Smeddy2

Alright, so I'm in the middle of checking all sorts of stuff trying to figure out my surging idle problem. I tested my AFM a while back and it was okay but I figured I'd give it another glance just to be sure. Everything checked out alright on the static test except for one thing. The E1-FC resistance did not read infinity. It read at 0.97 ohms (or k-ohms...I don't remember what setting I had my multimeter on). Well I came back to 4Crawler's test procedure and it looks like that is the circuit that controls the fuel pump. I am confused because I figured that if there is any continuity in that line with the AFM closed, that would mean the fuel pump would be running all the time. Any body know the electronics better than me that could explain my reading? Could this be why my engine won't idle smoothly? I can't even get it to idle smooth to check the timing with the jumper in.

TNRabbit

With AFMs, many find it requires changing out with a known good AFM to verify. You SHOULD be able to test for it, but that's not always successful.

As far as infinity, the computer is looking for a specified range of resistance. As long as it's in that range, it should function properly.

However, there are SO many things that could affect idle....could be that or a host of other things including air leak in the intake, clogged injector, fuel delivery issue, timing issue, etc.

sb5walker

If E1 to FC has continuity (say, zero to 100 ohms or so), then that will turn the fuel pump relay "on" to run the pump and provide fuel pressure which, of course, the truck needs to run. That won't have anything to do with idle surge, that just provides fuel pressure. Having E1 FC continuity with air meter closed just means the fuel pump will run whenever ignition is on, which probably won't cause any problems, except you won't have the safety feature of having the fuel pump turn off if the engine stalls while ignition is still on. I think the feature is intended to turn off fuel pressure in the case of a collision.

You could cut the silicone around the black plastic air meter cap and take a look at the fuel pump switch contacts. Probably by bending one of them you could get the switch to work as intended. Be sure to seal the cap back on there to prevent moisture getting in and causing corrosion.