1991 W/L98 ENGINE. SOMETIMES AFTER I SHUT OFF THE ENGINE I GO TO RESTART THE ENGINE WILL TURN OVER BUT NOT START. WHEN I TURN THE KEY ON THE ENGINE SERVICE LIGHT WILL NOT COME ON. I HAVE HAD A LOCAL MECH. CHECK THIS OUT .HE HOOKED UP HIS DIONASTIC MACHINE AND FOUND NO CODES.
I HAVE REPLACED DIST. MODULE,PLUGS,WIRES.AND MODULE FROM DIST TO WIREING HARNESS. HE TOOK THE ECM OUT AND DID A VISUAL INSPECTION. NOW THE CAR IS DEAD AND I DO NOT WHERE TO GO FROM HERE. ANY HELP WILL BE APRECIATED.
Submitted by: Thomas Chowanec Jr
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Even then codes are only read after the basics have been checked. Look at diagnosing a problem as being much like climbing a ladder. To climb a ladder you have to have all the rungs in the ladder or it ain?t gonna work; at least not properly. The same is true of testing which always has a correct sequence of steps that have to be followed. I?ve been in therapy for years for this. You see I have this compulsion I just can?t break no matter how hard I try --- I always do test step number one first!
It?s a shame more techs don?t do step one first because unless you do it that way every result you get by starting anywhere but on the first step could be wrong. In this case we have to know what is missing and causing the engine not to run. That could be one of the three basics needed by all engine for them to run. Those things are in order of frequency of failure: high voltage spark at the spark plugs, fuel in the cylinders and compression.
Here in the shop we would listen to the engine during cranking to make sure it has compression. If it cranks effortlessly like when the spark plugs are removed we know it has a bad timing chain. If it cranks with a normal sound we run compression on two cylinders that are not side by side. If both have good compression we move forward but if either or both are low we test compression on the remaining cylinders. If all are low we again suspect a bad timing chain. Verify all low compression concerns with a cylinder leakage test.
Once we make sure we have enough compression for the engine to start when cold which will usually be a minimum of 110 and above we move on to the ignition system. For the ignition system we use a simple 12 buck spark tester from the auto parts store. Following the directions that come with the spark tester we check for spark at the spark plugs on two separate cylinders that are not side by side in the distributor cap.
We need to see a minimum of 20,000 volts of clear blue-white spark for the engine to start. If we don?t have the 20K volts then we test the components in the ignition system.
If we do have 20K voltage at the plugs we then test the fuel system to make sure we are getting enough fuel into the engine for it to start. That means using a pressure gauge to make sure fuel pressure meets manufacturer?s specs and a graduated container to make sure there is sufficient volume. All engines must have a minimum of one pint of fuel in 20 seconds while cranking.
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Posted by Administrator on
2/5/2014 3:47:59 PM
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Keep in mind during testing, especially on a car that has had a lot of new parts thrown at it; there is nothing that guarantees that a new part is a good part. The only thing guaranteed on a new part is that it is new and that if it doesn?t work it will be replaced. If there were no new defective parts there would no need for warranties on anything.
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Posted by Administrator on
2/5/2014 3:46:16 PM
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