engine surging badly

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rob83ke70
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Posts: 193
Joined: Sat Jun 21, 2008 4:12 pm
Location: Orange NSW

engine surging badly

Post by rob83ke70 » Sun Nov 23, 2008 12:38 pm

i have a ea82 engine with standard carburettor in a subaru l series (1994 model). the engine surges under load, worse when cold.

doesn't surge straight away sometimes you have to be into it a little while to make it surge. got so bad this morning that i couldn't drive up mount canobolas...

carburettor has been rebuilt, throttle shafts rebushed. no manifold vacuum leaks, timing set at about 9 degrees btdc running 91 octane fuel, centrifugal advance working, vacuuum advance working. vacuum to the secondary barrel seems to be ok and doing what it supposed to be doing.

about to put a fuel pressure gauge on it but not sure that i'll find anything.

ignition coil has been replaced twice, doesn't make any difference. spark plugs are bosch equivalent of bp5es plugs (1 heat range hotter than stock)

i'm sure it doesn't feel like float issues as it just surges and jumps back and forward while driving, it doesn't cut and die then come good when the throttle is lifted like an empty float bowl would do.

i've noticed not as much ported vacuum is going to the secondary barrel as what goes to the vac advance on the distributor but i think this is normal, i tried hooking up distributor ported vac to the secondary and it opens a bit too soon i think...

any ideas? i'm on a budget and have other projects happening so i can't just put an ej20t straight into it to fix it... and i'd rather keep the car than get rid of it.... although the way this is going....

robert :mad:
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Busdriver
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Joined: Fri Oct 12, 2007 7:53 pm
Location: albury

Post by Busdriver » Sun Nov 23, 2008 4:42 pm

Sounds like surging caused by running lean, definitely check fuel pressure.
Have you replaced the fuel filter yet?
Had something similar happening to mine when the fuel filter needed replacing.
"i've noticed not as much ported vacuum is going to the secondary barrel as what goes to the vac advance on the distributor but i think this is normal, i tried hooking up distributor ported vac to the secondary and it opens a bit too soon i think..."
Just wondering, did you measure this?
[SIGPIC][/SIGPIC]Busdriver, 91 L Enduro Wagon, stock ,for now.
Lots of Ks,A/C, MP3 sometimes(if its not dark) singing steering wheel cover which I listen too when its dark.

Suby Newbie
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Storm
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Joined: Sat Sep 20, 2008 9:36 am
Location: NSW

Post by Storm » Sun Nov 23, 2008 5:40 pm

rob83ke70 wrote:spark plugs are bosch equivalent of bp5es plugs (1 heat range hotter than stock)
Why are you running plugs hotter than stock?

Without knowing to much about your car apart from what you have said here, I'd say fuel pressure is your problem. You say your carb has been rebuilt, is it setup properly? If your float is set to low you could get this problem especially if your fuel pressure is also to low.
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rob83ke70
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Joined: Sat Jun 21, 2008 4:12 pm
Location: Orange NSW

Post by rob83ke70 » Sun Nov 23, 2008 7:42 pm

found the problem. thanks for your help :)

fuel pump not supplying enough pressure, replaced with aftermarket facet type pump, not as neat as stock but doesn't look too dodgy anyway.

fuel filter is new genuine subaru item (it was free)

car runs beautifully now.

i'm running plugs one heat range hotter than stock because i managed to foul a set of plugs in under 25000km, and the next set fouled in under 5000km... car does a bit of short cold trips too. i've since replaced the coil with a transformer type electronic coil seems to have made a big improvement, plugs still look clean.

the last brumby i worked on i fitted ngk bp4es plugs to it, which are one hotter than mine... the plugs that came out of that were disgusting though.

robert
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