Well i just got the tank back from the radiator shop and i still start to lose fuel pressure after about 10 minutes... im stumped...i rebuilt the carb. put in new lines, new fuel pump, cleaning the tank was my last hope for solving this problem... what else could it be???????? vented cap or non vented cap? the engine is a 1968 289.. any thoughts are greatly appreciated ! ! how about time for a new engine??

thanks, RC

 

How about rigging up a temporary gas tank (like off a lawnmower), and plumbing that into the fuel pump. See if that fixes it. If it does, then the problem has to be something with the fuel lines and tank. Substitution is the quickest way to troubleshoot a computer, and it works pretty good on trucks too.

This probably isn't relevant to your problem: A friend's '89 Bronco once had a blocked fuel filter that was tucked away inside the frame: they went to about 6 garages, spent a couple thousand dollars on towing and "repairs" before they found a mechanic who knew about this hidden filter.

 

>Well i just got the tank back from the radiator shop and i
>still start to lose fuel pressure after about 10 minutes...
>im stumped...i rebuilt the carb. put in new lines, new fuel
>pump, cleaning the tank was my last hope for solving this
>problem... what else could it be???????? vented cap or non
>vented cap? the engine is a 1968 289.. any thoughts are
>greatly appreciated ! ! how about time for a new engine??
>
>thanks, RC

RC,

Seems like the only sure way to track this down is to run some tests to see exactly where the problem is. I wouldn't be looking for a new engine unless you really want to change it out for some reason.

1. Hook an auxiliary fuel container directly to the carb inlet and let it gravity feed while you idle the truck. Take a few minutes while hooking things up so you're safe and don't create a fire hazard. If the engine idles forever with a gravity feed directly to the carb then the engine and carb are fine. If not, you can stop messing with the fuel system and start looking for a problem with the carb.

2. Assuming test 1 is successful, hook the auxiliary fuel container directly to the inlet of the fuel pump. Repeat the idle test. If the engine idles forever and the fuel pressure stays up with a gravity feed directly to the pump then the problem is still in either the fuel lines, tank, or gas cap. More cleaning!!!

The auxiliary fuel tank can be as simple as a standard gas can with a siphon feed. Better yet is an old lawn mower or motorcycle gas tank with a molded nipple on the bottom for the fuel line. Make sure you have the tank higher than the carb and keep it full of fuel while the engine runs. And, of course, make SURE the auxiliary tank is clean and use new rubber or steel fuel line to connect it up.

Let us know what you find out.

 

RC, that's gotta be frustrating - I've had my share of similar hassles, but you've already covered everything I would have suggested.

A couple of rambling thoughts - do you have a phenolic or wood spacer under the carb to insulate it from the block heat?

Have you tried running it with the gas cap off since you got it back?

Did you put a new filter inline when you put it back together? I prefer those clear plastic filters so I can see what's going on in there.

I don't remember if the fuel pump is new or not - any chance it is failing when it gets warm. I don't think it can be a worn out cam lobe or it would do it all the time.

And last, are you sure your fuel line is far enough away from excess heat sources - esp headers/exhaust manifold/pipes?

Good luck man, it's probably something that will make you say, "well, duh!"

 

Ok, something I have seen before on several old engines is the part of the crank that the fuel pump arm rides on (a lobe that is offset and causes the pump arm to rise and fall) becomes worn and doesn't lift the pump arm consistently.

I would throw an electrical pump in it. An electrical pump can be purchased for about $40. Also you can remove the pump from this engine and cap it's old location with a plate. Some engines in late 70's had these plates. Any Ford engine 289/302/351 should have this plate.

Another quick "fix" would be to GENTLY bend the arm SLIGHTLY downwards if possible. Just the arm itself and be careful not to damage the pump.


Now I had similar tank issues and found my problem to be a silicon "slug" an inch long and the diameter of my little finger getting sucked into the tank feed. The last person to own my truck used silicone to seal the top gauge and used too much, instead of making a new gasket.

This is what I would do as I just spent an entire day with your exact problem:
1) remove and drain tank.
2) blow top fuel line into tank out and then see if anything came free.
3) you can clean the tank by using Muratic Acid (which about 1 or 2 gallons will work) and pour the acid in carefully and rotate the tank gently. Let it sit 15 minutes each way. Then put your water line in and keep flushing until acid is mostly gone (1/2 hour).
4) drain water and dry.
5) connect air line to top line by carb and blow thru to tank line.
6) reconnect everything.

 

Also your engine getting oil on the plugs is likely just leaking intake valves and having the heads rebuilt or seats replaced would probably fix the problem.

Remember the 289 is less than the thickness of a dollar from being a 351. It is a good engine and solid. I would have it rebuilt rather than trash it when it is dead.

 

thanks for all the answers guys.. well just to review i cleaned the tank at the radiator shop, new filter, rebuilt carb, new lines, (also blew out all the lines with the compressor), new fuel pump, tried running with and with out the gas cap.... SO..

i have a spacer between the carb and intake mainfold that has the new pcv valve and hose going to the breather on the valve cover..
on the othr side is a breather cap..quite of bit of smoke goes through these after about 10 minutes..?? could i be getting so much smoke recycled throug the PCV valve that the engine kind of "sufficates"?? there is only a trace of smoke coming out at the tailpipe..

i guess the next step is trying to to use a different source as a gas tank. and if that doesnt work i will try the elctric fuel pump using both the stock tank and then the secondary source...

the fuel lines are clear of any heat source and i already tried wrapping the line from the pump to the carb with cold wet rags and that didnt help either....(vapor lock was the first thing that came to my mind)

and dont worry im not throwing this engine away. i will have it rebuilt. i actually am going to have it rebuilt as soon as i can fix this fuel problem..... i want to have this truck all done by april because i need to finish working on my 57 #%$@$ Bel Air this summer.(i know i said the C word)

so i will work on the 2 options i have left and let you know how it went...

thanks for all the help. i love this site ! ! ! ! RC

 

sounds like you have some badly leaking intake valves. Do a cpompression test on a few cylinders and see what happens. Compression gauges are cheap but you can possibly rent one even.

 

I wouldn't overlook the fuel pressure guage symptom(falling pressure). The auxilary fuel source with gravity feed is a good idea though. It's funny you mention the car you are working on, because I had one, and I had this same problem with it. It got to where it wouldn't run at all. I ended up cleaning the fuel tank out, and running a whole new fuel line along the frame to the fuel pump. Well, it would run then, but it would only run for about 3 minutes, and then shut off. I could wait and it would then do the same thing all over. I ended up replacing the brand new fuel pump I had put on when installing the engine, and the problem went away. The only thing I could figure was all that dirt and rust got up in the new fuel pump and ruined it.

 

Will it keep running if you shoot some carburetor cleaner down the carburetor when the fuel pressure starts to drop? What kind of carburetor are you using?

 

well i never thought that i could have "re-contaminated" my new fuel pump.. i guess now i might just go get another brand new pump and blow out the lines one more time and also replace the filter just to be sure.... unless there is a way to unclog the fuel pump?

carburator is a stock 2 barrel. i will also see if the carb spray is any help....

thanks again. RC

 

Hears is two more things to think about. If the stand pipe in the fuel tank is cracked or has a hole in it. It will suck air bubbles into the system and cause a vapor/air lock. I had a johndeer do that to me. On the other end the carb. If the neddle valve is contaminated with something holding it open their would be nothing restricting the flow and makeing the fuel pressure to drop. Then the fuel will just pour out of the float vent. Or something could be wrong with the power valve under the float. Or just the wrong float hight. Most of the wasted gas will end up in your oil and make a lot of smoke in the crank case system looking like blowby. I know both of these sound far fetched but both has happened me several times.