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73-87 Chevy _ GMC Trucks => 73-87 Chevy & GMC Trucks => Topic started by: 87r10shorty on August 04, 2008, 12:48:58 pm
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87 r10 Short bed ~ Super Sexy
My fuel tank selector switch went out on me for the third time just recently. I just installed a brand new switch and now it won't switch over from left to right in fact it seems to be stuck in the middle not pulling gas from either side and as a result my truck is not starting. Any suggestions on how to remedy the current situation? If not how can I quickly and easily resolve this with an work around, say using only one tank and thus not needing the switch.
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Are you talking about the switch or the switching valve that has gone bad 3 times? Where are you getting the switch from? Or the valve?
Have you seen this: http://forum.73-87chevytrucks.com/smforum/index.php?topic=6537.0
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Do a search. you will find I posted a diagnostic flowchart and schematics on the switch and switching valve.
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Ok.... In an attempt to clean up my posts.
The problem started as my truck was running really rough, bouncy needle, hesitant starts, right tank running a little smoother than left.
Then one day the truck just wouldn't start at, and hasn't started since.
1. Checked coil,plugs,wires... all working order, great spark.
2. I replaced starter as it wouldn't crank at all.
3. I replaced actual in-cab fuel selector switch
4. I disconnected the switching valve, and have since learned it was good to go.
5. I ran lines directly to passenger tank.
6. I replaced oil pressure switch.
I have ordered a new fuel pump relay, hoping that will be my saving grace.
But up until now Still no luck! Truck will not start.... Any help would be greatly appreciated.
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IF you hear the pump priming in whichever tank you are on, I would start at the engine and remove the feed line and see if you are getting fuel to the TBI.
If you are getting fuel to the TBI along with spark and air, it should crank. You didn't say if you verified fuel at the TBI.
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Yeah your next logical step is to check your fuel pressure after you reconnect everything.
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where the heck is the fuel pump relay located?
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In the engine compartment. Slow down there cheif. Stop changing parts and unplugging things and bypassing this and that. There's a simple systematic approach you can take to diagnose it. There is a test lead right next to the fuel pump relay. Jumpering B+ to the test lead will energize your fuel pump. You can do this to determine if it's the control side of the circuit or the load side of the circuit that's causing your problem if in fact no fuel pressure is even your problem to begin with.
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Here's a pic of the relay for you. It's on the passenger side
(http://i6.photobucket.com/albums/y228/Sabaka454/fprelay.gif)
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I agree, we got more than 1 thread on this same topic that you branched out. Find out if you are getting fuel, air and spark and then work you way back. Ignore that there is a computer controlling everything and start with the basics.
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If there's no fuel at the throttle body, don't forget to check the fuel filter located along the frame rail on the passenger side of the truck. When you energize the pump, the fuel goes thru the filter first.
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ok i got spark 100%
i got air 100%
i removed air filter, poured gas into tbi, truck started right up.
so i'm not getting gas to engine.
replaced oil sensor switch
replaced both fuel pump relays
replaced fuel filter
no joy!
where do i go from here?
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Well I should hope you have air unless you moved to the moon. lol
Ok so do you have fuel pressure? Y or N?
Do you have injector pulse Y or N?
If you need help on how to check for either of the two please ask and I will walk you through it.
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i need all the help i can get
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Get yourself a TBI pressure gauge and tee in where your fuel filter is.
Get a noid light or test light to check for injector pulse. I will post how to if need me to.
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So I am using this at the fuel filter on the frame rail, correct? And I would place this after the filter. Now for the fuel pulse I have no ideal what that is.
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any way... both fuel pumps went out at the same time? what exactly will this pressure test tell me.... i don't have the tool nor do i know anyone with it... i will order one if it is absolutely needed.
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Neither pumps energize at all in either position? Even for 2 seconds when you first cycle the key on? Did you check the fuse?
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i checked every fuse in there all good.... i don't now if i ever could hear the pumps before, can't hear them now, when i open the hood and with the help of someone i can hear the fuel pump relay click, but i can't hear the fuel pumps no
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The power -12vdc- goes into the selector valve on a pink wire and then it goes to the left tank on a pink/white wire and to the right tank on a pink/black wire.
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I purchased a multimeter today and hopefully I will be able to get to the bottom of this. I have never used one of these before. The directions state to place the red test lead on the positive feed and the black test lead to the negative feed. looking back in the previous post there is only one wire running to the left side tank and one wire running to the right side tank, in this case would i ground the black test lead and then touch each of the wires running to the pumps?
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Yes, hook your meter up in parallel. The black lead to a good ground the positive lead to the B+ feed to the pump. Turn the key on and it should see battery voltage for 2 seconds. Then have an assistant crank the engine, it should see B+ during cranking also.
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R10shorty, are you ok with using the multimeter? When Vilezamboni says B+ voltage, he means battery positive voltage-which is 12 volts dc. So you set your multimeter on the dc scale- usually black scale- and on the 250 volts setting. That means your meter will read up to 250 volts dc. When you take your reading it should read 12volts or so.
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I have never felt more retarded in my life as i have trying to get a good read on this multimeter. My best guess is I'm getting between 4 and 4.5 volts to the right tank and still can't get a good read on the left tank
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This is a short video of me trying to start my truck... It usually starts and runs for a few seconds then cuts off. you'll hear at the end of the video i got it to stay running for 12 seconds. Please take a look and let me know what you guys are thinking.
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Make sure the negative lead is attached to a good ground. You need to verify the voltage to the pumps.
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How's it going with your troubleshooting 87r10shorty? Did ya get a good read for 12 volts at the pumps?
Here's what happens with a tbi system -when you turn the ignition switch on, the ecm (computer) energizes the fuel pump relay (and the oil pressure switch), and the relay sends the signal to the pumps. So that's how you hear a buzzing under the truck with the ignition on and the truck not running. The pumps are energized to bring the
fuel up to pressure.
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After beating my head against the concrete for several hours, I had a friend with an AAA card offer to have my truck towed to an auto electric shop. Diagnosed that all the wiring and electronics for fuel system needed to be replaced. Total cost with labor and parts $280. Truck is running now, just needs a tune-up and just found out yesterday it won't pass smog.