[Tryin2MakeIt]

hey guys im here again for some help. ok. so i still have this 74 f100 with a 390 in it. i set the timing on it today and it runs a lot better but i still can not punch the throttle and it stay running. it cuts out like it wants to die on me and then smooths out again. any suggestions?

[speedydude]

It would be nice to have more info.........engine, carb, etc. What's your fuel pressure?? Accelerator pump working??? Fuel filter changed recently???
Thx, JD

[Jmark]

My first suspect would be the accelerator pump OR the power valve, depending on the carb. Could also be "one of those things" where the engine/trans/gearing just won't allow you to mash it and go screaming away from a dead stop.

Other thing could be ignition problems. Do you still have points or is it electronic? Does the engine have enough compression to get that beast moving quickly from a dead stop?

The vac advance does nothing when you "mash the pedal down". Manifold vacuum goes to zero and there is no secondary vacuum signal either, so you can rule out the advance as the problem.

Mark

[Tryin2MakeIt]

i. more info... this truck had not ran is 6 years. i cleaned out the gas tank new fuel filter, new points, new solenoid,new master cylinder, new wires and plugs and a new carb (2bbl).the motor is a 390 wi 56,000 miles. also all of the cylinders have great compression.

[speedydude]

2 bbl on a 390??? Ok but a 4 bbl would be nice. Got a feeling it's starved a bit. At least that's my first reaction, but it's getting late here and I'm checkin out. Carb is new or rebuilt??? Float working properly??? Do you have a vacuum gauge to see what's happening at idle and higher rpm??? Bear in mind it sat for 6 years........there's a host of things that could be an issue. Me and "old fuel" have had issues in the past.

Any way to get a fuel pressure reading???? None of us are leaning over the engine so it's a bit hard to diagnose from a stinkin computer. Will check back in the AM.

[KULTULZ]

Originally Posted by Jmark

The vac advance does nothing when you "mash the pedal down". Manifold vacuum goes to zero and there is no secondary vacuum signal either, so you can rule out the advance as the problem.

The vacuum advance feature operates from a ported vacuum signal and will cause tip-in hesitation as will a bad accelerator pump. Check diaphram operation and breaker plate binding. It has mechanical points so make sure they are adjusted correctly.

[Tryin2MakeIt]

yes it is a new carb not a rebuild. the points was gapped properly with a feeler gauge. and like i said the gas tank was cleaned not drained. could vacuum have anything to do with it at all? i know that the vacume lines are messed up. i thik the previous owner pluged them up to wherever he thaught they should go

[speedydude]

What carb are you running??? First, I would disconnect the vacuum lines and plug. Plug the ports on the carb where removed. Set base or initial timing. Do you have a timing light??? Check mechanical advance to be sure it's coming in correctly. Visually inspect all vacuum lines and fittings for deterioration or leaks.

If you have vacuum leaks you can usually get it to idle but it will crap out when you add additional F/A mixture. (too lean). Also look in the carb throat , open the throttle and make sure the accelerator pump is giving a good squirt.

Check back, JD

[red65mustang]

here's a very handy trouble shooting link....

click on "feels" then "engine hestiates" for a prioritized causes listing.....

http://www.autozone.com/UseCase,S001...tInTheZone.htm

because it sat so long you really should put a clear plastic Purolator gas filter ($5) on the the fuel hose line into the fuel pump to catch the crap from the tank and fuel lines.....common for the first one you put on to be to be plugged full of crap (filter is totally full of gas) in just 200-500 miles

[Tryin2MakeIt]

o.k. so i went out this morning and did a pressure test on the truck. the fuel pressure didn't even read on the gauge. so i am going to change it and see if that fixes my problem. what i don't understand is how could it stay running is the fuel pump is not working

[Not A T 25]

Originally Posted by Tryin2MakeIt

o.k. so i went out this morning and did a pressure test on the truck. the fuel pressure didn't even read on the gauge. so i am going to change it and see if that fixes my problem. what i don't understand is how could it stay running is the fuel pump is not working

It will transfer some fuel just not generate pressure or volume I would look for a fuel filter up line from the pump it could be blocked. If no filter blow back thru the line to the tank to make sure there is no sludge or blockage could be a starved pump.

[speedydude]

I've always liked the clear fuel filters, easy to see what's happening. And ditto to T-25

[400smb_s10]

IMO I would fix all the fuel problems then unbolt the 2 bbls and intake and drive to the closest lake and throw them in it and bolt on a 4bbl set up. Theres nothing better then hearing the 4 bbls open up at 3000 rpm when you mash the gas and leave 40 ft of rubber

But thats just my opinion

Ed

[Not A T 25]

Originally Posted by 400smb_s10

IMO I would fix all the fuel problems then unbolt the 2 bbls and intake and drive to the closest lake and throw them in it and bolt on a 4bbl set up. Theres nothing better then hearing the 4 bbls open up at 3000 rpm when you mash the gas and leave 40 ft of rubber

But thats just my opinion

Ed

Theres nothing better than an armchair hot rodder He obviously put the 2bbl on there for a reason "Duh what he wanted" bet he beats your gas mileage

[400smb_s10]

Yes thats for sure but you still cant beat the sound of 4bbls opening up when you smash the gas and 40 people are watching you smoke the tires off that 390 ford I have no beef with 2bbls I used to have a 1984 ford branco with a 302 with 2 bbls and YES it was stupendisly great on gas Untill it rotted out the frame and I had to can it for a street vehicle.. I welded the frame put a 4 bbls intake and carb on it and jacked it up and put 44 inch swamper boggers on sold it as a non road werthy vehicle to my buddy for $9000 and hes won many many mud drags/bogs with it. I miss the old truck because I could put 50 bucks in gas in it and it would last me a week and a half but now Im hooked on my new truck a 1978 chevy stepside with a 400 sbc pushing 425 hp with super 40s on it oh my gooses I think I love it more then my girl friend. I dont even turn on the radio when im on a long drive just listen to the 1 5/8 headers straight into super 40's then into 5" blue chrome tips

anyways thats my .02 cents

Ed