Do I have a fuel pump pushrod problem?

[62 Dart Convertible]

Hi All

I pulled the stock mechanical fuel pump off the 413 today (following fuel starvation issues). I checked the pump valves whilst stroking the lever by hand, and the inlet side holds a vacuum and the delivery side holds pressure, so I would say the pump seems OK.

I removed the fuel pump pushrod and measured it - it is 3.2165" long, which from what I have read seems OK.

I then had my son crank the engine while I measured the pushrod stroke, and it measured at just over 0.275". From what I've read, this seems very low.

Can somebody please chime in with the proper measurement?

Cheers - Frank

 

[lewtot184]

the pump arm has something around a 1.5 lever ratio. so actual diaphragm travel will be over .400". i'm going to suspect you have a single diaphragm/two valve pump. sometimes the pressure on those will get down to 3lbs or less. you need 3.5lbs just to maintain proper fuel level in the carb. also look at any hose connections back by the tank or between the pump and fuel lines for cracks. the push rod is probably fine.

 

[62 Dart Convertible]

the pump arm has something around a 1.5 lever ratio. so actual diaphragm travel will be over .400". i'm going to suspect you have a single diaphragm/two valve pump. sometimes the pressure on those will get down to 3lbs or less. you need 3.5lbs just to maintain proper fuel level in the carb. also look at any hose connections back by the tank or between the pump and fuel lines for cracks. the push rod is probably fine.

Thanks mate.

Does anybody know what the pump pushrod stroke should be? I suspect my cam fuel pump eccentric may be worn.....

 

[Cranky]

How many miles are on this engine. It's pretty unusual for the cam lobe to be worn down on these but it can happen. I can measure a new cam in a little while.....

 

[62 Dart Convertible]

How many miles are on this engine. It's pretty unusual for the cam lobe to be worn down on these but it can happen. I can measure a new cam in a little while.....

Hey Cranky

I don't know how many miles on this engine. The engine is stock apart from a MP mechanical cam... Your help is highly appreciated!

 

[terzmo]

if the pump is good...and the rod is proper length, the cam lobe must be worn or the end of the pump rod is wrong

 

[lewtot184]

its simple to see if the cam lobe is bad. just pull the distributor and take a look.

 

[Cranky]

The lobe lift for the pump rod is right at .300" measured on a new cam.....

 

[RustyRatRod]

Put a Holley blue pump on it and forget about all this bullshit.

 

[62 Dart Convertible]

Thanks for the help lewtot and Cranky - much appreciated!

I want to keep car stock appearance thanks Rusty.

 

[lewtot184]

i'd bet you have a fuel pump problem or a leak on the vacuum side of the pump. if the cam lobe was damaged then the push rod would be trashed. its a little difficult to measure the cam because the fuel pump push rod lobe isn't a lobe like the tappets. its a circle thats center is cast offset to the center of the camshaft. the only true way to accurately measure is with a dail indicator at the push rod. i went thru a bunch of measuring and playing with pumps and lift a few years back. unfortunately i didn't write everything down but i do remember that lift at the diaphragm was less than .500".

 

[Cranky]

i'd bet you have a fuel pump problem or a leak on the vacuum side of the pump. if the cam lobe was damaged then the push rod would be trashed. its a little difficult to measure the cam because the fuel pump push rod lobe isn't a lobe like the tappets. its a circle thats center is cast offset to the center of the camshaft. the only true way to accurately measure is with a dail indicator at the push rod. i went thru a bunch of measuring and playing with pumps and lift a few years back. unfortunately i didn't write everything down but i do remember that lift at the diaphragm was less than .500".

I measured it with a dial indicator.....

 

[62 Dart Convertible]

I measured it with a dial indicator.....

Well now I don't know what to think.

When I posed this question, I had just read somewhere in internetland that the stroke should be close to 0.75", and I measured mine at 0.275" . So I thought that I had found the problem and just came here to confirm.

So my cam lobe is fine, the pushrod is fine, the pump seems fine... I'm running out of suspects...

 

[RustyRatRod]

Get a flat fuel pump block off plate. Knock the fuel pump arm off the mech pump. Put the block off plate between the mech pump and block. Stick a Holley blue pump on it, run the lines into and out of the now useless mech fuel pump and RIDE. Nobody will be the wiser. I don't understand why you're makin things so hard for yourself. If you want it to look stock, there's your answer.

 

[RedShadow30]

Check the gas tank. I did the same thing a while back and it was in the gas tank. Something may be clogging the sifter.

 

[WP29440SE]

Put a Holley blue pump on it and forget about all this bullshit.

LOL

i am running an electric carter pump through my mechanical pump. not because i care about the factory look , but because i like a rock steady 5.5 psi , and peace of mind

 

[RustyRatRod]

That's all well and good, but hope and pray that the mechanical pump doesnt fail. If it does, you'll have an oil pan full of gas in no time flat.

LOL

i am running an electric carter pump through my mechanical pump. not because i care about the factory look , but because i like a rock steady 5.5 psi , and peace of mind

 

[WP29440SE]

That's all well and good, but hope and pray that the mechanical pump doesnt fail. If it does, you'll have an oil pan full of gas in no time flat.

funny you mention that , as i was laying in bed last night , that thought actually occurred to me. i have a block off plate and i was trying to decide how i am going to set up the 440 after i yank out the 360 , and whether or not to use a mechanical pump in conjunction with the electric.



no threadjack intended

 

[RustyRatRod]

Yeah, that's kinda the whole point I'm tryin to get at with the OP. Mechanical fuel pumps have been used for 100 or more years. There are much better and reliable ways.

funny you mention that , as i was laying in bed last night , that thought actually occurred to me. i have a block off plate and i was trying to decide how i am going to set up the 440 after i yank out the 360 , and whether or not to use a mechanical pump in conjunction with the electric.



no threadjack intended

 

[coloradodave]

The reason they've been used for 100 years is because they are simple and they work. There have been many good ideas for the OP to check, but he has to be thorough if he's going to find the problem. First thing I would do is pull the sending unit and check the sock and also replace the rubber connector hose from the sender to the hardline with some modern FI hose. Then check the full length of the hard line for kinks or crimps and replace the rubber line on the inlet side of the pump. A good mechanical pump (like a Carter) from Mancini is pretty much all a street or even a street/strip motor needs. Yes, I have used the Holley pumps on race cars (read, lots of RPM) but on the street the noise is a bear. My opinion and it works for me.