Kevinea

I have a 1997 Tacoma that i've had for a couple of years.
It has been running fine and I love it! But it recently started to have problems.
Problem: When my truck is idling; its fine. But as soon as I turn my lights on, the rpm's drops and my truck starts to die. As soon as I turn the lights off, my idle gets back up again.
I have changed the fuel filter and now the alternator. It still has the same problem. does anyone have any suggestions?

Thanks in advance!

FogRunner

Put a voltmeter on the battery and watch the voltage when you turn on the lights and see what happens.

Also there is a fuse in the box that I believe is either a 10 or 7.5A that is marked ALT-S. Check this fuse because is supplies the alternator with a voltage sense lead from the main fuse box to account for voltage drop due to resistance on main power lead from the alternator to the fuse box.

If the ALT-S fuse gets blown then the alternator cannot sense the correct voltage at the fuse box.

If the alternator isn't getting a sense input it will go into a fail safe condition and use the voltage at the output terminal on the alternator itself as a reference. This will result in a lower voltage at the fuse box and when you turn on your headlights it could make it low enough for the EFI system not to function.

Also check the alternator wire connection at the fuse box and make sure its good,clean and tight. Same this with the 120 amp alternator fuse, pull and inspect the terminals. This can also cause voltage drop.

But you really need to get some voltage readings at the battery so we can tell whats going on.

Kevinea

I have never would have known that without your help FogRunner. Thank You. I shall get the voltage readings ASAP. I will put them up as soon as I get them. And I will try what you suggested. Thanks Again!

SEAIRESCUE

Get a new battery...it has a dead cell.

Kevinea

Changing my battery could help also. Its a regular battery and its not made to go off-roading with; but i still do any way. I was thinking of buying a optima red top. I think its that time for me to do that. Thanks SEAIRESCUE!

and i'll try to get the voltage readings up ASAP.

Kiroshu

I would say batterys bad. Does it read right in the gauge in the dash? Setting still engine off should read 12.6v engine cranking should read 10.5v, engine running should be 14.2v. If it reads like 11 or 10 sitting still engine off get a new bat.

Kevinea

I have another problem that I just ran into installing my fuel pump. I installed my fuel pump and it does not run properly. When I turned my key, the pump went on; but only for a little while and then it shut off. My truck does not start due to the lack of fuel. Does anyone have any suggestions on to what I could possibly do or maybe what I should look for?

Thanks!

eddieleephd

Fuel pressure Regulator may be culprit. lack of fuel pressure could cause original issue as well.
is this a toyota fuel pump? or after market?
spark and air flow have some thing to do with the operation of the fuel pump too.

Bad ground as well could be culprit to both issues!

I would start with grounds "engine, chasis, ECM."

FSM run diagnosis
http://www.ncttora.com/fsm/index.html

Kevinea

Thanks eddieleephd!
The fuel pump I isn't the OEM one but it isn't a racing one or anything. Its just a stock fuel pump made by another company.

eddieleephd

did you check your grounds?
yotas are kinda funny as to what may cause an issue!
the pump could be the issue however I would doubt it!

what have you checked so far?

Kevinea

i have checked the grounds so far. And i took an extra good look at the ground from the fuse box.
The weird thing is that I am getting 12.something volts from the batter into the fuse box, but when I go to check the fuses in the dash board, I get something like 11.74 volts.
And when i turn my lights on, the voltage drops to 6. something.
I'm not sure what to do next. I'm confused.

vital22re

iTrader: (2)

why did you replace the fuel pump? Have you had the batter load tested? are your battery terminals and cable connections clean?

atistang

how do you know it is not starting due to lack of fuel?

your pump should only run for 2-5 seconds when you turn your key on, once the engine starts then the pump will run constantly

eddieleephd

ok do you use di-electric grease? this would be my next step is to go in and pull the connections in the fuse block in the hood and dielectric them all positive and negative, Could be a bad connection on the positive side.
Also I am inclined to believe that it may be a bad relay!
The relay may be working but have bad contacts on the side that is contacting to supply power to the accessories! this would give you the drop in voltage.

So dielectric every thing and check the relays for resistance!

what is the charge coming off of the alternator when running? could be bad ground there or bad connection to the block from there.
\
As well as stated before which I assume you have checked is the battery load? what is the running voltage at the battery?
battery and alternator are the first two suspects!

atistang

if he has a bad connection then why would he put dielectric grease all over the connections?

eddieleephd

Dielectric will help repair the connections and it will prevent corrosion from being an issue in the future.
beings that corrosion is the leading cause of a bad connection this will eliminate that.
Especially in situations where there is either lots of salt or lots of water, or lots of salt water!!!!

I have fixed many vehicles by pulling connections and using dielectric and putting back together.
I do prefer to clean the contact points but in the case of a plug this is virtually impossible!
so I do it the other way It does work very well!

used to hate the stuff now I swear by it!!!
Especially when it comes to tune ups on our trucks!!!

Kevinea

I've fixed the fuel pump problem, and my truck starts up and everything! The problem the still remains is: i started my truck and it was fine. I let it idle for 5-10 minutes and it ran fine. But as soon as I turned my lights on, the truck died. so, i started it up again and it started. I decided to give it enough gas to bring the rpms over 1000rpms; and when i turned on my lights it still ran! the truck still ran even if I let the gas go. i checked my voltage from the battery and it was getting a solid 13.69volts. when i turned on my lights, i was still getting 13.64/5. I'm still a bit confused.

and on top of that, when I turn the key to the point before starting, i can hear a hissing noise coming from the engine area. I'm still confused!

thanks again for all of your help!!!!!!

Daryl Peterson

I have the same issue. did anyone find the cure to this original post?

TheDurk

Don't worry about the answer to one single case, just read what FogRunner wrote.

Daryl Peterson

Yes thats what I originally tried. My fuse looks good, I have got the battery and alternator tested, tightened and greased the battery terminals, and looked for broken or missing grounds and vacuum lines as well. Now I'm clueless where else to look? Thanks for replying.