Fuel Delivery Questions & Pics?

[Anonymous]

Ever since I installed my new rearend & gears it takes off hella fast but starts to lay down in 3rd gear.....it doesnt spit or sputter but just seems to lose power

Well I ordered some new parts from Summit and installed them and I have a fuel pressure problem it seems....

Heres a pic of the new fuel lines, filter & gauge,

And here is a pic of the fuel pressure gauge,

Anyone see the problem?

I start out with 5 psi of fuel pressure and after it runs for 4 or 5 minutes the fuel pressure starts dropping.

It'll drop down to 2.5 psi after 10 minutes or so....obviously this is a problem being the Holley needs 5-7 psi to work properly.

Any reason why my fuel pump should start to lose pressure after it warms up?

Its not a tank/sender unit, filter, line problem.

I'll just install a electric fuel pump on it but I was just curious if anyone would no why it would drop pressure like this. Usually in my experience, they will rupture a diapraghm and spew gas in the oil pan.

Anyone have a part number for a inexpensive electric fuel pump like a AC or Carter pump? I would like a Holley fuel pump but cant afford the $125+ price tag right now.....was looking for somthing in the $45-$55 price range.....?????

Thanks,

Doug

 

[wsa111]

Doug, I run a holley pump as a pusher to a carter mechanical pump on the engine.

I just ran my car at the drags & the engine still pulls great at the top end.

My pressure is in the 7# area.

Make sure your fuel cap is vented otherwise you will suck a vacuum in the tank & loose fuel pressure. When the pressure drops, open the fuel cap and see if the pressure picks up. If it does replace the fuel cap or clean out the vent.

I like 2 pumps one to push the fuel from the tank to the mechanical pump & the mechanical pump to the carburetor.

Years ago I picked up 2 tenth's & 3 MPH in the quarter just with proper fuel pressure.

After you get your fuel pressure solved, try 68 main jets in your carb & you need to lean the PVCR, thats the orifice covered up by the power valve to .055 or even to .052 to get your full throttle air fuel ratio to 12.7-12.9 area for the best power. Bill

 

[82F100]

Doug, How do you have the new pump wired? do you have a relay? Might be a voltage drop as the pump runs?

 

[addo]

Taking the present pump as mechanical, your check valve on the inlet side appears to be not closing properly. That will cause the drop in fuel pressure.

Also - I don't understand quite why, but the phenomenon of pressure instability seems to happen with Holley non-return regulators. A cheap fix could be to readjust the pressure for correct PSI at the hot idle condition. It will then read higher at cold start, but whether it floods or not, I cannot predict.

Regards, Adam.

 

[MandarinaRacing]

I would like a Holley fuel pump but cant afford the $125+ price tag right now..........

Thanks,

Doug

This is just my opinion, but I'd stay away from the Holley electric pumps, mine had an abnormal failure on the commutator terminals, if I could swap it I'd probably go with an Edelbrock fuel pump.

Alex

 

[82F100]

Duh! I didn't look closely at the picture,Thought you had installed an electric pump already.What about putting the pressure gauge on the other side of the filter? looks like it takes alot to fill that filter up.Maybe try a smaller inline filter?Maybe shorten the length from pump to carb?

 

[Anonymous]

The gas tank cap is vented and works fine with or without and I'm going to switch to 68 jets but I'm running 69's right now.

Yep Thats a Summit catridge filter not a electric fuel pump. The pressure gauge is mounted on the intake side of the filter so the size of the filter shouldnt (I think) cause a problem.

It looks big in the photo but once you pull the filter cartridge out it aint all that big. The pump to carb length is only 12" or so longer than what it was originally and I had a fuel pressure problem before with the other setup...just thought I would replumb the whole thing since I was installing a pressure gauge anyway.

I never thought of a malfunctioning check valve.

Thanks,

Doug

 

[65coupei6]

Doug, I would just install a Carter pump $60 at Summit and keep the mechan. Just like Bill said.

To check your problem I like simple things Since I guess this happened after you installed the new setup I would bypass it. Just run a cheap filter with some rubber line from the pump to the carb and see what happens. At least you can eliminate the new line, filter, etc...

 

[Anonymous]

Marco,

Nope this happened before I installed this new setup! I needed to add a pressure gauge to find the problem so I decided to replumb the whole thing while I was at it.

Later,

Doug

 

[Anonymous]

Update

My buddy at work decided that the old orginal style fuel line was not big enough so I'm gutting the complete fuel system and am installing all new 3/8 line along with a new Car Quest electric fuel pump in the rear and a new fuel pump on the motor finished off with braided fuel line where needed....

No more fuel problems!

Later,

Doug

 

[65coupei6]

Which Car Quest Electirc did you get?

Glad to hear you solved your fuel problems.

 

[kirkallen143]

Update

My buddy at work decided that the old orginal style fuel line was not big enough so I'm gutting the complete fuel system and am installing all new 3/8 line along with a new Car Quest electric fuel pump in the rear and a new fuel pump on the motor finished off with braided fuel line where needed....

No more fuel problems!

Later,

Doug

That was one of my problems w/ the turbo setup, 5/16' line from the tank to the pump and then to the carb. Installed 3/8" line everywhere and added the Carter strip pump...problem solved. This new pump puts out @ 8.5 to 9.5 psi at idle. I plumbed the gauge after the fuel filter.

Kirk
ps. It is also a good idea to put another inline fuel filter before the pump.