I have an 85 F150, 300 inline 6, single carb, 4x4, 4 speed manual trans old farm truck. I purchased it a year ago and spent time getting through Maryland state safety inspection, 2 attempts. I have now failed Maryland Emissions test for the second time. At first attempt the HC was 630 and CO was 6.47, state standards are HC-220, CO 1.20. I replaced the air breather, PCV valve, 2 rusted vacuum tubes, checked the EGR valve, cleaned and gapped the spark plugs, attempted to re-set timing(?), adjusted idle and adjusted the air/fuel mix. Results of second test are HC 1246 and CO 6.72. Obviously I have a problem and do not know where to start. Any and all suggestions would be greatly appreciated.

 

Your engine has a computer, you need to treat it just like it was a newer car or truck with fuel injection. The first thing to do is pull the codes from the computer. See what you get. Obviously you already know you have a EECIV system from your title on this thread, so try and use those methods to pull the codes.

To set the timing you need to find the wires leaving the distributor, in the group leaving the dist there will be one that is sort of by itself and it will have a jumper plug in it, or just a disconnect. You need to disconnect this plug and then you can set the timing. Taking this plug loose will take the timing control away from the computer so you can set the base timing. It will tell you this on your radiator sticker. The sticker will also say something about the spout. Once you get it set with the light, you plug the connector back in and the computer takes over again.

Just like a later fuel injected engine, everything has to be right on your truck or bad things will happen, and it will be hard to pass.

 

Assuming the truck was subjected to a tailpipe test (pre-OBD II)...is the catalytic converter still in place? If so, they do break down over time. If it's original, that's been a loooong time.

 

As Franklin said you need disconnect the spout before setting the base timing.

The high HC and CO is an indication that the truck is running rich (too much fuel)

The high HC is unburnt fuel in the exhaust and the CO is from incomplete combustion due to excessive fuel.

Follow the factory manual for setting the Idle air this will likely require a vacuum gauge.

Replace the O2 Sensor a failed or partially failed O2 sensor will lead to a rich condition, they do not last forever.
Make sure the timing is correct if the timing is out it will also lead to a rich condition.

Replacing The rusted out vacuum tubes sealed up that vacuum leak, that alone would increase HC and CO emissions as the extra air they were allowing in to the engine is now gone making the Fuel air mix richer. I would recommend using a high flow PCV valve from a later 460 application it may help reduce the HC and CO but at the cost of raising NOX. If they do not test for NOX then no issue.

There are tricks to fool the testing for HC and CO if NOX is not tested for.
Your truck is running rich so it needs to be leaned out.

Readjust the timing, replace the O2 Sensor, install a high flow PCV valve, set the carb as per the factory procedure, make sure you have a free flowing air filter and that all emissions equipment (ported vacuum switches diverter valves etc) are working as they should be.

As WhatsAChevy stated the Cat may be starting to fail. But I would leave that as a last resort if you fail it again. If you get a large after market cat it will pull the numbers way down. The closer you can get the cat to the exhaust manifold the better.

Regardless a properly tuned engine can actually beat those numbers with out a cat.

 

It was in fact a tailpipe test and I believe the catalytic converter is still on the truck. The print out from the testing facility states that the Catalytic converter passed.

 

If this is pre-OBD how do I find out what the computer is telling me? How do I pull the codes?

 

The test results does not mention NOX at all, so I presume they do not test for it.

 

It means they did a visual inspection and yes, you have a catalytic converter installed; they can't tell you if it's doing its job or not.

You have an OBD-I system, here is one write-up on pulling these codes:

Ford Ranger - Testing EEC-IV Equipped Engines

 

I Never could do it this way and not lose track of the sweeps, kudos to those that can .

Alternatively you could grab your self one of these guys.


Product Detail


I have had one (the 2 button one) for over 20 years still works like new. It sure makes the job of pulling codes super easy.

 

Here's another site. Plenty of info on the net, especially with the older mustang guys messing around with their cars.

EEC IV Self Test hookup

 

If it still has the original carburetor, the accelerator pump diaphragm may be ruptured/bad.
This will cause gas to dribble into the engine while it is running and cause a very rich condition.

 

I think you should post pictures of what you have. It is VERY common for these trucks to have had the "emissions junk" removed by a previous owner. The EEC-IV controlled feedback carburetors are especially prone to this fate. If you do not have ALL of the original components in place, you will never get your truck to run correctly or pass emissions.

 

[QUOTE=LARIAT 85;16580927]I think you should post pictures of what you have. It is VERY common for these trucks to have had the "emissions junk" removed by a previous owner. The EEC-IV controlled feedback carburetors are especially prone to this fate. If you do not have ALL of the original components in place, you will never get your truck to run correctly or pass emissions.[/QUOTE


I hope these pictures will help determine if this original equipment. If you need different angles or other areas let me know. Thank you very much for your time and assistance.

 

I went to the site you suggested, the one above. My truck does not have a check engine light. Where do I find the multi-pin plug so I can use a meter to check for codes?

 

It should be mounted on the Fender under hood. If I remember correctly drivers side closer to the fire wall. It will look like this. See Post #5
https://www.ford-trucks.com/forums/1...or-obd-ii.html