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Followup To
Question -
Hi
I have Concorde 1996. Sometimes, while I am driving on the highway (at around 70 mh), I feel that the engine stops for a moment giving a tough jerk. A couple of days ago the engine was completely off while I was driving at around 50 mph. I used to have a problem with starting the car. It used to take me 1 or 2 minutes of trying to start to get the car to start. Last week the car refused to start at all, so I had to leave it at work, but when I came the next morning, it started immediately. That happened twice. I called a mechanic to check it. He saw that the fuel pump relay was carbonated, so he just abrased it a little to enhance its connectivity. Now the car starts from the first or second try, but I am afraid it will turn off while I am driving, especially if I am driving in a crowded street and you know that the brakes don't work at all when the car is off.
Thanks
Answer -
Hi Sam,
You can tell if the fuel pump in the problem by noticing the noise that it makes when you first turn the ignition switch to the run position. It makes a humming sound that lasts for about a second and then it is shut off for safety purposes if you don't try and start the car. So next time it fails, see if that is the case and if not, then the pump or its relay needs to be replaced. Otherwise, if the pump seems to be working, I would investigate whether the engine controller has detected some other cause for the engine not starting or dying while in motion:
Reading out the engine controller memory for fault codes is the first step. Try using the ignition key: turn it "on-off-on-off-on" and leave it "on" (doing this quickly, no longer than 5 seconds). By "on" I mean just the normal position when the engine is running, not the cranking position. The 'check engine'light will remain on when you leave the key in the "on" position with the engine still not running. But then watch the 'check engine' light to begin flashing, then pause, flashing, pause, etc. Count the number of flashes before each pause and keep track of the numbers. Repeat the readout and verify the counts are correct. Then group them in pairs in the order that they came out, thus forming two digit numbers. You may notice that the pause is shorter between the digits of a given number, and longer between the numbers themselves. Then send me a 'follow-up' question telling me the results of your readout. By the way, 55 will be the last number (two groups of 5 flashes each) and that is the code for "end of readout".
I have the troubleshooting manual for the engines and we can look up the possibilities of what is wrong based upon what fault codes you show. There is also an essay on fault codes at the site:
http://www.allpar.com/fix/codes.html
which gives the meaning of the code numbers. But then you need to get specific info for what exactly might be the diagnostic tests or parts to replace to complete the repair. Let me know the codes and I can give you some direction. If there are no fault codes then the problem could be a spark issue.
Bu the way the brakes still work if the engine dies, the power assist will disappear but you can still stop the car if you press on the pedal harder.
Roland
Thanks a lot Ronald
I did as you asked me and got the following digits:
12
34
11
42
Thank you
Sam
AnswerHi Sam,
The codes are instructive. The 12 code indicates that sometime in the past 50-100 key on-off cycles the connection from the battery to the engine controller was interrupted. That may be due to someone disconnecting the battery, but if to your knowledge that has not been done it could be due to poor or loose connection of the battery cable clamps at the battery or a loose connection of the negative battery ground cables: one is at the frame rail nearby to the battery and the other to engine head. Or it could be due to a loose disconnector in the black wire connected to the + clamp (the disconnector is black and torpedo-shaped) or a loose connection of that wire where it meets the power distribution center box. But if you know the battery has been disconnected recently then I would believe that code will self-erase after a few more uses of the ignition key. But a connection problem like I have described could certainly cause the jerk.
The 11 code says that the spark timing sensor has failed momentarily or for any length of time while the engine was being cranked or was running. Usually these sensors will fail for a few minutes or hours and then recover, but if it was very early in its breakdown condition I can imagine it might just do so with a jerk. You could only determine that if it fails for a few minutes during which time if you checked for spark while cranking the engine you would find none. So that is a situation to consider the next time it wont start. If you carry a spare spark plug and can recruit someone to turn the ignition key, you could simply remove one of the spark plug connector caps from the engine and put your spare plug in it, then hold the connector so that the threads of the plug are pressed against the cylinder head and look for a spark to jump across the gap while the helper tries the starter. If you don't get spark then that would implicate the sensor as the cause of the jerk.
The 42 code however throws in a clinker. It says that the autoshutdown relay (locacted in the power distribution center near the battery) has a problem with its circuit. That device provides power to the spark coil and the fuel pump and if it was flakey could also cause the jerk. If it was responsible for a no start situation you could tell that because the fuel pump would not make that humming sound that it normally does for about 1 or 2 seconds when you turn the ignition key from off to the run position. So the next time you have a no start, see whether you can hear that brief humming of the fuel pump. If not, then I would suspect the autoshutdown relay is flakey, which would cause a jerk if it failed momentarily while driving.
The 34 says there is something wrong with the cruise control circuit. It wouldn't cause a jerk or failure to start so that issue can be set aside for now.
That gives you some ideas as to what to do and how to respond the next time you have a no start. You could throw some money at parts replacement: crankshaft spark sensor and/or autoshutdown relay but that often proves frustrating because it might be a faulty wire connection. So I would check the battery issues and be prepared to make some observations when you have a no start situation.
Roland
