Hi , hoping for some help.
I have a 91 4runner 3.0, engine turns but won't start. It does have a small sputter when trying to start. The fuel pump does not go on when key is on, I have replaced the circuit opening relay, fuel pump relay, Efi relay , checked & replaced fuses. But still no pump on at turning key.
I connected B+ & FP at diagnostic , and pump goes on.
Any ideas what else it can be other than the volume Air Flow Meter which does receive voltage.

Thanks

 

The fuel pump does not come on with the key, it comes on when you turn the motor over and air gets past the AFM which triggers the fuel pump. You can test that by opening the flapper valve with your hand in the AFM while the key is on and its connected to the wiring.

 

The CO relay (which powers the fuel pump) turns on with either the AFM Fp contact (when the engine is running) or with the STA signal while starting, likely an issue with that signal wire, the test jumper bypasses that and lets the pump run whenever the ignition is on:
- http://www.4crawler.com/4x4/CheapTri...shtml#FuelPump

 

As far as i know and don't quote me the fuel pump only turns on when you are cranking the motor. Since you already know it will turn on via the diagnostic port you have eliminated the fuel pump being faulty right? Try spraying the throttle body with some starting fluid to see if the engine fires. Are you getting spark? and what do the plugs look like? By the way welcome to YT. Wow that was fast 4crawler and cougar beat me to it!

 

Thanks for quick reply deathcougar, 4crawler, mightymouse.
I do have plenty of spark at plugs, igniter is good.
I'll try these suggestions & get back to you guys on my results.

 

I tested VAF flapper to turn the fuel pump on , it went on but still no start, small sputtering when tryiing to start.
After all relays, fuses, fuel pump works, good spark, what do you suggest to do next ?

Thanks

 

Well, unless you are holding the AFM flapper open while starting, that won't do anything for you. Two real options are to just keep the test jumper installed, I ran my 22RE that way for a few years before the starting problem magically fixed itself. Or you can troubleshoot why the CO relay is not getting activated while starting, either the STA signal is not strong enough or the secondary winding in the CO relay is not pulling in the relay coil and contacts.

 

The way I test the VAFM flapper is to crack the cold start injector line open at the banjo fitting, and push the flapper. If you are getting fuel spraying out of there, then the fuel pump is working and you are getting fuel to the fuel rail.

 

Hey guys, thanks for your help on the fuel pump issue.
Before i decided to take it out, i checked the pressure regulator, and i went ahead & changed the fuel filter. The other issue i discovered was the distributor wiring & some other wiring & i got it running. The guys who worked on this before i did , really did a hack job.
I'm going through everything so i don't have other issues electrically. or anything else for that matter.

By the way, what is the ECT button for ? What does it do ?