Auto Repair Articles

Auto Repair Articles

The following articles are case study reports on real auto repair problems that have been brought into our shop. All of the solutions are provided by our ASE certified technician.

Diagnostics:

1993 Honda Del Sol 1.6L

Symptom: Won’t start. Cranks Normally. Diagnosis: No spark. No fuel injector pulse. Fuel pressure is ok.

Testing Procedure: Check for Broken timing belt. Timing belt ok and distributor turns when engine is cranked.

Check Engine Light on more that 5 seconds after key is turned on (light should go out after approx 5 seconds after key is turned on) and Snap-On Modis (test equipment) won’t communicate with vehicle computer, 5 volt reference from vehicle computer OK. Battery Voltage at one side of injector connector key on all input powers and grounds at computer Ok. Indication: Bad computer.

Using Snap-On Modis, tested distributor for Crank sensor (inside distributor) signal. OK signal present. Also tested igniter (inside distributor) for operation using Snap-On Modis signal present. Tested Cam Sensor (also inside distributor). No signal from Cam Sensor and no spark Indication. Need to replace Distributor.

Repair: changed vehicle computer and Distributor. Car fixed.

1993 Chevrolet S-10 pick-up 4.3 Vin W throttle Body Injection

Symptom: Won’t start. No start cranks (turns over) normally. Spark from spark plugs is ok. Customer Changed the Ignition Module – no change. No codes in the computer. No fuel injector pulse. Customer changed the ECM (computer) – no change.

After being contacted through our web site and told what had been done in an attempt to correct the problem, I recommended some tests of the Pick-Up assembly in the Distributor. Customer found the following:

The magnet on the distributor shaft was cracked in several places. He changed the Distributor. Vehicle Started And Ran Fine after that.

1993 Plymouth Voyager van 3.3L

Symptom: after the vehicle gets hot after a long drive the engine “dies” and won’t restart for a few minutes

To duplicate the symptom I had to connect the fuel pressure gauge to the engine and close the hood, and run the vehicle at approx 2500 r.p.m. for about 45 minutes. The engine “died” fuel pressure stayed normal 42 p.s.i. I checked for spark. No spark. Checked for noid light. None. Replaced camshaft and crankshaft position sensors. Problem gone.

1991 Oldsmobile Cutlass 3.1L engine automatic Transmission

Symptom: After driving about 20-25 miles, the vehicle would seem to run out of fuel. After sitting for a little while (about 30 minutes) the engine would start and run again.

Diagnostic testing proved to have no stored codes in computer memory. Testing fuel pressure while running pressure reading was 42psi. Ignition system testing while running showed no misfiring cylinders at any time. Recreating the “problem” was difficult in the shop due to the vehicle needing to be driven for so long to have the problem re-occur.

With diagnostic testing equipment connected to the engine to monitor ignition system and snap-on MT 2500 connected to ALDL to monitor sensor activity, we started the engine and closed the hood to keep the heat in, at 2500 R.P.M. After 45 minutes at 2500 R.P.M. the engine “died”. Attempting to start proved to have spark available at the spark plugs, 42 P.S.I fuel pressure, and all sensors were within range, but the car wouldn’t start. The computer was able to produce a “noid” light pulse indicating that the vehicle computer was indeed functioning. The last thing to check were the fuel injectors themselves. This requires the upper plenum be lifted to gain access to the fuel injectors. Disconnected the injector connectors on each of the 6 fuel injectors and checkedto make sure the same “noid light was available on all six. It was.

Next, individual OHM testing of all injectors was done. I found four (4) injectors with ohms of 12.4 which is ok and two (2) injectors with ohms readings of 9.2 and 9.1 respectively. This is the problem! Replaced all six (6) injectors and the vehicle ran fine!