Hi Guys I have 305 sbc with a 600 cfm Edlebrock carb and a NEW manual fuel pump, New RCI Fuel cell and have random loss of fuel pressure. I can go weeks with no issues while driving and then all of sudden one day I'll be out driving and the motor bogs. I can pull over and it idles fine. I look at the fuel in my clear fuel filter and see just a small amount of fuels sloshing around. When its running normal the fuel filter is 100% full. I did disconnect from the inlet on the fuel pump and disconnect from the fuel cell and blew out the line. I did not see anything come out so I assume no blockage anywhere. Any ideas, I am stumped? Thanks
Since it only seems to occur randomly, that sort of rules out a venting problem. Does it happen with different amounts of gas in the fuel cell ? I wonder if there is something floating around in the cell and on occasion blocking the pick-up tube.
It does happen with different amounts of fuel. All the previous times its happen the fuel was low. So I initially thought the fuel gauge was just off, but I filled up yesterday, drove to the park. Stayed there for a couple hours. When I left, I'd say the car was running for about 5 mins and started bogging down. I pulled over and noticed the low fuel in the filter. Opened up the gas tank (thinking it was a venting problem) started it and stopped it a few times until the fuel filter filled up and then drove off. It started acting up again about 1 minute down the road. Pulled over again and stopped and started it again till it filled up and I was able to make it home with no issues, which was about another 2 min away. Is there any easy way to check the pick up tube inside the fuel cell?
Also I do NOT run a fuel return line, not sure if that has anything to do with it. I just left the red cap on there. Should I have something else on there?
Is the assembly around the pick-up tube able to be removed from the cell itself ? Either pull the whole assembly or gently blow back down the tube until you hear bubbling in the cell. I guess the other possibility is the fuel pump itself not working properly. As well all know these days, just because it's new doesn't mean it's right. I'm assuming that all the gas lines are located away from any exhaust right, right ? There is a vent line of some sort on the cell, isn't there ? If so, check to see if it's fully open.
No I cant remove it, the previous fuel pump did the exact same thing, which led me to change it. all the gas lines are routed correctly. There is vent line. I did NOT blow it out. Would a block vent cause an issue like this?
What's inside the fuel cell? A few obscure fuel delivery problem that defy logic have been tracked to some foreign object floating around in the tanks that blocks the pick up then moves away.
Yes a blocked vent line will cause this type of problem. Also do you have a pressure regulator in the system???
If it were a plugged vent, it seems you'd have the problem all the time and not just randomly. Are you using the vertical tube inside the cell as your supply to the fuel pump or one of the fittings down low on the cell ? Maybe the fuel pump isn't able to lift the gasoline up the tube and is cavitating on occasion.
You should know your fuel pressure,,,, That fitting and the entire take up unit should come off of there. You can see exactly what's there. If it's got a hole in it or any other place in the fuel line along the way it will be just like a drinking straw with a hole in it, no soda and same thing no fuel. Also, It's weird as hell but the lines can suck air but not leak fuel behind the pump, it has to do with atmospheric pressure vs the low pressure inside the line. The last fuel delivery problem I saw wasn't pretty, somebody stuck a lightweight fuel pump push rod in and the cam ate the end of it. The fuel pump never got a full stroke due to a short rod. It had a couple fuel pump changes before I saw it too.
A piece of clear plastic will play hell w/any fuel pickup [unless it has a sock] you can't see it in the tank. Remember almost everything comes packaged in it nowadays , so you never know what's found it's way into the tank.... dave
A local recently had similar intermittent problems, turned out to be the fuel cell foam breaking down and working its way through the system to the engine. Owner did the filters etc however it kept happening until he pulled the tank and finally worked out the foam had been deteriorating over time causing the same issues you are having.
look for an air leak in the lines on the suction side of the pump. Fuel pumps will raise hell if they start to suck air instead of gas.
Mechanical pumps have a tough time of lifting liquid and need head pressure against the suction side of the pump to work properly. I believe this is your problem. If the cell has a fitting down low, this is where you want to pipe your gas line to the pump from. The height of the gas in the cell should be enough to supply the head pressure the pump needs.
HUH??? every stock tank I've seen exits out the top of the tank & that's usually a bit higher than the pump ... dave
I had a similar problem with my sedan,I would be driving and all of a sudden the car acted like I was out of gas and sputtering,it might crank and it might not. I replaced both filters,test drive proved that didn't solve my problem. I was convinced after blowing out the fuel line it was my fuel pump,I replaced it. No dice,I had to call a roll back. Knowing there was one more piece that now was at least 15 years old I bought a new carburetor, I drove the car about 10 miles and was convinced my problems were over. The next Saturday we got in the sedan and headed out to a local cruse-in and dammit,the car cut off and the filter was dry,again I called my friend with a rollback and told him to take it to his shop and see if he could find my problem. Monday morning he called me and said,"I have fixed your car and you owe me a buck for the part and 2o bucks labor" He ask me how long had the car been built and I said almost 20 years,he laughed and said come get the car. When I arrived he was holding this small piece of rubber gas line,it was between the gas tank and the hard gas line and had split and probably sucking more air than gas. Not saying this is your problem but sure worth looking at,this ethanol gas is rough on rubber. HRP
Dave, if you're referring to late model cars with the exit on top, the ELECTRIC pump is usually in the tank submerged in the gasoline.
Nope , my '57-'65 '71 chevy's all exited the top of the tank as does [did] my '73 & '84 chev. p.u.'s all of which have/had mech. pumps. I could list more but that oughta be 'nuff... ALA the line outside the tank drops below the in-tank pickup point , a siphon exists & even if that's lost the mech pump is plenty capable of lifting a column of fuel a foot or so.. I think the OP needs to check the pickup line INSIDE the tank , if it was welded , it very well could have cracked!! dave
Maybe you should define the era. Once fuel senders and hookups moved to the top tanks all the fuel ever fed thru them has been well raised above the pump by suction. No head pressure, no gravity feed. The electric in tank pumps entered later and push fuel.
G'day from Australia. A couple of years ago I had a similar problem with a Holden V8 with Rochester 4 barrel. I had an inline glass filter between the tank and mechanical pump and another between pump and carb. The filter near the carb was acting like a pressure regulator and the pump was freewheeling thinking the carb was full, therefore not supplying enough fuel. It conked out one day and was able to coast safely to a stop, lift the bonnet and found no fuel on the delivery side of that filter. Pulled the element out of it and didn't have another issue in 2 years of driving.
next time the fuel pump shits itself pull the fuel cap. If it is a venting problem ,this will eliminate it [you should hear a "Hiss" as air sucks inwards] Venting DOES cause intermittent problems , because the fuel pump can "diaphragm" the fuel tank inwards enough to pull fuel. Eventually it gets to a point where it cant pull any more [usually on a long drive when you are furthest from home]
I'm think going to replace any rubber hose in the line. But if it's sucking air though, why does it work perfect sometimes?
I'll go this far - why does it work well enough to not make you not take notice of it sometimes. Perfectly ???? What your fuel pressure? What do you think it is ? What could be creating an on and off situation in fuel flow? What's the pump supposed to flow? What's it actually flow? Drive it with a fuel pressure guage under the wiper or taped to the windshield, are you sure it's intermittent ?
My 51 was giving me a similar problem, and it was intermittent. It ended up being a small pin hole in the fuel line above the rear axle. It did not leak... it seemed to happen after I drove it a little while, it would either shut off, or would not start back. I checked the pump - which I knew was fine, and of course it was pumping fine, but I wasn't getting any fuel. I knew everything else was new (tank and sending unit), I just hadn't replaced that stretch of fuel line. Since I've replaced it, I haven't had any trouble.
LOL I thought I lost a Mallory Comp fuel pump once and found a piece of paper in the screen in the pump after the filter. Who knows how it got there. Some but not all RCI fuel cells have the safety foam in them (as required by some circle track sanctioning bodies) I have seen it shift around and block the pickup, I have also opened up new RCI fuel cells ( as well as others) that were supposed to be foam free that had pieces of the foam in there anyway and loose bits of crap can cause real problems.
I don't have a clue but I drove almost 300 miles with no problem and the next day I left the house and didn't get 7 miles down the road before the car just quit running. Like I said earlier in the thread,it is a simple thing to check and even if it's not the problem a new piece of hose is cheap insurance.HRP
The Jalopy Journal
