To be honest I've been lurking around and posting here and there, but I've finally decided to ask a question....

I have an 1983 F150 XL 351W. When I bought it the themactor pump was not connected so I have since removed it. I have flushed the transmission, changed the oil and seafoamed (vacuum system, oil, fuel) with good results (as well as brakes, 4wd hubs, bearings, brake booster etc). My question is that at times it is hard to start. When it's warm it turns right over, but when it is't not it can take a few tries to crank it over. Once it is going (cold) it idles rough and then dies when I shift it into gear. Once I get out of the driveway and getting moving forward there are no longer any problems until I have to start when cold again. Further it actually seems to start better when the ambient temp is a little chilly say ~50-60F rather than 70-80F. Any thoughts? I'll add that I know just enought to be comfortable working on the truck, but not enough to figure stuff out (mostly with the chiltons manual).

Thx for any help.

-Steve

 

For what its worth I'll add that when I put the seafoam through the brake booster line it only bogged down the engine a little and didn't kill it (I acutally added 1/3 bottle pretty fast, so I was quite surprised it didn't die). I've also been told you can slowly pour it into the intake, maybe I'll try that next time..

 

A few things to add here. First, for your hard (cold) start problem - Assuming you have a stock carburetor inspect the vacuum system. Sometimes an old vacuum line can dry out and cause a leak. if its cold the tube is sealed because it's contracted; if its hot, the metal it's sealed against is expanded. For the seafoam issue - the videos posted on the Seafoam website are shown with a 4cyl car. As you have 8 it will take a larger amount and a faster rate of flow! Hope this helped.

 

Yes stock carb. I was thinking it was a vacuum problem, but now that someone else has suggested it I'll start poking around there. Thanks for the help.

 

Had that problem with my 85 F150, same problem, turned out to be a ruptured power valve, changed it now it runs just fine. My pickup has a 2bbl. carb so I expect youres is as well. This is just my input.

okie

 

Yes 2BBL carb....but I have to plead a little ignorance here, what is the power valve and how do I check it? I have looked at most of the vacuum hoses and they seem to be in good shape (checked the few that were previously blocked off and re-checked the ones I blocked off removing the smog pump). The EGR valve looks a little questionable, but I'm not sure how to check it.

 

The power valve is located in the fuel bowl and is unlikely to be your problem if the engine runs normally when warm. It essentially an enrichment valve that provides extra fuel when the engine vacuum drops (on acceleration) to a particular level. You might also check the way your choke pull off and fast idle screw are working. A very small vacuum leak may be related to the cold start problem. Before making these adjustments, it is presumed that you ensured that the choke plate and coil are functioning properly - the bimetallic spring shuts the plate when cold and gets heated to open the plate as the engine warms. In essence, if you pump the pedal once (when fully cold) the choke flops completely shut and one or two pumps should normally be enough to start the engine within a couple of cranks. Once the engine starts, the choke pull-off retracts the choke plate a very small amount to allow the appropriate amount of air and a very small press on the accelerator will allow the fast idle screw to drop to the correct tooth on the fast idle cam. Combined with the slightly open choke plate this should give you a fast idle. As the engine warms, the plate continues to open, the fast idle cam drops to where the fast idle screw has no effect, and the engine runs normally. Typically, these adjustments are totally screwed up since nobody wants to spend the time to set them up properly. More often than not, the choke plate/spring are simply cranked wide open because doing it right requires a degree of competence combined with patience. The result is the problems you describe. In reality, the cold fast idle can only be adjusted on a totally cold engine (sits overnight) and that has to be accomplished within about a minute. By then, the engine is already too warm and any further adjustment will be an approximation - and you will only know how good that approximation is the following morning when you try to start the engine cold. The whole thing is a fine balance, as engines all differ - you have to fine tune the amount the choke plate is pulled open *and* the fast idle screw. For the choke pull off to work, it must receive vacuum, so you need to ensure that a proper vacuum source is feeding the pull off. Once you know that it is getting vacuum, and if the diaphragm on the pull off is good, you adjust the setting by bending the pull off rod (some carbs have an adjustment screw - but not many). The fast idle screw is usually hard to get to and that is the adjustment that takes the most fine-tuning. Carburetors will never equal fuel injection for starting, but they can certainly be set up to work properly if you want to spend the time to do it right.

 

A very good write up by Tranas, perhaps a little to indepth for Scuba with his admitted limited experience. Have a question for Tranas, what is "", fast&quot" or what ever it was?

Back to Scuba the power valve is part of the carb. Its located underneath the float bowl, carb has to be removed and turned upside down. Small cover with four screws, beneath that is the power valve. These parts are all included in an overhaul kit along with description and pictures of the ckoke linkage, adj screws and pull off. Its a good carb and excellent to get aquainted with. As Tranas said, patience is good.

 

Great write-up it will just take me a while poking around to fully wrap my brain around it. I am fairly comfortable working on small engines (lawnmowers and such which are obvisouly much simpler) and don't have any issues tearing into a larger one however it's the little things that I don't fully comprehend...yet.

How fast should the choke begin to open? It seems to open much faster than I would expect. Usually full open within a minute or two (as soon as the engine starts it begins to open). Also when cold how closed should the choke be? Haven't actually measure it, but full closed it's looks like a gap of about 1/8".

I haven't yet played with the fast idle setting. I didn't want to start actually changing things that may be potentially unrelated causing other problems. So I'll check this next. As this is my project truck I have plenty of time to be patient.

NOTE: It takes a few cranks and pumps of the gas to get it going and once going seems the RPMs seem to hunt until warm. I should add that once I'm in drive applying the gas the problem sems to go away: I let it warm for a minute or so in the driveway, back out, may die in process, but luckily I'm not on a busy road, shift into drive and then gas out to get going.

 

I know some question my knowledge, but after 30+ years working on automobiles I do have a little insight as to solutions to problems. I also have personally performed this repair to two (2) seperate ford pickups with this problem simply by replacing the power valve. The symptoms were exactly the same as you have described on your vehicle. I pass on my knowledge to assist others in their quest for answers & never question others input.

okie