96 Chevy 5.7 Fuel Gauge Pegged and no Fuel


emiracleworker1
11-26-2010, 06:16 PM
I have a 96 Chevy Crewcab with what I believe is the 5.7. The fuel gauge is pegged way past full and the pump doesn't sing when I first turn on the ignition. The truck has been sitting for years. In normal circumstances this happens when the filter is plugged and the extra amp draw on the pump causes the fuel gauge to peg. Being that no fuel has been in the lines for at least 4 years, I would have expected to hear some pump singing the very first time I turned the ignition on... at least until it built some pressure.

I'm wondering if there is any way to trace the wiring to the tank or if there is something else I should be looking at? I don't have a wiring diagram. I'm wondering where do the wires exit the engine compartment? Which side of the vehicle do they run? I can test the wires for continuity if I can find them!

ctwright
11-26-2010, 08:26 PM
It can get alot more complicated than this if you have dual tanks, but you should have a dark green and white wire from the ecm which goes to your fuel pump relay under the hood. The relay should have an orange wire going to it, if you hook a test light to that orange wire and it lights when you first turn the key on, that means that the wire from the ecm to the relay is good and also the contacts are good in the relay, if it doesn't light up, then check your fuses, the orange wire then goes to an oil pressure switch, and from that switch a grey wire goes to your fuel pump, if the orange wire is lighting up at the switch with test light when you first turn the key on but not the grey wire, the oil pressure switch may be bad, What is your oil pressure showing on your gauge? if the grey wire does light up there, then you would want to check it at the pump, which is the first place I would check to start with anyway, and if the test light lights up there, then you are going to need a new pump, which is more than likely your problem due to the time it's been sitting.

emiracleworker1
11-27-2010, 10:01 AM
Thanks... also learning the wires travel down the frame in the same loom as the taillights. Luckily this is a single tank. The oil pressure was up to about 40 in what little cranking I did. I remember the fuel pump was pretty audible when you first turn the key last time I drove the truck, so I kind of knew automatically that something was going on. Just decided to give it a little crank in hopes for a little luck... just ticks me off that I put a new pump in it maybe 5K before it was parked! Any idea of what color wires I should be looking for near the tank?... grey? I won't be able to test at the tank unless I remove it, so I just need to tap into the wires as close as I can get. Figuring with the ignition ON if I am hot 6" from the tank, it's time to pull the pump. If I remember correctly, the ground is black and goes from the pump and bolts to the frame nearby, right? Need to be sure the ground is functional as well.

emiracleworker1
11-27-2010, 03:31 PM
Update: Well, decided to hit the throttle body with some carb cleaner just to see IF it would start IF I could get fuel flowing. It kicked and started which made me feel a little better. Then something odd happened.... fuel gauge rolled back to 1/4 tank and I heard a faint humming. Decided to flip the key one more time and it fired right up. Idled for a good 5 minutes before I shut it off.

It's backfiring when I let off the gas and doesn't like when I romp on it... bogs down pretty bad. The plug wires are a little chewed, so that's the obvious starting point. I'm hoping there isn't anything preventing the timing to advance. Am I wrong to assume that now it's running, I should be able to plug in my code reader (an expensive one, not the cheapos) and pull codes for anything causing the misfire? Thanks for the advice!

j cAT
11-27-2010, 07:40 PM
Update: Well, decided to hit the throttle body with some carb cleaner just to see IF it would start IF I could get fuel flowing. It kicked and started which made me feel a little better. Then something odd happened.... fuel gauge rolled back to 1/4 tank and I heard a faint humming. Decided to flip the key one more time and it fired right up. Idled for a good 5 minutes before I shut it off.

It's backfiring when I let off the gas and doesn't like when I romp on it... bogs down pretty bad. The plug wires are a little chewed, so that's the obvious starting point. I'm hoping there isn't anything preventing the timing to advance. Am I wrong to assume that now it's running, I should be able to plug in my code reader (an expensive one, not the cheapos) and pull codes for anything causing the misfire? Thanks for the advice!


wires chewed ??? I have seen rodent nests in the exhaust causing poor start/run after long storage..

don't use carb cleaner as this will damage plastic/gaskets/and other rubber products used on the throttle body..

USE THROTTLE BODY CLEANER INSTEAD !

ctwright
11-27-2010, 08:11 PM
Glad to hear you got it running, somewhat, well, the truck been sitting that long you may have a lot of rust in the tank, I would suggest taking a look at if you can, definitely replace your fuel filter, and fill the truck up with some clean gas, and maybe add some fuel injector cleaner. You should get a pressure gauge and hook up and see what the pressure is, the specs for your vehicle is 60 to 66 psi, check it and come back with the results. The way to test the pressure on your vehicle is you relieve the pressure by hooking up a pressure gauge with bleeder valve to your test valve, and relieve the pressure. Then with the ignition off you will take a jumper wire from the positive battery terminal to the test connector under the hood near your fusible links, do that and come back with the results.

emiracleworker1
11-28-2010, 09:48 AM
wires chewed ??? I have seen rodent nests in the exhaust causing poor start/run after long storage..

don't use carb cleaner as this will damage plastic/gaskets/and other rubber products used on the throttle body..

USE THROTTLE BODY CLEANER INSTEAD !

You should have seen the nest under the hood. I started using by using a shovel! The truck was parked in a poorly insulated shop up in the mountains, so the packrats had a field day under the hood. Even the fenders are packed full with leaves. All the other wires look fine, but the a few of the plug wires are down to the braids. The exhaust seems fine... it smoked a little bit after it started but "feels" like normal flow at the tailpipe. I had an Audi that absolutely wouldn't run until I pulled the exhaust off at the downpipe, so I was kind of expecting that headache.

I need to do the fuel pressure test, but I think step 1 (or maybe this is step 2) is getting the shop vac and a pressure washer to the motor. Can't hardly work under the hood with all the droppings and things packed into every crevis.

emiracleworker1
12-04-2010, 05:45 PM
Back to the weekend and back to resurrecting this old beast. Haven't touched it since my last post. Brought home the new plug wires and misc parts... decided to start it before I swapped anything just to be safe. We all know the insanity of swapping a part then wondering if it's the new part or something else. It wont start. I have fuel and well within specs regarding pressure. Now I have no spark, which is odd considering the truck sat for 7 years and fired fairly quickly last week once the fuel pump got moving.

First things I did after not starting: The coil wire was down to the #14 wire inside the insulation thanks to the critters. It ran on that last week. Also swapped the #4 cylinder wire, as it was pretty bare itself. Still nothing. The motor is cranking evenly and "dead" like there's not even a couple cylinders trying to fire.

Is it possible that the bad plug wires caused a crack or damage to the cap?... maybe killed the coil. Being down to the little thin wire inside the insulation, we know there was plenty of arcing going on. I'm wondering how to test the coil when it's just me and no remote start control? I've been tricked by Fords with a bad cap that will show spark at the plugs even when the cap is bad, so not even bothering there. I figure if spark is good at the coil, must be the cap. If there's no spark at the coil, where do I start looking?

j cAT
12-04-2010, 09:44 PM
Back to the weekend and back to resurrecting this old beast. Haven't touched it since my last post. Brought home the new plug wires and misc parts... decided to start it before I swapped anything just to be safe. We all know the insanity of swapping a part then wondering if it's the new part or something else. It wont start. I have fuel and well within specs regarding pressure. Now I have no spark, which is odd considering the truck sat for 7 years and fired fairly quickly last week once the fuel pump got moving.

First things I did after not starting: The coil wire was down to the #14 wire inside the insulation thanks to the critters. It ran on that last week. Also swapped the #4 cylinder wire, as it was pretty bare itself. Still nothing. The motor is cranking evenly and "dead" like there's not even a couple cylinders trying to fire.

Is it possible that the bad plug wires caused a crack or damage to the cap?... maybe killed the coil. Being down to the little thin wire inside the insulation, we know there was plenty of arcing going on. I'm wondering how to test the coil when it's just me and no remote start control? I've been tricked by Fords with a bad cap that will show spark at the plugs even when the cap is bad, so not even bothering there. I figure if spark is good at the coil, must be the cap. If there's no spark at the coil, where do I start looking?

check for voltage at distributor. no spark or a weak spark may mean the ignition module is defective. this is common with plug wire /high voltage arcing damages the module..
carbon tracking in the coil rotor can short out any voltage generated. usually threw the rotor contact to the distributor shaft.

emiracleworker1
12-05-2010, 05:22 PM
Well, I did decide to check for spark at the plugs... had to pull one anyway to test the coil, so why not lay it across some metal and crank, right? I put my video camera under the hood since it's hard to see under the hood as this truck is a standard... clutch, key and a good point of view is nearly impossible!

#1 had a good, bright spark but it seemed like it only fired once in what I thought to be 2 or 3 revolutions. Decided to move to #3. Seemed like it fired 3 different times and was fairly quick in between- forgive me, I'm rusty and can't remember how fast each cylinder fires off the distributer. First fire was orange, second was very bright and third was a little less impressive, but still a good spark. Weird thing was, I saw it firing from the cab but the camera doesn't show it firing at all.

I'm guessing the smart thing to do is replace the cap and rotor first, as it could be arcing inside? After that, probably means the ignition module that j cAT suggested... figure it's worth trying the cap and rotor first. It's cheap and needs to be replaced anyway. Sound like I'm on the right track?

emiracleworker1
12-06-2010, 01:38 PM
Sometimes the simplest things... We all know this truck has bad gas in it. Apparently the throttle body cleaner I started using didn't have enough to get the truck running. Bought a can of starting fluid (I know, never use it) just to see if I could get some sort of pop before I started tracing parts again. Fired right up and had been running the last 10 minutes... Actually fairly smooth with the new plug wires.

The unofficial diagnosis: the fuel in the tank doesn't have enough to start the truck while cranking, but once started with a faster than cranking RPM will run semi-fine. Sure is looking like new fuel (draining the tank), filters and fluids all around and this thing will be good enough to run regularly.

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