36 replies to this topic

[fezzasus]

And you have a Pro Alloy tank? It's not pressure/vacuum build-up, just fuel temperature that creates gas bubbles...

 

No I don't. I have a standard tank which I assume makes the problem worse (less fuel volume).

 

So are we saying the heating is purely from the higher volume fuel pump rather than the fuel lines being exposed to engine bay heat? I've fitted steel overbraid hoses and the uprated fuel pump in one go, so the fuel system is completely different to before this point.

 

I suspect the wider bore return hose with overbraiding will transfer more heat into the fuel vs the OEM installation due to routing, residence time and the fact that they're covered in metal. I can insulate these but if it's the rate of pumping that's the problem I should probably consider a larger tank or derated fuel pump.

[fezzasus]

This is the plan unless anyone has a better idea:

 

- Firesleeve the fuel lines

- Replace coil pack (not fully convinced this didn't have anything to do with it - it is 15 years old!)

 

Test above fixes and see if I get the same issue at low fuel volume. If so, i'll be asking Joe for his best ProAlloy price.

[gaffer1986]

I thought you had a supercharged car?

[fezzasus]

I thought you had a supercharged car?

 

I do

[gaffer1986]

So NA ish means supercharged or do you have two?

[fezzasus]

So NA ish means supercharged or do you have two?

 

Only one, I used N/A in the title because SC and NA are essentially the same for any hardware faults.

[Exmantaa]

 

And you have a Pro Alloy tank? It's not pressure/vacuum build-up, just fuel temperature that creates gas bubbles...

  No I don't. I have a standard tank which I assume makes the problem worse (less fuel volume).   So are we saying the heating is purely from the higher volume fuel pump rather than the fuel lines being exposed to engine bay heat? I've fitted steel overbraid hoses and the uprated fuel pump in one go, so the fuel system is completely different to before this point.   I suspect the wider bore return hose with overbraiding will transfer more heat into the fuel vs the OEM installation due to routing, residence time and the fact that they're covered in metal. I can insulate these but if it's the rate of pumping that's the problem I should probably consider a larger tank or derated fuel pump.

 

  Which pump do you have now? Dominique heat-sleeved his lines and the fuel rail, but heat is mainly coming from the dissipated pump power.(that is cooled by the fuel)...   Did you already try out if the problem is solved with more fuel in the tank?

[fezzasus]

I've got the DW65c detailed on the previous page. 

 

I haven't had the issue since refilling, and didn't have the issue for the first 140 so miles... seems to suggest fuel temperature. :/

[fezzasus]

Quickly compared measured flow data for my DW65c pump vs a Walbro 255 (selected because there are plenty of people here who run them)

 

the DW65c flows around 280 L/h verses the W255 250 L/h at 55 PSIG (3.8 bar - standard fuel rail pressure). Given that this problem manifested itself at about 1/2 tank volume, this means the pump was recirculating the tank content 21 times an hour verses 14 times for the Walbro 255.

 

However that doesn't seem that different. Let's take a refill scenario of 5 L in the tank.

 

That's a recalculation frequency of 75 times for the DW65c and 50 times for the Walbro 255. Since a rate of 50 times an hour is okay for people with a Walbro 255, it seems my issue at half tank volume may not be related to fuel heating from tank recirculation.

 

Going to pull the plugs to see what state they're in. Still running the standard Saab ones so might contribute to the problem

[siztenboots]

is the SC vacuum bypass working?

[The Batman]

Bypass wouldn't make it cut out

[Exmantaa]

It's about the heat power that is dissipated in the fuel.

Your 65c pump draws about 13A @ 60psi and at low load most of that power is all dumped in your fuel amount... 

[fezzasus]

have insulated the fuel lines with fire sleeve and performed a logging session. Can't see anything odd

 

file uploaded here: https://ufile.io/bp8qg

Edited by fezzasus, 21 May 2017 - 05:23 PM.

[fezzasus]

Fire sleeve-d fuel lines. Spent the day in similar temperature and driving conditions without repeating the issue so this seems to be helping. Will be fitting a 48 L tank tomorrow to ensure I don't get it again (better cooling from larger volume of fuel)

 

[CHILL Gone DUTCH]

Tom what is the big pipe running over the fuel rail?

[fezzasus]

Crankcase breather. There's a provent 200 mounted by the air filter

[Bargi]

Years ago after getting thvse fuel pump upgraded to the walbro the float is I 7j88to Sent from my SM-G920F using Tapatalk