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  1. #1
    Join Date
    May 2008
    Location
    Cambridge
    Posts
    131

    Injection fuel pump arrangement

    I need to replace my Bosch 044 fuel pump, which I'm pretty sure is failing. I think the problems started after I almost ran out of fuel early the year before last, and I have been getting cuts in power more frequently ever since on longer drives. I suspect the pump is picking up inside when it gets hot, and stopping. It's always possible it's an electrical problem, and I'll make sure that the electrical side is OK when I refit it all.
    The existing arrangement is that the fuel pump is on it's side on the boot floor next to the fuel tank, with a fuel filter between tank outlet and pump inlet. Pump outlet goes to a regulator in the boot, with feed to engine and return to tank from this. I'm pretty sure there is no fuel filter after the pump. I'll try and add a picture to this thread.
    I had been thinking of just replacing like for like, but the setup doesn't seem right to me. The pre pump fuel filter looks like it might be far too fine, but I've not confirmed exactly what it is, and a post pump fuel filter would be a good idea. Also, with the pump where it is I will always be at risk of starving the pump of fuel going round left hand corners, and these pumps don't like being starved of fuel...
    I am considering adding a swirl pot and lift pump, good idea? If so, any recommendations? I have a pretty standard LS6, run by a LinkECU, about 400bhp. I've never done a track day, but I keep toying with the idea.
    The fuel tank on my GD is too small really, I think it's only about 39litres, and with the fuel gauge being wildly inaccurate I've been juding when to fill on the trip, so I think I'll fit a spiyda gauge wizard too.
    I think the latest GD build manual has the fuel pump mounted behind the diff, but it still isn't really lower than the lowest part of the fuel tank, so I'm still concerned by this approach needing the fuel pump to suck fuel. These high pressure pumps don't seem to be good at that, hence the swirl pot idea. I'm pretty happy to leave the pump in the boot, I haven't had much in the way of fuel smell in there. At least not until I accidentally had fuel foaming out when I filled up too fast, then running down the roll bar hole into the boot...

    Any opinions very garefully received!

    Thanks, Richard
    --
    Richard
    GD Mk3 LS6

  2. #2
    Join Date
    May 2008
    Location
    Cambridge
    Posts
    131
    20190916_154328_m.jpg
    Picture of existing pump arrangement.
    --
    Richard
    GD Mk3 LS6

  3. #3
    Join Date
    Apr 2004
    Location
    on the edge...almost falling off
    Age
    57
    Posts
    8,529
    If you're getting fuel starvation maybe the filter is blocked or slightly blocked? Maybe try a larger filter first?

  4. #4
    Join Date
    May 2014
    Location
    Birmingham
    Age
    43
    Posts
    768
    Pull it all part and give it a clean flush with fresh fuel, maybe change the filter/element?

    Alan.
    AK Gen II on the road Jan '19
    GM LQ4 364ci, LS9 cam, Omex 710.
    Tremec T56 Terminator.
    3.27:1 Powr-lok LSD

  5. #5
    Join Date
    Dec 2013
    Location
    Newark, Notts
    Age
    69
    Posts
    1,535
    Fuel Pump 1.jpg Pre filter with metal gauze filter and then paper filter after pump (supplied by Merlin). Fitted to LS3 on Chassis
    Fuel Pump 2.jpg
    Charlie
    Joint Area Rep - East Midlands Region
    AKCharlie - ''AKA SOOTY'' - AK GEN2 - LS3 - 6.2litre - 434bhp - A dream come true
    .

  6. #6
    Join Date
    May 2004
    Location
    Finchampstead, Berkshire, UK.
    Age
    54
    Posts
    3,636
    Hi Richard,

    I had lots of fuel starvation problems on track days when the tank went below 1/4 full (on long left handers mainly), when I put the blower on I changed the setup to include a facet red top lift pump into a swirl pot (all in the boot) - zero problems since then

    Rgds

    Jim

  7. #7
    Join Date
    Jul 2012
    Location
    NW England
    Posts
    440
    You really need a swirl pot with a fuel injection pump.
    I made one up for mine which sits along side the fuel tank and has the pump mounted to the back of it with a prefilter.
    I'll try and get a photo over the weekend.

    The main (EFI) filter is after the pump which is standard as far as I'm aware and means the fuel if 'pushed' through at EFI pressure rather than pulled through.
    your regulator location is strange (to me) mine is in the engine bay as it needs a vacuum feed from plenum to maintain a constant pressure across the injector rather than a constant absolute pressure. Guess your system must be different.

    From the tank the fuel route is:
    pre-filter - Lift pump - swirl pot - pre-filter - EFI pump - Pressure feed to engine bay - Fuel rail - Regulator - Return line to boot - Feed into swirl pot - return from top of swirl-pot back to tank.

    Arguably this could result in the swirl pot fuel getting warm as it's been around the engine bay and possibly may be better to return fuel direct to tank but it's never been a problem so I'll leave it.

  8. #8
    Join Date
    May 2008
    Location
    Cambridge
    Posts
    131
    Thanks for all the advice!
    I think I'll go for a swirl pot and lift pump. I guess if a facet red top lift pump is good enough for Jim and his supercharger, then it will be plenty for me! If I could mount the pump below the fuel tank it would be fine, but it's just not really possible on my GD.

    So, my plan will be tank to lift pump (facet has built in pre filter), then into swirl pot. Swirl pot bottom outlet to a pre filter, then EFI pump, then post filter, then the regulator. Regulated feed to engine bay. Regulator return back to swirl pot top inlet, and swirl pot top return to tank. It won't take up much room in the boot, so should all be fine with a bit of planning.

    I guess I was also a bit surprised the the regulator location, I kind of expected it in the engine bay, but the boot location makes the return line very short and convenient. I think it just regulates to a pre set absolute pressure. The regulator has a port for connecting to an air pressure feed, so I guess it would be simple to run a vacuum pipe back into the boot should I choose to do so. I'm not sure I quite understand; I thought the injectors were happy to see an absolute pressure at the fuel rail, and the car has been running fine like this since built. I did read about using the air pressure feed on these regulators if using forced induction, so that the fuel pressure is increased to compensate for the boost pressure working against them. I guess in a normally aspirated setup, the vacuum could serve to drop the fuel pressure at idle and cruise conditions, so would take load off the injectors?

    I'll check all the fittings and connectors I have, then I was thinking of asking someone like Merlin Motorsport to recommend a setup. For example, looking at the fuel filters I'm not sure of the best choice for pre and post EFI pump filter. I'm tempted to replace the Bosch 044 like for like, but GD recommend the Walbro pump as being fine, and it is nearly half the price!

    I'd love to see pictures of your setups!

    Thanks, Richard
    Last edited by richard8166; 14-02-20 at 11:20 PM.
    --
    Richard
    GD Mk3 LS6

  9. #9
    Join Date
    May 2004
    Location
    Finchampstead, Berkshire, UK.
    Age
    54
    Posts
    3,636
    My regulator isn’t vac referenced either, don’t change from one to the other unless you are happy scaling the injector data.

    I did the maths yonks ago and got to about 40 seconds of WOT before the facet couldn’t top up the swirl pot and it would start to run out of fuel - in real life I haven’t been that brave

    Cheers

    Jim
    GD Mk3 Jag based
    Supercharged LS1
    GD J1M

  10. #10
    Join Date
    Nov 2003
    Location
    West Midlands UK.
    Posts
    2,989
    Learnt the hard way , by burning out two Bosch 44's, that in a fuel injected car you need a swirl pot. I put one in the tank with a single in-tank pump with one filter between the pump and the injection rail.

    If you have a return feed put the return into the tank so that it empties into the swirl pot so that after a wide open throttle situation when you do lift off, the excess fuel is being fed into the swirl pot thus replenishing the fuel available.

    Cheers,

    Tony
    Supply by blagging, engineering by bodge......

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