New fuel system for the Dart

-
cpearce

cpearce

Well-Known Member
Joined
Sep 1, 2010
Messages
1,502
Reaction score
1,310
Location
Edson
In the recent hot weather a fuel delivery issue has showed its ugly head on my Dart.

I am running the Mopar performance P4529368 6 valve mechanical pump, 3/8 line to pump, 3/8 sending unit, and 1/2 inch line from pump to carb. Pressure when I start car is 6.2psi, after I drive a while in heat, the pressure falls to the point of not registering and car begins surging.

As a potential remedy, I insulated fuel lines to pump, and put a Holley heat shield under carb, this helped, but didnt solve problem. This issue only occurs when ambient temps are high during summer.

I quickly tired of this problem, and began looking for a solution, as this is not a safe situation for the engine. I have ordered a new tank with electric fuel pump from Hyperfuel. Hyperfuel now has a line of stuff for Mopar applications including a tank setup for 67-69 Dart. The kit features a 340gph pump, tank with baffling around pump, and a new sending unit. I also ordered a regulator designed to knock down high EFI pressures to pressures suitable for carburetors. The kit for the 69 style tank is so new it isnt even on the website, although available.
Screenshot_20190803-122043_Samsung Internet.jpg
Screenshot_20190729-095056_Samsung Internet.jpg


Here are images of similar items, although I got 69 style tank and regulator for 1/2" -8 AN fittings.

I am hoping these modifications remedy the hot fuel delivery issues, and aid in reliability. The potential also exists that the knock down across the regulator from 60 to 6 psi may also cool the fuel through the JT (Jewels Thompson) effect.

My parts are 3 weeks away, I'll keep everyone updated on results.
 
I'm sure your carb will be just fine taking 50psi of fuel pressure. No need for the regulator. In all honesty it sounds like you have a vaporization problem, are you sure the gas tank venting is working properly?
 
Willyrd said:
I'm sure your carb will be just fine taking 50psi of fuel pressure. No need for the regulator. In all honesty it sounds like you have a vaporization problem, are you sure the gas tank venting is working properly?
Click to expand...
Yes, vent is working fine, can pull cap of while running and fuel pressure does not change. Nor does the cap come off with vaccuum.
 
Willyrd said:
I'm sure your carb will be just fine taking 50psi of fuel pressure. No need for the regulator. In all honesty it sounds like you have a vaporization problem, are you sure the gas tank venting is working properly?
Click to expand...
What? 50 psi to a carb, no way.
 
cpearce said:
In the recent hot weather a fuel delivery issue has showed its ugly head on my Dart.

I am running the Mopar performance P4529368 6 valve mechanical pump, 3/8 line to pump, 3/8 sending unit, and 1/2 inch line from pump to carb. Pressure when I start car is 6.2psi, after I drive a while in heat, the pressure falls to the point of not registering and car begins surging.

As a potential remedy, I insulated fuel lines to pump, and put a Holley heat shield under carb, this helped, but didnt solve problem. This issue only occurs when ambient temps are high during summer.

I quickly tired of this problem, and began looking for a solution, as this is not a safe situation for the engine. I have ordered a new tank with electric fuel pump from Hyperfuel. Hyperfuel now has a line of stuff for Mopar applications including a tank setup for 67-69 Dart. The kit features a 340gph pump, tank with baffling around pump, and a new sending unit. I also ordered a regulator designed to knock down high EFI pressures to pressures suitable for carburetors. The kit for the 69 style tank is so new it isnt even on the website, although available.
View attachment 1715373560 View attachment 1715373561

Here are images of similar items, although I got 69 style tank and regulator for 1/2" -8 AN fittings.

I am hoping these modifications remedy the hot fuel delivery issues, and aid in reliability. The potential also exists that the knock down across the regulator from 60 to 6 psi may also cool the fuel through the JT (Jewels Thompson) effect.

My parts are 3 weeks away, I'll keep everyone updated on results.
Click to expand...
You should not need to have an electric fuel pump to make it right.
How close are your fuel lines to heat sources?
I have no where near the system you have and I suffer no issues at all in bad heat here in MO.
Have you tried a different pump? I run an Edelbrock pump on my iron head 340 with factory A/C.
Is your fuel pressure gauge under the hood, the two that I had went to zero when they got hot. One was a Jeg's and the other was a Holley gauge.
 
512Stroker said:
You should not need to have an electric fuel pump to make it right.
How close are your fuel lines to heat sources?
I have no where near the system you have and I suffer no issues at all in bad heat here in MO.
Have you tried a different pump? I run an Edelbrock pump on my iron head 340 with factory A/C.
Is your fuel pressure gauge under the hood, the two that I had went to zero when they got hot. One was a Jeg's and the other was a Holley gauge.
Click to expand...
True that my pressure readings on under hood gauge are very likely inaccurate. I am familiar with the error that liquid filled fuel pressure gauges present when heated.

This is a 550 hp w2 head 408, the issue only occurs when ambient air temps are very hot, like 80 plus degrees. There is no issue when temps are cooler. Lines are several inches away from TTI headers at lower portion of engine compartment. The insulation on line to pump through engine compartment helped. To some degree I was Jonesing for an electric in tank setup, this might have been the final excuse to prompt the change. In the event of a change to EFi down the road, my fuel system will be ready.
 
If that's a regulator set up for a return line, and you install a return line to the tank, all the problems will all go away. I had to do this (a similar system) to my car to get rid of the same heat problem(s).
 
69_340_GTS said:
If that's a regulator set up for a return line, and you install a return line to the tank, all the problems will all go away. I had to do this (a similar system) to my car to get rid of the same heat problem(s).
Click to expand...
You bet, it is going to be a full return system. Done with this issue.
 
cpearce said:
You bet, it is going to be a full return system. Done with this issue.
Click to expand...
I played around for several summers, changed everything everybody suggested, spent a lot of time and money, and the problems would never go away. Finally bit the bullet and got basically all the same stuff you got and the problem was solved. Might as well do it right the first time!
 
69_340_GTS said:
I played around for several summers, changed everything everybody suggested, spent a lot of time and money, and the problems would never go away. Finally bit the bullet and got basically all the same stuff you got and the problem was solved. Might as well do it right the first time!
Click to expand...
Yep, plus the risk of hurting an engine I cant afford to replace. In life, I've found it is cheaper to do it right the first time.
 
cpearce said:
True that my pressure readings on under hood gauge are very likely inaccurate. I am familiar with the error that liquid filled fuel pressure gauges present when heated.

This is a 550 hp w2 head 408, the issue only occurs when ambient air temps are very hot, like 80 plus degrees. There is no issue when temps are cooler. Lines are several inches away from TTI headers at lower portion of engine compartment. The insulation on line to pump through engine compartment helped. To some degree I was Jonesing for an electric in tank setup, this might have been the final excuse to prompt the change. In the event of a change to EFi down the road, my fuel system will be ready.
Click to expand...
I ran a 512 big block 600hp on the same pump you currently have, the only provision I took to fight heat was a thick thermal gasket under the 900 cfm holley. Drove it everywhere in dam hot weather - no issues, just alot of gas $ pains. LOL
Good luck with your new system, keep us informed.
PS I ran the whole system in braided line, no aluminum that transfers heat.
 
512Stroker said:
I ran a 512 big block 600hp on the same pump you currently have, the only provision I took to fight heat was a thick thermal gasket under the 900 cfm holley. Drove it everywhere in dam hot weather - no issues, just alot of gas $ pains. LOL
Good luck with your new system, keep us informed.
PS I ran the whole system in braided line, no aluminum that transfers heat.
Click to expand...
My line from tank to engine compartment is stainless steel 3/8 hard line. The Holley heat shield kit came with a 3/8 thick gasket that is supposedly a thermal insulator also.
 
cpearce said:
My line from tank to engine compartment is stainless steel 3/8 hard line. The Holley heat shield kit came with a 3/8 thick gasket that is supposedly a thermal insulator also.
Click to expand...
All cars a different, if hard line is away from a heat source you should not be having issues. There are many many many cars out there running around in the heat that do not have electric fuel pumps.
 
A lot depends on the available gas. Ours is at least 10% alcohol and since they mandated that mixture, things have gotten worse. Cars that ran fine in the Summer heat suddenly don't anymore.
 
69_340_GTS said:
A lot depends on the available gas. Ours is at least 10% alcohol and since they mandated that mixture, things have gotten worse. Cars that ran fine in the Summer heat suddenly don't anymore.
Click to expand...
That is a valid issue.
We can still get 91 octane no ethanol here in central MO
 
Sorry, but I have to ask...and I apologize in advance if this is a stupid question. I understand the 3/8" line currently from tank to pump, but why the 1/2" line from current mechanical pump to carb? What's the benefit of the larger pump to carb fuel line?
 
ocdart said:
Sorry, but I have to ask...and I apologize in advance if this is a stupid question. I understand the 3/8" line currently from tank to pump, but why the 1/2" line from current mechanical pump to carb? What's the benefit of the larger pump to carb fuel line?
Click to expand...
In theory, lol, to act as a capacitor or volume surge tank when instant transition to full throttle. Whether or not it functions that way.............
 
cpearce said:
In the recent hot weather a fuel delivery issue has showed its ugly head on my Dart.

I am running the Mopar performance P4529368 6 valve mechanical pump, 3/8 line to pump, 3/8 sending unit, and 1/2 inch line from pump to carb. Pressure when I start car is 6.2psi, after I drive a while in heat, the pressure falls to the point of not registering and car begins surging.

As a potential remedy, I insulated fuel lines to pump, and put a Holley heat shield under carb, this helped, but didnt solve problem. This issue only occurs when ambient temps are high during summer.

I quickly tired of this problem, and began looking for a solution, as this is not a safe situation for the engine. I have ordered a new tank with electric fuel pump from Hyperfuel. Hyperfuel now has a line of stuff for Mopar applications including a tank setup for 67-69 Dart. The kit features a 340gph pump, tank with baffling around pump, and a new sending unit. I also ordered a regulator designed to knock down high EFI pressures to pressures suitable for carburetors. The kit for the 69 style tank is so new it isnt even on the website, although available.
View attachment 1715373560 View attachment 1715373561

Here are images of similar items, although I got 69 style tank and regulator for 1/2" -8 AN fittings.

I am hoping these modifications remedy the hot fuel delivery issues, and aid in reliability. The potential also exists that the knock down across the regulator from 60 to 6 psi may also cool the fuel through the JT (Jewels Thompson) effect.

My parts are 3 weeks away, I'll keep everyone updated on results.
Click to expand...

It probly wont unless its a return style system. Or id I misss that ?
 
cpearce to run an electric fuel system safely please run an inertia switch , the ford ones are cheap and easy to hook up .
 
jimjimjimmy said:
cpearce to run an electric fuel system safely please run an inertia switch , the ford ones are cheap and easy to hook up .
Click to expand...

My system that's going on my car as we speak is similar to this setup and I have been thinking about an inertia switch myself. Do you have a part number?

JW
 
jimjimjimmy said:
cpearce to run an electric fuel system safely please run an inertia switch , the ford ones are cheap and easy to hook up .
Click to expand...
Thanks for this insight, I actually hadn't considered this. I assume this is a safety device to disable the fuel pump in the event of an accident? Does it just wire in between your keyed 12 volt power source and the pump?
 
You must log in or register to reply here.
-

Back
Top