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3.5 V8 SU Carb Issues

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

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  1. hef19898

    hef19898 Well-Known Member

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    Thanks! And thanks for the encouragement! I already considered a new engine, refurbished engine if the price was right! So some more toying around for this week. What calms me down is, that engine is almost running good when cold and she did run good before I changed the relay and took the carb tops of. So it shouldn't be anything too serious, just something really tedious...
     
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  2. kermit_rr

    kermit_rr Can't Remember Full Member

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    Might i ask, why did you take the carb tops off originally?
    Has the ignition been touched since it last ran well? I think your car has a distributor? Has this been moved at all?
     
  3. hef19898

    hef19898 Well-Known Member

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    Because the left one is loosing damper oil and I wanted to check the diaphragms. I didn't touch anything else, so. The only part of the ignition that was changed was the relay between the transistor ignition and the fuel pump.
     
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  4. hef19898

    hef19898 Well-Known Member

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    So far so not good... I changed the mixture, from what with my non existent knowledge can say the mixture should be fine on both carbs now, or at least fine enough based on the rvs when I left the caliper with a screw driver. Both carbs are in sync as well, I don't have a gauge to be certain so.

    Engine revs up to roughly 5k on less than full throttle, on full throttle revs drop back again to 3.5k. Idle is again at 600, with choke at 1.1k.

    Ignition maybe? Or a blocked fuel line somewhere? Or something with the float chambers?
     
  5. hef19898

    hef19898 Well-Known Member

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    I did some digging, and found some other potential root causes from other people having had the same issue:

    - coil

    - fuel pump

    - fuel lines (cheap enough to replace, so I'll order some suitable ones)

    - Distributor cap (I have a spare one, so easy enough to check)

    - Vacuum valve (?) between distributor and carbs

    Some other, maybe related issues, I just remembered: Previously, before having changed the relay, it smelled fuel, now it doesn't anymore. And the fuel tank was replaced like 1k km ago. The new tank sometimes leaked from the filler cap when full, now not anymore. The old tank was rusted through.

    Did a test with the fuel tank open, didn't change a thing. Slowly, I am ruling out the carbs. Cold performance and the lack of issues can be explained by the cold start / temp thermostat enriching the mixture. Under load it is better, but nowhere near what it was initially. So I slowly suspect fuel (not getting enough) or something ignition related. Only thing I didn't check on the carbs is the float chambers. I'll tackle distributor cap and fuel lines next, maybe it changes something.

    Man, fixing faulty stuff is fun. Diagnosing the fault not so much...
     
  6. marjon

    marjon Well-Known Member Full Member

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    Your looking for this bit i think marked in blue but maynot be your number so do a proper search.

    J
     

    Attached Files:

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  7. hef19898

    hef19898 Well-Known Member

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  8. Shippers

    Shippers Well-Known Member

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    Don't over think it start from the tank and check everything up to the carbs and dont assume...
    @marjon how do I know??...got insurance on 101 last Friday from UK company so can drive on reg plates long story...went for a short run through valley halfway through loud bang and a vibration and rumbling sound...got it back home and started checking uj's thinking halfshafts etc baring in mind first time it's been driven on a road in 18yrs!...ehh no front left wheel nuts I forgot to tighten (slap on the back of the head) sorted a quick drive up the road and bang bang again yep front grill loose from clips sorted...next day engine cover and panels fitted adjust seatbelts rearveiw mirrors fitted a quick tidy up and off to pick partner up from work...wouldnt bloody start...spent a couple of days checking electrics etc then 2 days ago bought easy start fired up ran for couple of mins then died did that twice...back on it today started checking from tank with containers to catch 1/4 tank of fuel...guess what tank empty! fuel guage fubar...back on it tomorrow...
     
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  9. marjon

    marjon Well-Known Member Full Member

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    @Shippers I didn’t think anything the Q was about the vac advance unit, and OP seemed unsure what said item was, that was my post. I haven’t really got involved too much with his issues, as I am sure it should be easy to sort but as always doing it over internet rather than hands on, is not so easy:)

    So you finally drove the 101 on the road (legally?;))

    J
     
  10. Shippers

    Shippers Well-Known Member

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    Yes went to an insurance company here that can give cover with my mate the still owner of the vehicle and got cover "at a cost" being mot and tax exempt OK on those fronts...Here in Portugal the car is insured and anyone can drive it but we took out UK style insurance with me as named driver...
     
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  11. marjon

    marjon Well-Known Member Full Member

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    Green card?

    J
     
  12. Shippers

    Shippers Well-Known Member

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    Anywhere in EU after 30 days of policy inception but does not include UK but does breakdown here and Spain...
     
  13. marjon

    marjon Well-Known Member Full Member

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    So I didn’t miss anything on your thread then, it’s still not reg in PT ?

    sorry @hef19898 we are just chatting :) We will leave now:).

    J
     
  14. Shippers

    Shippers Well-Known Member

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    Correct and also apolagise for side track...but I am confused over his fault diagnosis and fault results...I made up long clip leads for DMM yesterday so could check coil voltage on cranking and everywhere else to delete electrics from problem that done it's only down to fuel hence my fuel guage fault...once I sort out filling tank and make sure pump is working as it should then it's a carb problem...he needs to do the same not jump around as it seems he is doing...
     
  15. hef19898

    hef19898 Well-Known Member

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    Ah, never mind guys! Everyone and everything is welcome here!
     
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  16. hef19898

    hef19898 Well-Known Member

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    So, I had another look at things trying to figure things out. And the wire to the fuel pump has seen better days, I tried fixing it with some tape, but some wires (phases? no idea how those are called in English) are broken. I guess I'll order a new one just for that anyway. And the fuel lines. Found a spare coil. And a spare distributor cap. So it seems I'm mostly set. Will be a nice weekend, fuel lines should be here by Saturday.

    Ah, thr pleasures of having old cars!
     
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  17. hef19898

    hef19898 Well-Known Member

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    So, the new fuel pump will be delivered on Saturday (DHL is shipping fast from the UK). Fuel lines Monday, but being handed over to DHL in Germany today, I'd wager on Saturday as well. Unless my old friends over at DHL slowed down, that is! Regardless, next week I should know more!
     
  18. hef19898

    hef19898 Well-Known Member

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    Good news! The new fuel pump is here, as are the fuel lines! It was rainy, and when it wasn't there was a tree to trim and enjoy some dry weather with the kids. I did tidy up the workshop, so. And guess what, I rediscovered the fuel pump I was sure I saw a year ago in a box... Well, spares don't hurt I guess.

    I'll start fitting the new parts tomorrow, if the weather permits.
     
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  19. hef19898

    hef19898 Well-Known Member

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    Good, took longer than expected as work and weather conspired against me. I fitted ne fuel lines from the tank to the pump and from there to the filter. And the new pump.

    No change, still the same full throttle issue above 3k rpm.

    Battle plan now: Replace all fuel lines, including return. Double check vacuum. Clean the carbs in-situ with brake cleaner. Check if this has an impact. And take of the carbs, disassemble them, clean them and put them back on.
     
  20. Hicap phill

    Hicap phill Well-Known Member

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    What pump did you get?
    Does it run all the time or does it stop once up to pressure?
     
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