Mechanical Fuel Pump Replacement

[mykers]

Hello all, new to this forum and new to Mopar. Anyhow, had old cars most my life, just has a question regarding a fuel pump installation. I have installed several mechanical fuel pumps before, but just a basic install. I have heard some nasty rumors about the pushrod (and some interesting stories) that does or does not need to be replaced when I replace the fuel pump? Keep in mind its an old 383 that I'm just trying to get road worthy until the greenbacks come for a full resto...like my old man says, "what good is an old car if it isn't driven in the interim."

Any advice on this matter would be appreciated and thanks for your time in helping me out

 

[451Mopar]

This is pretty good:
http://www.fmcowners.com/mbbs22/photos/photo-thumbnails.asp?albumid=100

 

[Ski 61701]

Welcome to the board, there are quite a few talented people here, and are willing to help one another out. I do have a question for you, is your current fuel pump leaking externallly or just not moving fuel?
Yes depending on the mileage of the motor and how often oil was changed with proper additives it could be possible the fuel pump pushrod could wear.
Even tjough the fmc article says don't remove hex plug, I would in your case remove it to measure the length. Right now too many unknowns going on. Could you just throw a pump on and ir work...sure, but whar if it doesn't, or you have poor performance and you spend time and money chasing things when in all reality its you aren't getting enough fuel. If it was me, I'd pull the pushrod out measure it jusr to make sure its the proper length, if its worn, Hughs engines sells a properly hardened pushrod, get one of those and reassemble and enjoy the car until funds allow you to do things the way you want for the restoration.

 

[moparedtn]

Regarding your basic question:
Yes, replace the fuel pump pushrod when replacing the pump.
I have an old thread on here somewhere all about this topic. Learn from my mistakes.

 

[747mopar]

I'd do as Ski recommends, no point in buying a new one until you measure the old one. The only 3 things that could really complicate the rod removal would be if the plug is seized or the rod is damaged or gummed up enough that it won't pass threw the bore. Straight forward easy job if you don't encounter any of those issues.

 

[451Mopar]

I used the Comp Cams pushrod with the bronze ends on the stroker engine in the Convertible (has a roller cam), and it worked good. Later went to EFI, so I don't know how long they last?

 

[mykers]

Welcome to the board, there are quite a few talented people here, and are willing to help one another out. I do have a question for you, is your current fuel pump leaking externallly or just not moving fuel?
Yes depending on the mileage of the motor and how often oil was changed with proper additives it could be possible the fuel pump pushrod could wear.
Even tjough the fmc article says don't remove hex plug, I would in your case remove it to measure the length. Right now too many unknowns going on. Could you just throw a pump on and ir work...sure, but whar if it doesn't, or you have poor performance and you spend time and money chasing things when in all reality its you aren't getting enough fuel. If it was me, I'd pull the pushrod out measure it jusr to make sure its the proper length, if its worn, Hughs engines sells a properly hardened pushrod, get one of those and reassemble and enjoy the car until funds allow you to do things the way you want for the restoration.

Thanks for your reply. Please explain why I’m measuring the rod? Is it to make sure I find the correct replacement (which I guess is rhetorical). I understand I need to pull it and see if it’s worn but I’m a little hazy on the measurement aspect of the current one if the one in their works then the measurement would be for a similar replacement and not some other aspect right?

Also if the plug hole is gummed should I just use a fine tip screwdriver to gently pry the gum out? Just trying to get as much info as I can and I appreciate everyone’s help.

 

[mykers]

Welcome to the board, there are quite a few talented people here, and are willing to help one another out. I do have a question for you, is your current fuel pump leaking externallly or just not moving fuel?
Yes depending on the mileage of the motor and how often oil was changed with proper additives it could be possible the fuel pump pushrod could wear.
Even tjough the fmc article says don't remove hex plug, I would in your case remove it to measure the length. Right now too many unknowns going on. Could you just throw a pump on and ir work...sure, but whar if it doesn't, or you have poor performance and you spend time and money chasing things when in all reality its you aren't getting enough fuel. If it was me, I'd pull the pushrod out measure it jusr to make sure its the proper length, if its worn, Hughs engines sells a properly hardened pushrod, get one of those and reassemble and enjoy the car until funds allow you to do things the way you want for the restoration.

Oh and the fuel pump not moving gas.

 

[mykers]

I'd do as Ski recommends, no point in buying a new one until you measure the old one. The only 3 things that could really complicate the rod removal would be if the plug is seized or the rod is damaged or gummed up enough that it won't pass threw the bore. Straight forward easy job if you don't encounter any of those issues.

Ok this makes sense now. Just needed a little push. Due to typical wear of the push rod if it is less than 3.25 inches then it needs replacement or more than 1/8 wear. Is this correct?

 

[super-bee_ski]

Welcome aboard and thanks for joining the Forum!

 

[747mopar]

Ok this makes sense now. Just needed a little push. Due to typical wear of the push rod if it is less than 3.25 inches then it needs replacement or more than 1/8 wear. Is this correct?

I think I'd replace it if it was even 1/16" (.0625") short.

 

[oldbee]

Never heard of this problem myself but I guess it’s a viable concern. Not hard to check & better safe than sorry.

 

[Ski 61701]

A couple of replies to your questions.
If more than an 1/8" of rod is missing you have more than fuel pump probs, that metal has go somewhere eg:bearings, via oil pump. Ive had fp rods wear a 1/16" or so and still push fuel but upper end running was weak.
The gummed up part, yes it probably will have oil coked up around the rod, you'll get a good idea once uou pull pump off what the insides are gonna look like. Get ypurseld some walmart brand carb spray, thar stuff is cheap and pretty good at dissolving gunk. Might take some time, but if you do this be prepared to change oil before starting it up.
I'd remove the alternator so you can see everything and aren't working at weird angles. I forget what size allen wrench is needed to remove the plug for rod. But if you start to remove it and its really tight stop. I usually get a mapp gas propane torch and gently heat the area around the plug up. Theory is two dissimilar metals expand and contract at different rates hear cool heat cool, tap on head of pipe plug to shock it then try and loosen. Again coked up oil can play havoc on things.
All fuel pump push rods are not created equal some brands don't have the proper hardness, and if that happens, one or both ends of rod starts to mushroom over and that is a royal pita to remove. Of course there are bronze tipped rods, I myself have never used one on a ft cam, not sure how it would hold up, cant give you a straight answer on that.
How many miles on motor?? Just curious here.

 

[mykers]

A couple of replies to your questions.
If more than an 1/8" of rod is missing you have more than fuel pump probs, that metal has go somewhere eg:bearings, via oil pump. Ive had fp rods wear a 1/16" or so and still push fuel but upper end running was weak.
The gummed up part, yes it probably will have oil coked up around the rod, you'll get a good idea once uou pull pump off what the insides are gonna look like. Get ypurseld some walmart brand carb spray, thar stuff is cheap and pretty good at dissolving gunk. Might take some time, but if you do this be prepared to change oil before starting it up.
I'd remove the alternator so you can see everything and aren't working at weird angles. I forget what size allen wrench is needed to remove the plug for rod. But if you start to remove it and its really tight stop. I usually get a mapp gas propane torch and gently heat the area around the plug up. Theory is two dissimilar metals expand and contract at different rates hear cool heat cool, tap on head of pipe plug to shock it then try and loosen. Again coked up oil can play havoc on things.
All fuel pump push rods are not created equal some brands don't have the proper hardness, and if that happens, one or both ends of rod starts to mushroom over and that is a royal pita to remove. Of course there are bronze tipped rods, I myself have never used one on a ft cam, not sure how it would hold up, cant give you a straight answer on that.
How many miles on motor?? Just curious here.

I’d say roughly a buck 12 for mileage. Thanks for your reply. Very helpful. Happy thanksgiving.

 

[khryslerkid]

If you need a new pushrod, go with this one. If it's a little snug just sand it with some real fine emory. The one I used went right in with no problem.

https://www.summitracing.com/parts/hrs-92152

 

[Wietse]

I had a lot of trouble with my fuel supply caused by a worn push rod, see below link FYI.
Some pictures and info provided from the members as well regarding these components.


http://www.forbbodiesonly.com/moparforum/threads/new-mechanical-fuel-pump-not-working.136537/

 

[miller]

Keep in mind its an old 383 that I'm just trying to get road worthy

Of the handful of 383s I've overhauled, not once have I had to replace the pump rod. Lucky, maybe. But, most of the parts those days were good.

So, that's just for what it's worth. ALWAYS pull the rod, when dealing with the fuel pump, simply to inspect it, and clean it. Of course you have to pull that plug. That's the access hole, to get the rod in, and out.
But, why would you always replace it, if it's in good shape???

 

[Wietse]

There would be no direct need to replace it, but at least you can measure it to see if it still is within specs.
If there is too much wear, make sure to get NOS or a good brand (Howards as mentioned) replacement!

Wear will cause less fuel supply/pressure, which you initially will never notice.
After inspecting my old push rod it becomes clear that once it's too short it will be just be bouncing around between the cam lobe and pump lever which will cause more damage to the rod, as well to your camshaft.
Think i will make it a yearly practice to pull the rod and measure it to keep track of it.

 

[mykers]

Question: when replacing the pump, saying the engine is at TDC, will the rod be retracted (or fully extended depending on your own view) to install the fuel pump easily? I ask because I’m doing a timing chain replacement and would like to swap both the rod and pump out in one run along with the timing chain while at TDC.

 

[miller]

Off hand, I don't recall, if the cam's pump lobe would be down, or not. Really not that big a deal. Install the timing chain first. Be sure to soak the chain in oil first, then allow it to drain off, before installing it. Even go ahead with the chain cover.

At the fuel pump, pull the hex plug 'under' the pump. That's the access for the drive rod, that will come out through the hole. The plug 'can' be fairly tight.
Once you have the timing chain in place, then it's easy just to turn the engine by hand, a little pressure against the pump rod, to see which way it goes. Of course, this is with the pump off.
You bet, the rod being on the bottom of the lobe, will make it easier to install the pump! Just look the rod over, mainly both ends, clean and measure it. (I've NEVER had to replace one!) Lube it with assembly grease, or oil, install it, and back on with the pump.

Of course, the pump lever goes 'under' the rod end, and pretty much has to be forced into place, getting pressure against the lever. Normal! Close as you can, get both bolts started, and run them in even. Simple.