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Old 05-27-2013, 09:23 AM   #1
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My Ford 7.5 carburated motor is running rough

I checked all the plugs and found one on each side wet, cleaned them all up and reinstalled them and it started right up but ran a little less rough. it is still misfiring a tad,
The motor has new oil, new plugs, new filters I have NOT changed the distributer cap or the plug wires, the cap is almost impossible to get at and the wires look new, waddayathink guys???
Anyone have the firing order?? and can someone tell me which is the number one plug and how the rest are numbered, I do not have that info.
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Old 05-27-2013, 12:45 PM   #2
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Changing the cap, rotor arm and plug wires would be my next step. It's several years since we had a 460, which was an '85, but I think #1 plug is the front starboard side. The smog gear got pretty complicated in the late 80's, so there may also be problems there.

Since you're getting wet plugs, (if its fuel wet, not oil), there may be a blockage in the fuel overflow line. I was surprised to find that on my rig. It takes excess fuel back to the tank from the carb.

I'd suggest getting a shop manual for one of the big Ford cars of the same year as your RV (Crown Vic, Mercury Colony Park, LTD) that had the same motor. That would have the #1 cylinder identfier and firing order.
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Old 05-27-2013, 09:52 PM   #3
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Is carb. Holly, motorcraft or bendix?
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Old 05-28-2013, 03:28 AM   #4
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i am working on one of these my self, first finish the tune up, make sure your choke is opening all the way and the air valve in the snorkel hose is open.
check your vacuum advance to make sure it works and is on ported vacuum
this is very important, i just put a re-manufactured carb on mine and hooked the vacuum to manifold like i do on my chevy's and it does not like this.
check for vacuum leaks if none you may need to have carb built professionally.
i completely de smogged my rig so i can't offer any advice on that part other then if you can get by with removing the smog equipment it will simplify your life.
also check your exhaust system mine had started to clog up internally was turning blue from heat and restriction i pulled it off and installed a magnaflo
36 inch long 3 inch inlet and outlet all stainless steel muffler on mine and it helped with the power tremendously and the engine runs smoother to boot
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Old 05-28-2013, 06:28 AM   #5
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i am working on one of these my self, first finish the tune up, make sure your choke is opening all the way and the air valve in the snorkel hose is open.
check your vacuum advance to make sure it works and is on ported vacuum
this is very important, i just put a re-manufactured carb on mine and hooked the vacuum to manifold like i do on my chevy's and it does not like this.
check for vacuum leaks if none you may need to have carb built professionally.
i completely de smogged my rig so i can't offer any advice on that part other then if you can get by with removing the smog equipment it will simplify your life.
also check your exhaust system mine had started to clog up internally was turning blue from heat and restriction i pulled it off and installed a magnaflo
36 inch long 3 inch inlet and outlet all stainless steel muffler on mine and it helped with the power tremendously and the engine runs smoother to boot
My smog stuff is all shot and I want to remove it too, What size plug did you use to plug the intake manifold. I am thinking to use brass plugs but they come if diff sizes and diff threads. I am sure there is hose's disconected but it is so crowderd I cannot figure anything out and only the top of the doghouse is removable
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Old 05-28-2013, 11:09 AM   #6
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Old 05-28-2013, 12:25 PM   #7
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Thanks Dave
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Old 05-29-2013, 03:34 AM   #8
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Egr valve will make it run rough and they are real bad about going out?
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Old 05-29-2013, 11:53 AM   #9
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Egr valve will make it run rough and they are real bad about going out?
I have so much useless stuff all over the top of this engine I have no idea where the EGR valve is.
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Old 05-29-2013, 12:06 PM   #10
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By running rough I take it you mean a cylinder is miss firing?
First step is to locate which cylinder. Pull plug wire off distributor cap one plug at a time and see if the missing is the same or worse. Same = problem cylinder. Missing worse (more than one cylinder miss firing) is an OK cylinder.

Once problem cylinder is known possible problems are (most likely to most severe):
Bad plug
Bad Plug wire
Worn Rotor or Distributor cap
Cracked distributor cap
Cracked vacuum hose that attaches to intake manifold in area of problem cylinder
EGR Valve stays open if in area of missing cylinder (carbon deposits on pintle)
Intake manifold air leak
Cam Lifter not pumping up
Burnt Valve
Broken valve train component
Bad cam lobe
Broken piston ring
Hole in Piston

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Old 05-29-2013, 09:43 PM   #11
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before you start de smogging your engine you need to get a repair manual for
it to help identify the various components.
i pulled the egr valve and put a steel plate over the opening left when removed, cut the air tubes off on the back of the heads and flattened them then brazed them shut removed the air pump and hoses and valves removed the extra vacuum lines and re-plumbed so the distributor is on ported vacuum the cab is on manifold vacuum and the trans and brake booster also on manifold vacuum readjusted the carb and set timing to 8 degrees btdc
this will get you in the ballpark
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Old 05-30-2013, 10:22 AM   #12
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before you start de smogging your engine you need to get a repair manual for
it to help identify the various components.
i pulled the egr valve and put a steel plate over the opening left when removed, cut the air tubes off on the back of the heads and flattened them then brazed them shut removed the air pump and hoses and valves removed the extra vacuum lines and re-plumbed so the distributor is on ported vacuum the cab is on manifold vacuum and the trans and brake booster also on manifold vacuum readjusted the carb and set timing to 8 degrees btdc
this will get you in the ballpark
Like to see pictures of what you did for now I want to just want to find the EGR valve, where is it located?
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Old 05-30-2013, 11:09 AM   #13
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If memeory serves me correctly you have downloaded the 89 service manual to use for your JD Chassis. Turn to pdf page 70 (20-05-12) and look at the portion for steps 19-20. That view is on the rear of the intake. You can see a light grey vacuum can (flying saucer like thing) with a hose attached to it (If the line for the A key symbol were extended straight on out to the left it would go through the valve.). That should be your EGR valve. You can also see it in step 18 (between and directly above the A and B key symbols).

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Old 05-30-2013, 01:55 PM   #14
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When I took the air-pump system off my '85, I went to NAPA and asked about air injection port blanking plugs and the counter guy went straight to a drawer and got a packet of 8 of them out. He didn't even have to look up a part number. They were brass with a hex head.

One caution - a friend of mine who worked in Product Development at Ford in the 80's reckoned that the late 80's engines with the dual air-injection system had carbs that were deliberately set to run rich so there was enough unburnt fuel in the exhaust pipes for the injected air to burn all of it off and meet the emission rules. Replacing your carb with one off an older 460 (or even a 429) might be worth considering.

Taking the A-I system off mine didn't improve gas mileage much. While I was thinking about a replacement carb, we decided to sell the clunker.
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