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Tahoe with 6A6 option cranks but won't start

autoguts

By autoguts
in Ask A GM Technician

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autoguts Enthusiast

autoguts

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I have a 1999 police tahoe with the dual battery setup. As far as i can tell the second battery is only a backup battery, not an aux battery. the reason i think this is that there is no switch to choose one batt or the other. also the positive of one battery is wired directly to the other battery positive terminal. Anyway my problem is this... I removed the secondary battery to use in another car i was working on, and now, after reinstalling the battery (fully charged), my tahoe won't start. it just cranks and cranks t won't fire. I installed new plugs and thioroughly cleaned all the battery terminals. anyone have any advice? Its very strange. it ran perfectly fine until i removed and the reinstalled the secondary battery. the truck has the 6A6 battery option.

Jsdirt Senior Enthusiast

Jsdirt

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Could be anything on these electronic wonders these days ... but I'd check all fuses first - under hood and inside the cab.

Doug_Scott Senior Enthusiast

Doug_Scott

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Where did the ground cable go from the aux battery? You may want to take a look at that device for bad connections.

Did the truck run with just the one battery in it? In other words, if you disconnect the aux battery now, does the truck start and run?

autoguts Enthusiast

autoguts

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I checked all the fuses and they are good. i did start it once with only the one battery in it and it ran fine. but now it won't start either way.

Doug_Scott Senior Enthusiast

Doug_Scott

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Posted

I checked all the fuses and they are good. i did start it once with only the one battery in it and it ran fine. but now it won't start either way.

 

You didn't say where the negative cable from the battery went. Have you checked if there is fuel being pumped? You can check at schrader valve for fuel. You should also be able to hear the pump in the tank run after you turn key on, but don't try to start. Pump should run for a few seconds before stopping, something like 5 seconds I think.

autoguts Enthusiast

autoguts

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So today i replaced the crankshaft position sensor. sstill no luck getting it started. its getting plenty of fuel. i pulled out the plugs and they were soaked. i do hear the pump run when i turn the ign to onn. And the neg term from the secondary batt just runs to a grounding bolt. i really thing I'm just gonna have to borrow a scanner from somebody and hope that leads me in the right direction. i can't afford to just throw money blindly at it . i can't belive that basic little CPS unit cost 80 bucks! ALSO the guy at the part store told me that if my VIN # Hhasan R as the eigth numeral (which mine does) than i need the more expensive unit. i opted to go with the cheaper onne. is there really a difference?

Doug_Scott Senior Enthusiast

Doug_Scott

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So today i replaced the crankshaft position sensor. sstill no luck getting it started. its getting plenty of fuel. i pulled out the plugs and they were soaked. i do hear the pump run when i turn the ign to onn. And the neg term from the secondary batt just runs to a grounding bolt. i really thing I'm just gonna have to borrow a scanner from somebody and hope that leads me in the right direction. i can't afford to just throw money blindly at it . i can't belive that basic little CPS unit cost 80 bucks! ALSO the guy at the part store told me that if my VIN # Hhasan R as the eigth numeral (which mine does) than i need the more expensive unit. i opted to go with the cheaper onne. is there really a difference?

 

Are you saying the dual battery option on your truck was just a battery, two cables and a hold down? Every dual battery vehicle I have ever seen used an isolator.

 

You may want to pull all the plugs, crank the engine over to get the fuel out of the cylinders, Watch the spark plug leads don't get between the spark plug hole and the cylinder head while cranking. You can get quite an impressive fire from the fuel being shot ouf of the cylinder. Either clean the plugs, or replace them as well.

autoguts Enthusiast

autoguts

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Are you saying the dual battery option on your truck was just a battery, two cables and a hold down? Every dual battery vehicle I have ever seen used an isolator.

 

You may want to pull all the plugs, crank the engine over to get the fuel out of the cylinders, Watch the spark plug leads don't get between the spark plug hole and the cylinder head while cranking. You can get quite an impressive fire from the fuel being shot ouf of the cylinder. Either clean the plugs, or replace them as well.

I did exactly that. dried out the cylinders and replaced the plugs. still not starting. cranks over, tries to fire (barely) and kicks back like the timing is way out.

Doug_Scott Senior Enthusiast

Doug_Scott

Posted
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I did exactly that. dried out the cylinders and replaced the plugs. still not starting. cranks over, tries to fire (barely) and kicks back like the timing is way out.

First off, I have no idea if your engine has a traditional ignition system. I mean old people traditional. Distributor, coil, cap, rotor, and 8 plug wires from the cap to the plugs. I will treat it like it does have traditional ignition system.

 

If 'kicks back' means while cranking over, the engine almost stops at every cylinder, then goes on to the next cylinder, you need to check a couple of things. Disable the ignition, so there is no spark at all and crank the engine over. If it now cranks normally, then you do have a timing issue. Make sure distributor is not loose. Take cap off and look inside the cap. Look for water, or carbon tracking, cracks, that sort of stuff. Inside the distributor, near the base of the shaft, you should see a couple of wires doing to a part that goes around the shaft. Pull gently on the wires at the part that is going around the shaft. If the wire pulls off(and leaves the terminal connected) then the pickup is broken and needs to be changed. If wires are good, leave the cap off, and rotate the engine until timing marks align on the balancer. Look for a thicker line or someway to set it at either TDC or 0 degrees. At this point the rotor will either be pointing at number 1 cylinder, or number 6 cylinder. If it is not even close, I would suspect timing chain. If it is close, then you have an issue with a part in the ignition system itself. About the only part left if the pickup coil wiring is not broken, is the modual in the distributor.

Keep in mind that I am going on the idea that your truck has a conventional ignition system. If the above does not appear to look like that on your truck, then you will need to instructions for the system you have. My working days ended when my back ended, 20 some years ago. Basic diagnosis has not changed, but specific diagnosis has.

Jsdirt Senior Enthusiast

Jsdirt

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Old people? Careful kid ... :P

Bigg_Ron New Member

Bigg_Ron

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I have a 1999 C2500 that has given me starting problems off and on for months, I replaced the CKP Sensor and got it running, then found a TSB on that subject that a bad CKP sensor can cause additional 50 degrees advance timing. Worked for approx. 2 months, left me dead in the road next time and had to have a tow, same symptoms and same fix, again this Monday no start after setting the weekend, same symptoms that you are having, I found thread on this forum about the cap and rotor on these 454's and how they seem not to last long, I pulled it off yesterday and I didnt think it looked that bad, however I purchased it from AZ and it has a warranty on it so I got a new and it fired right up (must say it was the most difficult cap and rotor I ever replaced)

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