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V8 spark problems


candpdoyle
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Hi All

Wonder if I could reap some forum expertise? This will be a long post as I have an ongoing fault that is doing my head in :-(

vehicle is a series 3 swb fitted with a 3.5 v8 engine number starts 38A has twin strombergs and dizzy is the 38dlm8 with 2 lucar pins

was running and starting well when i bought it so started renewing ignition bits.

red rotor arm, powerspark blue 8mm ht leads, new dizzy cap, new set of ngk bpr6es (i think) plugs gapped to 0.08mm

had an lpg system fitted (second hand) By Gordon Findlay and all was good bar a little fluffiness on lpg

decided to renew dizzy with a simonbbc unit and matching coil which is where my problems started.

after lots of cocking around I have sent the simonbbc parts back as i could get no joy( would not start on gas at all and felt gutless. also down to 8-10mpg from 17mpg) and the old parts seemed to work better

been ok except for intermittent spark issues. spark is not very strong and appears to be intermittent ?? will spark for a second and then goes away. 12v at the coil, but does seem to drop on cranking.

have tried direst feed from my battery and from another spare battery while cranking and still carp spark. tried 2 spare coils I have and same(except 1 was dead)

have tried jumper cable to various different earthing spots on starter, engine and chassis with no difference

there is no ballast resister and coil is a 12v item

switch to petrol and it starts and runs as it should.. struggles to fire on change to gas but will do so after a second or 2 and then runs but i think not on all cylinders...seems smooth enough but sluggish... still faster and more powerfull than a 2.25 but definately not like it normaly runs

sorry for the essay, but not sure what to check next???

thanks in advance

Chris

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amplifier is wired up correctly I think... the problem seems to start before the dizzy though... I have been testing with a spare plug in the king lead, and the spark is carp from the coil???

my tester has blown up now, so have resorted to old school checks :-)

Chris

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Ah I see what you mean... only problem with that theory is It was worse with the new simonbbc one? is there any way of testing them? might pop down to the local landy specialist and see if he has any spare 2nd hand units i can try :-)

Cheers

Chris

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Starting at Page 1 of the V8 problem solving book - the best thing you can do is replace all the ignition bits with genuine ones. It sounds like you're running non-gen leads & rotor at least. LPG puts extra strain on the ignition system and the standard setup isn't that great to start with.

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would you call these genuine?? they are marked Lucas and states oem?

http://www.ebay.co.uk/itm/280607607297?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1438.l2649

have noticed other sites charge up to £300 for "genuine" HT leads :blink:

have ordered a dizzy cap, rotor arm and coil from matford, but could not bring myself to pay what they want for ht leads :blush:

Chris

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me thinks we are on the right track :-) took all the plugs out, cleaned and regapped them at 0.6mm.. replaced the powerspark rotor arm with the old lucas one, and tidied up the ht leads using nige's nice pic on the routing (thank you)

started and sounded sounded a bit better, so i advanced the timing to the old mark on the dizzy (where it was before all my troubles) reset the idle and took it for a blast around the block :D much better.. picks up revs quickly and barks like a goodun... nice and wheel spin happy again as well which has been lacking lately

so will definately replace and renew all ignition components with genuine over the next week.. have also ordered some new earth cables which i will fit over the weekend hopefully

cheers

Chris

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I think the culprit has been found :-) I Fitted the new earths yesterday, and while removing the battery to chassis cable I discovered the po had spliced the cable to extend it... was a good 3/4 inch gap in the splice :blink:

Ran a nice shiny new cable to chassis, and from there to bellhousing. Have another from engine to front panel and another chassis to gearbox.. should cover it I think cleaned up all the mounts with wire brush as well.

turns over much quicker now and spark is nice and strong, even runs better... muchly happy and will sort the vacuum advance next

Cheers

Chris

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