walbro we have. Looks like a perfect upgrade.

[marcjero]

Update !
We tested the pump out of the car. We ran it with restricted output in order to add pressure to the flow. After 45 minutes the pump started to slutter. The pump was still running (noisy) but the flow was like interrupted. The pump was warm also.

[Thrumbleux]

Update !
We tested the pump out of the car. We ran it with restricted output in order to add pressure to the flow. After 45 minutes the pump started to slutter. The pump was still running (noisy) but the flow was like interrupted. The pump was warm also.

That was with the pump running in the tank submerged in fuel - yes?

[marcjero]

That was with the pump running in the tank submerged in fuel - yes?

No. It was running in a basin outside. Weather is cold.

[Thrumbleux]

Pump runs submerged in fuel to cool it.

[marcjero]

Yes some are saying that. But when the tank is empty a fuel pump shouldn't slutter. And I wonder how external fuel pumps are cooled then. They are very similar.

[Thrumbleux]

Submerged pumps are submerged at all times, mounted in a pocket with the pump's inlet above the minimum fuel level, This to prevent the motor sparking in gaseous environment and causing explosion. Or so the accepted wisdom goes. It could be wrong!

[tolsen]

Fuel pump for my Kangoo Trekka gave up the ghost a few years ago so I opened it out. I found the fuel runs through the whole pump unit entering at pump end and exits at top having passed through its motor and brush gear. The motor is therefore cooled by the fuel.

[marcjero]

The pump is a walbro gss. It's a well known design. What happened during the test is the pump wasn't able to push fuel all the time. I saw walbro failures video on youtube where the walbro pump is running and nothing is flowing at the exit. In my cause the flow is sluttering : it still flows but there a a lot of interrupts. These interrupts could create severe fuel pressure drops in the rail.

[marcjero]

We got a used pump for testing today. Guess what : problem is still there. Massive fuel pressure drop at wot and misfires when warm. FPR was changed, filter has few mileage. No visible leak. So what ???

[tolsen]

Perhaps there is a problem with power to pump? Not uncommon on diesel 450 Smarts with SAM. The cure is to fit external relay to power fuel pump.

[marcjero]

Already checked : steady 13.7v at the fuel pump connector during the test. Will try to block the return line when the pressure drop occurs. Can a fuel rail fail ?

[tolsen]

Fuel pressure drops to about 1 bar when misfire occurs. Fuel pump noise is different too when this happens.

Fuel rail regulator is purely mechanical. Must be power to pump. I would try external supply.

[marcjero]

Well weak power supply should show low voltage reading