I am banging my head on the wall and sucking down the Capt Morgan with this. Hope someone can give me some help. BACKGROUND-'77 Mav 250 with A/C and AT (not Calif) came with an '81 Motorcraft 1bl carb and vac lines that someone really had messed up. The carb was leaking gas, because they obviously tried to rebuild the carb, then used sheet metal screws to hold the bowl top and bottom together because they lost the original screws. I bought vac hoses and a newly rebuilt Carter YFA 1bl carb. I want to restore the car as stock. I haven't run across the '77 Ford tech service manual, so don't have much except a Chiltons Maverick book to go on. Vacuum Lines-They also butchered the vacuum lines and had them at all the wrong locations. I used Marks Maverickcomet.com site with his Mitchell 1977vacuumdiagrams.pdf to verify and route the vac lines right. I don't have the wide open throttle valve or a mount on the front that it shows, so I put a three-port tee in between line that runs from the 2-port PVS valve(top port) to the EGR Valve. The third port of the tee in this line goes to the venturi port on the Valve Cover side of the Carter YFA (new rebuilt)carb. The bottom port of the PVS valve runs to the passenger side bottom port of the Carter YFA carb(right above the EGR plate). All other vac lines run according to the diagram, although the 3-port connector on the firewall may have those hoses run the wrong way. Mitchells diagram doesn't show those. Timing-I advanced the timing from the emissions label 6 degrees BTDC to about 10 degrees BTDC. This was to accomodate the fuel difference today and the old engine. Not sure whether this would cause the problem, but I had more success trying to start the car this way. Carb-I have the idle mixture screw out about 1-1/2 turns. The curb idle screw is out about half way. Fast idle-the linkage from the tranny that has the adjustment screw doesn't come close to the carb for it to even touch. Carb has electric choke. PROBLEM-When I depress the gas to the floor and release it, the car will turn over but not attempt to start. I have spark at the spark plugs. If I pump the gas pedal fast and furious, the car will try to start but will not idle. Instead, it seems to spray gas out of the carb(kind of like a carb backfire without the fire). I want to get this car to start nice and easy without a lot of trouble. Can someone give me some areas to check or some changes to make?
First off, was the car running before? Sounds like you might have a massive vacuum leak still. Make sure all your ports that aren't being used are plugged off and double check all your lines and where they go to. If this thing wasn't running before and it seems to want to start by advancing the distributor, try bumping it a little further and see what happens. This could indicate a timing chain that has jumped a tooth. Check all your plug wires and firing order. All of these issues can cause a spitting of the carb as indicated. Hope this helps.
If the fuel is spraying out of the bowl vent, it could be the float, either sunk, stuck or not adjusted properly.
answer OK. This is an easy one.. Timing chain, timing chain, timing chain.... Every thing you stated is cam timing related. I have ran into this many times. if it were distributor timing problems you would most likely get a massive, flaming backfire. The people who worked on it before probably thought as you and did all that work trying to find the problem.. Hope this helps you and good luck....
The car was started and running before with the other carb. The dist. timing was set way advanced when I put a timing light on it at the start of these problems. I moved it back to close to normal so that I could adjust the carb idle mixture and curb idle. Firing order and plugs/wires are correct. All vac lines are connected according to the Mitchell diagram and others are plugged if not listed on the diagram and if I couldn't determine from the Chiltons where they should be. So if the timing chain needs replacement, how tough a job is it on the 250? How do I check it or do I have to go through the replacement teardown just to check it? Thank you in advance for your help! I really want the car running for the summer, as I garage it in the winter. TeenMav
timing gear How difficult depends on your skill level.. but on a 250 it should be pretty easy. if you can follow a manual for your vacuum routing you can follow for a timing chain.. you will need to remove the timing cover on the front of the motor. this usually requires a pulley puller for the harmonic balancer. once you have it apart you can check your timing marks to see if they line up. Now remove the center cam bolt and remove the top and bottom gears and chain. ( you will get new ones in a kit) Now get your new ones and put them on... be very careful to get the marks lined up!!!!!!!!!!!! Or you will have the same problem and will have to redo all your hard work.. Now everything goes back together in reverse of your tear down. pay special attention to your gaskets and seals. don't want any leaks to ruin your garage floor . and fire it up...:bananaman wish I could be more help but I have confidence in ya more q's tomeriker@yahoo.com
might i suggest..that if you think it is the timming..don't keep turnimg the motor. i don't know about the valves on the 250 but on some motors you can get the timming out so far that the valves will hit the pistons. we don't want this to happen. replacing the timming chain and gears is not a bad job...think of it as "bonding with your car"...frank...
Cant you just run the first cylinder in the firing order up to tdc on the compression stroke and verify timing on the balancer and dizzy? That would at least give a rough estimate on whether you have jumped a tooth or not without having to tear the engine down. I use a long skinny screwdriver down the spark plug hole on 302s to help me find TDC. Not sure if you can do that on a 250 though.
If you are blowing gas out the carb then it has to be the timing chain. You have cylinders with the intake valve open while the cylinder is on the exhaust or compression stroke. If you don't want to remove the valve cover just do a compression test on all the cylinders. Otherwise ... take the valve cover off and verify that at TDC on the compression stroke both valves are fully closed. This is a little tougher because you have to follow the firing order and verify all the valves. I put a new timing belt in a pickup truck once and had the timing off by a couple of teeth. When I did a compression test some cylinders had decent compression and some had 0 compression. Vaccuum lines shouldn't be a concern. You can actually block them all off and engine should run. Are you postive the carb is fully seated with a new gasket?
Based upon what has been explained, I'm going for the timing chain kit and doing it. Autozone had it for about $79 and add a puller for $15, it's not enough to worry about spending. With the mileage that this car has, it is probably good to change it anyway. I'll let you all know how it turns out. Ralph
