Just finished rebuilding the carb, and place a new lin line fuel filter on my 1982 (5.0L) f150. Truck ran great for a week or so and then began to stall out while in Drive. Runs fine at idle in neutral. My fuel level indicator does not work so the first time this happened I though I had run out of gas. After I filled the tank with about 5 gals. of fuel it started and I reached home. However since then no matter how full the tank is (front or rear) it will stall after I drive a few times around the block. I can then restart it and it will run again for a short while before it stalls again.

I was told the problem was the fuel pump. Sounds reasonable enough however that is expensive and may not solve the problem.

I suspect that the new in-line fuel filter may have clogged up with nasty gasoline from the bottom of the tank. I left the fuel filter that is screwed on the the carburetor figuring two fuel filters are better than one. However this may not be sound thinking I don't know.

Before replacing the fuel pump should I remove the in-line fuel filter and leave the carb filter only? Should I try replacing the in-line filter with a new one and try again? Are two filters too much for the fuel pump to handle?

 

I would recommend getting a fuel pressure/vacuum gauge tester for ~$20 from your local parts store; remove the fuel line from the carburetor inlet and measure the fuel pressure being delivered to the carburetor (should be 4-7 psi IIRC). If that passes, can then do a volume output test; remove the gauge and direct the fuel into a container (glass jar, milk jug, whatever) and measure the output over a certain timespan; I don't recall what the specs for that test are but let Google be your friend.

Are you sure the problem isn't a too-low of idle speed?

OH, btw, welcome to FTE.

 

Um, define expensive. I think you should be able to get a quality brand pump for less than $25. But first, I'd test the pressure and volume as previously described.

I'd also suggest losing the inline filter. The stock one that threads into the carb is perfectly adequate by itself. I'm sure the stock pump can push through two filters but there really isn't any advantage to that dual setup. If the first filter clogged, the engine would stop. It's not like the second one is offering any reserve filtering capacity to get you home after the first one clogs. If the first one clogs, you're done. Might as well just stick to the single stock one. Carry a spare in the glovebox if desired.

I'd cut apart both filters and look for any crud in there. If you find any, drain and flush the tank at the very minimum. Install the stock filter at the carb and refill the tank with fresh fuel. Since any crud would have gone through the pump, that also points to a pump replacement after you get the tank cleaned up.

How old is the fuel in the tank? If more than two or three months old, drain and replace it. With old gas, the easily volatile portion tends to evaporate away. You are left with stuff that looks like gas and smells like gas, but doesn't burn reliably like gas. This will defy all normal troubleshooting attempts. I do not care to discuss how I know this.

 

2 or 3 month old gas isn't a problem. Pure gas anyway, should last a year or more, if kept from wide temp swings. Treated gasoline in a suitable container, 2+ years. Best way to tell in a pinch is give it a sniff. If it smells like gasoline - Good. Smells like varnish or paint -Bad. Stale fuel is nasty stuff, and should not be burned in an engine but let's not slip over the line into silliness.

A fuel pump from 1982 though, should normally be replaced on general principles. It's not realistic to operate a thirty or forty year old truck and not expect to drop some hefty coin on it.

 

Agreed on the first statement, but only with pure gas like you said. Ethanol blends are another story, unfortunately, and are pretty much everywhere. Throw in a near empty tank, wide temperature swings, lots of condensation, ethanol's propensity to absorb water, and all bets are off.

As far as silliness, I've even had bad gas straight from the pump, or at least it appeared that way. I've always made it a point to run one brand whenever possible, Chevron in my case. On a camping trip to Yellowstone, I couldn't find my preferred brand so filled up with Conoco. Within a few minutes, the truck started running poorly, bucking on hills, etc. That afternoon I changed a thrashed fuel pump. The fuel that drained from the lines looked like Coca-Cola. Either the fuel was like that when purchased, or it had dissolved years of varnish that had built up in the tank.

Here's the best part. I had managed to burn off most of the bad gas from the rear tank. It was only half empty when I filled it, so the bad stuff was diluted by the existing half a tank of good stuff. I refilled that tank with fresh Chevron and was back in business. The front tank was another story. It was nearly empty when I filled it with the bad stuff and I had no way to get rid of it, as the truck would barely run on it.

Lo and behold, some scumbag did me a huge favor. We left the truck parked for the day in Cody, Wyoming, while exploring the town on foot. Said scumbag used an Oklahoma credit card, and conveniently for me, syphoned all the bad fuel from that one tank. I never did get a chance to thank him. Probably would have been easy enough to find him if I had just looked for a stalled car with the hood up.

 

LOL, siphoned off a load of bad fuel? That's just beautiful.

 

I guess the first question that I would ask is...what area/region are You from? Environment plays a huge part. Cold,hot, fuel line icing, vapor lock conditions,etc,etc.
The more we know about your truck specs and the environment that it operates in....the better the results when starting a thread to get answers to an issue.
Keep in mind that when manufactured, your truck's fuel system operated as stock without the added fuel filter and if the added filter has captured a lot of gunk, it may be time to drop the tanks and flush, as well as internally re-line them.

 

I think You answered You're own thread,lol. I would still consider dropping,flushing, and looking into the Eastwood fuel tank re-line kit...

 

Ooh, really good point! Reading the original post again, the problem could be carb icing. Prime conditions are 35-50 degrees, high humidity, and to a lesser degree, an engine that hasn't fully warmed up yet. You can drive a short distance, the engine loses power and then dies. It won't restart for a few minutes, but then when it does, it fires right up (after the ice melts) and the process repeats itself.

Does the truck still have the stock air cleaner with the snorkel intake and corrugated tube connected to the shroud at the passenger side exhaust manifold? One purpose of that system was to keep the intake air above a certain temperature to prevent carb icing.

 

Was that suggestion for me? The incident was about 15 years ago. Never had a problem again. I'm pretty sure the fuel itself was the issue. If it was caused by dislodged varnish, I've seen no evidence of it reoccurring, even with the occasional different brand of fuel in the tank.

 

Welcome to the forum.


I have nothing to add as everyone has said it.
I would first test output & Vol of fuel pump and if good move on to the next of maybe filters. Cant hurt to change them anyway just to be safe before the pump test. Is this a in tank pump or one on the side of the motor? If on the side look at my add on below before pump test also.


I just thought of something I can add I don't think I saw posted.
Replace ALL rubber lines. They may look good on the outside but todays mixed gas eats the insides up and you would never see it.
Dave ----

 

Vapor lock?