She left me hanging today

[Pineyguy]

Well, kind of ironically, I was on my way to get my truck inspected for the year when the engine seemed to be breaking up a little, let off the gas, ran fine. Got some gas, got the sticker, the breaking up started again, but much worse. I pulled over at the best spot I could find. Here is the run down-

-230 with a holley 2300 style carb
-Engine breaking up/ backfired once or twice.
-I have a clear filter in the line between the pump and the carb, you could see bubbles in there, checked all the fittings I could get at for tightness, no leaks to suck air through.
-Blew air back through the line, didn't seem like it was blocked at all, after getting it started again, the bubbles were still there.
-Took apart the tank to fill neck vent (It did have gas in it), nothing different.
-Had to start it by pouring gas in the carb once or twice while monkeying with it, sometimes it would run and break up, sometimes not.
-I was going to try a fuel line from the pump into a gas can but I didn't have any fittings to try to safely rig that up and my help's patience was running out.
-This happened twice before, last fall, when the old carb was on it, so I don't think its the carb. Both of those times were after long periods of idling, or not moving very fast and I chalked it up to the gas vaporizing.
-I rebuilt the fuel pump like 3 years ago, but with a kit I bought from Ebay that came in a sandwich bag.
-I noticed since I put the clear filter on that the gas backflows through it when the truck isn't running, usually if I had it running the day before, the next day it would be empty, no leaks on the garage floor.
- A nice local gentleman in an MVPA hat stopped to help, his best guess was new gas+old rebuild material= This.

I ended up getting a buddy with an F250 to pull me back to a fire company I belong to. As luck would have it, I have a spare fuel pump "in the mail" from a member. Does it seem logical that the fuel pump is the problem, or should I be looking at the line more?

Edit: forgot to mention that the fire company (I learned not to call it "hose house" around Doug) has an M715 brush truck, and I had to fight the urge to start swapping parts around.

[kwai]

Sounds like a fuel pump problem. The parts in a "sandwich bag" are most likely nos parts from ablinn. They are good for a while but won't last with the ethanol and new fuel formulations.

Rebuild the fuel pump. You can get a new rebuild kit that will last longer. It's in another thread on here somewhere. Or you can spend $20 for a new fuel pump that doesn't have the vacuum chamber on it from the parts house.

[randyscycle]

Have you just disconnected the fuel line at the carb and cranked the engine to see what actually comes out? With the fuel line in a suitable container of course.

These things are famous for the fuel pickup in the tank clogging/rusting shut and starving them for fuel. I wouldn't be too concerned with the things you see happening in the clear filter. I've seen filters empty overnight, bubble, etc even in perfectly functioning vehicles. That isn't much of a good indicator. The old ethanol incompatible parts may in fact be a problem too.

All that said, if it is in fact a fuel problem then a shot of starting fluid or gas down the carb will get it to run every time if everything else is OK.

[Pineyguy]

I didn't take the line off the pump discharge, I was just going by what I saw in the filter. Along with the bubbles, there wasn't much fluid coming up through. I had to pour gas down the carb to get it going a couple times, it started and ran every time I did that. Guess I'll wait for the other pump, swap them and rebuild the original again, with the Then and Now kit. Hopefully the other pump remedies the problem for now.

[Barrman]

Don't trust the filter. Check for flow, if that is ok then pull the carb apart to clean and put it back together. I have had clear G2 filters with junk in the carb before on the M715.

[kwai]

If you can't fill a half-liter water bottle in about 10 seconds then the fuel pump isn't working well.

[Pineyguy]

Well, I didn't get the pump yet, but I figured why put all my eggs in one basket? I forgot one of the bags I was going to bring with me, so I didn't do the water bottle flow check. I also didn't change the filter that's in the suction line right after the tank for the same reason. The truck started and idled like normal. Anything off idle and it stumbled, ran rough, or died. I checked the float level, made sure the accelerator pump worked, broke the line and saw flow (from what Kwai said about the water bottle, I would guess its not as much as it should be.) I tore down the carb, nothing dirty, nothing blocked up. I tried moving the timing back and forth, a little change, but not really. Took the distributor apart to look for anything obvious, nothing. Blocked off the PCV, wiper motor, and distributor vacuum lines, nothing. So, I guess I'm back to waiting for the pump. I keep going back to when the problem started and seeing the bubbles and very little gas going up the line, so to me it makes sense that its the pump. If I get a chance sometime later on I'm going to check the fuel flow, change that filter, pull plugs and make sure I have a good feed to the distributor.

If the pump flowed, but didn't hold good line pressure, could that cause the symptoms?

[kwai]

If the pump flowed, but didn't hold good line pressure, could that cause the symptoms?

I think so, yes. The fuel pump just isn't putting out enough pressure (flow) to get enough fuel to the carb for it run at anything above idle.

[Wintermute]

Basically yes. A fuel system must have the correct volumetric flow rate and the correct total pressure. If either is less than required, fueling within the carburetor won't be correct.

--Wintermute

[Pineyguy]

I still didn't get the pump in the mail, so I called Napa- they'll have a civvy one for me tomorrow am.