Carburetor Troubleshooting Guide.
Contents
1. engine is running Note 1 often removing the carb from the manifold amp shaking it hard a couple of times will effect a cure 1 Dirt stuck on tip of the needle amp seat 2 Idle speed is set too fast Note 2 if procedure in note 1 doesn t cure it the problems is almost always dirt or bad gas getting into the carb Carb will then need to be 3 Idle solenoid is not disassembled to fix it functioning 4 Fuel pump pressure too high 5 Fuel pressure is fluctuating or pulsing common on Colts Mitsubishi amp other Chrysler imports Carburetor Troubleshooting Guide Problem CONDITION POSSIBLE CAUSE CORRECTION 6 This causes the fuel to expand amp be forced past the needle amp seat Also fuel can boil in the carb if there are improper or missing gaskets or spacers between the carb amp manifold A heat riser stuck in the closed position will also cause boiling and flooding 1 Clean the tip off carefully or replace the needle amp seat and clean the entire fuel system out Check for defect cannister causing debris or fuel contamination 2 Reduce the idle speed to factory specs If it will not idle slowly the mixture is set too lean or the idle solenoid is not functioning right or there is a vacuum leak somewhere usually not in the carb 3 Check for power ground up to the solenoid Look for dirt stuck in the solenoid or blocking the passageways 4 Check pressure Use a regulator to2. control the pressure or put on a new pump don t use high pressure type 5 Control pulsing with a regulator 6 Float is heavy crushed 6 Replace float Is often caused by spit back or sunk up through carb 7 Gas is very gummy old or has too much alcohol or other chemicals 7 Clean bad gas out of carb Clean out of in it 8 Choke not working 9 Needle not seated properly during initial fill 10 On Mikuni carb the overturn ball fell out of place fuel system Use only good quality gas 8 Check cause of choke failure choke pull off failure or loss of heat to the choke 9 Try tapping the fuel inlet or needle amp seat area with the handle of a screwdriver If this doesn t work unbolt carb from manifold and shake it hard a couple of times 10 This is caused by the carb being overturned or turned on its side Remove top and reinstall the ball 11 On carbs with externally adjustable float 11 Excessive adjustments have caused the levels seal to break Replace the seals Laan Engine stalls when During transmission is put into Acceleration gear 1 Incorrect choke pull off 1 Readjust the pull off or replace if adjustment necessary Carb Trouble Shooting Guide xls Carburetor Troubleshooting Guide Problem CONDITION aj 2 Fast idle RPM incorrect 00 siom 3 Engine running too lean because of vacuum leak 3 Check for vacuum leak Flow test carb to or dirty jet check jetting 3 Chec
3. 0 Diagnose amp fix automatic transmission 11 Wrong or malfunctioning thermostat in cooling system Replace thermostat 12 Blocked or leaking exhaust heat passage in intake manifold 12 Remove manifold amp fix it 13 Defective accessory power steering pump air conditioning compressor etc causing drag on 13 Diagnose amp repair or replace the engine accessory unit 14 Wheels out of alignment 14 Have wheels professionally aligned 15 Reduce speed quick acceleration 5 Poor driving habits screeching around corners etc 16 Float level much too 16 Set to factory recommendations amp check high or float partly sunk float weight replace if necessary 17 Do complete tune up amp physically inspect 17 Ignition problems or the cap rotor wires coil plugs points etc needs a tune up in addition to checking on the scope 1 Charcoal cannister is 2 Replace the defective valve or fix other 2 Vent valve is not cause of it s malfunctioning like loose pede properly connection etc 3 Kinked hoses in venting 3 ater the kinked hoses with correct 4 Stuck or blocked check tees in the vent hoses or elsewhere in the system 4 Replace the check valves 5 Gas tank vent is 5 Fix it or replace the gas cap if vent is in blocked the cap Carb Trouble Shooting Guide xls 6 Gas line located too close to a heat source such as a radiator hose or exhaust manifold Gas pours out when the
4. 3 Caused by installer allowing engine to spit 3 Crushed float back up through carb Replace the float i Venting system problem 4 Check entire venting system amp repair 1 Incorrect choke pull off 1 Readjust the pull off or replace if adjustment necessary 2 Fast idle RPM incorrect too slow 2 Speed up the fast idle to factory specs 3 Engine running too lean because of vacuum leak 3 Check for vacuum leak Flow test carb to or dirty jet check jetting 1 Vacuum leak 1 Check for vacuum leak amp repair 2 Ignition timing retarded 3 Accelerator pump 4 Accelerator pump cup irae up from contact with bad gas or chemicals Replace the pump cup 5 Economizer jet too 5 Clean out economizer jet amp check the small or partially blocked size 6 Choke pull off open too far 6 Adjust the pull off tighter 7 Secondary throttle plates not closing all the way 7 Check for binding or bent linkage Repair 8 Connect up right Be especially careful of 8 Vacuum hoses hooked a EGR amp Dist connections sometimes the pipe locations are reversed on Rochesters 9 Idle jet partly blocked 9 Clean out the jet amp any other dirt that is in with dirt there Carb Trouble Shooting Guide xls CONDITION POSSIBLE CAUSE CORRECTION 10 Distributor timing not advancing properly worn breaker plate worn shaft pin hole in distributor diaphragm cracked hose 10 Check distributor and all rela
5. POSSIBLE CAUSE Ca ea nape rossi r choke adjustment and for 2 Lube with WD 20 and check for 3 Check fuel delivery Look for plugged filter or clogged lines bad pump stuck 3 No gas in carb needle amp seat and fuel pressure 4 Replace the pump Problem is usually caused by bad gas dirt in gas or vacuum 4 Accelerator pump leak or ignition problems causing engine defective or blown out spitback 5 No spark or engine problems such as bad compression 5 Diagnose amp correct the problem 1 Choke not closing 1 See notes above Adjust choke if properly necessary 2 Use vacuum gauge to check Fix the leak You may have put the base gasket on wrong 2 Big vacuum leak on or it is the wrong one for this carb amp engine engine somewhere combination 3 Adjust to factory specs Carb can get 3 Choke pull off setting bumped in shipping or transportation and incorrect can accidentally change the setting 4 Fast idle RPM set too slow 4 Adjust to recommended RPM 5 Correct oa to carb Usually itis a x Electrical or compression problems on 6 Do complete tune up amp diagnosis Fix the the engine problem 7 Check amp adjust the float level to factory 8 No voltage ground to 8 Check for power amp ground Repair the 1 Choke not set tight enough 1 Set choke a little tighter and retry 2 The setting varies depending upon the exact application One carb may fit several 2 Choke pull off opening applicatio
6. as crimped pipe dirt or other foreign matter in Mileage 1 Plugged exhaust pipe Poor Performance 2 Remove gas cap amp see if performance improves If so clean or replace the gas cap Check the charcoal cannister hoses to it amp any check valves Check the electric vent 2 Clogged gas tank vent valve on the carb if there is one amp make or fuel venting system sure it is getting power at the right time 3 Check timing at idle and also for full advance when revved up Look for bad or loose hose hose hooked up to wrong pipe on distributor bad thermal switch leaking vacuum advance can on the distributor a worn breaker plate worn distributor shaft 3 Ignition timing retarded sticky weights point gap closed up etc Carb Trouble Shooting Guide xls Carburetor Troubleshooting Guide Problem CONDITION POSSIBLE CAUSE CORRECTION 4 Clogged air filter 4 Replace air filter 5 Choke not opening z Fix choke or heat source problem 6 Check the lockout secondaries won t ne unless choke is coming off all the way Check for sticky or bent shaft or linkage If air valve type Rochester check the spring tension the plastic cam amp metering rods for 6 Secondary not opening dragging or sticking 7 Wrong main jets or rods 7 Check and replace as necessary 8 Dragging brakes 8 Fix brake problem 9 Low tire pressure 9 Increase tire pressure to factory specs 10 Automatic Transmission malfunction 1
7. aying closed 2 Slow flooding 2 Fix cause of flooding Carb Trouble Shooting Guide xls Carburetor Troubleshooting Guide Problem CONDITION POSSIBLE CAUSE CORRECTION 3 Ford amp Holley Only Power valve blown out by 3 Replace the power valve Possibly spitback up through carb damaged by a backfire condition 4 No power or heat source to choke 4 Repair as necessary Hesitation under heavy throttle Deadspot amp 1 stumble May backfire or Defective accelerator 1 Look for dirt in pump nozzles swollen cup spitback oh bad gas or check ball missing or stuck 2 Metering rods or power Te sticking or binding 2 Repair as necessary 3 Locate leak and repai iret level setting very 5 Plugged up fuel filter defective fuel pump or sa or kinked lines 5 Inspect and repair as necessary ee alae air valve set 6 Check amp adjust the secondary air valve 7 Set T factory specs Make sure 1 Bad or misadjusted BCDD if equipped 1 Adjust to specs or replace as necessary 2 Check throttle positioner with a vacuum a Replace if defective Replace 2 Bad throttle positioner cracked hoses Check vacuum hose a bad vacuum source to connected to the correct pipe on carburetor or thermal switch Idle speed and mixture 3 Reset to specs See the adjustment nore adjusted instructions 4 Loose or defective float 1 Check exhaust Look for plugged catalytic converter bad muffler baffle kinked or or G
8. e and pressure a for clogged lines filter or pump Check 5 No fuel for kinked or swollen fuel lines 6 Check for clogged air filter especially after 6 No air driving through muddy or dusty area 7 Look for big vacuum leak such as broken hose blown gasket bad power brake 7 Too much air diaphram bad PCV valve Rough Idle z Choke is staying closed z Plagne and fix Choke problem 5 ord amp Holley Only oe the power valve ee 4 Check out entire fuel system venting sae inluding the vent valve on the carb the charcoal canister all hoses amp check valves in the system and any solenoids that 4 Venting system failure trigger the vent system to operate 5 Idle jet plugged up with 5 Clean out the idle jet and any other dirt in 6 idle air bleed plugged 6 Check idle air bleed Clean or replace as Carb Trouble Shooting Guide xls CONDITION POSSIBLE CAUSE CORRECTION 7 Idle cut off solenoid not 7 Check idle solenoid especially for working power ground replace solenoid if necessary 1 Find the vacuum leak amp fix it Also look for wrong base gasket or one that is installed wrong If engine has been spitting back it 1 Big vacuum leak may have blown out the base gasket or a somewhere gasket in the carb 1 Ford amp Holley Only Power valve blown out by 1 Replace the power valve Possibly spitback up through carb damaged by a backfire condition 2 Slow flooding 2 Fix cause of flooding
9. k for vacuum leak acceleration Backfiring or spitback up through carb 1 Vacuum leak 1 Check for vacuum leak amp fix it 2 Ignition timing retarded 3 Accelerator pump 4 Accelerator oump cup ai up from contact with bad gas or chemicals 4 Replace the pump cup 5 Economizer jet too 5 Clean out economizer jet amp check the 6 Choke pull off open T00 Hesitation stalling stumbling flatspot or deadspot during ETEN throttle plates not closing all the way 7 Fix it 8 Connect up right Be especially careful of 8 Vacuum hoses hooked the EGR amp Dist connections sometimes the pipe locations are reversed on Rochesters 9 Idle jet partly blocked 9 Clean out the jet amp any other dirt that is in with dirt there 10 Distributor timing not advancing properly worn breaker plate worn shaft pin hole in diaphram 10 Check distributor and all related systems crack in hose etc carefully Replace defective parts Hesitation deadspot or stalling that only seems to occur after the first 1 Defective electric assist mile of warmup pot on choke 1 Replace it 2 zhao ee ne level aE very PEN Bad ignition condenser jp reeet r Replace it 5 Inspect and clean passages in the intake 5 Plugged heat crossover manifold and heads Test heat riser valve system in manifold E if defective 6 Check and replace as necessary heat 6 Defective source of hot a hae duct temperature sensor vacu
10. ns Set the pull off so the choke is too much a little tighter 1 Choke set too tight 1 Adjust a little 1 8 looser 2 Pull off set too tight 2 Adjust so it is open a little more 3 Slow flooding 3 Fix cause of flooding 4 Float level very high 4 Rare Set to factory specs Carb Trouble Shooting Guide xls CONDITION POSSIBLE CAUSE CORRECTION a r 5 Ford amp Holley Only C E the power valve Possibly Power valve blown damaged by a backfire condition 6 Pull off diaphram 6 Caused by installer allowing engine to spit blown back up through carb Replace the pull off 7 Carter Only Pump 7 Caused by installer allowing engine to spit blown out back up through carb Replace the pump 8 Caused by installer allowing engine to spit 8 Crushed float back up through carb Replace the float 9 Choke spring may be backwards and is getting 9 Remove choke cover cool off choke tight when heating up reverse spring reinstall cover and set instead of loose tension to factory specs 1 Correct the vacuum leak Make sure you haven t forgotten to hook up a hose 1 Big vacuum leak somewhere Base gasket may be wrong one somewhere or on wrong 2 Find amp fix cause for choke staying closed 2 Choke is closed when Look for no heat source spring in me is hot ie or something jammed or bent 3 Do complete tune up 4 No compression 4 Diagnose cause of no compression amp fix 5 Check fuel delivery volum
11. ted systems etc carefully Replace defective parts 1 Defective electric ARI 2 Defective accelerator 3 Float level setting very 1 Inspect and clean passages in intake 1 Plugged heat crossover manifold and heads Test heat riser valve system in manifold replace if defective Check and replace as necessary heat 2 Defective source of hot shroud duct temperature sensor vacuum air up to the carburetor door motor manifold vacuum supply 1 Vacuum leak 1 Inspect hoses Route and lead the hoses somewhere or hose off or correctly Look for leaks caused by the hooked to wrong vacuum wrong base gasket or if it was installed port upside down 2 Inspect and adjust pump stroke pump plunder discharge nozzles and check 2 Accelerator pump valves Inspect the accelerator pump look problems for swollen pump cup 4 Set to factory specs Make sure 5 Dirty idle jet or 6 Idle speed set too fast 6 Richen up the idle mixture reset the idle amp mixture is too lean speed to factory specs then reset the common mixture using the lean drop method 7 Idle cut off solenoid not 7 Check idle cut off solenoid especially for vor power ground replace solenoid if necessary 8 Frozen or binding nie air inlet stuck in full hot or full a LU 8 Inspect and repair as necessary 9 EGR valve stuck on or ae on too early hose Inspect hose routing to EGR valve amp ined 7 wrong valve Replace as necessary Choke st
12. um air up to the carburetor door motor manifold vacuum supply Carb Trouble Shooting Guide xls Problem CONDITION POSSIBLE CAUSE CORRECTION 7 Check all thermal switches especially 7 Defective thermal those connected with the distributor EGR amp switch vacuum motors in the air cleaner housing 1 This will isolate bad rings or valves worn 1 Run a compression cylinder walls defective cylinder head or Compression or Misfiring check gaskets and excessive carbon deposits 2 Check at variable speeds for excessive 2 Check dwell variations distributor shaft wear faulty Carb Trouble Shooting Guide xls
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