Engine Mechanical problem
1998 Jaguar XJR V8 Two Wheel Drive Automatic 90,000 miles
My car is rough starting after sitting for 6-8hrs. It will crank, and if lucky, fire on the 2nd or 3rd try (sometimes not at all). Once fired up, it will start right away and run good as new for the rest of the day (until it sits for another 6-8 hrs). This happens even on warm days.
So far, I've replaced the coolant temp sensor, MAF sensor, and spark plugs. I've had the battery and fuel pressure tested - battery is fine, and it is not losing fuel pressure. Compression is also fine. So far two mechanics have not been able to figure it out. Sometimes after work I am left stranded in the parking garage. I should also point out that my engine was recently replaced (with a used engine), and this problem has been there since day#1 with the " new" engine. Please advise (thanks!).
Ok lets get some info here. How old is the fuel filter? Now have you been able to figure out what is missing when this happens, are you missing spark or fuel? One or the other must be missing or it would start fine. Now you said fuel pressure is fine when it is running right I assume? So with that what is the fuel pressure when the problem is persistant? Now what I would like you to do when this happens is cycle the key meaning turn the key on (do not try to start the car) then off and wait 15 secs or so and do it again do this about three times (you should hear the fuel pump come on for about 3 secs or so) then see if starts. If it starts fine then fuel pump is bleeding off when it sets for extended time. Let me know what you come up with and we will go from there.
December, 3, 2008 AT 4:16 PM
Thanks for the reply. The fuel filter is less than a year old. When it was in the shop, there were unable to check for fuel and fire because unfortunately it kept starting for them. (Then I got it home and it wouldn't start for 3 days). They did, however, check fuel pressure in the morning when starting, and it was normal. They didn't seem to think it was losing abnormal amount of fuel pressure when sitting overnight, but who knows.
I've tried " priming" before, but not in the way that you described. I'll try it like that tomorrow morning and let you know how it goes.
December, 3, 2008 AT 9:51 PM
OK that will work let me know what you come up with and we will go from there and check a couple of sensors too.
December, 4, 2008 AT 9:14 PM
The priming technique didn't change anything. It's been consistently starting on the 2nd or 3rd try from cold start. This is OK, but I fear I'll be left stranded in the cold again soon. Let me know if you can think of anything,
December, 5, 2008 AT 10:17 AM
Ok you will need a digital multi meter for this test ok. What we need to test is the coolant temp. Sensor to see it is telling the computer false reading making it think it is colder then it really is. SO what you need do is set the multi meter on ohms and read the ohms of the sensor the colder the sensor the more the resistance ok. So what you will do it find it first, it is at the end of the upper hose either on the thermostat housing or intake manifold very close to the thermostat housing. It will be a two wire plug in on it. You need to unplug the sensor and read the ohms across the sensor terminals let me know what the resistance is and what the temp of the engine was at the time of the test ok. So if the engine is fully warmed up what does the gauge say the temp is. The resistance will be anywhere between 1180 to as much as 92500 ok. I know you replaced it but that doesn't mean it can't be bad if this tests out ok then we will move to the air charge temp sensor.
December, 6, 2008 AT 12:57 PM
Before I do that, I'll run this by you. I have an OBDII reader with live data stream. When the engine is cold (i.E, when the problem is), the OBDII gave me a coolant temp reading that seemed spot on (the same temperature that is in my garage). Thus, I reasoned that if the computer is reading a coolant temp that is appropriate at cold start, then I can rule this out. Let me know what you think.
December, 6, 2008 AT 3:49 PM
Well no we can't rule it out but if you can use the live stream to tell you what the ohms are at that temp and give me both the temp and ohms then we can determine if it is bad or not.
December, 7, 2008 AT 10:09 PM
Ok -- I'll need to buy a multi meter this week, and I'll let you know how it goes.
December, 8, 2008 AT 12:26 PM
Ok that will work let me know what you find once you have answers ok. Thanks again talk to you later.
December, 9, 2008 AT 9:13 AM
It has not started in two days - very annoying!
I haven't had time to buy the meter yet (busy week); however, I thought I'd run this idea by you for now: The shop that did my engine swap did not do a cam sensor re-learn procedure. I know that this is supposed to be done with an engine swap. Do you think it's possible that this can explain my cold start problems?