Quick question on 'no start' condition - Third Generation F-Body Message Boards

87GTAj · 07-01-2009, 04:33 PM

I've been reading up on a problem I've been having for a year or so and believe I've narrowed it down to two possible sources.

Problem: car will sometimes start, sometimes not, but when it does, it takes an insane amount of cranking until I see the oil pressure build according to the gauge. When the car won't start, if I jump the battery with another car, my car starts immediately, like almost before I even turn the key to START, lol. So after reading, I think it could be a lousy battery, or starter switch. All of my connections/voltages are good and the alternator tested good. One member here reported the same problem and said it was his starter switch. Is there a way to test which may be my problem?

Also, does starter switch = ignition switch, or something else, like solenoid switch?

Thanks in advance.

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Rolling Thunder · 07-05-2009, 01:56 AM

Sorry im a tad confused here. Is the problem your having with the cars ability to crank over or does it crank and just not start?

87GTAj · 07-05-2009, 04:01 AM

The car starts when it wants to - sometimes it starts right away with no problems; other times I have to continue to crank it until the oil pressure builds and then it starts. It cranks, no problem, but actually starting is where the issue lies.

Rolling Thunder · 07-05-2009, 12:05 PM

I would start by checking for good fuel pressure when trying to start and it wont. Ide also check out to see if you have a healthy spark when it wont start. I figure youll probably have a problem with one of the two.

87GTAj · 07-05-2009, 12:50 PM

I don't think it's either of those, only because like I said, when it won't start, if I jump it, it starts immediately. So that tells me it must be electrical related, since the added boost of the second car does the trick. Also, fuel pressure and spark have been tested as good recently, and oil pressure is what seems to be the indicating factor in start vs. no start. When the car starts right away, the oil pressure is there, when it doesn't, the oil pressure sits at 0 and then after much cranking, it hits ~30 and then the car starts.

Rolling Thunder · 07-05-2009, 01:08 PM

Well thats kinda what im getting at. See theres only 3 things you need to have to have combustion fuel air and spark in the right combination at the right time. However even if one of this isnt quite right it will pop or do something so that kinda indicates to me that your just missing one of the 3 all together. Now what you may not know is that ive heard that if the fuel pump relay goes out or fails for whatever reason the oil pressure switch can activate the fuel pump ect because they are in parrallel. But to really know if this is what is happening youde need to do a fuel pressure test when typing to start the car and it dosnt want to start.

87GTAj · 07-05-2009, 01:32 PM

Okay, well I can check on fuel pressure while attempting to start today, but why would the problem only occur intermittently? Wouldn't a fault in the system be a constant problem? And why does a jump start solve all problems? Just trying to understand the situation here.

UPDATE:
Went out and checked the fuel pressure and spark during the cranking but not starting condition: Fuel pressure is a steady ~43psi during cranking and there is spark at all eight cylinders. After continuous cranking for a little over 20 seconds, the car did start and the fuel pressure remained steady at ~43psi. This is basically what happens. Once the car starts it runs fine. I would think if spark was messed up the car would idle funny and possibly even die once started. That's why I believe it must be related to something electrical.

Rolling Thunder · 07-05-2009, 01:56 PM

Well why its intermittin and why does it only do it sometimes and why does a jump fix it are question that really can only be answed once we have an idea as to what the problem is then we can hypotisize the rhyme and reason to it. Have you ever had your battery load tested?

87GTAj · 07-05-2009, 02:09 PM

No, I've never had it load tested that I can recall - unless that's a standard test done at the auto parts store. The battery has tested good at the parts store, but I really feel like it may be the problem.

87GTAj · 07-09-2009, 11:55 AM

Anyone have any thoughts? Battery problem? Something else?

Billy_Bob · 07-09-2009, 12:43 PM

Check voltages...

With intermittent problems, you need to be able to "see" what is happening when the problem occurs.

What can happen is there can be a loose connection. You can have a very good battery, but the loose connections makes the electricity downstream from that bad connect like you have a bad battery!

And electronic gizmos like the computer which controls the engine will not function under around 9 volts.

So you could have a good battery, bad connection, battery drops to 10 volts when starting, but beyond the bad connection, voltage it drops to 7 or 8 volts and the engine computer will not work - it will not start. Then you jump the battery and then maybe up the starting voltage to 11 volts when starting (just guessing), and also up the downstream from bad connection up a few volts to maybe 9 volts, then the electronics work and the engine starts.

So with that said, we need to monitor what is going on as this problem occurs.

Let's use some test leads, wire, an open window, and a volt meter...

Test leads...

So connect the test leads to the battery and to two wires you run through your open window, then connect these to a volt meter.

Now you can see the voltage of the battery as you start the vehicle. It should be 12 something volts with just the ignition on (not starting). Then drop to around 10 volts when starting.

If it drops below 9 volts when starting, charge the battery with a battery charger and try again. Try jump starting and see what the voltages are.

If you charge the battery and it still drops below 9 volts, replace the battery.

But if the battery is good and is measuring 10 volts when starting, move the test wires down the line. Maybe tap into the cigarette lighter. See what the voltage is reading inside the vehicle.

If there is a big difference inside the vehicle from what the battery is reading, then there is a bad connection somewhere.

Test various spots in the + positive wires between the cigarette lighter and the battery. And test various negative locations. (Move the test leads around.)

Don't forget the main ground wire to the engine block.

Check on one side of a connector, then check on the other side.

More on this and other testing methods...
http://www.engine-light-help.com/voltage-drop.html

87GTAj · 07-09-2009, 05:16 PM

Ok, that sounds like a plan, and that would explain why the car starts when jumped, and the battery tested good today (held 10.25V under load and returned to 12.5V). Since the one thing that may be related is the oil pressure rising - would it be logical to check at that connection as one of the first downstream checks? And then am I right in thinking the oil pressure sensor by the dizzy is the one that feeds into the dash? I thought that is how the system works, from when I changed out that switch last year. Will try it tomorrow hopefully and report back.

87GTAj · 07-14-2009, 02:10 AM

Sorry for the late response, stuff was hectic. I checked the voltage at the battery directly during cranking while it doesn't start, and it drops from 12.38 to 9.5. It then returns gradually to 12.38. Checking voltage inside the car, it also dropped to 9.5 and then returned to 12.38. Is there any place in particular (i.e. at the starter, or oil pressure sensor, etc.) that I should look at the voltage of?

87GTAj · 08-02-2009, 11:36 AM

So since the interior read what the battery read, is it safe to assume the bad connection lies somewhere around the starter, oil pressure sensor, etc.? If so, where would you suggest looking given the symptoms I see?