95 Jimmy Low Batt = No Start - One for the experts

Original owner of a 1995 4x4, 4.3L, 144K miles - Nothing done to engine except replace spark plugs.

This may help someone with the no-start situations.

Recently I had a problem with the battery going dead after sitting a week or so. Then I noticed after sitting a couple days the battery seemed to be low, and although it would still turn the engine over at a good rate the engine wouldn’t start. (I could tell the engine wasn’t turning over quite as fast as it should, but the average person would never be able to tell the difference) The engine would hit a couple licks when I first turned the key, like it was going to start, but it wouldn’t hit enough to start. Further running of the starter did nothing – it wouldn’t even hit a couple more licks. I found by bumping the starter, then turning the key off, then bumping the starter again, and repeating this procedure 4 or 5 times the engine would finally start. Once started it would run and idle fine. I also found that upon charging the battery it would start immediately on first try. I replaced the battery and no more problems.

No doubt, with the 3/4 charged battery, something wasn’t receiving enough current to allow the engine to start. Anyone have any ideas about what was going on – i.e. not enough current to fire the plugs or not enough current to run the fuel pump? What are some of your thoughts?

In case you're wondering if I could hear the fuel pump running, I couldn't - I've never been able to hear the fuel pump run. I know people say the fuel pump should run a few seconds when the key is turned on, but I've never been able to hear it run. Course, my hearing is not what it should be!!


DelC

If you're battery is draining after only a couple of days by that much, you have 1 of 2 issues

Either your battery plates are dying

or

You have something drawing on your electrical system when turned off..


Look at all your aftermarket stuff (stereo system, alarm, etc). Meter the voltage and amperage draw.


If you're not finding anything out of the ordinary on those components, disconnect them completely and check draw at the battery. The start checking everyything else.

If all that checks out, it's probably your battery and a battery tester MAY or MAY NOT tell you it's bad. Even if those things say it's good, with all the process of elimination you just did, it's most likely bad..

It doesn't have any aftermarket equipment, and without doubt the old battery was shot, as it's about 5-years old and it failed on the battery tester. I also checked the output of the alternator which was fine.

My questions is: "Why won't it start with a 3/4 charged battery"? The starter still turns it over fast enough that I feel it should start. Like I said, the average person would never be able to tell it wasn't tuning the engine over as fast as it would with a fully charged battery.

Apparently the starter was drawing all the current away from a component that was needed for the engine to start. It appeared not to be getting fuel, as it didn't smoke when it finally started, like it would if the plugs weren't firing and allowing fuel to build up in the combustion chambers. Does the engine have a means to shut off the fuel if the plugs aren't firing?

I can see where this type scenario could lead someone to replace the fuel pump, poppet valves and everything else before discovering the real problem. It's just weird, and it's something others need to keep in mind when trouble shooting. I don't drive it that often and if it hadn't sit for two weeks to allow the battery to go completely dead, I doubt I would have realized the battery was the problem. By driving it every day the battery would stay about 3/4 charged and would cause hard starting or no starting.


DelC

It doesn't have any aftermarket equipment, and without doubt the old battery was shot, as it's about 5-years old and it failed on the battery tester. I also checked the output of the alternator which was fine.

My questions is: "Why won't it start with a 3/4 charged battery"? The starter still turns it over fast enough that I feel it should start. Like I said, the average person would never be able to tell it wasn't tuning the engine over as fast as it would with a fully charged battery.

Apparently the starter was drawing all the current away from a component that was needed for the engine to start. It appeared not to be getting fuel, as it didn't smoke when it finally started, like it would if the plugs weren't firing and allowing fuel to build up in the combustion chambers. Does the engine have a means to shut off the fuel if the plugs aren't firing?

I can see where this type scenario could lead someone to replace the fuel pump, poppet valves and everything else before discovering the real problem. It's just weird, and it's something others need to keep in mind when trouble shooting. I don't drive it that often and if it hadn't sit for two weeks to allow the battery to go completely dead, I doubt I would have realized the battery was the problem. By driving it every day the battery would stay about 3/4 charged and would cause hard starting or no starting.


DelC
It's actually a fairly common problem. It is caused by the pump not receiving enough power to produce the proper amount of pressure. There has to be 60 psi for the engine to start right up. With a weak battery the pump can't build up enough pressure during the 2 seconds that it runs when the key is turned on. Cycling the key let's the pump run a few extra times allowing it to build the proer pressure. After the engine starts, the alternator supplies enough power and the engine continues to run.

This problem has caused a lot of people many headaches in cold winters. When either the battery or pump are not performing properly, the problem is made worse by cold weather. This is because the battery's capacity is diminished at cold temperatures. Someone may go out in the morning and their car won't start. They have it towed to a shop. The shop let's it sit for a while, during this time the weather warms up. They go out to work on it and it fires right up. They can't find anything wrong. The customer picks it up takes it home and the next morning, it won't start again.... the problem continues until they get smart and come here asking for help and then one of our members tells them what's wrong. :wink:

Ok, Thanks

I thought that was probably what was going on, but I wasn't sure.

I can see where a dishonest or even an honest repair shop could make a lot of money off of it.

How do you know the battery was 3/4 charged? What value did you use to come up with that???? Anything less than 11.5v can be hard to make some vehicles start. Couple that with a bad cell or 2 and it shouldn't ever start. You don't just need voltage to start a vehicle but AMPERAGE. I've had batteries with over 12v at rest but drop down to 9v. when cranking. It's the same difference when looking at engines. People get all worked up on horsepower but it's torque that gets you going. A lower HP engine with higher torque is usually a better way to go. Don't think so? Just look at diesels.

Well, it was more half charged and less than a full charge, and it turned the engine over at a good clip. So, maybe it was 66 2/3 or 80 percent – it doesn’t really matter. The fact is; it was low enough not to start the vehicle, but high enough to turn the engine over fast enough that your wife wouldn’t have noticed the difference in the cranking speed.

I have a load type battery tester and the battery tested about ¾ of what a new and fully charged battery should test at under load. So, go figure.

If diesel engines are such good performers, why don’t they run them at NASCAR??

i need a wiring harness map. i have a 1991 olds bravada with serious fuel pump probs. its not getting fire to the pump and i need to see a diagram of the wiring system to check my wires.

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