engine cranks but does not light off
Thread Starter
Heel & Toe
Joined: Aug 2002
Posts: 23
Likes: 0
From: layton ut
engine cranks but does not light off
1990 L-98 automatic 143,987...the car was ran for about an hour and then left to sit for about 15 min. tried to start but would not light off...no codes or check engine...tried three different keys...left till next morning then starts right up...this is the second time this month...the pick-up coil and ign. control module have been replaced two years ago...possible fuel pump??...any ideas i can try before i hand it over to the dealer would be helpful...thanks bjc
Team Owner
Joined: Dec 2000
Posts: 90,675
Likes: 304
From: SE NY
Cruise-In II Veteran
Hold the trigger while cranking the engine and you will see flashes if there is spark to the plugs. The dist. must apply fire to the plugs even while cranking and this will be observed as flashes of the light, albiet rather low frequency flashes.
I also use the light to tace engine misses at idle.
I also use the light to tace engine misses at idle.
Race Director
Joined: Dec 2000
Posts: 17,551
Likes: 26
From: El Paso Texas
They only really need 4 things to run.....
1. The correct amount of fuel and air (pump, regulator, injectors, ECM).
2. Suitable compression.
3. A good spark (coil, cap and rotor, wires, plugs, module).
4. Correct valve and ignition timing (timing chain, distributor).
Something is amiss with one of the 4. Start troubleshooting. Now the fact that it runs sometimes means we can rule out #2 and probably #4. That leaves the fuel system and ignition/emissions systems.
65 Z01 is off to a perfect start. When you get the no-start condition, determine how much fuel pressure you have, and if the plugs are getting fire. Determine if the injectors are firing. Determine if the timing is correct. When was the last major tune up? Plugs, wires, cap, rotor. Ensure that all grounds are solid and not corroded.
Now, you say no codes. Are you getting the 12 code, indicating operation of the ECM? Does the check engine bulb light up when you turn key on (bulb not burned out)?
The fact that the problem is intermittent and that it starts cold and not hot leads me to believe it is either ignition or emissions control related, not fuel related.....but check your fuel pressure during a no-start episode, post how much you have, and we'll go from there.
1. The correct amount of fuel and air (pump, regulator, injectors, ECM).
2. Suitable compression.
3. A good spark (coil, cap and rotor, wires, plugs, module).
4. Correct valve and ignition timing (timing chain, distributor).
Something is amiss with one of the 4. Start troubleshooting. Now the fact that it runs sometimes means we can rule out #2 and probably #4. That leaves the fuel system and ignition/emissions systems.
65 Z01 is off to a perfect start. When you get the no-start condition, determine how much fuel pressure you have, and if the plugs are getting fire. Determine if the injectors are firing. Determine if the timing is correct. When was the last major tune up? Plugs, wires, cap, rotor. Ensure that all grounds are solid and not corroded.
Now, you say no codes. Are you getting the 12 code, indicating operation of the ECM? Does the check engine bulb light up when you turn key on (bulb not burned out)?
The fact that the problem is intermittent and that it starts cold and not hot leads me to believe it is either ignition or emissions control related, not fuel related.....but check your fuel pressure during a no-start episode, post how much you have, and we'll go from there.
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Team Owner
Joined: Mar 2001
Posts: 54,124
Likes: 30
From: Cincinnati, Oh USA
If you have spark and at the right time, and you have fuel pressure, then turn the ignition off and watch how long it takes to lose fuel pressure. It should be very very slow and if not, then you have leaky injectors causing too rich a mixture to start. If spark and fuel pressure are ok, then buy a noid light at the auto parts store, or use a low power 12v lamp and unplug an injector and put the lamp across the injector plug. The lamp should pulse while cranking the engine showing that the ECM is exercising the injectors.
Le Mans Master
Joined: Feb 2000
Posts: 9,715
Likes: 27
From: Kempner Texas
Originally Posted by bjcenter
1990 L-98 automatic 143,987...the car was ran for about an hour and then left to sit for about 15 min. tried to start but would not light off...no codes or check engine...tried three different keys...left till next morning then starts right up...this is the second time this month...the pick-up coil and ign. control module have been replaced two years ago...possible fuel pump??...any ideas i can try before i hand it over to the dealer would be helpful...thanks bjc
Another thing to consider is that you have a hot start issue. Engine starts when cold but won't when at operating temperature.
I'd first suspect the distributor module. You can have it checked for free at AutoZone or another of the larger auto parts stores.
Hope this helps.
Jake
Thread Starter
Heel & Toe
Joined: Aug 2002
Posts: 23
Likes: 0
From: layton ut
i thought if it was a vats issue it would not even turn over i tried all three of my keys at the time and it did not light off...the next morning it started fine...i drove it again and let it sit 15 minutes and it works fine...gonna carry a toolbox with me now but i feel i cant trust the car this intermittent stuff is frustrating
Team Owner
Joined: Mar 2001
Posts: 54,124
Likes: 30
From: Cincinnati, Oh USA
VATS does both, if it does not measure the correct resistance pellet, then it will not close the start enable relay which will not allow the starter motor to run and it does not give a signal to the ECM to exercise the injectors. Since you could crank the engine, it isn't VATS!