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73-87 Chevy _ GMC Trucks => Engine/Drivetrain => Topic started by: Red87 on February 21, 2017, 09:15:29 am
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My truck is an '87 R10 SWB 5.7L TBI (dual tanks) w/ ~160,000 miles on the clock, and off and on over the past few months, I've been experiencing misfires and lack of power, mainly on takeoff with a heavy foot. Well, the truck will not start now and the injectors are not firing. Up to this point, it was driveable, but then abruptly stopped last week (2/15) and had to be towed home.
Things done recently to the truck & what I've tried:
1. Replacing the fuel pump relay (didn't work, so returned it)
2. Banging on gas tank while my wife is cranking
3. Used a multimeter to check the electrical connections on the injectors and the connector to the right tank's fuel pump
4. New fuel filter (1/14/17)
5. New spark plugs and wires (8/9/16)
6. New EGR valve and MAP sensor, and new hoses for both components (2/2/17)
7. New battery (1/15/17)
8. New distributor cap & rotor (11/13/16)
9. New PCV valve hose (8/21/16)
I got voltage at the injectors' plugs but nothing on the plug to the fuel pump. So I'm not sure if it's an electrical problem or a fuel pump issue at the moment. I am going to try using the jumper wire to energize the fuel pump, just to make sure I didn't test the wiring wrong. Also, I've read where the fuel tank selector valve could be causing problems, and I have had a heck of a time switching between the two tanks, but it could be that the left tank fuel pump is shot too. I don't think the fuel pumps have ever been changed out, and because of the switching problem, we've been exclusively using the right tank. Also, the fuel gauge isn't working accurately for the left tank, but it does for the right tank.
I would appreciate any feedback on what else I could try to be absolutely sure it's the fuel pump that is bad before I drop the tank and replace it. Sorry for the ramblings...I'm an IT guy trying to be a mechanic. ;D
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If the tank switching valve isn't working it will prevent the pumps from energizing. I would encourage you to replace the tank switching valve since you know it needs to be replaced anyway.
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If the tank switching valve isn't working it will prevent the pumps from energizing. I would encourage you to replace the tank switching valve since you know it needs to be replaced anyway.
That is the plan. I put a jump wire on the fuel pump bypass lead and heard nothing, so it has to be either the selector valve and/or the fuel pump.
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Just to be sure I was checking the fuel relay bypass correctly, there is a red wire on the relay connector that has a black spade connector on it. From what I read, I used a jumper wire from the positive terminal of the battery over to that connector, and while my wife turned the key on, I was under the gas tanks to listen for the pump to energize within ~2 seconds (which they didn't...checked both tanks). Is that the correct procedure?
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if you jumped the red wire on the relay you dont need to turn the key. did you check both tanks that way?
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if you jumped the red wire on the relay you dont need to turn the key. did you check both tanks that way?
Well the wire was hooked up before she turned the key on, but I wasn't down by the tank to listen within the ~2 seconds.
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it will be constant power if you jump straight from the battery. your pump will be on as long as its getting constant 12v
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Duh...that makes sense. Well, I definitely didn't hear either pump energize, so they must be toast. Time to get some new parts and get her up and running again...my rental is a Ford F-150.
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if both pumps dont pump then it could be the switch.
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if both pumps dont pump then it could be the switch.
You mean the selector valve near the right tank? That's where I'll start, but I think I have to drop the tank to get it off. Not sure, but I'm about to find out. I think I can get one locally, but it won't be ACDelco. But if it works, I'll be happy.
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You do not need to drop the tank to replace the switching valve. There are 3 bolts holding the cover on over the switching valve and two bolts holding it to the frame. Get yourself a length of fuel injection rated rubber hose and good quality clamps too. Take a before picture before removing for reference. I've seen guys screw this up time and time again. You can also directly energize each pump at the connector with a fused jumper wire to quickly test your pumps.
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what about the switch in the dash, vile?
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You do not need to drop the tank to replace the switching valve. There are 3 bolts holding the cover on over the switching valve and two bolts holding it to the frame. Get yourself a length of fuel injection rated rubber hose and good quality clamps too. Take a before picture before removing for reference. I've seen guys screw this up time and time again. You can also directly energize each pump at the connector with a fused jumper wire to quickly test your pumps.
I got it off...didn't even need to use clamps. Just a little gas came out. So the fused jumper wire would go from the battery to the small, 2-wire pump connectors, correct?
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what about the switch in the dash, vile?
I thought about changing it, too. Does the dash need to come apart to get to it?
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the valve in the dash come out by just pinching the ends in. You have to be flexible to get to it though.
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the valve in the dash come out by just pinching the ends in. You have to be flexible to get to it though.
Cool...thanks.
Well, here's my update: replaced the tank selector valve and no dice. However, I correctly made a 10-amp fused jumper wire and verified that the right fuel pump is energizing. The right tank fuel pump connector has two wires, but the left tank has only one wire (at least, I believe that was the left fuel pump connector...it looked identical to the right fuel pump connector, except for just that one wire). So I put my jumper wire on that one lead and did not hear the left pump energize.
So now I believe it's an electrical problem. I guess I could've had my wife start the truck while I was down below energizing the fuel pump, or is that a bad idea?
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heres my little run in with that switch
http://forum.73-87chevytrucks.com/smforum/index.php?topic=29825.0
some more info on the switch
http://forum.73-87chevytrucks.com/smforum/index.php?topic=23517.0
and a refurb of the switch
http://forum.73-87chevytrucks.com/smforum/index.php?topic=6537.0
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heres my little run in with that switch
http://forum.73-87chevytrucks.com/smforum/index.php?topic=29825.0
some more info on the switch
http://forum.73-87chevytrucks.com/smforum/index.php?topic=23517.0
and a refurb of the switch
http://forum.73-87chevytrucks.com/smforum/index.php?topic=6537.0
That will be the next step...thanks for the info.
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Got the switch out of the dash, but I can't figure out how it comes apart. I'll order a new one anyway, but I'm about to "go postal" on this one.
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There should be 3 wires at each tank unit. One goes directly to ground. Cavity A is B+ to the pump and cavity B is the sending unit wire. See attached
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Well I'll be a monkey's uncle. Bought a $14 switch tonight, after going postal on the one I yanked out...and the dang thing started. I can switch between the tanks, she idles great and got her power back, too. Now on to getting my motorcycle back up and running...missing the great riding weather down here.
Thanks for y'alls help! 8)
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did you change the switch or just mess with the wiring?
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did you change the switch or just mess with the wiring?
Bought a brand new switch.
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did you change the switch or just mess with the wiring?
Bought a brand new switch.
The rocker switch is cheap and 8 out of 10 times it's the problem.
I replace em if they aren't brandy new.
Sent from my SM-P605V using Tapatalk
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did you change the switch or just mess with the wiring?
Bought a brand new switch.
The rocker switch is cheap and 8 out of 10 times it's the problem.
I replace em if they aren't brandy new.
Sent from my SM-P605V using Tapatalk
I wish I had known that before I tried all the other stuff, but now I know something else about the truck that I didn't before. Another problem has come up, though...I have a fuel leak somewhere on top of the left tank. My wife filled up the left tank a week or so ago, and when she came home, I told her there was a strong smell of gas from the left side of the truck. Peeked down between the cab and bed and saw a pool of gas sitting there. I ran that tank out and am now just using the right tank again until I can get to it to fix it. Given the age of the truck, I'm thinking about just biting the bullet and replacing everything fuel related: tanks, pumps, sending units and lines. It looks like some of the lines are metal...is this correct?
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well if its on top of the tank more than likely its the rubber hose
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well if its on top of the tank more than likely its the rubber hose
Yeah, but if I'm dropping the tank to replace that hose, might as well replace the other stuff, too.
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Depends on what the tank and steel sender lines look like. If they aren't rusty and leaky don't just replace them.
Replacement senders typically don't operate as well as the original Delphi parts. The only reason to replace the fuel tank is if the tank is full of crud or rusty and full of holes.
I'd get about 10" to 12" of SAE J30R10 submersible fuel hose for the fuel pumps and 5' or so of SAE J30R9 Fuel Injection hose for the supply and return line connections from the senders to the frame lines and connections to the valve.
Use new German Fuel Injection clamps or new spring loaded constant tension band clamps in the correct size for your hoses.
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Depends on what the tank and steel sender lines look like. If they aren't rusty and leaky don't just replace them.
Replacement senders are typically don't operates as well as the original Delphi parts. The only reason to replace the fuel tank is if the tank is full of crud or rusty and full of holes.
I'd get about 10" to 12" of SAE J30R10 submersible fuel hose for the fuel pumps and 5' or so of SAE J30R9 Fuel Injection hose for the supply and return line connections from the senders to the frame lines and connections to the valve.
Use new German Fuel Injection clamps or new spring loaded constant tension band clamps in the correct size for your hoses.
Good info to know...thanks.