[Magikal]

1983 K5 Chevy Blazer (originally had 6.9diesel but now have 350SBC) 700R4 tranny

Recently I have been getting random rapid drops on my gas gauge. There is no increase in fuel consumption. It will drop down to zero in about 30 seconds or so and stay there (or up to about an 1/8) for 10-60 minutes (while driving) and then will come back up to normal.

Anyone got any ideas as to what specifically is causing this?

[Deuce]

Because I view this as more of a electrical question ... as Moderator ... I am moving it to that question area ...

Deuce ...

[docvette]

Doc here,

First disconnect the fuel sender..which way does the gauge go..up? or down? Next ground the wire which way does it go? which ever way the gauge drives to zero, (ground or open) is the mindset of your troubleshoot..

If say, grounding it causes it to zero, check the harness for pinches to the tank from the gauge..

Also, might be a Diesel float may not stay buoyant in gas.. (although I wouldn't know why not..but stranger things have happened I guess..) ask a part dealer about that , anyway you will want to pull and inspect the sender and it's float for "a Pinhole" The sender may be "Spreading " on the variable resistor..place a DVOM on the sender..and set it for OHMS, RX1, Calibrated 000, and SLOWLY move the float arm up and down..It should give a steady reading..If it "jumps or is jerky.." get a new one it's worn past runout.

Check and clean the connections at your Gauge!

Install a Ground wire from the tank Ground lug, to the frame using a proper star washer ..clean and burnish all paint and dirt.

Doc

[Magikal]

Just an update as I surf through old stuff...

Doc Vette, I never have torn into the cluster yet nor dropped the tank to examine the sender but the problem has smoothed out. I mean that it isn't as erratic as before and is functioning well enough to use. It has it's moments but doesn't exhibit the extreme symptoms it was before. Regardless of the problem, I attribute the cause to the new premium stereo system that I have installed (namely the Bass from the subs) as it has been causing me grief throughout the truck. I recently installed two 1300watt subs in addition to several other component speakers. I noticed the other day that when the bass 'hits' my speedometer will drop 4-5 mph for a second....funny, eh? Probably be replacing that soon along with the entire cluster. I think that all the gauges are just wearing out. I run this truck pretty hard whether out 4x4 ing w/ friends or sneaking into my favorite hunting spot.

I am gonna do the grounding out procedure u mentioned whenever I next get into the dash. till then, as long as it works it will have to wait.

thanx for the help!!

This site is sooooo great!!!!!

[docvette]

Doc here,

If this all tracks back to the stereo system, My guess would be it is installed incorrectly, and under gauge for the current draw , Taxing the whole electrical system..

On a high power system they should be wired with 8 gauge wire (or better) and have DIRECT battery connections, not through the fuse buss..So you may want to look into that before you tear the truck apart.

Doc

[Magikal]

no, not the electricity...the sound ('BOOM') I believe is the culprit.

I am running 4 gauge wire direct from a second battery (dual battery setup) which is charged via an isolator. I have no electrical problems to speak of at the moment other than a speaker ground wire came loose in my headliner (where the stereo is mounted (kool item from LCD Trucks)) and giving me an engine whine from a ground loop. I may be due for a high output alternator but all is operating fine at the moment. Vehicle harnass load is seperated from the Subwoofer load and with the isolator I wouldn't think that one could affect the other.

I have dual amps and a 100 amp inline fuse right before each amp. I am just about to cross the line of needing a cap for the power draw though. Early in the mornings I can slightly (and I mean slightly) see the headlights flicker if I have the stereo up (up being that you cannot hear yourself think, talk, etc.) The stereo even drowns out the dual 2 1/4" exhaust with flowmaster mufflers.
It only flickers at this point cause everything is on (heater on high, headlights on brights (dual beams), phone charger, onboard compass/thermometer. My charging meter in the dash rarely goes above 13volts or so. When I have a heavy load that charging rate will go up to 15 or so (hard to tell with that small dial gauge).

Could my window issue be related to the switch or window motor by chance? I do notice that when I hit the button to roll up the window the voltmeter drops down to 8 or so....a real heavy taxing load for that 20 seconds or so that it is operating. Is this normal? The switch feels fine and never acts goofy or anything nor does the window motor (no noises, smells, etc)

[docvette]

Doc here,

Never seen one react to sound (not to say it couldn't..I mean if it will rattle glass.well you never know) Then then cure for that is "LOW VOLUME"

As for the windows, check the door grounds..common cause in slow windows. Also be sure the window is square in the frame, not dragging at an angle. Renew the gasket with some ATF (a very small amount on a rag..it's hard to get off glass.) Check the regulators for grease, and renew any binding regulator parts.

IF all that is good , the motors are most likely headed for a burn out..it happens about every 10 or so years.

Doc

[TailGater]

Originally Posted by docvette

Doc here,

First disconnect the fuel sender..which way does the gauge go..up? or down? :

The gauge in my truck 78 GMC will go past full until it points straight down with the sending unit disconnected.
I cant really offer any advice on your problem Magikal but I thought I would throw that little tidbit in.

Chris

[docvette]

Doc here,

If properly working, When you remove the resistance (sender) From the gauge circuit, the gauge should peg in one direction or the other.

Doc