Do the pushrods that move the pump wear over time to the point that even a new pump might not work properly? Made of a softer metal than the cam that pushes it?
Older GM 5.7L engine with mechanical fuel pump
- Thread starter Donald
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Never seen a pushrod wear like that...but I've seen the bolt that holds the eccentric on the timing gear work loose and then the eccentric won't push on the rod any more...rendering any fuel pump inoperative...
You can also, IIRC, install the wrong bolt for the timing cover. One that's too long will impact and bind that rod...rendering it unuseable...
Edit: I may be thinking of an Oldsmobile when I am thinking of the eccentric...
One other issue with the rods is that they can get bent and bind in the hole...
You can also, IIRC, install the wrong bolt for the timing cover. One that's too long will impact and bind that rod...rendering it unuseable...
Edit: I may be thinking of an Oldsmobile when I am thinking of the eccentric...
One other issue with the rods is that they can get bent and bind in the hole...
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Yes they can wear. My 440 Mopar fuel pump rod was worn over 3/8". Had Carter street pump on it and was running out of fuel. New stock rod installed problem over. When you change yours out put some cam lube or STP on the ends until oil gets splashed on them.
The fuel pump was not working so a new one was installed but it's not pushing fuel either.
Might want to pull the pump & crank it over with a starter switch & see if the rod moves in & out-cam lobe issue?
They wear out in time, leak, or just fail. How about an electric fuel pump? They're easy to install and work quite well. I make a plate to cover where the mechanical pump was, remove the mechanical pump and cover up the opening with it. We're doing that with the iron duke that's going into the boat we're working on now.
Friends 71 elcamino with a 307 ate that lobe off the cam.one end of the push rod is hardened and goes against the cam.if it gets put in backwards it will wear and destroy the cam
You may also want to check to make sure the line going back to the tank is not damaged or collapsed. I have worked on a number of mechanical fuel pump vehicles where the pump acted like it stopped working and the feed line was damaged or rusted through and it was sucking air or nothing at all.
Somehow stories like these are lost when people express a longing for 'the good old days' of automobile maintenance.
Originally Posted By: Chris142
Friends 71 elcamino with a 307 ate that lobe off the cam.one end of the push rod is hardened and goes against the cam.if it gets put in backwards it will wear and destroy the cam
Are you sure? I would think the hardened end would go against pump lever and softer end against the cam. You want the push rod or pump to wear. not the cam.
Friends 71 elcamino with a 307 ate that lobe off the cam.one end of the push rod is hardened and goes against the cam.if it gets put in backwards it will wear and destroy the cam
Are you sure? I would think the hardened end would go against pump lever and softer end against the cam. You want the push rod or pump to wear. not the cam.
Originally Posted By: Donald
Originally Posted By: Chris142
Friends 71 elcamino with a 307 ate that lobe off the cam.one end of the push rod is hardened and goes against the cam.if it gets put in backwards it will wear and destroy the cam
Are you sure? I would think the hardened end would go against pump lever and softer end against the cam. You want the push rod or pump to wear. not the cam.
once the push rod wears it eats the cam anyway. You want hard on hard just like the rest of the cam and lifters
Originally Posted By: Chris142
Friends 71 elcamino with a 307 ate that lobe off the cam.one end of the push rod is hardened and goes against the cam.if it gets put in backwards it will wear and destroy the cam
Are you sure? I would think the hardened end would go against pump lever and softer end against the cam. You want the push rod or pump to wear. not the cam.
once the push rod wears it eats the cam anyway. You want hard on hard just like the rest of the cam and lifters
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I'm not sure if I remember this right. But the pushrod is case hardened to the same hardness on both ends, but the cam side is a nearly flat surface and the fuel pump side is rounded somewhat. Putting it in upside down will cut a groove in the cam lobe and start scraping material off the fuel pump actuator arm. Depending on the year of the block, the pushrod can be replaced without disassembling the engine. I remember changing one out by removing a plug in the block below the fuel pump and it fell out in my hand. Later 5.7 liters did not have this plug and very recent 5.7 liters did not have a fuel pump boss at all. My 99 Suburban does not have a boss for mounting the fuel pump. When mounting the pump to the engine, it should not sit flat against the mounting boss. An indication that the pushrod is bad is if the pump will sit flat on the boss. The fuel pump has a small amount of pressure applied to the actuator in the at rest position, otherwise there would be a rather annoying tapping noise when the engine was running and the cam or the actuator would fail rather quickly.
To test the fuel pump, ground the coil, disconnect the fuel line to the tank and hold a small piece of paper up to the fuel inlet on the pump, crank the engine and see if suction is present or use a vacuum gauge. Never use you finger, it could be very painful. If there is suction, check the lines to the tank for damage. It could be the fuel pickup in the tank rusted or broke off.
Hope this helps.
To test the fuel pump, ground the coil, disconnect the fuel line to the tank and hold a small piece of paper up to the fuel inlet on the pump, crank the engine and see if suction is present or use a vacuum gauge. Never use you finger, it could be very painful. If there is suction, check the lines to the tank for damage. It could be the fuel pickup in the tank rusted or broke off.
Hope this helps.
I forgot to add. When you remove the fuel pump, if the pushrod doesn't slide down by itself, the pushrod may be damaged. Every fuel pump I have had to replace this rod has to be pushed back up into the block, so you can get the pump into the housing and the pushrod resting on the actuator lever. I use a long handled feeler gauge to hold it up out of the way during pump installation. I haven't had to change a mechanical pump in over fifteen years, so it took a little while for the process to come back to me.
It can but its rare, the easy way to check it s turn the engine over with a socket with the fuel pump out and feel if the push rod is moving.
When you change the pump on these you get the push rod all the way up and hold it in place with a longer bolt don't tighten the bolt just pinch it.
Once the pump is in and tightened down replace the bolt with the original. I'll bet the rod fell down as the new pump was going in and its sitting along side the pump arm.
Edit: Added picture.
When you change the pump on these you get the push rod all the way up and hold it in place with a longer bolt don't tighten the bolt just pinch it.
Once the pump is in and tightened down replace the bolt with the original. I'll bet the rod fell down as the new pump was going in and its sitting along side the pump arm.
Edit: Added picture.
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Do what Trav said.
On a small block Chevy camshaft the first big lobe behind the front bearing drives the fuel pump. This lobe is part of the camshaft casting and can’t move or be changed.
http://www.rockauto.com/en/moreinfo.php?pk=5576220&cc=1030093&jsn=523
The stock fuel pump push rod is the same on both ends but you should see a different wear pattern on each end when removed.
On a small block Chevy camshaft the first big lobe behind the front bearing drives the fuel pump. This lobe is part of the camshaft casting and can’t move or be changed.
http://www.rockauto.com/en/moreinfo.php?pk=5576220&cc=1030093&jsn=523
The stock fuel pump push rod is the same on both ends but you should see a different wear pattern on each end when removed.
What Trav and Ron350 said is correct on all small block Chevies ...
The fuel pump lobe on the camshaft is rounded & off center of the push rod, This makes the push rod spin in it's bore so the rod & cam lobe don't wear. Now.....I have seen the aftermath of idiots over tightening a bolt to hold the rod up in the bore & mare the rod so it can't spin & quickly wears the cam lobe off.
I personally do not use a longer bolt to hold the push rod up, I use the fuel pump lever to kick the push rod up & then the fuel pump seats, I glue the gasket to the fuel pump with plastic model glue (It dries fast).
I don't see how one would get the lever beside the push rod & still bolt-up the fuel pump without bending the lever by force......
I personally do not use a longer bolt to hold the push rod up, I use the fuel pump lever to kick the push rod up & then the fuel pump seats, I glue the gasket to the fuel pump with plastic model glue (It dries fast).
I don't see how one would get the lever beside the push rod & still bolt-up the fuel pump without bending the lever by force......
You don't leave the longer bolt in there, its only temporary to just pinch enough to stop the rod from sliding not tighten it. GM mechanics have been doing it this way longer than I'm alive all the back to the 265 ci.
The arm on early models can move sideways just enough for the rod to sit next to it, later models usually end up with a bent rod.
The arm on early models can move sideways just enough for the rod to sit next to it, later models usually end up with a bent rod.
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I screwed up and did the "bent pushrod" exactly as in Trav's picture above on a '71 350. Learned my lesson, and the "long bolt" trick for ever after.
Originally Posted By: Trav
You don't leave the longer bolt in there, its only temporary to just pinch enough to stop the rod from sliding not tighten it. GM mechanics have been doing it this way longer than I'm alive all the back to the 265 ci.
The arm on early models can move sideways just enough for the rod to sit next to it, later models usually end up with a bent rod.
I was just stating I don't use a LONGER BOLT TO HOLD THE PUSH ROD UP, I kick the push rod up with the lever, The original 265 didn't have the bolt hole tapped for this "GM" procedure or any small journal small block I have ever seen. I guess without that hole....We ran around in circles cursing??
You don't leave the longer bolt in there, its only temporary to just pinch enough to stop the rod from sliding not tighten it. GM mechanics have been doing it this way longer than I'm alive all the back to the 265 ci.
The arm on early models can move sideways just enough for the rod to sit next to it, later models usually end up with a bent rod.
I was just stating I don't use a LONGER BOLT TO HOLD THE PUSH ROD UP, I kick the push rod up with the lever, The original 265 didn't have the bolt hole tapped for this "GM" procedure or any small journal small block I have ever seen. I guess without that hole....We ran around in circles cursing??
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