'76 F100 Emmisions
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'76 F100 Emmisions
I have a 1976 F100 that I puchased several months ago. I cannot get it past emissions testing. I have changed the PVC valve and checked the plugs, put high octane fuel in and changed the oil. I've heard that I might need to change the EGR valve, but have not been able to get more specific info on that.
Three things I have noticed, but unsure if they could be a problem with the emissions. 1. The engine is caked in 20 years of oil deposits. When you look under the oil cap, it looks like black sludge. Consequently, when I check the oil, even a week after changing it, it is very dark. 2. I have a leak in the pipe going into my gas tank. It only appears to leak when I actually put gas in the car. once in the tank, it seems fine. This probably isn't a problem, but any advice for this would also be helpful. 3. The oil cap is very loose. It almost lifts directly off.
Any help would be appreciated.
Three things I have noticed, but unsure if they could be a problem with the emissions. 1. The engine is caked in 20 years of oil deposits. When you look under the oil cap, it looks like black sludge. Consequently, when I check the oil, even a week after changing it, it is very dark. 2. I have a leak in the pipe going into my gas tank. It only appears to leak when I actually put gas in the car. once in the tank, it seems fine. This probably isn't a problem, but any advice for this would also be helpful. 3. The oil cap is very loose. It almost lifts directly off.
Any help would be appreciated.
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Joined: Jan 2008
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Welcome to FTE! 
The oil cap can be cleaned or replaced.
Fuel:
The fuel tank hoses on 76's are prone for fuel shoot back due to their design and the fact that the truck box settles over time which can crimp off the fuel tank hose and cause this problem.
Carbon:
I can only assume this engine has been running rich and the wearing out of the internal engine parts is causing this carbon deposits situation.
Here is the EGR system.I also have the Emissions diagram IYNI.
The oil cap can be cleaned or replaced.
Fuel:
The fuel tank hoses on 76's are prone for fuel shoot back due to their design and the fact that the truck box settles over time which can crimp off the fuel tank hose and cause this problem.
Carbon:
I can only assume this engine has been running rich and the wearing out of the internal engine parts is causing this carbon deposits situation.
Here is the EGR system.I also have the Emissions diagram IYNI.
Last edited by Mil1ion; Jun 24, 2006 at 12:05 PM.
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Joined: Jan 2003
Posts: 312
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From: Huntsville, AL
If you think you want to troubleshoot your EGR there are a few things I would examine. I just went through getting my EGR on my 73 to work. First, to see if the EGR is working, take a vacuum line from the intake to the EGR, increase/ decrease the throttle if the shaft in the EGR moves up and down in correlation with the throttle your assured the possiblity the EGR can perform once you get the vac routing in order. Then I would check the condition of all vac lines and their routing according the diagram. Then get a vac guage and check the vac at the base of the carb, the vac advance on the distributor and the 2 ports on the PVS Valve (ported vac switch). The PVS was the culprit on my system. Once replaced the EGR worked properly.
You may be missing some emissions parts as people tended to remove these items. If you look at the EGR set-up for the earlier models (1973), the only parts in the system were the EGR valve and PVS. Some of my original parts had been removed but I used the EGR set-up for a 73 Bronco with the same engine configuaration as my truck.
The EGR may not be the answer to your problem(s) but it might help combined with other improvements. Did you change the oil breather filter in the air cleaner and/or the air filter?
You may be missing some emissions parts as people tended to remove these items. If you look at the EGR set-up for the earlier models (1973), the only parts in the system were the EGR valve and PVS. Some of my original parts had been removed but I used the EGR set-up for a 73 Bronco with the same engine configuaration as my truck.
The EGR may not be the answer to your problem(s) but it might help combined with other improvements. Did you change the oil breather filter in the air cleaner and/or the air filter?
