351 Cleveland losing prime

[jbojo]

I wonder if the vapor line is clogged? Have you checked that? It's the line over the transmission, going to the vapor/charcoal can.

I was thinking that too but it was mentioned earlier on the thread that the issue occurs with the gas cap off too. I was thinking that there was a vacuum in the tank after running awhile. That would cause fuel to drawn back into the tank again when the engine was shut off. After the hose is removed air would be sucked back in eliminating the vacuum. With the cap off it destroys that theory. This is an interesting problem and I would be interested in the finding out want the issue was.

 

[oldmountainfarm]

I'm still working on it. Have not had time to put the new sending unit in yet. I went back and tightened all the hose clamps. I was thinking of the vapor line also. Is that the hose that is hooked at the top of the gas tank? I understand with the cap off it would have nothing to do with it but I'm trying everything.

 

[jbojo]

I'm still working on it. Have not had time to put the new sending unit in yet. I went back and tightened all the hose clamps. I was thinking of the vapor line also. Is that the hose that is hooked at the top of the gas tank? I understand with the cap off it would have nothing to do with it but I'm trying everything.

Yes, that's the one. The vapor line goes to the charcoal canister in the engine compartment. My understanding is that it was supposed to capture any gas vapor either from the tank or air cleaner to prevent it from escaping into the air. With the gas cap off and the issue still occurring it pretty well eliminates a plugged line theory there. Weird things happen so you can remove the rubber hose connection at the rear axle and just blow air through that line from the engine compartment to eliminate that from the cause. I would be surprised if that fixes the problem but you never know.

 

[oldmountainfarm]

It just cut off again. I've been cranking it every day for the last week. Been cranking up fine. I decided to let it sit there and run today. After about 4 minutes at an idle, it cut off. No fuel coming out of the gas tank. I took the gas cap off and took the little one foot line from the tank to the fuel pump off and no gas coming out at all. I know I can blow into the line and hear bubbles in the gas tank, I can suck on the line and get gas to come pouring out. I just fill like it has to be the sending unit. I don't know if it's cracked or the screen thing is getting clogged and when I take the air hose and blow back through it, it sort of unclogs it. If I can tomorrow, I'm going to pull the sending unit.

 

[oldmountainfarm]

Replaced the sending unit. I took the hose off the pump and there was no gas coming out. I held it towards the ground and it started pouring out. I drained a little over three gallons out of the tank till it was empty. Put the new sending unit in and put the three gallons of gas back in it and nothing was coming out the line when I held it towards the ground. I sucked on it and it started pouring out. I hooked the hose back up and it cranked right up. Fuel pressure was registering and it ran about 5 minutes and the pressure went to zero then it cut off. I changed fuel pressure regulators and cranked it again and it ran a few minutes and the pressure went to zero and cut off. The line to the charcoal canister is not clogged and I had the gas cap off. Darnest thing I have ever seen. Been dealing with this problem since I put the car back together.

 

[CZ-75]

Is the stalling part new, or has it been doing that all aong?

I don't remember that part.

 

[turtle5353]

Run a hose from the fuel pump to a 5 gallon can and run it like that. If it stays running your problem is from there back to tank if it shuts off and runs dry you got a bad pump.

 

[oldmountainfarm]

Maybe have it! My electric fuel pump was just shutting off after a few minutes. I took one off another one of my Mustangs and put it on and it ran for 15 minutes and the fuel pressure remained constant. What's the chances of buying a bad new mechanical fuel pump then buying a bad new electric fuel pump? I'm going to go plumb it in and we'll see how goes it.


This one has been mindboggling so far.


This one has been mindboggling but maybe can get her in the Parade.

 

[CZ-75]

Sounds like you got it figured out!

They don't make parts like they used to...

 

[oldmountainfarm]

I've plumbed a new electric fuel pump in and it cranks up and holds pressure. It pours gas out the tank line now, Go figure. I've spent countless hours trying to figure out what was wrong. Hopefully it's cured.

 

[rottenralph]

Interesting read, I had a fuel filter inline on my car between fuel pump and tank. Moved it between carb and fuel pump and now car is fine. Cost me a new carb and a bunch of frustration as well. What pressure do you run your electric pump at? What regulator are you using?

 

[oldmountainfarm]

I reckon this didn't really cost me anything major. I was totally restoring the car. Everything on it is new or rebuilt. Cost me a lot of time and frustration though. When I bought the car, it was running but in really bad shape. I put a new fuel tank, lines pump and carb and it wouldn't stay running. I decided to go electric fuel pump and it still wouldn't stay running. It's a shame to finish all the paint and body work, put in the new interior, rebuild the drive train but can't keep the car running. I have a fuel filter between the tank and pump and between the regulator and carb. I'm running a Holley regulator, now a Holley fuel pump and a Holley carb. Pressure is at 3 and 1/2 today. Haven't dialed anything in yet beins I just got it running today.

 

[rottenralph]

Does a Holley require different needle and seat in bowls for 3.5 lbs of pressure.(Turboed my Sportster and that is my only reference point ore carb mods for pressurized systems.)

 

[mjlan]

Electric pump right?

 

[oldmountainfarm]

I think the Holley needs close to 6.5 fuel pressure. I just haven't dialed a thing in yet.

 

[mjlan]

If I remember correctly, if the fuel pressure at the carb is between 5-7 psi, your Holley should be ok.

I had an electric Holley pump that was doing the same thing that you are describing, and I think it was because it wasn't mounted low enough. I think those pumps work best when plumbed to a 'sump' with the pump mounted lower than the fuel level.

I wound up going back to a good mechanical pump and all was good. The mechanical pumps are better at creating a vacuum at their inlet, and if the strainer isn't clogged you should be ok.

Also, where and what type of fuel filters located?

 

[oldmountainfarm]

The problem seems to be fixed. Cross my fingers, knock on wood and all that stuff. I now have a Holley pump, before it was a POS electric fuel pump and before that just a regular mechanical pump from Advance Auto. I had it mounted right next to the tank on the trunk drop off. I moved it under the hood and high on the fender apron and it didn't work at all. I moved it back to the trunk drop off and it again works fine. The filter is located between the regulator and the carb. The other POS pump had a filter on it between the tank and pump. So the Holley works fine as long as it is low and near the tank. It would be hard to get it lower than the tank at the rear of the car.

 

[jbojo]

Yeah, electric fuel pumps are better at pushing the fuel vice drawing it from the tank. So the closer it is to the tank the better it works.