[James408]

Ok as in my previous threads I have been fighting fuel starvation. I'm running a Robbmc 550 pump with new 3/8 lines, new sending unit, new spectre fuel tank, new areomotive 40 mic. filter before the carb and an areomotive 100 mic. before the fuel pump. The car is running alot better at wot down the highway and now the only time it starves is on wot at take off(on the street with street tires) it starves in second gear. Now the new tank does not have the 1/4 inch vent tube on it so I tried a vented fuel cap but it had alot of pressure when pulling the cap off. So I drilled a 1/8 in. hole in the cap and no pressure build up. I tried off the line wot with the cap on and then without it. both times I would nose over in second gear but when the cap was off I barely let off the gas and it took off again. when the cap was on it was more of a distinct stall in second gear.

I know I need more vent than an 1/8 inch vent. but my question is this:

If I put a vent on top of the filler neck, is it possible for the fuel to be pushed back and block the vent/air to the tank and cause low fuel pressure.

I have a Carter p4600hp on standby as a helper but I'm still holding out to see if I have a vent problem first. Thanks

[beastmaster]

Are you running stock tank ? If so sump my be needed
Do you have jet extensions in carb?
Do you have a return fuel line on pump?

[James408]

i'm running a stock replacement tank. No return to pump. No jet extensions.

[FrankieT/A]

I have a RobbMc 1/2 in fuel sender, 1/2 stainless fuel line to a RobbMc 550, and 1/2in line to carb, vented gas cap with an 1/8 hole drilled in it, and the car still noses over at the top of second. Left the gas cap loose, no improvement! Put a temporary fuel gauge(dry) on it and the pressure is all over the board. Just driving it's at 6 1/2 PSI, no wait it's at 3, wait a second it's at 0! Whew! It's back to 7. Ok, 3 1/2, back to 7....finally a pusher pump, problem solved! 6.5-7 under all conditions

[James408]

Same here pressure all over the place with that pump. Mine goes down to 3 under load.

[James408]

Then it'll be at 7 then slowly creep down to 5. Hit wot 3-3.5 let off and it goes to 7 then in creeps down again

[2002Z4CSS]

Try running it with the cap off and see if the problem goes away.

[grandville455]

I would get the extensions that slip over the Jet and not the screw in style. You want the jet on the metering block not away from it. Use a 3/8 or 7/16 drill bit set under float to set floats.

[James408]

thanks guys, I've tried no fuel cap and it still nosed over.

thanks for the input. Darby on the quick fuel carb it has sight glasses. I have the fuel level set a little higher than half in the windows. Quickfuel recommends setting the level at half of the site window. the carb is actually set up pretty rich from the factory, prob. richer than a 750 double pumper or about the same.

[James408]

Quickfuel sets the slayer carb fuel level at half of the site glass at 6.5 psi. So if my pressure is dropping does that mean I could raise the fuel level in the carb just so its not shooting out the vents?

Ive been over thinking this mofo for some time now and I guess its time to hook up the 4600hp electric as a helper. also gonna put a real vent on the replacement fuel tank somehow to prevent spillage.

[grandville455]

Originally Posted by James408

thanks guys, I've tried no fuel cap and it still nosed over.

thanks for the input. Darby on the quick fuel carb it has sight glasses. I have the fuel level set a little higher than half in the windows. Quickfuel recommends setting the level at half of the site window. the carb is actually set up pretty rich from the factory, prob. richer than a 750 double pumper or about the same.

Thats probably close, U could check it just to see if its close to one of those bits at the setting your at now. Get the Extensions tho for sure. Have u tried with a full tank of fuel just to eliminate uncovering sump?

[HWYSTR455]

I had a mild delivery problem in the clone, and issues with the crappy mech pumps that are available for Olds. So since I was doing the engine, figured I'd do a RobbMC 550 pump. After reading a number of posts, folks still having delivery issues, I bailed on that idea and am going electric.

On a couple other threads I commented, and promised to do an install thread of a 1/2" line feed & return system. Tomorrow I will finish the install, hopefully sunday I will get that thread posted.

Thing about an electric setup is that there are other benefits than just delivery, like being able to fight vapor lock so much better, for one.

.

[tr709]

Fuel lines pre-bent or DIY bent? Reason I ask is that I chased a similar problem for years that ended up being due to a horrible bend in my fuel line that was hidden by insulation wrapped around the line. Just a thought.

[James408]

thanks guys. Darby the tank was not totally full but close to it over 3/4 full. I'll look at the floats again.

Hwy, I would not recommend this pump. Big dissapointment.
Tr, pre bent lines. no kinks any where.

[James408]

ok, my adhd kicked in and I pulled the Robbmc pump and put my old Carter M6907. I hadnt tried the Carter since my new fuel system and guess what, I don't nose over in second gear! grrrrrrrrrrrrrr It pulls through all gears but is a little lean in third but hey I made it to third gear. I'm sure a helper electric pump will cure this. Not sure I even need the Carter 4600hp....may trade it in for the cheaper 4070. Thanks for your help. Anybody interested in a slightly used Robbmc 550 pump. Cheap!

[RobbMc]

Ship the pump to us James so we can check it out. Something is not right. No way a M6907 will pump as much as one of our 550HP pumps unless there is something wrong.

[James408]

Thanks Robb. I love your 1/2 inch pickup I installed but I'm through with this pump. I just don't have the time or want to, to jack with this pump anymore. Thanks anyway.

[FrankieT/A]

Thank God! I thought I was the only one.

[James408]

No your not Frankie. Im actually pretty pissed off about the whole deal. By the way what helper electric pump are you using.

[FrankieT/A]

On mechanical RobbMc, the car will run fine as long as I don't floor it for more than a lane change or such, but as soon as I tax it, it falls off. I put NOS on the the car but I wanted to make sure I had good fuel pressure. That's when i started delving into the situation. I put a Holley Blue on it because that's what I had. It was brand new in the box sitting around for years. If I had to buy a new one I certainly would try to find something a little quieter for sure. But, I control it manually so noise isn't too bad cause it's just when the car is running. I installed a check valve and bypass system because you can't pull through the Holley Blue when it's not running(and the RobbMc has enough to deal with) I drive my car a lot and take it on trips so I didn't want to rely solely on a electric. Now when I click on the electric I have a solid 7 lbs. even at the top of third with NOS active. So I now have at least $1000.00 in my fuel system between the RobbMc sender, fuel pump and filter, Holley Blue, regulator, bypass valve, 1/2" stainless from tank to mechanical, 1/2" line to carb. I believe I have everything possible to eliminate this problem only to be short cicuited by the fuel pump. If I would have known at the beginning what I know now I surely would have done things differently. Incidentally that's($1000.00)one Edelbrock head!!! Hey Robb if you're reading this how 'bout sending me a new pump instead of asking me to send you mine and have my car downed for that time and I will send you the old one. The reason I don't want to send it to you first is because I drive my 3 or 4 times a week plus week ends. Sorry can't be without my car that long! The $200.00 doesn't mean that much to me.

James sorry long winded but I felt a background on my efforts would make a little more sense.