Hi Everyone,
My 80 F250 has a problem when first giving it some throttle.
When the throttle is depressed the engine stutters and tries to stall (usually successfully) unless I pump it quickly to keep it running. It makes normal driving almost impossible because as soon as you try to drive away from a dead stop the engine will try and stall.

I suspect the EGR may be bad. Would this account for the type of problem I am having? The engine starts well enough and idles decently (once warmed up a little) but that first little press of the gas pedal makes it try to stall. Once you get past the initial acceleration it seems to do OK.

Help?

 

sounds more like your carburator needs rebuilding. Specifically the accelerator pump. If it were the EGR, then it would be running really rough all the time and wanting to die. Thats if it were stuck in the open position....Has the carb ever been rebuilt?


DB

 

I do not know if the carb has ever been rebuilt but I doubt it is in the greatest of shape. I just have a limited amount of time and money to work with and have no experience with rebuilding or adjusting carbs so I HOPE that is not the problem.

I read about how to test the egr valve by pulling the vacuum line and sucking on it. Unfortunately it appears that it is indeed bad according to those instructions. I just did not know if the egr would be the cause of the hesitation problems.

Last summer the head gasket blew out, the engine overheated and it bent a valve. I pulled the engine, replaced the valve and the oil seals and put it all back together with new gaskets. It seems to run well enough now except for the hesitation when trying to accelerate. When I say well enough I do not mean it runs great but it runs as one would expect a beat up old truck to run.

I have been trying to locate info on how all the vacuum lines are supposed to be connected on this engine. The truck has seen much abuse in the past and things under the hood are not all as they should be. My cheapo Haynes manual does not show me how all of the vacuum lines are supposed to be hooked up though and in the past someone has stripped out most of the emissions controls so I do not have a solid foundation in how this is supposed to be working as a basis to diagnose what is going wrong now. It has reached a point though that I have no money to spend buying manuals or replacing parts not knowing if that part will actually resolve the issue at hand.
I would love to get it running well enough to sell and then use what little I get back to put into getting my 60 F100 back together.

Even after I get the engine running in the F250 it still has bad ujoints and I just do not have the tools or facilities to do that kind of a job at home.

 

Egr's can fill up with carbon. My expierence is with an old dodge minivan. Chiseled it out with a screw driver. But I didn't expierence any hesitation problems.

 

aight...when you say that you checked the EGR by sucking on it, do you mean by using a hand vacuum pump and doing a leak-down check on the diaphragm?


Aight...here's the deal...one of my dads older tricks that I don't really like to brag about. It seems kinda harsh...but I have seen it work too many times to not believe the magic there....

Take a decent sized screwdriver....don't matter if its slot or phillips....and tap MODERATELY on the float bowl....on the bowl and not any of the parts sticking out anywhere....It especially helps if its running at the time....tap a few times and goose the throttle. don't do it too much, though. I will have to set up my scanner at the house, but I will try to send you a vac diagram, okay?

DB

 

You could try the fuel pump to see if it has enough pressure going to the carb. I would also try the fuel filter, it cheap and easy to change and will affect performance if it's dirty.

 

I would try the air filter and check for restrictions in the EGR lines to and from the carb as well.

 

I had found instructions on this site for testing the egr. If I remember correctly it was with the engine idling. I pulled the vacuum line to the egr and sucked on it. The post I read indicated you should not be able to freely pull air through the EGR if it is operating correctly and it had no resistance letting the air go through so I assume it is a bad valve. I do not know if that is the cause of ALL of my problems though.

 

Air filter is not a problem there is not one in it currently.

I am not certain all vacuum lines are in their correct positions and there are locations that seem to be missing connections so I am hunting around for a vacuum diagram to make sure everything is setup correctly. One of the previous owners yanked out some of the emissions controls and things are kinda mixed up under the hood and I am trying to make certain everything critical is connected and everything else plugged but have not identified it all yet.

 

How would I go about testing the pressure from the pump? I assume I would need a special tool for the purpose. I should probably pick up a vacuum gauge as well but there are so many things I SHOULD buy and so little money at the moment.
I am a mechanic of necessity rather than of interest. I guess it would be different if I were working on a vehicle as a hobby and that I cared about and could spend the time and money to do things correctly rather than just trying to keep something running so I had transportation. I get kind of depressed that I have 4 vehicles and not one of them is reliable at the moment and that I do not have the necessary resources to make any of the reliable.

I have my 1960 F100 that I planned on spending a lot of time rebuilding and customizing but my plans keep getting cut back out of necessity and I have to do things like getting junkyard engines and trannys for it rather than doing it right and making it like new. Compromise sucks and it keeps leading to other problems and then I get discouraged and find it hard to even continue working on it.

 

niteowl I am having the same problem that you are om my 1980 F250 has anything worked on yours yet. Just thought that I could learn some lessons from all of your hard work. Good luck.

 

I have not spent any more time working on the truck. I am still looking to find information on how all the vacuum lines are supposed to be connected.
Rather than just having normal problems they are complicated by the fact that so much has been altered on the engine before I got the truck that troubleshooting is difficult.
I suspect a vacuum leak may be at fault. I know the EGR is bad but from what others have stated here, my symptoms should not be EGR related.

I had this problem prior to tearing the engine down and replacing the valve and head/intake gaskets but it seems to be much worse now.

Maybe the vacuum advance is not working or I have a bad seal at the carburetor. Not sure of anything at this point.
If you have the same setup maybe pictures of your setup would help me in diagnosing my own or at least help me to eliminate some possibilities and between us we may come up with a solution.

 

Niteowel
Hello My name is Steve
I had the same truble that you are having. In my case it was a 460 in a Marquis, It sat for too long and the carb was gummed up very bad. It would idle rough and when you gave it some gas it would try to die, give it a little more and it would burn the tires off! lol A new carb did the trick!

I would get a carb kit, reman or new carb. But you said you would like to sell it I would go with a reman or the kit.



Just a note on that! The Marquis had more vacume hoses than wires! And I tryed sucking on a few to get the valve to open and close! NO WAY Needs more vacume than you and I can suck!!! You will have to buy a vac tester.

 

sounds like you need to rebuild your cab.

 

See that was the problem. From what I was told I should NOT be able to pull air through with the engine idling but I was able to pull it through freely meaning the valve was not closing as it should. This makes me wonder if there is a vacuum loss through the EGR since there is no resistance to the air pulling right through and part of the problem.

Several people here have expressed suspicion of the carb and they are probably right. I have to check and see how much a kit would cost to rebuild it. Just afraid that once I get it all together that I will not be able to get it adjusted correctly and it still will not run right and I will not know if it is the carb adjustments or something else.