I'm having problems with the 289 I put in my 52 f1. The engine skips on acceleration only under load. When I pull the throttle while the truck is at rest, no problem, but when I start driving and hit the gas this loud puffing noise seems to be comming from the carb and it skips. At slow acceleration it doesn't do it. So far I changed the plugs, plug wires, re-gaped the Petroniox element, changed the pcv valve, replaced air filter and re-timed the ignition. Also new fuel filter. I thought maybe the new fuel filter was restricting fuel flow, so I put back in the old one. Same thing happens. It sounds like the carb is starved for fuel. One last clue, when I changed the fuel filter, there was hardly any gas in the line from the filter to the carb. Hmmm. New fuel filter ? The engine did sit for a long time when I was completing body work and paint. This did not happen at all before it sat after putting 10,000 miles on it. Could the diaphram in the stock fuel pump dry out or get bittle ? Anyway, I ordered a new fuel pump. Going to put it in this weekend. Any other ideas??

 

You could get a low cost pressure/vacuum gauge and check the fuel pressure. You can disconnect the fuel line from the carb & put the gauge on....then start the engine. There should be enough fuel in the carb float bowl to run it long enougt to get a steady reading on the gauge. For an ordinary carburetor, it should be around 3 psi.

 

It sure sounds like the pump. Testing at idle won't give you the whole picture unless it's really shot. AutoZone lends a tester that I believe Tee's in so you can test it under load, if you can figure a way to snake the gauge under the hood edge.

A new pump costs so little I'd be inclined to just replace it, if it isn't the problem now it will be later.

 

It's an Edelbrock performer and according to the specs,it needs constant 6psi fuel pressure. Don't mean to be stupid, but what would this test prove? I have a vacuum gauge to tune the carb and general trouble shooting. I'll try it, after you explain why. Thanks

 

Under load, the pump may not be able to keep up with demand. Doesn't sound right, but it happens. Checking the PSI under load would tell the tale of the pumps ability to keep up.

Check your oil for gas also. Failing fuel pumps can dump fuel into the engine.

Any other fuel system contamination evident? Damage to or debris in the pickup in the tank for example? Damage to any lines?

Timing set in good condition?

 

No gas in the oil, thankfully. I'm going to pick up a new fuel pump after work today, if work ever ends! LOL

 

With a new new one?

You don’t say what model, but if this uses an electronic control box (transistors) of any kind then that is the problem.

(Nonguaranteed long distance cyberspace diagnostic help?)

 

Well.....the other guys are right...if you can test under load you'll get a better picture.

The technical answer is that the pump produces flow...the system makes the pressure. So if you simply put the pressure gauge at the end of the fuel line, you'll see if the pump is pumping and if the internal pressure regulator is regulating to the right pressure. If you are able to T in a pressure gauge you should see the pressure rise and fall while the engine is running. When the float valve opens, the pressure will go down. When the bowl is full, the valve will close and the pressure will climb back up to the regulated set point.

The other test would be to check for volume of flow....it can be hazardous if you're not careful, but unhook the fuel line...put it in a big can that is positioned so it won't spill, then crank the engine (or start if if you want). The edelbrock manual should tell you the pressure and flow. A healthy pump will fill a coffee can in a couple of minutes.

Tell me about the filter that you changed...on the old 289's that I've had, the canister on the fuel pump contains a cartridge filter that is often forgotton about if there is an in-line filter.

 

Being that you've covered the ignition system ( plugs,wires and primary ignition) it's always an assumption to proceed to fuel next but don't forget things that set for any length of time do deteriorate, that is gaskets and seals. A vacuum reading at idle and partial throttle would be helpful in further diagnosis.
Check for manifold, carb gaskets and or vacuum lines deterioration which will be more pronounced under throttle acceleration. Close Inspection of the plugs after a brief drive will tell you if you have one or more cylinders running lean and or Rich and which bank to concentrate on when diagnosing fuel rich or lean problems
Also the Performer Carb is a metering valve and rod assembly similar to the Roschester so be sure the metering piston and metering rods are not sticking under throttle and are properly adjusted. The slightest of gum residue in or on a metering rod and/or jet can effect performance.

 

I had a similar but not quite the same problem with mine. It would idle fine but when i stepped on the gas it would sputter and wouldn't hardly run. It turned out to be a crack in the distributor cap.

 

I had a rotor rivet come loose allowing the top electrode to flop around, that caused similar symptoms. It's amazing how the smallest things can create the biggest headaches.

Another thing to check would be to make sure the distributor advances, mechanical and vacuum, are working properly.

 

if dist cap does not have carbon tracks, and, fuel pump proves to be good, rebuild that carb! do not forget the power valve--we are talking full rebuild of carb. you don't say (how) long it sat, but if it ran good before, with todays fuels, i'd bet on the carb.

 

The fuel filter you replaced, where was it located?

Did it thread onto the carb, then had a neoprene hose attached to its nipple that routed to the steel fuel line?

That's one type, there may be another.

C4AZ-9365-B .. Cannister Corrogated Paper Fuel Filter (Motorcraft FG-1A) / Available from Ford/Autoparts stores.

Applications: 1960/77 FoMoCo vehicles / This filter fits inside a metal cannister that threads onto the fuel pump. Since peeps are unaware, it rarely gets changed.

 

OK here's an update. Thanks for all the suggestions guys. The new fuel pump did not change anything. The air filter is an Edlebrock supplied with the air cleaner. The fuel filter is a universal Fram paper element. Leaks in hoses and intake manny checked. The vacuum at idle is about 18 psi..when I rev it the vacuum gauge is steady, no jumping. When I drive it under load there is a ticking sound when it misses. Valves or electric ground out ? I finally through in the towel and took it to a mechanic I've been using for years and I trust him. See what he has to say.

 

Going back to drg racing days of yore, I faguely remember having a similar problem that turned out to be a failed power valve in the carb.