Billyjoebob007

iTrader: (1)

Dieseling and surging after hot engine shutdown, after turning ignition off the engine does a little chug a lug dance then it diesels and then a quick engine surge before finally shutting off, when it does the last part of the surg(with air filter removed) i see gas spurting through the top of the carb. + i put in a fuel pump kill switch to try and cut off fuel flow to engine b4 shutdown to see if that would prevent the motor from doing it and the engine continues to run forever with the power cut to the pump ! I turn the ignition on and i hear the pump going and then i flip off the secondary cut off switch i installed and hear the pump go off, but yet motor still continues to run for minutes on end. I was thinking perhaps a timing issue but car runs sooper strong through out the rpm range. What could the possibilities be to cause this situation ?

Engine specs:

SBChev 400 HP - block # 3951511 - 1970-73
.40 flat tops / roller rockers / edelbrock performer rpm heads / comp cams thumper cam / eldebrock performer rpm high rise intake / Holly 600 carb #80457-7 .
Ignition:
Mallory coil # 29440 / msd street fighter cdi multispark ignition # 5520 / Msd distributor #8361

Oh, its an '84 firebird, i just bought it a couple weekends ago, the PO had a lot of stuff on 'er goober rigged which i have now spent an additional $800 on fixin his F' ups, probably will soak another grand into 'er to get everything up to par with my standards. Good looking car though and shes the fastest bird ive ever owned ! Will gets some good pics tomorrow after i take 'er in for a good bath. It feels good to get back in the saddle again, ive been without a bird for the past 7 years, way too long ! My last one was a beautiful 87 GTA i regretfully sold to start getting into JeePs, My first bird i bought was in 1988, a 1974 T/A with a 455 in it and was painted a 1974 corvette yellow, others i have had was a 1970 TA (which was my baby) I put 10 g's into building that one up to be one Bad mother of a street strip racer, dynoed at 448 hp at the rear wheels, i built that off the original 365 hp stock motor that was in it, used to take that car and drag it all over the place mostly out here at bandemeire speedway, took out to pomona once, and raced in SLC UT and out in Iowa, That car got stolen on night in 1997 and totaled out by the thief whom died in the wreck. Ive also had the years 85,86, 80,77,78 & now i have the 84
Boy im a bit rusty on how to tune up carbed engines and point ditributors got a lot to relearn , LOL.

SpitotRs305

only way to diesel with the ignition propery shut down would be hot spots...

vetteoz

iTrader: (13)

Killing the pump has little immediate effect on a carb engine because it has to use up all the fuel in the carb bowls before it runs out of gas.

I would be looking at a upgrade to a HEI dist ( any HEI ) over playing around with a old skool points dist

SpitotRs305

he doesnt have a points dist if his part numbers are acurate

vetteoz

iTrader: (13)

Maybe he is confused as to what style dizzy he actually has

Billyjoebob007

iTrader: (1)

Its not a HEI distro

http://www.msdignition.com/Products/...m_Advance.aspx

TTOP350

iTrader: (8)

Sounds like the floats are set to high in the carb or maybe some gunk in the needle and seat or just a internal leak, all cause fuel to leak into the motor and if its still warm will cause the problem your asking about.

Billyjoebob007

iTrader: (1)

Thankx, I was gonna pick up a bigger carb today, Edelbrock 1413 800 cfm for $135.00 today, i hope its not too much carb for my car. The po said he ran a 750 demon on it with no issue.

LilSki

iTrader: (1)

There are a few reasons a motor can diesel on shut down.

Too high of an idle is a common cause. When the key is turned off the motor takes so many extra rotations to stop it sucks in a lot of extra fuel which can ignite on its own if hot enough

Too rich of an idle and also too lean can also cause it. Rich because of the extra fuel and lean because of the higher temps it causes.

Improper ignition timing can cause higher than normal combustion chamber temps and on shut down causes it to ignite any extra fuel left after shutdown.

Billyjoebob007

iTrader: (1)

Ok, thankx. I did have the idle set a bit high, lowered that and it seemed to help, but at cold start up its too low, i think perhaps the elect choke isnt working right and needs adjusted or cleaned.
I wonder too if perhaps my fuel pump is pushing too much gas unregulated, its a napa Rotary vane design elect performance pump which is pushing 18 psi.
http://napapartsfromfederalmogul.com...s/electric.php

I wonder if it would help to install a fuel pressure regulator ? Perhaps tone it down to say 9 psi ?

LilSki

iTrader: (1)

Yeah 18psi is way to high for any carb. Get it down to 5-9psi and then tune your carb.