Tacoma electrical mystery


#1

Over the winter I replaced my starter and solenoid on my 1996 Toyota Tacoma. Everything worked fine until about a month ago when it would not start on cool, wet mornings. I have an after market security system – I tried re-arming and dis-arming the system several times and then the truck started – some mornings I would have to do this two or three times; other mornings half a dozen times. A buddy and I traced all the wiring for the security system and tested the “brain,” and all seemed well. We also made sure the solenoid hot wire was connecting properly by adjusting the male spade connector in the solenoid. Next morning, same problem. This time I bypassed the clutch switch and the truck started immediately. Next morning, back to the same problem. This time I jiggled the solenoid hot wire and the truck started immediately. Next morning, same problem. This time I resorted to the arming/disarming cycle and finally the truck started again. All battery connections and cables are functioning properly. The ignition switch certainly seems fine. We’re stumped!


#2

I am not sure you have eliminated the ignition switch.

One other thing. When it does not start, do you mean the starter is not energized or do you mean the starter is turning the engine over, but it is not starting?

I have to add something you likely already know, those after market security systems are known for problems.


#3

Thanks for your reply, Joseph. When I turn the key in the morning I hear a faint humming sound. At first I thought it might be coming from the solenoid, but now I suspect it is coming from the fuel pump in the gas tank; I’m not sure. In any case, the starter is certainly not turning the motor over. The cool wet conditions and the truck sitting all night seem crucial. Even if I drive only two miles in the morning, turn the truck off for an hour or two, it nevertheless starts afterwards just fine.

Unfortunately I no longer live in the city where I had the security system installed, so cannot return to the stereo store that did the work. I was shocked to see how many wires they spliced into and regretted getting it installed on those grounds alone. We removed the brain and the truck started just fine, which would seem to indicate that all their splices were good.


#4

It sounds like you have a test light probe at least to check for power. Check to see if power is getting to the small starter solenoid lead while the trouble is happening. If power isn’t getting there then you need to check the areas you mentioned using the tester and see what is causing the break in the circuit. If power is getting to the solenoid and it doesn’t work then the solenoid is intermittent.


#5

You’re right; ultimately I am going to have to do all this testing when the problem occurs, not after driving to the shop when it cannot be duplicated. But I just thought of something: if the faint humming sound I am hearing is indeed the fuel pump, wouldn’t that indicate a good ignition switch? At least we could eliminate that factor on the spot.


#6

Your logical thinking is correct and I suspect you are hearing the fuel pump. Some ignition switches have more than one power connection that is made when the key is turned. I don’t know for sure how yours is designed. Just something to be aware of. I also doubt your trouble is due to the ignition switch but proper testing will tell you if that is true or not.


#7

It shouldnt be too much trouble to fiqure out which wires were opened up to provide starter interupt. Just hook these back together (you can use solderless connectors if you have a good quality crimp tool,the wires will be of a heavier gague and one side will go hot when you turn the key to hot. With this done you have eliminated the alarm as a possible source of the concern.


#8

Hey oldschool, thanks a lot for a great tip and to everyone else who offered assistance. Electrical work is my weakest suit (among many) and I need all the help I can get!