car is cranking and getting gas but wont start need help

slow3gt

New Member
Nov 30, 2005
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nashville tn
my 84 5.0 is have some starting issues we got it started fine last night after i replaced the starter soleniod but today it wont start it will just crank but the car will not fire we did the test where you attach a plug to wire and ground it and it didnt spark at all we replaced the coil that the main wire from the distributor runs to i dont know what is wrong with it any help would be great
 
Cranks Ok but no start for carb’d cars.
Updated 4-Sep-2006
Carb'd cars require an old time approach to troubleshooting.

1.) Remove push on connector from starter solenoid and turn ignition switch on. Place car in neutral or Park. Remove coil wire from distributor & and hold 3/8” away from engine block. Jumper the screw with the red wire to the big bolt on the starter solenoid that has the battery wire connected to it. You should get a nice fat blue spark.
Most of the items are electrical in nature, so a test light, or even better, a voltmeter, is helpful to be sure they have power to them.
No spark, possible failed items in order of their probability:
A.) Coil
B.) Distributor PIP sensor or points & condenser
C.) Bad ignition Box or Duraspark unit
D.) No power to ignition system wiring or ignition box (if used)
E.) Bad ignition switch
F.) Bad fuse links.

AutoZone wiring diagrams

http://www.autozone.com/servlet/UiB..._us/0900823d/80/16/71/3c/0900823d8016713c.jsp for 79-88 model Mustangs

http://www.autozone.com/servlet/UiB..._us/0900823d/80/19/59/5a/0900823d8019595a.jsp for 89-93 model Mustangs

http://www.autozone.com/servlet/UiB..._us/0900823d/80/1d/db/3c/0900823d801ddb3c.jsp for 94-98 model Mustangs

2.) Spark at coil wire, pull #1 plug wire off at the spark plug and check to see spark. No spark, possible failed items in order of their probability:
A.) Moisture inside distributor – remove cap, dry off & spray with WD40
B.) Distributor cap
C.) Rotor
D.) Spark Plug wires
E.) Coil weak or intermittent - you should see 3/8" fat blue spark with a good coil

3.) Spark at spark plug, but no start.
4.) Pull the air cleaner and sniff for fuel vapor - look for signs of flooding. If so, then press the accelerator to the floor and crank for a while – if the engine is flooded, this will clear it out. You may want to have a jumper battery & cables handy.
5.) Electric fuel pump if you have one, is it getting power? Use a volt meter or test light to probe the wires at the pump.

Don't see any evidence of flooding? Then pump the throttle - does the accelerator pump squirt fuel? If so then you should have enough fuel to start the engine. If not look for fuel delivery problems. Check the fuel pump, and fuel filter. Remember that most carbs have a fuel inlet filter that protects the float needle valve from trash.

Next, get a can of starting fluid (ether) from your local auto parts store: costs a $1.30 or so. Then pull the air cleaner, open the throttle, and spray the ether in it. Reinstall the air cleaner and try to start the car. Do not try to start the car without reinstalling the air cleaner. If it backfires, the chance for a serious fire is increased. If the engine starts now, you have a fuel delivery problem.

A warning about backfires: Holley carbs may have damaged power valves as the result of a backfire. The engine may be hard to start. Other symptoms are that it may seem to load up on fuel and be slow to accelerate until it clears out a bit.

6.) Fuel & ignition OK:
Firing order off: HO & 351 use a different firing order from the non HO engines.
HO & 351W 1-3-7-2-6-5-4-8
Non HO 1-5-4-2-6-3-7-8
Check to verify that it is indeed an HO engine. Remove the #1 & #3 spark plugs. Put your finger in #1 spark plug hole. Crank the engine over until you feel compression on #1 cylinder. Slowly turn the engine until the TDC mark and the timing pointer line up. Mark TDC on the balancer with chalk or paint. Put your finger in #3 spark plug hole and crank the engine 90 degrees. You should feel pressure trying to blow past your finger. If you do not feel pressure, repeat the process again. If you feel pressure, it is a HO engine.

No pressure the second time, remove spark plug #5. Put your finger in #1 spark plug hole. Crank the engine over until you feel compression on #1 cylinder. Put your finger in #5 spark plug hole and crank the engine 90 degrees. If you feel pressure now, the engine is not a HO model, no matter what it says on the engine.

Using a small carpenter or machinist square to mark the harmonic balancer off into 90 degree sections may be helpful here.

A 15/16 deep socket & breaker bar or ratchet may be used to turn the engine.
 
jrichker said:
Cranks Ok but no start for carb’d cars.

A warning about backfires: Holley carbs may have damaged power valves as the result of a backfire. The engine may be hard to start. Other symptoms are that it may seem to load up on fuel and be slow to accelerate until it clears out a bit.

OMG, I hate those things. My dads jeep eat a half dozen of those things for some odd reason. It eat 3 or 4 just trying to diagnose a intake leak. Them things suck. Could you explain to me what exactly they do? I've never understood their purpose? Does it kick in and give you extra fuel on hard acceration or something, and close at cruising?
 
slow3gt said:
thanks for the info that will help out it was the module it is running now but it has a miss the module is off a multiport injection 5.0 would that have anything to do w/it
My mechanical skillz are about at the sophmore level so I really dont know. But my guess is yes because I "think" there is a difference because of the elctronics. Also, did you use the new electrical "grease" on it? Check that as well.
 
90_Red_LX said:
OMG, I hate those things. My dads jeep eat a half dozen of those things for some odd reason. It eat 3 or 4 just trying to diagnose a intake leak. Them things suck. Could you explain to me what exactly they do? I've never understood their purpose? Does it kick in and give you extra fuel on hard acceration or something, and close at cruising?
Im pretty sure its loss of vacuum (like at WOT) its got a little diaghram and it lets tons more fuel go by when theres no vacuum...Im more of an efi guy myself...Someone please correct me if im wrong
 
Black1987Stang said:
Im pretty sure its loss of vacuum (like at WOT) its got a little diaghram and it lets tons more fuel go by when theres no vacuum...Im more of an efi guy myself...Someone please correct me if im wrong
That's the basic principal. The power valve opens up at a specified manifold pressure to allow more fuel to be atomized by the main fuel circuit. Power valves have a number on them that reflects the vacuum at which they open. The typical power valve has a diaphragm that has vacuum on one side and a needle or check ball valve on the other. The vacuum acting on the diaphragm opens the needle or ball check valve and allows more fuel to flow into the main metering circuit.

The failure mode for power valves is when the engine backfires through the intake. That ruptures the power valve diaphragm and allows fuel to be sucked back into the intake. Some of the newer carbs have a check valve that protects the power valve diaphragm from backfire damage.
 
But it opens at a greater pressure right? A motor always gains vacuum when you mash the throttle because it sucks more because the cylinders are firing faster right? Sorry if thats hard to understand but I get the principle anyway lol. Thanks.
 
90_Red_LX said:
But it opens at a greater pressure right? A motor always gains vacuum when you mash the throttle because it sucks more because the cylinders are firing faster right? Sorry if thats hard to understand but I get the principle anyway lol. Thanks.

Yes but with the throttleblade/blades at wide open there is no pressure drop from the intake manifold to the outside air...simple words, theres no vacuum at Wot, since the throttle blade is open all the way and theres no restriction like there is at idle with the throttle plate closed which makes vacuum.
 
Engine vacuum decreases as the throttle opens.

I probably should have explained it better: the vacuum holds the power vavle closed until it drops past a certain point. Then the spring on the power valve causes it to open the ball check or needle valve and add more fuel. The numbers on the powe valve tell you what the vacuum has to be before the power valve starts to open.