krisner89

Hi everybody. Having a new problem with my camaro this summer. Seems to hesitate now and then like its not getting fuel. Has a full tank of gas so thats not it

FYI its a 1987 camaro sport coupe that came factory with a 305, 4bbl carburetor and automatic transmission. Now has wild 350, edelbrock 1405, and still automatic. I'm running a bare bones setup. All things have been removed for performance like ecu,sensors,a/c, unneeded wiring, vapor canister removed, etc...

I have a fuel pressure gauge mounted inside my car and noticed today that fuel pressure is dropping to like 3 psi OR LOWER and erratically goes back to 6-7 psi and drops again. So I assume its fuel related. I have a CLEAR rubber fuel line from the metal feed line to the mechanical pump. As engine is running I noticed ONLY SMALL BURSTS of fuel being sucked into the pump. The rest is air which seems odd to me. Then when I shut the car off I hear gurgling in the gas tank which is even more odd. I took the gas cap off and it made a slight swoosh and gas cap is soaked with fuel and the tank keeps on gurgling. I have had this car for years and have never had any of these symptoms. They all started today. What could it be?

Also does my car have a additional electric fuel pump in the tank? Read somewhere I do even though its got a mechanical pump.

naf

iTrader: (7)

Fuel pressure fluctuations are normal. Pressure will drop momentarily as the needle comes up.

In tank pump may or may not still be working now that you've removed the computer or some of it's stuff. Don't know how thorough your conversion was.

krisner89

So there is another fuel pump in the tank. Interesting. Wonder if I should remove it or wire it up to a toggle switch. The car has always started hard after sitting a few days. Once fuel gets to it it fires right up. That elec. pump might fix that if its working.

Then again maybe I should remove it and not have any restrictions or would there be if elec. pump was working? Engine makes 450hp and got 150hp shot nitrous. 3/8 fuel line should feed that but i dont know with a dead pump in the tank restricting

Thanks naf for the info. Im going to look into that in tank elec. pump. Thats one thing I haven't touch on the car is the fuel tank.

sonjaab

The extra in tank fuel pump along with the pump mounted on
the engine block was only on the L-69 cars.

On other models/later years I am not sure.............

naf

iTrader: (7)

in tank on 87 LG4s

keep it. it's there for a reason

with key in run it should flow through the line feeding the block mounted pump

or jump the relay and look for flow

krisner89

well i finally got some time away from work for a few days and got my tank out to see what i got exactly. There is a electric in tank pump on my car that I know has never worked since I have had the car. I ran a jumper wire to it and it came on but sounded sick and only put out 1 psi. So I ran to Napa and got a new one (part# E3903). New one puts out about 4 psi and doesn't rattle like the old one did. I looked up the specs on the new airtex electric pump and its 3-5 psi which is fine but only 20-35 GALLONS PER HOUR. That is not going to be enough for 600hp estimated. Even if I put a bigger pump on the block the elec pump is going to end up being a restriction at WOT with the 150 shot of nitrous. But then again I like the idea of a elec pump being there to prime the system after it sits a few days because Im always grinding on the starter for long time to get it to fire AFTER it sits for awhile.

krisner89

Ive seen how to just do away with the whole elec pump by adding more 3/8 tubing with a compression fitting but what i am thinking is how to have both the elec pump and no restriction for high hp applications. So with some scavaging of parts I had laying around I made this.

I cut the 3/8 tubing so a compression fitting would fit. I had a 3 way compression fitting laying around and installed it. Actually it was a 2 way compression fitting. The third outlet was npt threads but had a barb/npt adapter so I used that. I then put a rubber hose on and a one way check valve on the end(I believe it was for some type of air line check valve) . I know its a cobbled up ordeal but I am trying to experiment with out spending $. If it works I might actually buy some parts and make it more professional. But for now I just want to see if it works.

krisner89

As you can see the rubber hose allows the check valve to rest at the bottom of the tank. There is a baffle in the tank that wont allow the check valve to come into contact with the elec pump and float arm for fuel gauge.

krisner89

I then put the tank in the car and connected all fuel lines back up. Ran a jumper wire again to turn the elec in tank pump on(plan on running a toggle switch in future if all goes well). The pump kicked on, I heard the check valve inside the fuel tank click closed, and fuel pressure built to 4 psi at the carb. It worked. I unhooked the jumper wire and heard the check valve click again to open which will allow the block mounted pump to suck fuel through it when the elec pump is turned off. What do you think. or

MSgt Luttrell

That should work fine. I went a different route with my 383 swap, I installed an external tank electric pump rated for 45 psi. I then installed a return style fuel pressure regulator under the hood, reducing the fuel pressure to 5 psi for the 750 Holley carb and returning what fuel the carb doesn't use back to the tank in a return line. This helps reduce vapor lock in the fuel lines during hot weather as the fuel that isn't being used by the carb is constantly being rotated back into the tank instead of sitting dead headed under the hood absorbing heat from the engine.