1. This site uses cookies. By continuing to use this site, you are agreeing to our use of cookies. Learn More.
  2. Welcome To LandyZone!

    LandyZone is the biggest Land Rover forum on the net. We have plenty of very knowledgable members so if you have any questions about your Land Rover or just want to connect with other Landy owners, you're in the right place.

    Registering is free and easy just click here, we hope to see you on the forums soon!

3.5 V8 SU Carb Issues

Discussion in 'It's A V8 Mate!!' started by hef19898, Aug 6, 2020.

< Previous Thread | Next Thread >
  1. hef19898

    hef19898 Well-Known Member

    Joined:
    Mar 27, 2019
    Posts:
    344
    Likes Received:
    179
    Location:
    Germany
    Sorting the carbs it is. After vacation, no time to tackle that before. The more I investigate, the more I'm convinced the carbs are the root cause.

    Thanks again everyone, I'll keep you all posted how things develop!
     
    Dippypud and Ratae like this.
  2. hef19898

    hef19898 Well-Known Member

    Joined:
    Mar 27, 2019
    Posts:
    344
    Likes Received:
    179
    Location:
    Germany
    One good thing over the weekend end was the identification of the root cause for the sudden engine shut downs. Turned out the relay between the aftermarket transistor ignition and the after market contactless ignition, an original Jaguar relay, is at fault. Easy fix, so there is that. But still, the carbs need some new gaskets and seals and stuff as well.
     
    Dippypud and kermit_rr like this.
  3. adrian hogg

    adrian hogg Well-Known Member

    Joined:
    Jul 20, 2017
    Posts:
    304
    Likes Received:
    216
    Location:
    WEST MIDLANDS
    if you do not go off-roading i would stick a pair of SU carbs on if you can find em they give much better economy than horrid horrid strombergs. Years ago i did this on my v8 90 and it gave me another 4mpg which does not sound much but given i was averaging around 15mpg i was delighted!
     
    kermit_rr likes this.
  4. kermit_rr

    kermit_rr Can't Remember Full Member

    Joined:
    Dec 9, 2018
    Posts:
    11,693
    Likes Received:
    10,377
    Location:
    North Shropshire
    Never had a problem with the SU on my 2A off road in fact i got better power delivery
     
  5. hef19898

    hef19898 Well-Known Member

    Joined:
    Mar 27, 2019
    Posts:
    344
    Likes Received:
    179
    Location:
    Germany
    I actually do go off-roading. The carbs seem to work again, so. Had them partially dismanteled last week, and diaphragms look prestine. Turned out to be a vaccum issue, and the calibration seem to be off to the meager side. But some more fuel economy would be nice... When I can track down, and afford more importantly, some other carbs. Or I go for an EFI-conversion one day. or I just leave it like it is if I can get it working.
     
  6. hef19898

    hef19898 Well-Known Member

    Joined:
    Mar 27, 2019
    Posts:
    344
    Likes Received:
    179
    Location:
    Germany
    I just finished replacing the vacuum hose from the carb to the distributor. Now the engine revs nicely up to 4.5 k rpm. The catch is, so, that revs fall back to 3k on full throttle. Every time. Take the gas back a little, and they go up again.

    Any idea what could cause that? I would hate to have to go to the stealership over this, and there aren't that many mechanics left who know carbs, let alone Rover V8s...
     
    marjon likes this.
  7. marjon

    marjon Well-Known Member Full Member

    Joined:
    Jul 15, 2018
    Posts:
    6,294
    Likes Received:
    8,388
    Location:
    Bulgaria
    Have you got any manuals to set them up "as rule of dumb" close enough:) then after you need something like this.

    But it sounds like you are getting close in the setup.

    Not sure I fully understand, you talking about backing of on the "loud" pedal or turning any screws?
    J
     

    Attached Files:

  8. hef19898

    hef19898 Well-Known Member

    Joined:
    Mar 27, 2019
    Posts:
    344
    Likes Received:
    179
    Location:
    Germany
    I meant releasing the throttle. I am a total noob on how that stuff works... So I am just experimenting based on the workshop manual right now...
     
  9. kermit_rr

    kermit_rr Can't Remember Full Member

    Joined:
    Dec 9, 2018
    Posts:
    11,693
    Likes Received:
    10,377
    Location:
    North Shropshire
    dealership wouldnt have a clue what to do with a carburettor, from my experience :) last time i spoke to someone in a dealership (not JLR) I was told petrol engines dont need spark plugs anymore, thats obsolete technology
     
    hef19898 and marjon like this.
  10. marjon

    marjon Well-Known Member Full Member

    Joined:
    Jul 15, 2018
    Posts:
    6,294
    Likes Received:
    8,388
    Location:
    Bulgaria
    Which Manual is that?
    I would suggest you search the tinternet and find a Stromberg manual if you are using the car manual.
    But you are getting close keep with it mate:)

    J
     
  11. kermit_rr

    kermit_rr Can't Remember Full Member

    Joined:
    Dec 9, 2018
    Posts:
    11,693
    Likes Received:
    10,377
    Location:
    North Shropshire
    if revs are not dropping back to idle when you release the pedal, then there is still an air leak somewhere, or the mechanism is not returning properly
     
  12. hef19898

    hef19898 Well-Known Member

    Joined:
    Mar 27, 2019
    Posts:
    344
    Likes Received:
    179
    Location:
    Germany
    Funny enough, the local JLR garage seems to pretty ahppy to get there fingers on old cars, they even have a discounted hourly rate for those. A rate that isn't that much higher than the free garages are charging.

    On the carbs... I removed and remounted the piston assemblies. And I just discovered a funny thing... The gas pedal is moving, by some excentric disc assembly (sorry for that, I hope you understand what I mean) some lever on the carb / engine. When I move said lever with a screw driver, there are no issues reving up. At all. When I do the same thing with the gas pedal cable, revs are dropping and I have the issues I discribed above. So, I would imagine it is not the carbs nor engine but rather the pedal mechanism... Well, good thing is that I feel much more comfortable to touch that kind of things!
     
    kermit_rr and marjon like this.
  13. hef19898

    hef19898 Well-Known Member

    Joined:
    Mar 27, 2019
    Posts:
    344
    Likes Received:
    179
    Location:
    Germany
    So, just tried something else. When I push the gas pedal around three questers of the way the revs start to drop. Before that, I get almost 5k rpm without any issues, then the revs drop down to 3k and th engine starts to stutter. What in the name of the cylinder head can be the reason for that? Meager mixture? Ignition? The whole mechanical assembly is moving freely. So out of my comfort zone again...
     
  14. kermit_rr

    kermit_rr Can't Remember Full Member

    Joined:
    Dec 9, 2018
    Posts:
    11,693
    Likes Received:
    10,377
    Location:
    North Shropshire
    with the engine switched off, lift the piston in the carb so you can see the butterfly, (or remove if its easier) then operate the linkage by hand and check the butterfly opens fully and returns to fully closed.
    next, have a friend operate the pedal while you watch the butterfly and check it opens and closes fully.
    do the above on both carbs. both butterflys should open equally.
    if all looks OK, start the engine with the air filter off. the piston on both carbs should be almost closed. rev the engine and you should see both pistons move up and down equally as you increase/decrease revs
     
  15. hef19898

    hef19898 Well-Known Member

    Joined:
    Mar 27, 2019
    Posts:
    344
    Likes Received:
    179
    Location:
    Germany
    Good tip. Here's what happened: At the sweet spot, around 4k rpm, the pistons are around 30% up. Pushing the pedal all the way down, the pistons go up all the way and the revs drop and the engine starts to stutter until revs stabilize around 3k rpm. The stuttering stops when the pedal is released. My instinct is telling me that the engine isn't getting enough fuel. Either due to a lean mixture or something else. or am I totally on the wrong path here?

    EDIT: Butterflys are moving equally with the engine of. And the pistons are almost closed with the engine idling.
     
  16. kermit_rr

    kermit_rr Can't Remember Full Member

    Joined:
    Dec 9, 2018
    Posts:
    11,693
    Likes Received:
    10,377
    Location:
    North Shropshire
    sounds like you're on the right path. I can't remember, have you stripped the carbs and checked/cleaned the jets? it could be you've got a blockage somewhere, thats what i'd be checking first
     
  17. hef19898

    hef19898 Well-Known Member

    Joined:
    Mar 27, 2019
    Posts:
    344
    Likes Received:
    179
    Location:
    Germany
    Possible that something blocked the jets when I checked the diaphragms... Needles are moving freely on both pistons with the pistons out. Do I have to remove the carbs from the engine to clean the jets? Would rather not have to do that... Fuel filter is next. maybe I have to replace the fuel lines all together.

    Another thought. I had the engine dying randomly, which turned out to be a relay between the fuel pump and the transistor ignition. I replaced the relay and moved the ignition from the engine bay into the car behind the dashboard. Could it have something to do with that? That the pump isn't synced properly with everything else?
     
  18. Dippypud

    Dippypud Never Knowingly Understood Full Member

    Joined:
    May 2, 2011
    Posts:
    57,101
    Likes Received:
    34,214
    Location:
    The Wooly Witch
    Also look at the gas pedal return don't know if it's spring or cable related, any slack or loss of movement ?
     
  19. hef19898

    hef19898 Well-Known Member

    Joined:
    Mar 27, 2019
    Posts:
    344
    Likes Received:
    179
    Location:
    Germany
    The gas padel is working fine, double checked. Was my preferred scenario, so. But hey, if I just did things I'm comfortable with the car would be a rust bucket by now!

    The special carb tool was dispatched today, so I will hopefully be able to fix it soon enough. Im case it's the calibration, that is.
     
  20. kermit_rr

    kermit_rr Can't Remember Full Member

    Joined:
    Dec 9, 2018
    Posts:
    11,693
    Likes Received:
    10,377
    Location:
    North Shropshire
    It could be a fuel pump or fuel filter problem, if the filter hasn't been changed in a long time then it's a good thing to start with. All the pump does is maintain a full float bowl, if it can't for whatever reason then the carb will struggle with a high demand for fuel.
    If the filter and pump are ok, including the electrical supply to the pump, then the carb should come off for a clean. It's the only way to be sure everything is good. They aren't hugely complicated.
    One last thing, have you tried running it without the site filter?
     
< Previous Thread | Next Thread >