Mechanical Fuel Pump 101

[Turboomni]

I did a search on here on the Howards and found five or six post on them wearing prematurely clear back to 2015. This is inferior material or not having the correct heat treatment.

Did they say what fuel pump this pushrod was up against? Just looking for a pattern.

 

[khryslerkid]

Did they say what fuel pump this pushrod was up against? Just looking for a pattern.

Not that I can remember.

 

[Turboomni]

The plot thickens,,,,,lol,,,

 

[khryslerkid]

Wish I had a stock one to fall back on....
I have a gauge on my fuel line too. I'll check it out right now, in fact....
of course, who's to say how accurate any of these little gauges are, anyways?

EDIT: Just went out and fired the GTX up. At idle, the fuel gauge on the rail
says 6psi. Sorry, I know that doesn't help anyone.
Could be my pushrod is already shortened, rendering a lower psi?

Hard to say but I'd think you might have a "good" pump with the correct spring. If the pressure keeps decreasing over a period of time then you might want to pull the pump and check the length of the pushrod.

This is what everyone has to put up with now days with the lack of quality control.

 

[khryslerkid]

Well I ordered a new Carter M6903 off ebay cheap and will send it off immediately to these guys. Sucks that they don't assemble them correctly to begin with. If I have any problems down the line they can rebuild it for me.

The one you ordered might have the correct pressure. I would at least install it first and see what pressure you have. Then you'll have a base line before making any changes to it.

 

[Thunderlugs]

The one you ordered might have the correct pressure. I would at least install it first and see what pressure you have. Then you'll have a base line before making any changes to it.

Kid,... Just checked my new parts bin, and there sits a a brand new Carter 6903 that I purchased from Mancini 2 years ago. I guess i too, will have to run it to see how it works, and go from there. Thanks for bringing this to everyone's attention!

 

[Turboomni]

The one you ordered might have the correct pressure. I would at least install it first and see what pressure you have. Then you'll have a base line before making any changes to it.

Yeah I hear ya but based on their report that your pump was not assembled correctly at the factory and would fail soon ,I;m going to send mine in anyways.
I want to minimise any possible problems like raw gas into my crankcase of my new stroker cause some guy or girl had a Monday hangover. I am in no rush.

 

[Chargered]

I've been using the Carter 4862 for years now and have had no issues. I have no idea what kind of pressure or flow it has.

 

[Turboomni]

What carb are you using with the Carter 4862? Summit says it has 9 psi fuel pressure.

 

[Chargered]

What carb are you using with the Carter 4862? Summit says it has 9 psi fuel pressure.

I have the 440 6-pack set up.

 

[hunt2elk]

So I have been having some issues with a new motor and decided to hook up a fuel pressure gauge to rule out a low pressure condition. Check this out, brand new Carter 6903 at idle.
Does anybody make a good reliable mechanical pump that puts out 7.5 psi or so and will support a 600 hp motor? Kind of leary buying another one of these Carters.

 

[dadsbee]

Running a bit rich Joel.. with the float needles popped!?

 

[hunt2elk]

Running a bit rich Joel.. with the float needles popped!?

It was running rich at idle and cruise, but not terrible. Can't believe it didn't cause any damage to my Quick Fuel carb. Probably put 400 miles on the car with that pump. Threw on an old spare I had and couldn't even see any fuel on the bowls.

 

[Turboomni]

Do you mean 6903?

 

[hunt2elk]

Do you mean 6903?

I did and edited the post, thanks for catching that.

 

[khryslerkid]

So I have been having some issues with a new motor and decided to hook up a fuel pressure gauge to rule out a low pressure condition. Check this out, brand new Carter 6903 at idle.
Does anybody make a good reliable mechanical pump that puts out 7.5 psi or so and will support a 600 hp motor? Kind of leary buying another one of these Carters.

View attachment 957325

I've read your other thread on your detonation problems and you might be beyond this point now but when you're having that high of a reading it could be air in the line. I experienced this with the latest pump that I just installed. It was showing 10 psi at first but after it warmed up it came down a little. Then after a 15 min drive it was down to the 5 1/2 psi. Some cold start ups after sitting overnight or for a day or two I'll still experience the same thing. I never had this with the pump before the new lighter spring and diaphragm.

 

[hunt2elk]

I've read your other thread on your detonation problems and you might be beyond this point now but when you're having that high of a reading it could be air in the line. I experienced this with the latest pump that I just installed. It was showing 10 psi at first but after it warmed up it came down a little. Then after a 15 min drive it was down to the 5 1/2 psi. Some cold start ups after sitting overnight or for a day or two I'll still experience the same thing. I never had this with the pump before the new lighter spring and diaphragm.
View attachment 957516

It would stay at 10.5 - 11 at idle. Cruise was 9 - 9.5. And wot it would slowly drop to 6 until I let off. By that time I was going to fast for not being on a track.

 

[Turboomni]

I've read your other thread on your detonation problems and you might be beyond this point now but when you're having that high of a reading it could be air in the line. I experienced this with the latest pump that I just installed. It was showing 10 psi at first but after it warmed up it came down a little. Then after a 15 min drive it was down to the 5 1/2 psi. Some cold start ups after sitting overnight or for a day or two I'll still experience the same thing. I never had this with the pump before the new lighter spring and diaphragm.
View attachment 957516

Have you contacted the place you had it done and ask how this could be possible??

 

[khryslerkid]

Have you contacted the place you had it done and ask how this could be possible??

As far as the higher psi when first started, Mike agreed with me that air in the line could be what's happening. I took it out today and I checked the guage before backing it out of the garage and it was on 8 psi. When I returned it was on 5 1/2 psi.

 

[Turboomni]

So in your opinion with your Edelbrock carbs you don't feel that's a problem or should it be corrected somehow? Maybe a dual quad scenario?