MK2 fuel pump upgrade(?)

Discussion in 'General Chat' started by jimmy2gti, Dec 2, 2019.

  1. jimmy2gti New Member

    Joined:
    Mar 27, 2018
    Likes Received:
    0
    Hello,
    I noticed that my fuel pump housing has been leaking a lot, as it has a big crack under it, and the problem has effects on the fuel pressure on my 8v k-jet. I can't find any decent boxes in my area and online, its a bit too expensive for me atm, so i decided to ditch the whole assembly and install a walbro 255 pump.
    My question is, is it possible to run the stock in tank pump along with the walbro in-line? What other things do i have to take care of? Is it better to just install the new pump in-tank?
     
  2. Tristan Forum Junkie

    Joined:
    Apr 25, 2006
    Likes Received:
    307
    Location:
    Southern IRELAND
    I would say high pressure in tank only, or else oe in tank feeding a swirl pot for an external walbro.

    Or, go look for a mk3 vr tank.
     
    jimmy2gti likes this.
  3. rubjonny

    rubjonny Administrator Admin

    Joined:
    Oct 31, 2003
    Likes Received:
    1,886
    Location:
    Bracknell
    yeah you'll either need to mod the pump into the tank, maybe fabricate a crude pot for it to sit in so you don't get starvation cornering when fuel is low, or run it externally with a swirl pot between it and the lift pump. can still buy the mk1 cabrio/scirocco/g40 shape polo ones from VW heritage though are a bit pricey. fab up a frame to hold everything up under the car
     
    jimmy2gti likes this.
  4. jimmy2gti New Member

    Joined:
    Mar 27, 2018
    Likes Received:
    0
    Thank you, swirl pot on its way, I'll post updates after everything is finished.
     
  5. jimmy2gti New Member

    Joined:
    Mar 27, 2018
    Likes Received:
    0
    Hello again.
    I started working on the old golf and set up the new pump system. (in tank pump, swirl pot, walbro inline gsl392 and oem filter.)
    I jumped the pump and got about 4bar of system pressure. I added a shim on the pressure regulator(facepalm), and managed to get the pressure up to about 4.8 bar, which was enough to open the injectors. I started her up and drove around a bit. It shut off after a few minutes tho, and i had a blown fuel pump fuse. Replaced the 15 amp fuse with a 20amp one to match the walbro(facepalm) and got her running again, after installing a multimeter on the pump. The voltage, however, was rather low (about 7.5-8 volts) and it smelled like burnt plastic. I shut her off but it was, well, too late. I saw smoke coming from the pump terminals, the wires were almost melting and my 3 days old pump was toast.

    I used the factory wires for the cis high pressure pump.
    So far i suspect some possible causes of my fail:
    -bad connection on the pump wiring, causing the current to go up and frying everything
    -major f*ckup with the swirl pot setup, causing the pump to suck in air
    -simply the walbro, although theoretically up to spec, not being able to perform well enough for CIS

    Any ideas on those?
    Classic case of trying to save a few bucks only to pay more at the end[8D]
     
  6. rubjonny

    rubjonny Administrator Admin

    Joined:
    Oct 31, 2003
    Likes Received:
    1,886
    Location:
    Bracknell
    swap a 17, 18 or 100 relay into slot 2 this will allow you to power the fuel live with ignition. Then have a look at voltage at the pump plug after you replace all the wires, making sure to use correct 1.5mm2 gauge or higher. if voltage is still low look at the fusebox pump relay socket and fuse holder for signs of melting or corrosion.

    all 3 of those ideas could be correct based on the symptoms you saw, I would try to get OE spec bosch fuel pumps for CIS as they have to work hard. a standard mk1 golf fuel pump will do you fine, and will even accept the mk2 golf fuel pump plug housing so you can use the standard mk2 sealed fuel pump connector.

    the main pump wiring unplugs at a white 2 pin plug near the lifter pump assembly so this would be a good way to go if its only the section under the car which melted.
     
  7. jimmy2gti New Member

    Joined:
    Mar 27, 2018
    Likes Received:
    0
    Sorry for my relatively dumb question,
    I supposed, since the early 8v mk2's and mk1 1.8 gti's had essentialy the same engine, they also had the same pump setup? Don't they also have a twin pump setup with the housing underneath? Please educate me on this, its not as easy to find info on mk1's online as it is for mk2's.

    Isn't a mk1 pump "swap" a possible solution for us mk2 k-jet guys struggling to find a proper pump housing?
     
  8. rubjonny

    rubjonny Administrator Admin

    Joined:
    Oct 31, 2003
    Likes Received:
    1,886
    Location:
    Bracknell
    the mk1 golf doesnt haver the big plastic fuel pump assembly underneath, instead it has a swirl pot built inside the fuel tank. the external pump is a more traditional inline style pump, I suggested it as I assumed thats what the walbro pump you have is?

    for a normal mk2 guy you couldn't just swap a mk1 pump straight over, but if you were to add an external swirl pot then you can use a mk1 pump. this is what my mate did for his rallye, picture shows it mid way through but you get the idea:
    g1latereservoir.jpg

    the white tank is a post-84 cabrio/scrocco & g40 shape polo external swirl pot, the plastic fuel filter carrier is from a mk3 golf and the black rubber thing with 2 jubilee clips round it is a mk1 fuel pump in a rubber housing. you would also have to make a bracket for the fuel accumulator as well on a kjet car
     
    jimmy2gti likes this.
  9. jimmy2gti New Member

    Joined:
    Mar 27, 2018
    Likes Received:
    0
    Ok. I purchased a bosch CIS fuel pump (from mk1) and put it on the lift pump-swirl pot-main pump-filter setup. I also replaced the wires from the pump to its first connector. Im getting enough fuel from the swirl pot to the pump. I ran only the lift pump and got around 11 volts. I ran both pumps and got 10 volts at first, but as pressure built up i got a drop to around 8 volts again. I shut everything off in fear of boiling another new pump.

    Should I power the pump directly from a battery and test voltage again?
    Note that my accumulator was leaking as well, and I temporarily ditched it and use a switch to run the pumps before cranking hot.
     
  10. jimmy2gti New Member

    Joined:
    Mar 27, 2018
    Likes Received:
    0
    Update, turns out it was because i just used an old battery, fuel pump gets a decent amount of volts. (10.3 at max pressure). The car started right up and i drove around for 20 mins with no problems.
     
  11. rubjonny

    rubjonny Administrator Admin

    Joined:
    Oct 31, 2003
    Likes Received:
    1,886
    Location:
    Bracknell
    great news :thumbup:
     

Share This Page

  1. This site uses cookies to help personalise content, tailor your experience and to keep you logged in if you register.
    By continuing to use this site, you are consenting to our use of cookies.
    Dismiss Notice