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73-87 Chevy _ GMC Trucks => 73-87 Chevy & GMC Trucks => Topic started by: MitchThor14 on March 08, 2016, 05:53:00 pm
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Hello everybody
I have a 1984 C20 and when i try to start it it dies right away. It only starts if i pour fuel down the carb because it is not getting fuel. I have a brand new fuel pump, the lines are clear and i have cleaned out the tank and the sock on the spending unit is clear. Im not sure why it is not getting fuel so if anybody has some answers that would be great.
Thanks!
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Sounds like either the lines are backwards or wiring might be backwards..
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Quadrajet? Fuel filter in the carb changed?
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Quadrajet? Fuel filter in the carb changed?
Yes its the quadrajet and no i havent changed the filter but the fuel isnt even getting to the carb
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Sounds like either the lines are backwards or wiring might be backwards..
How would the lines be backwards? And wiring for what?
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Did you put a new fuel pump in or did you buy the truck with a new fuel pump? Sometimes people forget that the black wire is actually the positive and red is the negetive..
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Hello everybody
I have a 1984 C20 and when i try to start it it dies right away. It only starts if i pour fuel down the carb because it is not getting fuel. I have a brand new fuel pump, the lines are clear and i have cleaned out the tank and the sock on the spending unit is clear. Im not sure why it is not getting fuel so if anybody has some answers that would be great.
Thanks!
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What's the history on the fuel pump - why is it new? Did the symptoms develop before or after replacing the pump? Does loosening or removing the fuel tank cap make any difference?
Pick up a pressure-vacuum gauge (such as imaged below) and connect it to the 3/8" nipple on the fuel pump that normally connects to the tank. Crank the engine for 20+ seconds and measure how much vacuum the new pump draws. When stabbing the new pump, the installer may have missed the push rod with the pump arm so that the rod and arm are side-by-side instead of end-to-end.
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Hello everybody
I have a 1984 C20 and when i try to start it it dies right away. It only starts if i pour fuel down the carb because it is not getting fuel. I have a brand new fuel pump, the lines are clear and i have cleaned out the tank and the sock on the spending unit is clear. Im not sure why it is not getting fuel so if anybody has some answers that would be great.
Thanks!
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What's the history on the fuel pump - why is it new? Did the symptoms develop before or after replacing the pump? Does loosening or removing the fuel tank cap make any difference?
Pick up a pressure-vacuum gauge (such as imaged below) and connect it to the 3/8" nipple on the fuel pump that normally connects to the tank. Crank the engine for 20+ seconds and measure how much vacuum the new pump draws. When stabbing the new pump, the installer may have missed the push rod with the pump arm so that the rod and arm are side-by-side instead of end-to-end.
It was doing it before i changed the pump as well. I will check tomorrow with the gas cap open and if the pump was installed incorrectly. Do i have to prime the pump in any way after I have had all the lines off? Thanks for the reply!
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No priming needed,
Check your rubber hoses from the tank sender to the metal lines and the short pieces between the metal lines.
The rubber can become restricted when they get old.
The bigger line is the fuel feed 3/8. The 5/16 line is the vapor canister and runs to the drivers side.
Pump outlet is hard lined to carb.
Pretty hard to mix them up.
Do the pump test like bd suggested.
Make sure you can draw fuel from the tank to the pump.
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I surmised from your initial post that you already inspected/replaced the fuel hoses using clear lines. If that was incorrect, then checking the hoses as blazer74 recommended is fundamental to the tasks I suggested.
Mechanical fuel pumps are self-priming as long as internal check valves seal as they should. If you intend to remove the fuel pump again, you can have an assistant bump the starter two complete engine revolutions while you hold the pushrod against the camshaft and watch how far the pushrod travels in and out. IIRC, the pushrod should travel proud of 5/16". But, be careful! Disconnect the primary power lead from the distributor cap to ensure the engine cannot start, avoid entanglement with the fan belts and pulleys, and make sure you don't trap your finger between the end of the pushrod and the fuel pump adapter plate or you'll risk serious injury.
Referring to the attached image, the silver bolt that protrudes from the front of the block threads into a hole that is drilled through into the fuel pump pushrod bore. The hole is there so that a "long" bolt can be temporarily inserted and lightly retain the pushrod in the up position to help facilitate fuel pump replacement. Any bolt threaded into that hole from the factory is surprisingly "short," penetrating no deeper than ~3/8" - 7/16". A bolt penetrating that particular hole any deeper will bind the pushrod. Under the circumstances, it would be prudent to verify that someone did not previously thread a 'long' bolt into this hole and inadvertently lock the pushrod in its extended position. Be advised that the hole requires a bolt to seal against "mystery" oil leaks.
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im sure bd is spot on about the fuel pump but you never did mention if its mechanical or electric
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I surmised from your initial post that you already inspected/replaced the fuel hoses using clear lines. If that was incorrect, then checking the hoses as blazer74 recommended is fundamental to the tasks I suggested.
Mechanical fuel pumps are self-priming as long as internal check valves seal as they should. If you intend to remove the fuel pump again, you can have an assistant bump the starter two complete engine revolutions while you hold the pushrod against the camshaft and watch how far the pushrod travels in and out. IIRC, the pushrod should travel proud of 5/16". But, be careful! Disconnect the primary power lead from the distributor cap to ensure the engine cannot start, avoid entanglement with the fan belts and pulleys, and make sure you don't trap your finger between the end of the pushrod and the fuel pump adapter plate or you'll risk serious injury.
Referring to the attached image, the silver bolt that protrudes from the front of the block threads into a hole that is drilled through into the fuel pump pushrod bore. The hole is there so that a "long" bolt can be temporarily inserted and lightly retain the pushrod in the up position to help facilitate fuel pump replacement. Any bolt threaded into that hole from the factory is surprisingly "short," penetrating no deeper than ~3/8" - 7/16". A bolt penetrating that particular hole any deeper will bind the pushrod. Under the circumstances, it would be prudent to verify that someone did not previously thread a 'long' bolt into this hole and inadvertently lock the pushrod in its extended position. Be advised that the hole requires a bolt to seal against "mystery" oil leaks.
The pushrod should be fine, and i don't think that there is a long bolt in there because my grandpa was the only other owner of the truck and the reason he parked it was because of bad valve seals not a fuel problem. Ill check it out though, thanks for the help!
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No priming needed,
Check your rubber hoses from the tank sender to the metal lines and the short pieces between the metal lines.
The rubber can become restricted when they get old.
The bigger line is the fuel feed 3/8. The 5/16 line is the vapor canister and runs to the drivers side.
Pump outlet is hard lined to carb.
Pretty hard to mix them up.
Do the pump test like bd suggested.
Make sure you can draw fuel from the tank to the pump.
Yeah ill probably rip everything apart, before i just blew air through the lines and it went through so i assumed it was clear. Thanks!
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im sure bd is spot on about the fuel pump but you never did mention if its mechanical or electric
Its mechanical
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Did you put a new fuel pump in or did you buy the truck with a new fuel pump? Sometimes people forget that the black wire is actually the positive and red is the negetive..
Its a mechanical pump
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something i would do if it was me would be to blow on the supply line at the fuel pump with the gas cap off and listen for bubbles in the fuel or even try to pull some fuel up with a electric pump
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I've seen people install new mechanical pumps and not get the pushrod properly on the pump lever, then the pushrod just falls past and never causes the fuel pump to pump
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I surmised from your initial post that you already inspected/replaced the fuel hoses using clear lines. If that was incorrect, then checking the hoses as blazer74 recommended is fundamental to the tasks I suggested.
Mechanical fuel pumps are self-priming as long as internal check valves seal as they should. If you intend to remove the fuel pump again, you can have an assistant bump the starter two complete engine revolutions while you hold the pushrod against the camshaft and watch how far the pushrod travels in and out. IIRC, the pushrod should travel proud of 5/16". But, be careful! Disconnect the primary power lead from the distributor cap to ensure the engine cannot start, avoid entanglement with the fan belts and pulleys, and make sure you don't trap your finger between the end of the pushrod and the fuel pump adapter plate or you'll risk serious injury.
Referring to the attached image, the silver bolt that protrudes from the front of the block threads into a hole that is drilled through into the fuel pump pushrod bore. The hole is there so that a "long" bolt can be temporarily inserted and lightly retain the pushrod in the up position to help facilitate fuel pump replacement. Any bolt threaded into that hole from the factory is surprisingly "short," penetrating no deeper than ~3/8" - 7/16". A bolt penetrating that particular hole any deeper will bind the pushrod. Under the circumstances, it would be prudent to verify that someone did not previously thread a 'long' bolt into this hole and inadvertently lock the pushrod in its extended position. Be advised that the hole requires a bolt to seal against "mystery" oil leaks.
I tried to run the pump from a Jerry can so i could see if it was the lines or not, and it wouldn't even suck anything up from the can. This was after i took it off and put it back on. I couldn't find the bolt you were talking about like in the picture instead mine has 2 a little more inwards connecting a bracket to the block. And should the rod be able to move freely with just my hands? I have to use pliers to push it up so that i could get the pump back on.
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I tried to run the pump from a Jerry can so i could see if it was the lines or not, and it wouldn't even suck anything up from the can. This was after i took it off and put it back on. I couldn't find the bolt you were talking about like in the picture instead mine has 2 a little more inwards connecting a bracket to the block. And should the rod be able to move freely with just my hands? I have to use pliers to push it up so that i could get the pump back on.
Of the two bolts that retain the bracket to your engine, the upper bolt is probably the one with which you are concerned.
The FP pushrod should slide freely in its bore. Generally it will slide out of its bore by gravity alone. You should remove the fuel pump adapter plate and the rod for cleaning and inspection. Roll the rod on a truly flat surface to determine whether it is bent and inspect the shaft for grooves. Also, take a close look at both ends of the rod for wear and post some pics.
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I tried to run the pump from a Jerry can so i could see if it was the lines or not, and it wouldn't even suck anything up from the can. This was after i took it off and put it back on. I couldn't find the bolt you were talking about like in the picture instead mine has 2 a little more inwards connecting a bracket to the block. And should the rod be able to move freely with just my hands? I have to use pliers to push it up so that i could get the pump back on.
Of the two bolts that retain the bracket to your engine, the upper bolt is probably the one with which you are concerned.
The FP pushrod should slide freely in its bore. Generally it will slide out of its bore by gravity alone. You should remove the fuel pump adapter plate and the rod for cleaning and inspection. Roll the rod on a truly flat surface to determine whether it is bent and inspect the shaft for grooves. Also, take a close look at both ends of the rod for wear and post some pics.
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I tried to run the pump from a Jerry can so i could see if it was the lines or not, and it wouldn't even suck anything up from the can. This was after i took it off and put it back on. I couldn't find the bolt you were talking about like in the picture instead mine has 2 a little more inwards connecting a bracket to the block. And should the rod be able to move freely with just my hands? I have to use pliers to push it up so that i could get the pump back on.
Of the two bolts that retain the bracket to your engine, the upper bolt is probably the one with which you are concerned.
The FP pushrod should slide freely in its bore. Generally it will slide out of its bore by gravity alone. You should remove the fuel pump adapter plate and the rod for cleaning and inspection. Roll the rod on a truly flat surface to determine whether it is bent and inspect the shaft for grooves. Also, take a close look at both ends of the rod for wear and post some pics.
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That is the bracket and bolts. The wrench beside it is a 1/2 inch. Ill take the fuel pump off and the rod out to see if it is damaged.
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I tried to run the pump from a Jerry can so i could see if it was the lines or not, and it wouldn't even suck anything up from the can. This was after i took it off and put it back on. I couldn't find the bolt you were talking about like in the picture instead mine has 2 a little more inwards connecting a bracket to the block. And should the rod be able to move freely with just my hands? I have to use pliers to push it up so that i could get the pump back on.
Of the two bolts that retain the bracket to your engine, the upper bolt is probably the one with which you are concerned.
The FP pushrod should slide freely in its bore. Generally it will slide out of its bore by gravity alone. You should remove the fuel pump adapter plate and the rod for cleaning and inspection. Roll the rod on a truly flat surface to determine whether it is bent and inspect the shaft for grooves. Also, take a close look at both ends of the rod for wear and post some pics.
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That bolt that i took out seems to be the short one because i put it in all the way and the rod still moved up and down the same. The rod seems to be straight and good. What gasket will i need now that i took that cover off the get the rod out? Thanks
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I see you have the three line pump, the smaller 1/4 line is a return to the tank.
Possible you have a bad pump if the pushrod is not the fix.
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Did you roll the pushrod across a flat desktop or other planar surface to make sure the rod isn't bowed? To function correctly, the rod must be absolutely straight and move easily in its bore. You should never need to apply any kind of force to slide the pushrod in its bore.
My immediate concern is whether the pushrod is sticking sufficiently that it cannot track the fuel pump eccentric on the camshaft, thereby, limiting or preventing full travel of the fuel pump arm. The pushrod is induction hardened (shallow surface hardened) only at its ends where it contacts the camshaft and the fuel pump arm. Consequently, the rod can bend rather easily if any lateral pressure is applied to the rod, such as might occur during pump replacement if the pump arm isn't squarely aligned against the tip of the rod while attempting to stab the pump into position. For example, if the arm accidentally presses against the side of the pushrod instead of directly against its tip and the fuel pump bolts are tightened, sufficient side thrust can be applied to the pushrod to bend it. It doesn't take much distortion to seize the rod in the bore or cause it to stick.
Once you've confirmed the rod is absolutely straight and there are no burrs or scoring, polish it with fine steel wool, alternating with B12 and WD-40 as solvents. Then spray some WD-40 into the pushrod bore and test fit the rod for easy movement. Before you reassemble, check the pushrod travel by bumping the engine over as previously instructed. This simple step will tell you whether the fuel pump eccentric on the cam is worn excessively. Once the pushrod slides easily in its bore, lubricate it with clean engine oil and some white lithium grease. Purchase new fuel pump plate and base gaskets (imaged below). Scrape and clean the sealing surfaces of the pump, plate and block using some B12, starter fluid or acetone and then reassemble with a smear of Ultra Black, or Ultra Copper silicone sealer on both sides of the gaskets. Tip: stabbing the pump is much easier if you retract the rod into the block by rotating the engine a little at a time. You can retain the rod in the up position by temporarily threading a long clean bolt into the block hole previously discussed - thread the bolt into the hole with your fingers, only enough to keep the rod from sliding down-hole. But, don't forget to remove the long bolt after the pump is tightened down, BEFORE you crank the engine!
Once it's all back together, check the fuel pump draw using a vacuum gauge as previously described.
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Okay, so after breaking off a bolt in the block trying to put the pump mounting plate back on, i had to buy a right angle air drill to get it out and i also got the vac/fuel tester. I got the bolt out and reinstalled the pump. It read good so my dad and i tried it back near the tank as well and it worked their too. I cranked it for about 5 seconds till fuel started coming out of the pump, so i hooked up the hard line and the truck fired right up. Not a clue why it wasnt working before but it works now! Thanks for the help everybody!
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Good job! Glad to hear it's back on the road.