Help! Fuel/Carb issue

[chevota]

OK.... The truck is a 65 C20 with a stock 283 with a Rochester 2G carb. The truck is my daily driver at the moment and was running great. The other day I was headed across town and cruising about 50mph. All of a sudden the motor cut out and then continued running normally. It was only for a second, but then it happened again. I pulled over and kept it running. I crawled underneath and looked at where I have a fuel filter. It looked pretty dirty, so I headed to the parts store and got 2 filters. Im just running the cheap fram clear plastic filters. I had one right underneath the cab where the hardline comes through the body. I also had one just before the pump. My reason for this is that the truck had sat for many years before I bought it and there was a little crud in the tank. I put in new filters and it fired up and I drove the rest of the way without issue. The next day I was driving and had the same cutout/stumble while cruising at around 45mph. I opened the hood and looked at the filter just before the pump (mechanical). The filter barely had any fuel in it. I figured that there was a possibility that I had put too much of a load on the pump because of the debris that was in the filters I had replaced. (I was thinking that clogged filters = lots of restriction making the pump work harder than it was supposed to). I had replaced this pump 8 months prior (which is just after I bought the truck) because it was bad. The pump I had replaced it with had a 1 year warranty so I went and switched it out. I replaced the pump, fired up the truck, and all seemed well. The following day, I didn't have any cutout or stumble, but when the truck was just sitting at idle, i could hear it slowly decreasing RPM's and almost stall, then pick back up. I went underneath the truck while doing this (as of this point I only have 1 filter and eliminated the other due to me thinking of the resistance it was placing on the pump) and saw that the fuel filter had barely any fuel in it. Then, while still underneath the truck I would hear the RPM's rise, and I could see fuel filling the filter again. I took apart the fuel line from the pickup to the carb and blew it out with air. All was good and no problems or debris were found. Then I thought maybe air was being sucked into the system in the 2 places where hardline met rubber fuel hose. I was originally using the spring type hose clamps. I switched to the type that tighten with a screw. I ran the truck after this and it did seem to improve the problem some, but the problem still exists. At idle the RPM's will slowly drop and rise as does the coming and going of fuel in the filter. I am at a loss as to whats going on. Getting pretty frustrated. New pump, good lines, new filters, new clamps, I even tried taking the fuel cap off thinking it was a vent issue with no success or change. Do you guys have any ideas? I really need to get this figured out so I can go to work. It was running good for about 6 months with no issues other than an alternator rebuild. I thank anyone with advice in advance. I appreciate any help.

[jjzepplin]

Pickup inside tank has a sock on it. Could be clogged. I always just take it off and run a better filter to eliminate the socks deterioration and clogging etc.

[chevota]

I took everything apart from the pickup to the carb. I blew air thru all the lines. They all seemed to have no restriction.

[chevota]

http://youtu.be/uaHXQBBZFMk
http://youtu.be/uaHXQBBZFMk

I tried to post the video on youtube of what im talking about. Hopefully the link works

[chevota]

jjzepplin.... I see what you're saying. Maybe I should just get the sock filter and ditch the stainless mesh one thats on there now. Can I get that style fairly easily?

[jjzepplin]

Are you talking about the pickup on the end of the sender inside the tank? That's what I am talking about.

[chevota]

Yes sir. We're talking about the same thing. I don't see a replacement filter/screen available locally. Where did you get one?

[66Submarine]

Your tank pickup sock/filter is plugged. Take it from me, you will be stopping up filters like clockwork for thousands of miles if you don't fix it.

Take the tank out and clean it out with a chain. I did this to my last truck that had a horrific tank, and it never plugged a filter! Pour out the old fuel and let it dry, then pour some water in, add a length of chain through the sender hole, and shake well until it's clean. Wash all the rust out with water until the water comes out clean. Pour all the water out, and then pour a little kerosene/diesel in it and slosh it around to get the water out; just pour as much of the kerosene/water out as you can afterwards, and set it in the sun to dry. Mine still "flashed" over with a very slight amount of rust while it dried, but never gave me any trouble.

Just clean the filter sock gently with a wire brush and some carb cleaner--no need to buy another.

YMMV, but that's what worked for me.

[chevota]

I could blow through it with my mouth fairly easily.... You still think its clogged? I should take the tank out and do the chain routine like you said.

[66Submarine]

It sounds exactly like what my truck did when it was like that and the in-tank filter was plugged. The fact that the filters didn't have fuel in them would suggest that it's plugged, unless the line has a hole in it that's bleeding air into the line or something. It probably picked up a bunch of crap while you were driving it, or maybe you have some loose stuff floating around that falls back off when it's not pulling fuel; hard to say without looking.

[66Submarine]

BTW, here's one of mine; didn't drive it, but the truck ran fine around the yard like this! The one that was plugged to the point of cutting out going down the road was actually worse than this one! (Cleaned on side of road, so no pics ) Both of the trucks in question had some lame old mechanical pumps that had been on there for decades, and the one from the sender in the picture actually leaked, I think. So I wouldn't guess it's a problem with the pump being lame, especially considering you've tried more than one. That really only leaves the lines/pickup, unless the fuel pump cam is flat or something like that, which I personally think would be very unlikely.

[jjzepplin]

Eliminate it and clean the tank. Use an inline filter that easily replaced.

[chevota]

Well I took out the screen.... It looked good but I cleaned it with carb cleaner anyway. I put it all back together and fired it up. Looked at the filter and it filled pretty good. It did start to empty but quickly filled again. I have to drive roughly 60 miles round trip so I will report back after the trip. Something is still up, but it's better. I might do as suggested and just remove the screen all together.

[66Submarine]

Huh. Your initial problem of running out of fuel at speed certainly sounds like a plugged filter sock, but that actually looks clean (IMO). Weird.

Let us know how it does on the road; if it doesn't cut out when driving, then I suspect you may have a different issue. In my case, the fuel demand exceeded the supply above 45MPH, and the truck would buck violently and cut out when the carb ran dry, then start running again when it filled back up a little; It would idle or drive slowly without any apparent issue.

What kind of fuel pump are you running? FWIW, I don't buy those stamped-together ones anymore; I use the old OE style that go together with screws and can be rebuilt (the one on my 283 was actually an old one I rebuilt).

[chevota]

Well, I drove the truck this morning about 30 miles. No issues at any time. I will note that it was about 80 degrees outside. I could get on the gas from a stop and it would pull fine. I could get on the gas while cruising around 55 and no issue. This afternoon I fired up the truck for the return trip. Things went fine until about halfway home. While driving around 60 mph the truck cutout and somewhat bucked and then continued. I could feel I had just a little power loss as well. In my mind the carb is just barely getting enough gas. I got it home and kept it running. Climbed underneath to look at the filter and I could see it slowly losing fuel, then filling. When it lost fuel, the rpms would drop until it was just barely running and then the filter would fill and the rpms would pick back up. I'm a little lost now. I really dont know what could be wrong. The only difference from the morning trip to now is the temperature. It is around 105-110 here. The truck runs on the low side of normal temp and when it starts to have problems it is approximately one needle width higher on the temp, but I believe this is because it is running lean due to the fuel starving issue. Any other things to try besides a different pump? This is a stamped pump as 66Submarine mentioned. It is a Precision brand pump. I don't know what to try next. Any suggestions? Thanks for your help so far guys!

[chevota]

I just thought about this... Since the problem only exists when its hot, could fuel be boiling in the line? The fuel line does run very close to the block in certain places.
The other thing I thought about... Could the fuel pump pushrod have an issue... extreme wear causing it not to press the pump lever down as far as it should?

[chevota]

Well, if anyone is interested, or has a similar issue, the problem was that the fuel line from the pump to the carb (steel hard line) runs very close to the block and intake. On a hot day I guess the fuel was boiling and starving the carb. I got a heat shield sleeve that slips over the fuel line. So far so good. I made a 20 mile round trip without issues. I have to make a long trip tomorrow so we'll see what happens.

[Jeff La]

Glad you got it figured out.

[jjzepplin]

Any more issues with this?
Is it fixed?
I have had some peculiar issues lately and have a steel line going to the carb.
Never had one before but thought it looked cleaner.