quick check list when ITS just not running correctly

grumpyvette

grumpyvette

Administrator
Staff member
quick check list when ITS just not running correctly

--------------------------------------------------------------------------------

If you were local it would be easy to diagnose, but lets start with the basics

http://www.eugeneleafty.com/Corvette.asp

whats the COMPRESSION TEST reading for each cylinder?

HOW did you adjust the valves?

ARE ALL THE FUSES GOOD?
first check your shop manual for the fuse and fuse able link locations
fuses are located in several locations and fuse-able links near the battery


CAN you post detailed pictures of EACH spark plug?

whats your FUEL PRESSURE?(does it stay steady as the rpms build?)

HAVE you verified the throttle blades in the carb and linkage fully open?

how are the carb FLOATS SET?

what air filter SIZE and is it clean?

whats the TOTAL IGNITION ADVANCE?

whats the VACUUM READ AT IDLE?

whats the VOLTAGE at the COIL?

AT WHAT rpm does the advance reach MAX advance?

WHAT is the exhaust back pressure reading? (IDLE and 4000rpm under load)

HOW did you determine true TDC or did you just assume the timing tab and damper are correct?

What color is the ignition spark?

what is YOUR OHMS reading on the plug wires?

whats your spark plug gap?

CARB JETS? METERING RODS?

HAVE you REPLACED the cap and ROTOR?

ANY indication of a MISS or BOG?

HAVE you tried a DIFFERENT CARB?

have YOU verified EACH cylinder is firing?

have you VERIFIED the FIRING ORDER IS CORRECT?

HAVE you VERIFIED the LASH/PRELOAD on the rockers RECENTLY, and are you sure the cam is not worn?

are you SURE the trans fluid and rear differential are filled to the correct levels?

whats the engine temp after it warms up?

whats the trans fluid temp?


AND even if its a carb,equipped engine or if its injected ,ID add about 8 OZ of marvel mystery oil and two cans of separate and different brands of injector cleaner to my first full tank of fuel to dissolve crud in the lines and fuel tank, Id replace the fuel and air filters, and do a basic tune up , plugs,set the timing check for vacuum leaks, meter the plug wires with a V.O.M. and replace defective ones, verify the plug gap,you might be surprised at the number of times that helps.


links might help

http://www.clarks-garage.com/shop-manua ... tm#oil-low

viewtopic.php?f=32&t=2701&p=6996#p6996

viewtopic.php?f=50&t=609&p=5672#p5672

http://www.davidfarmerstuff.com/
 
throwing parts at a problem is wasted money, if you don,t ..know whats wrong,
I had two long time friends stop by and ask my opinion as to why franks 1967 chevelle just was not running as well as they thought it should be, now these guys are long time hot rodders, but engine builders and tunners they are NOT!
both these guys have cars that are more SHOW than GO!
I just wish I could get a car to LOOK as good as these guys can!
but tuneing and trouble shooting sure escapes thier expertise.
anyway I ask whats wrong, and they can,t tell me other than to say the cars missing and not running correctly, they are basically clueless as to the cause and have swapped carbs, distributors,(three times)set the timing,(more times than they can remember)ETC. and can,t seem to nail down the problem.
they ask me to take a look..........now the cars got a crate 502 bbc, replacing the 325hp 396bbc that came in the car, and its got headers and a crower solid lifter cam, 850cfm holley and a rpm air gap intake, and what they assure me is a stock 1967 distributor.(dual points cast iron, mechanical tach drive, LOOKS to be a 67-68 corvette dissy to me)
heifire.jpg

first thing I find is that the nicely labled plug wires are arcing to the headers in two places, and the ohms meter reads over three thousand ohms on two so they need replacing, and that the plug gaps vary from .045-.070 :confused:
while Im checking that I do a compression check and Im not all that impressed with the numbers but they are semi reasonable so I let that slide for now, I do a valve lash check and they are in need of adjustment.(BADLY) seems they have not set the lash since the solid lifter cams install over 18 months ago :smirk:......... the valves set, I check the timing and its jumping all over, seems they forgot to seat the rotor correctly, and the brass tabs bent sevearly and the screws holding it are loose ., pulling the distributor and checking the slack, I find I need to add a new distributor gear, its worn,(looking at the cam gear it seems far less worn) AND shims as its got almost 3/32" vertical play. while I do that I talk them into getting a pointless electronic conversion kit.
75191181.jpg
I install that and the new wires/plugs all gapped at a CONSISTANT .045.
next I check the carb,its float levels to high in the rear and too low in the fron,t, that gets adjusted and I test for vacuum leaks......yeah, they had one, gasket gets replaced and intake re-tested, it now passes. next the timming gets set..its now remarkably more consistant :smirk:
anyway, a hours trouble shooting and a few parts replaced resulted in some very happy campers.....especially since they had been screwing with it for two LONG WEEKENDs prior to bringing it by with little success!
the reason I bring this up, is that durring the whole process , they constantly kept insisting it was a flat cam lobe or a jumped timing chain,or a cracked cylinder hear ETC.
NOT ONCE had they dropped back to the basics and set each and EVERY component to its ideal setting and checked that each component was working as designed....no! they were convinced that it needed a new (NAME YOUR FAVORITE PART HERE, THEY WERE SURE IT WAS ON THE LIST)
GUYS I see this stuff frequently,if you cars not running correctly find out WHY, don,t just start installing parts randomly and expect things to get better!
 
You must log in or register to reply here.
Back
Top