My car tries to crank but then starts having issues and dies. It only does it every once and a while and when I unhook the battery and let it sit for 10 min it starts working fine. It has new spark plugs and fuel filters. My father-in-law said it's the computer controlling the fuel system. If that's true, which computer is it and can I replace it myself or do dealers have to do that?
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1995 Lincoln Continental Question: Car won't start (computer problem?)
Answer #1DaveJHM December 06, 2010, 22:37Master
I'm sorry to say your concern is more complex. You will need to have a diagnosis performed. The engine processor is not typically the cause of failure.
I'm not certain if your concern is a slow cranking issue or a cranking with no start issue. If the former, look at battery and charging system issues. If the latter, look at fuel pressure issues, PCM or fuel pump relay issues.
ReplyVisitor, December 07, 2010, 06:31
It's the no cranking with no start issue. Does cranking mean turning over? Basically turns over, and then that's it. The engine never really runs. Are relays able to be reset?
ReplyDaveJHM, December 07, 2010, 12:04Master
So are you saying that the engine cranks and cranks but never starts?
Relays don't get "reset", if they are failed, they can intermittently work, but intermittently fail causing possible lack of power to the PCM or fuel pump.
ReplyVisitor, December 07, 2010, 12:18
Correct. It will turn over as long as I'm turning the key but once I let off the car immediatly dies. The other problem with having a diagnosis run is that there is no "check engine" light that comes on. This would suggest no power is getting to the computer I assume. I recently opend up the hood and noticed some bare wires that were connected to the computer (or I assume it's the computer). It's silver box about the size of a desktop computers hard drive located on the drivers side on the anterior of the engine compartment (aka close to the driver). So far it seems to only do it when it's really cold outside in the evening. Might this be the effect of dew on the wires?
Another mechanic said this:
"I would first check or replace the computer relay. This is what usually goes bad. "
Thanks for the help so far.
ReplyDaveJHM, December 07, 2010, 21:35Master
The check engine light should be on with the key on and the virtual instrument cluster lit up. Does this happen? This is prior to cranking. You turn the key to the on position and do not crank it.
Look in the long retangular relay box under the hood. You will find 18 fuses, 8 mini-fuses and 4 relays. The bottom right relay is for the PCM (Powertrain Control Module). If this relay is faulty, the processor will not get power and you will not start. You can actually swap that relay for the one beside it - they should be identical. (the one beside it is for the horn...).
The fuel pump relay is part of the "integrated relay control module (IRCM)", which is located above the cooling fan motors. It's a box that contains the relays for the cooling fan and fuel pump and AC clutch. This could be bad too. No easy fix there, rather expensive, and if you are not testing it, it's not worth it to just swap out.
Just so you know, the PCM is located inside the firewall at the middle (slightly towards the passenger side) of the rear of the engine compartment. It does not appear to be the item you are mentioning. It is concealed pretty much entirely in the firewall, except for the connectors that stick out.
I'm not entirely sure what the box you are mentioning is off the top of my head...
Hopefully it will end up being the PCM relay after all. I have had this happen before...so I wouldn't be terribly surprised. Good luck!