While doing a little off-roading today, my truck died - stalled. The only way I was able to get it to start was to remove the top of the airbox, put my hand into the AFM, and manually hold the air gate there open while my friend started the truck. It will only run with something holding the air gate open, and even then it idles around 500rpm and blows a little black smoke. Has my AFM died? Is it getting the right signal, but just can't open? Is it getting the signal to stay closed? Any ideas would be helpful. The engine cranks fine, and when the AFM is not manually held open it will turn over for about 2-3 seconds then die. I tried disconnectinf the wires to the AFM and starting it, same thing, it turns over for about 2-3 seconds then dies.

 

I'm betting that you have a leak somewhere between the afm and the throttle body. Possibly a crack in one of your intake hoses. Or one of the hoses may have become disconnected. Inspect them all thoroughly.

 

Checked and re-check and re-re-checked all the hoses, they are all in good shape and connected to where they need to be.

 

creeve, that flapper is what controls your fuel pump. As suggested above, the most likely cause is a lack of vacuum in the intake that results in that flapper not opening... I've never actually messed with one myself, but does it seem to open easily? Maybe pick up a used AFM if you're sure it's not a vac issue.

 

The flapper does open easily, I took it off and cleaned it up really well. Tomorrow I will go through and check all of the hoses connected to the intake (not just those between the AFM and the intake). I am really hoping that it is not the AFM, I don't want to fork out the $$ for a new or used one.

 

Here's instructions to test the AFM.

http://personal.utulsa.edu/~nathan-b...92volumeai.pdf

 

Fuel pump test jumper will bypass that part of the AFM until you can fix it:
- http://www.4crawler.com/4x4/CheapTri...shtml#FuelPump
- http://www.4crawler.com/4x4/CheapTricks/AFM/index.shtml

 

The AFM is still necessary for proper fuel metering. I suppose that it could be a switch failure..

A used AFM shouldn't be real expensive.. I think I sold my last one for $30-$40.

 

Thanks for all the help! I'll will recheck all the hoses this afternoon. If they check out ok, then I'll get an ohmmeter and test the AFM. If it checks out ok then I will try the fuel pump jumper bypass.

 

Recheck all the hoses, they are good. Tested the AFM and it is good. I put everything back together and it started right up and runs beautifully. I did the ISR mod a month or so ago and I believe that while off-roading the engine got hotter than usual, causing the rubber tubing between the AFM and the pipe to the throttle body to heat up and loosen, thus eliminating the vacuum that should exist there. Next time I drive a long distance I will tighten the bands on the rubber tubing while it is hot, to make sure they stay tight.

 

Learn now to use a DVM, get an FSM and check the AFM. Worth any implicit headscratching.

Hmm... appears you did that... good work...

 

I got one off an 88 I will sell you for $30 +shipping if you need it.