Hi All,
First I an new to this forum and wanted to say thank you in advance for any suggestions provided. I have two main issues at the moment;
I am the proud owner of a 1985 F250 5.8L (351) 4B Holley, 4x4 automatic. I have owned this vehicle for many years and have done quite a bit to keep it alive. I bought it from a friend who was the original owner. The engine has only 65K original miles. My problem is that it is running rich and I have done everything I can think of to get to run leaner without luck. I have had the carb rebuilt both professionally and myself. I checked for vac leaks, etc. The truck starts and runs good and I have installed a manual choke so that is not the issue. The issue is that you can smell the extra fuel at the tail pipe, and the plugs will eventually get fouled after many months. So any other suggestions please shoot them my way.This has been like this for many years.

2nd issue(and it maybe related to the first). cold start is great and truck will run forever. Once you stop it will not start again until several hours of sitting. Engine turns fine but no ignition. Seems to be getting fuel so I can only suspect an electrical issue but I have not ruled out vapor lock. Again not sure and it has progressively gotten worse so it happens every time now.

Let me know your thoughts and thanx in again.
Mike

 

The cold start that you mention is an indication that the mixture is too rich. Are the
factory installed jets in the carb? The factory jetted these 4180s fairly lean. Next check the choke to make sure it is opening like it should. If it sticks it will definitly make for a too rich mixture. These 4180s also have sealed idle mixture adjustments. They can be accessed by pulling/grinding out the plugs and then they can be adjusted with an allen wrench. Some 4180s have idle mixture adjustment on all 4 corners and some have the adjustment only on the primary side. In any event adjust these carefully for the best lean idle by using a vacuum guage. A lot of things can happen to a carb that has been rebuilt several times. If the rebuild was done right the flatness of the sealing surfaces would be checked to make sure the gaskets sealed well. As a last resort check the power valve to make sure it is not leaking as this will cause a overly rich mixture.
Timing and plugs can also play a role a too rich mixture. Check those as well to make
sure everything is in spec.

 

my 84 f150 seems to have the rich running issue as well since I can smell the fuel when running. as far as the not starting after running a while, mine did that too but then I put in a manual choke which you state that you've done, have you tried spraying carb/choke cleaner on it? it may just be a matter of it sticking. just throwing random thoughts out there, a bit of a novice myself, still trying to learn the ins and outs of carbed engines.

 

Well, a vacuum leak would usually make it run lean (unless the vacuum leak is in the carb itself)

Some possible options:

1. Either the power valve is opening too soon or stuck open all the time. If it was blown it probably wouldn't even idle. But if you had it rebuilt twice; you probably replaced it twice. Also if your engine has a big cam in it then it would pull low vacuum, potentially causing the power valve to open during cruise.

2. An internal vacuum leak. If the o-rings for the accelerator pump transfer tube are shot then the vacuum inside the power valve chamber will pull fuel from it. This happened to my Holley. The o-rings were flat. This tube is located directly above the power valve. It has an o-ring on each end so be sure to pull it out of the metering block or the carb itself, whichever it got stuck in.

3. Fuel level too high. It should just trickle out of the side sight hole. Some people set it a little higher though.

4. Clogged/Malfunctioning PCV valve. The carb is/should be set by the factory to account for the loss of vacuum created by the PCV valve. If the valve is clogged or something it is possible that it could cause a slight rich since it doesn't have that leak that it was calibrated for. This is probably unlikely though. I'm just adding it because it's possible and it doesn't even take a minute to check.

5. If none of the above fixes the problem, drop the main jet size. The jet size of Holley carbs are calibrated for sea level. This may not be true for factory trucks though.

 

Have you checked your dizzy? I pulled mine and replaced it and it fixed all my truck problems and I swore it was the carb. Also, for anyone that wonders to remove the idle plugs in the 4180's center punch and then get a drill bit in there, you have two choices. Get one of those screw on struck deals screw it in and then reverse the plug out, or you can just drill it out and then adjust the screw with an allen wrench. I picked this up from my Ford manual.

 

Thank you to all who replied so far. I will take a look at your suggestions and post when/if I solve, for now please keep em coming.

Can you tell me what you mean by a "dizzy?" I am an old school backyard mechanic and have not heard that term or part reference yet.

Thanx again
Mike

 

Distributor sorry, I asked the same when I signed up.