Blazer starting / electrical problems???!!!?
 

’99 GMC Jimmy (Chevy Blazer)

I’ve got two problems with my truck, and I don’t know if they’re related, or how to solve them… anybody out there give me a hand?

1) Sometimes when going to start the vehicle, the starter will turn, and the engine will turn over, but it won’t start. It’s almost like it’s out of gas, but it isn’t. Sometimes when releasing the key, the engine will act as if it’s going to run, but it immediately dies… other times, the engine will act as if it’s going to die, and run. But when it has this problem, it will just crank and not start.

This is not electrical… it will happen with a fully charged battery (well, until it dies…) and when hooked up to a charger.

2) Frequently, when the vehicle is parked overnight or longer, I’ll return and the battery will be dead or have little charge. Certainly not enough to start the engine. Also, the voltmeter runs about 12.5-13v when running.

The battery is new (April), starter is new (March), and the alternator has bench-tested good. Advance has run their test on it, and their computer might come up with a “starter low cranking amps” fault, or no fault at all…

Any hints or advice? Thanks!!!

Not sure about number 1, but my 99 jimmy has gone thru a couple of alternators and batteries in only a few years. I found that if I stopped using the alarm, my draining of the battery stopped. I still lock it but dont use the alarm and I have been on the same battery for about four years with no problems even after long vacations.
I am not sure but shouldn't your voltage be closer to 14 with it running. Maybe have the alternator checked again somewhere else??
Good luck.

Both your problems may be related at the ignition switch. There is a known issue regarding the ignition switch and fuel problems. One function of the switch is to trigger the Powertrain Control Module, which in turn sends 12 volts to Fuel Pump Relay for roughly 2 seconds upon start up and ignition off. In the case of start-up, the relay will run the pump for those 2 seconds to bring the fuel pressure up to about 66 p.si. to start the engine. At that point, pulses from the crankshaft sensor will keep the pump running.
For now, you need to find the Fuel Pump Relay. If you have a 4-door, it will be in a "fusebox" under the hood - I believe on the passenger side. If you have a 2-door, there are 3 relays behind a plastic cover in the glove box. With the 2-door, the Fuel Pump Relay is on the left. A simple check can be done by placing your finger on it and turning the ignition on - you should feel the relay energize and hear a click. If it doesn't, the fuel pump will not turn on and the engine won't start.
Failure of the relay to activate is not proof that the relay is bad, but a quick check is to - strange as it sounds - make sure your horn blows! If it does, then your horn relay is good; it is the one in the middle on the 2-door. Switch it with the Fuel Pump Relay - they're the same. If you get consistent relay activation, that suggests you need to replace the original Fuel Pump Relay.
Having said all that, my suspicion is still on the switch, especially in light of your comment that when you turn the ignition switch to off, it seems like the engine will run. This suggest that the part of the switch that activates the PCM is out of alignment and is sending the control voltage at the wrong part of the switch's travel. Additionally, any other problems with the switch may be keeping some portion of the electrical system energized that shouldn't be when the engine is off.
Replacing the switch is moderately difficult, but well within the range of anyone who is handy with tools and has a Chilton's or other service manual.
I should also mention that one reason why folks have trouble with their ignition switches is the common habit of using an ignition key ring with a lot of other keys and paraphernalia loaded on it. The additional weight of all that metal swinging around with the motion of the vehicle over a long period of time will accelerate the "aging process" of the switch.

I agree. Very well put, Jeff.

That is exactly what I was thinking, very nicely put.

Thank you both for the kudos, but I think I should have been a bit clearer when I said " . . . you should feel the relay energize. . ." That could be interpreted as getting shocked!
Ooops . . .

Lol, well nothing wakes you up like a nice shock.... :D

Wow... is this really that common of a problem on these trucks? Makes you think...

But should this likely account for all of the problems I am having (battery drain, no/hard start, low voltage)? Because if it did, that would be *awesome*...

-One problem at a time, please...

Yes, I think it could quite possibly cause all of that.

Read through all the info in these two posts:
98+ No-Start - Engine Cranks OK
96+ Fuel System Diagnosis

Your first issue could be electrical or fuel related. Your second one sounds like a battery drain problem.