Hesitating at full throttle ?

[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.

[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!

[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]

Pump runs submerged in fuel to cool it.

[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]

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]

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.

[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]

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]

Cheapest complete fuel sender unit is £116.90 on misterauto.

Yes I found it. But no clear specs again. I plan to run e85 and tune a bit in the future. The problem is the Smart engine is running high pressure fuel flow : 4 bar + 1 to 1.5 bar boost so we have to cope with a total of 5.5 bar (80psi). Most of the time turbo cars run a 3 bar fpr only.

http://www.autoperformanceengineerin...l/fpspecs.html shows some interesting data about the most famous Walbro pump. If you consider the smallest 190 lph model (gss242) you see that the flow drops a lot at after 80 psi. So the standard flow rate of a fuel pump doesn't matter a lot. What is the important is the flow rate at full boost. I see that gs242 could still flow a large amount of fuel at 80psi. Would be interesting to compare with gss284 figures. I guess that gss284 is flowing 110 lph at low pressure and 65 lph at 4.9 bar. gss242 could feed about 100lph at 4.9 bar. This is the reason I consider this model. It could support 120 bhp with E85 without any problem.

[marcjero]

According to the book you have to, but in practice you can remove it without doing so .... just! I replaced the large O ring from under the pump & managed to do so without moving the tank.

Yes. The tip is you have to pull the fuel sender unit and clock it. Then you can remove the ring from the car.

[tolsen]

Cheapest complete fuel sender unit is £116.90 on misterauto.

[EmilysDad]

How much is an OE pump? I've found the MB aren't that badly priced & you'll know you have the correct part ....
mine cost me over £400 but that included diagnostics and 4 hours labour (MB) charge for 1.4hrs

[marcjero]

Yes that's not clear. Some sites are stating a flow of 65 lph. I found ones stating 120 lph. Could be replaced with a gss340 I think. But it's overkilling. gss242 could be a better match.

[tolsen]

The Walbro GSS284 pump is also used in the diesel 450 but then only deliver 2.5 bar. Perhaps there is a regulator built into fuel sender unit. Fuel pump as fitted in sender unit for the Roadster appears to be rated at 4.9 bar.