Vehicle starts and runs ok , for any length of time. Just turn it off and it may not start again for another 36 hours. What might this be?
Please define this. Won’t crank? Cranks but won’t start? Cranks and tries to start but just can’t?
Car details, please. Is the check engine light on? How many miles? What engine?
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2002 Rendevous starts up and runs until switched off after sitting a couple of days, then
it won’t start(run) again, just 5 minutes later. May have to wait a couple more days??
Okay… let’s try Mustangman’s questions again:
Won’t crank? Cranks but won’t start? Cranks and tries to start but just can’t?
Is the CEL lit up?
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Cranks but won’t start until it sits for a couple of days. It starts and runs ok, no alarms, runs smooth
just don’t turn the switch off. Thanks for your interest in trying to help me isolate this problem
Hot engine runs ok, then shut off, then cranks but won’t start could be a heat soak problem. Crank position sensor, fuel pump, fuel pump relay all are likely culprits. The first objective is to determine if it is a spark or fuel problem. Done by a shop w/ either visual spark test at a spark plug or fuel pressure test.
I replaced fuel pump. New pump now runs for a few seconds every time the switch
is turned on. Kept cranking , no start. Removed several spark plugs and the plugs were dry.
The plugs would have been quite damp with fuel if injectors had turned on and been
dispensing fuel while cranking engine. Thanks very much for your reply. I know there is spark as
I was able to get the vehicle to run using starting fluid.
That’s interesting. It’s possible you are getting sparks ok at first, then they stop sparking for some reason. One idea, generally you’ll get sparks with most ignition systems during cranking even if the crank position sensor isn’t working, but the computer will turn the spark off once it detects the crank position sensor isn’t working with the key returned to “on”. So maybe that’s the problem. A shop w/a Buick scan tool can easily test the crank position sensor. A failed crank position sensor often won’t throw a diagnostic code, another reason to hold it as a suspect until proven otherwise. A fuel pressure test might be required for this too. A shop would probably use a device called a “noid light” as part of the diagnosis to determine if the fuel injectors are getting pulse. noid-lights are diy’er priced, inexpensive. You seem to be following a diagnostic path that will eventually result in the solution.
Thanks george for your reply. I did put a scanner on and I am getting a Map error
and crank position sensor error (Po336)So, I will replace those 2 items and then,
get a real mechanic if no success.
The MAP rarely fails, and is quite expensive. Suggest to start with the crank position sensor.
Ok, I am looking for that part right now. I think it is down behind the power steering
pump.
Re: MAP
If the MAP were to fail, the most common reason is the internal rubber diaphragm springs a leak. That’s easy to test with a hand-held vacuum pump. The MAP should hold vacuum to 20 inches. Generally this test can be done with the MAP remaining in place.
Thanks for that info on the map. I/ll deal with that Poo121 later. Meanwhile, I just completed
replacing the Cam Shaft Sensor, fuel pressure switch and a couple of windshield washer electric
pumps that fell apart when I removed the tank(both were rotted)Tomorrow I will go for the
Crank shaft sensor that is located right near the AC compressor.To tell the truth, thru all of this
it seems like I am dealing with a solid state electronic switch that is failing (opening up when it warms up(
shortly after the engine starts) and closes back (temporarily repairing itself) after about 36 hours).
I am not quite sure where this solid state device is located( could be an intergrated Chip in the main or another computer. Just a thought from someone who was once a Computer Systems Technician.
Not sure how it works on a 2002 Buick, but the crank position sensor is often configured as a hall-effect device, which is a type of solid state switch. Crank position sensors failing when hot is a well known failure mode. Sort of unusual it would take 36 hours to revert to normal though.
Hi George ! Sorry I too so long to reply. Just got thru changing the sensor. Had to re-tap crank shaft hole, get a new screw,etc.Put everything back. Now has new cam and crankshaft sensors installed. Vehicle started up right away. I let it run for about 15 minutes. Shut it off, waited 3 minutes. Guess what! NO START. The engine is cranking good. Getting good spark. It’s just that the fuel injectors are just not being turned on !! I’ll be checking the electrical diagram,but, it’s looking like it might be an engine computer problem. Any input of any kind would be greatly appreciated.
Well that is indeed frustrating. I’m guessing it’s a fuel pressure problem. One test that’s pretty easy to do is a noid light test. “noid” I believe refers to “electric solenoid”; i.e. an electric operated valve, which is what a fuel injector is. I’ve never used a noid test light, but it’s an easy way to confirm a fuel injector is being pulsed or not. If you discover the fuel injectors are being pulse, and you have spark, about the only thing remaining that’s a likely cause is a fuel pressure problem. In that case you may still have a problematic fuel pump, or the electrical power supply to the fuel pump is faulty for some reason.
I used to own a VW Rabbit that would quit for no apparent reason, right on the freeway. Let it sit for 20 minutes, it would start right up and away I’d go. Until the next time. In that case the fuel pump relay and the bus-bar wiring inside the relay plate both failed. The fuel pump was ok, but intermittently (due to heat presumably) no electrical power was getting to it.
If fuel pressure isn’t the problem, you’re getting a good healthy spark, but you aren’t seeing the injectors pulsed using a noid light, whatever is causing that remains a mystery at this point. Might be a power supply problem to the fuel injector pulse circuity on the computer, or the computer hardware itself. I suppose it could be related to a faulty MAP sensor, but that seems unlikely to me, esp if the MAP sensor passes a simple vacuum hold test and the electrical connector to it looks solid. I think it’s possible to test a MAP sensor using a DVM and a hand-held vacuum pump. All it does is sense air pressure relative to an absolute vacuum; i.e. in essence a MAP sensor is a barometer or altimeter.
THanks, George for your interest and responses. I will be checking into that “noid light test”. I am currently following the sequence
through the diagrams. I will keep you posted on my findings. Interesting about that VW relay. The first thing I did was to replace the fuel
pump relay. (no help).
Is there a security warning light on when the engine won’t start?
No, no problem with the security system. I just have a lazy vehicle. It wants 2 days off after every startup. Still checking
the electronic circuit diagrams and flow charts. Just keep those good ideas and suggestions coming. Thanks
Please let us know what fixed it when you figue it out, mine does the same thing but will start back up after 30 minutes(in the cold winter weather it started perfect every time)