QuestionQUESTION: Hi! I recently picked up a 1993 Chrysler 5th Ave. When it starts it runs great, but sometimes it will crank without getting fuel. I have been told that it needs a new computer, but the guy I purchased it from had just put one in just over a year ago for the same reason and it did not fix the problem. The car has only 60,000 miles on it and when I bought it I had the mechanic run a scan and it checked out fine (at the time it was starting). The previous owner swear it was just a battery cable problem..but that doesn't make sense because it cranks just fine so is clearly getting juice to the starter. I know the computer resets when you disconnect the battery cable, would this explain why it would 'fix' the problem? I have also heard that you can't test the computer with a dead battery (I drained it when it finally stopped starting for good. I thought the computer was just an electronic sensor/relay...so if it were really the problem once it burnt out wouldn't it always not work rather than intermittently. I tried to ask the mechanic about this, but he just tells me I need another computer and he can't do anything with it until I get one. It seems to me that something else must be wrong if the car loses 2 PCMs...the second in less than 10000 miles. Any suggestions?
Thanks!
ANSWER: Hi Lisa,
I would suggest that you recharge the battery, then reconnect it, and then try to start it. If it doesn't start then check the computer for a fault code using the ignition key:"on-off-on-off-on and leave in on" doing that in 5 seconds or less elapsed time. Then watch the check engine light, which remains "on", to begin to flash, pause, flash, etc. Count the number of flashes before each pause. Then repeat to be sure you have an accurate count. Combine the numbers in pairs in the order of readout to form the 2-digit fault codes. You should get a 12 (battery disconnected recently) and a 55 (end of readout). But then what other fault codes appeared? Write back or go to www.allpar.com/fix/codes.html for a code translator.
On the "without getting fuel" issue, the pump should be audible when you first turn the key to the "run" position for about 1 second, then it shuts off until you begin to crank it. If you hear it for 1 second, you probably don't have a fuel supply issue. I don't believe you have a computer issue. But there are other reasons that a fault code might reveal.
Have you checked for spark when it won't start? Take a screwdriver with an insulated handle, remove one of the spark plug caps, insert the tip of the screwdriver into the cap so that the tip touches the center wire inside, then holding only the screwdriver insulated handle place the shaft of the screwdriver about 1/4" from the cylinder head and have a helper operate the starter. Watch for a blue spark to jump between the shaft and the cylinder head, or not.
Let me know what you learn, this should be easy to fix. You might also want to check the egr valve for whether it is closed all the way when the engine is shut down. But I need to know which engine is in the car to tell you about that.
Roland
---------- FOLLOW-UP ----------
QUESTION: Hi Roland, The mechanic changed the computer out, car ran, had fault code of 12-53-55 (mech said 53=misfire and could be ignored if running smoothly) Allpar site says 53=internal logic mod. fault - car started/ran smoothly ~15-20 starts. Today turned over but immediately died. Ran fault code again now only reads 12-55. Checked for spark as you described and it had spark...then tried to start and it fired up without a problem...before the computer change the problem started as an intermittent problem before it finally quit entirely...any suggestions what else I should check the next time it fails to start?
Thanks again, Lisa
By the way, about the egr valve, I have a 3.3L V6.
ANSWER: Hi Lisa,
The fact that it did start up quickly after first not so makes it tough to figure out why that would be the case. I would see what happens in the next days and let me know if/when it becomes a consistent pattern, or a permanent no start. The 53 code is relevant but I am not sure why it showed up originally unless he tried to start it before the installation was finished. It means there is some communication failure that is internal to the computer. But now that you don't get it again, as with the "no start" we have to see if it returns.
The egr valve is located by looking at the exhaust manifold on the right side of the engine. You should see a small diameter pipe branch off and upward toward the rear of the engine where the air intake/throttle body is located. Along that pipe is the egr valve, which is then attached to the intake manifold. The valve is mounted horizontally and has a round top which is separated from the body of the valve by a flange. Inside the flange you will see a rod with a circumferential slot. That rod is the valve stem and it moves back and forth which represent the valve opening and closing. You can insert the tip of a scredriver in the slot and move the valve stem back and forth against spring-action in one direction which tries to close the valve. See if it closes easily and firmly. If not then spray some WD-40 on the stem where it enters the valve body and work the stem back and forth with the tip of the screwdriver. If that valve was hanging up slightly ajar, that would cause the engine to not start or idle well because the exhaust gas getting through the valve leans out the fuel/air mixture.
Keep your fingers crossed and lets see what happens.
Roland
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---------- FOLLOW-UP ----------
QUESTION: Hi Roland,
I have some more info that I hope will help pinpoint the problem. First, after the new computer, the problem did not start until I went on a trip ~100 miles. Since I don't drive much and most trips are under 10 miles, this is the only time the temp gauge moved off the bottom end of the scale. Second, the car became progressively harder to start after this...first requires cranking 2-3 times, then cranking with gas, finally would not start at all. Never showed any check engine lights and showed no codes (flashed 12-55). I disconnected the neg. cable from battery and the car started just fine. Started 5-6 times and always ran smoothly that day. After one drive I ran it at low-med rpm for ~5min until temp gauge increased slightly to the mid-lower third of its range...at time the car has a rougher idle than it had when the computer was initially changed. but still started with 1-2 cranks when shut down. Once I let the car sit overnight, however, it again would not start. I again disconnected the neg. term of the battery, reconnected and the car started right up. Incidentally, I noted that when you made the initial connection with the neg. cable to the battery, you can hear a small amt of sparking...I have not seen this with my other cars but it was similar to the arcing you see if you connect the neg term first and then with the ignition off connect the pos term. (something I learned by accident with a previous car). Since the start problem seems to be temporarily fixed with this brief power disconnect, an electrical short seems likely, but I'm not really sure where to start looking. Sorry to be long-winded, but I hope this helps pinpoint a good troubleshooting spot.
Thanks again!
lisa
AnswerHi Lisa,
I would try the battery disconnect trick some time during the day immediately after you have driven it, and you are at home so you won't be stranded if something fails on you. Notice whether or not you get the same arcing sound and see a spark upon reconnection. If you do then presumably that is normal. There a couple of computer memories that run when the car is off, and so if you disconnect the battery and then reconnect that might be what you are hearing when you do after an overnight sit. If you don't then we have something that is different and to consider. To pinpoint it we would need to remove fuses one at a time to find which circuit, when defused kills the arc. But you have to first establish that it is reproducible and that it is different depending upon how long the car sat. There are also some circuits related to the lights that time out after 30 seconds or so that can confuse things.
I wonder if you checked the egr valve yet? And I wonder if you have a thermostat that is opening at too low a temp if the gauge is not moving up until you drive for such a long distance. Lastly, I would suggest that you check the resistance of the coolant temp sensor located near the thermostat housing on the top front of the engine to see if its resistance is at 10,000 to 14,000 ohms when the engine is cold and that it drops down to 700 to 1,000 ohms when the engine is a operating temperature. It has a plug with a lift tab to release and the wire colors are black/light blue and tan/black. If that sensor was not responding well that too would affect the mixture (of which you speak about having to use the pedal to help start, etc.).
Roland
