Fuel Pump Not Firing After Rebuild

[IBFJ62]

Greetings gents. I've just finished a rebuild on my 3FE (harmonic balancer went haywire..), and when trying to fire it up last night, it was trying to run, but starving for fuel. I noticed I'm not hearing the fuel pump at the tank start up when I turn the ignition. I'm assuming the pump is fine, the engine ran perfectly prior to the rebuild, so I'm going to re-plug all the connections, just to make sure I didn't miss anything, but it feels like there's just something not connected. Any suggestions to direct attention toward before I start chasing the ignition wiring diagram..? Thanks!

 

[NeverGiveUpYota]

62 has an electric fuel pump? Or your talking the pickup in the tank? Did you try opening up the cover and wiggle the wires at the plug?

 

[unklwedy]

Bang on underside of fuel tank by hand or rubber malet. Might bring tired fuel pump back to life for a short while.

 

[Randy88FJ62]

go to your diagnostics port and wire +B and Fp together. It bypasses ECU and fires fuel pump directly. That will tell you where your issue is.

If you crush your exhaust on a rock and rip the 02 sensor wire then this won't work and you'd have to give 12V directly to the wires going from your driver's real quarter panel down to your fuel pump.

 

[RockDoc]

I believe the pump doesn't get power until the engine is cranking (signal from starter circuit or the vane air flow meter? Can't recall off top of my head.) I would verify no pressure before chasing the pump as the culprit.

 

[Randy88FJ62]

Rockdoc,
I can hear my 3FE pump when the key is in the start position but not cranking. I can also verify that pressure is being built since you can crack a fuel line and gas will come out.

 

[Kleatus]

Rockdoc,
I can hear my 3FE pump when the key is in the start position but not cranking. I can also verify that pressure is being built since you can crack a fuel line and gas will come out.

This is not normal. Has someone wired things up differently? The fuel pump should not be on unless the air flow meter measuring plate has opened (or if you have the test pins jumped). I would suggest digging into the 3FE EFI manual and running the checks on the AFM if you believe everything is still in stock configuration. One reason you don’t want the fuel pump on simply with the ignition is in the event of a crash, the pump could continue to run and spraying fuel out through severed lines (and possibly fueling a fire.) Some vehicles are equipped with an inertia switch that interrupts the fuel pump circuit in the even of a crash for that reason.

As already mentioned, jumping the pins in the diagnostic port should power up the fuel pump and if things are quiet you should be able to hear it run (you’ll also hear fuel gurgling through the FPR.) If the fuel pump works in this fashion, you could have an issue with the AFM or the circuit opening relay or any of their associated wiring.

Sometimes it’s good to step away for a while and go back at it with a new frame of mind and maybe you’ll find that random hose/plug you forgot to hook back up - that’s happened to me a few times.

 

[Randy88FJ62]

hmm. Thanks for the response. I'll look into it.

 

[IBFJ62]

Is it possible to have the cold start injector giving a shot of fuel, but the fuel pump not run? I was getting some fuel, enough to fire and run smooth for a few seconds, then sputter out. If I opened the throttle at all, it would instantly die. I did used to hear a buzz from the tank when the key was in the ignition position, I assumed that was normal since it's always done it. There was fuel at the CSI valve if I pushed in the plunger.

 

[Kleatus]

It’s predictable to have residual pressure in the fuel rail from the previous starting attempt. The cold start injector will not have fuel independent of the injectors, they are fed from the same source.

The first test is jumping the pins in the diagnostic port listening for the fuel pump. The next way I would suggest to test the fuel pump operation is to remove the AFM from the air box (so it can be manually manipulated), install a pressure gauge at the cold start injector (you can get a bolt that goes through the banjo fitting on the fuel line that has a provision for 1/8” NPT for a gauge in the end), and with the ignition on, manually open the AFM Flapper and watch the gauge. This way you are testing the pump, FPR, AFM, and circuit opening relay.

 

[RockDoc]

Is your AFM wiring in place? Could you have damaged the internal wiring in the AFM? (removing the screws to detach the wiring rather than the spring clip...) your behavior matches what I got when I forgot to reconnect the AFM once. The engine catches initially (fuel pump relay on while cranking) but dies a second or two after due to no signal from the AFM to the ECU / no AFM switch power to fuel pump relay.

 

[IBFJ62]

The AFM is my suspect as well. I only had about a beers worth of time after work before I had to head to the little league field to watch a game, but I did jump the +B and fP, and the fuel pump did fire up. I wire brushed the connectors at the AFM, and pulled it to make sure the flap wasn't stuck or something, but didn't have the time to attempt to fire the motor again.

 

[red66toy]

To make sure the AFM is kicking on the fuel pump, unbolt the AFM from the airbox but keep it plugged in still. Turn the ignition on and then manually open the flapper with your hand. You should hear a click and the fuel pump kick on when you open the flap in the AFM.
I need to learn how to read better.

 

[Kleatus]

To make sure the AFM is kicking on the fuel pump, unbolt the AFM from the airbox but keep it plugged in still. Turn the ignition on and then manually open the flapper with your hand. You should hear a click and the fuel pump kick on when you open the flap in the AFM.

Hey Chase, catch up on the conversation!

 

[red66toy]

Hey Chase, catch up on the conversation!

Bahaha, I should have figured you already posted that!

 

[IBFJ62]

So I seem to recall, I'd hear a 'click' in the passenger kick panel from the EFI relay when the key went into the ignition position. I'm no longer hearing that. I'm getting voltage to the EFI fuse in this same key position. Haven't had a chance yet to take the AFM off and try to move the flap to get a response.

 

[IBFJ62]

Ok, so I pulled the AFM and manually opened the flap with the key in the ignition position, lo and behold the relay tripped and the fuel pump turned on. I cleaned the connections and messed around with the gap on the AFM, and I could now hear the relay click when I attempted a start and the AFM flap opened with vacuum from the engine. She fires up for a few seconds fine, then chokes out. I'm pretty sure we don't have a crankshaft position sensor (right??), but it acts like something isn't sending a signal to the fuel pump to continue pumping once it starts. Ideas? Thanks!

 

[pandasfj]

Is your AFM wiring in place? Could you have damaged the internal wiring in the AFM? (removing the screws to detach the wiring rather than the spring clip...) your behavior matches what I got when I forgot to reconnect the AFM once. The engine catches initially (fuel pump relay on while cranking) but dies a second or two after due to no signal from the AFM to the ECU / no AFM switch power to fuel pump relay.

This is what happened to me. I had my cruiser sitting for a month and when I went to start it up, it would just crank but not turn on. It was starting fine before that. I thought I had a bad pump but I was not getting power to the pump. Well I went thru the fsm procedures and ended up unscrewing the afm and not unclipping it, in turn I broke it cuz I was too lazy to pull the fsm and read it. So come to find out I would get 12v at the relay but get voltage drop when turning the key trying to start it and would not get full power at the fuel pump. It turned out to be a faulty fusible link plug. I bypassed the plug and used a new fusible link wire and bought a used afm and everything works again.

 

[IBFJ62]

So, I pulled the service codes and things seem to point to the AFM.

Code 24) - Intake Air Temp Sensor Signal

Code 32) - Air Flow Meter Signal

I'm assuming the AFM isn't telling the ECU to keep firing the fuel pump. The weird thing is that after attempting to start it, I get fuel pressure at the CSV, but I'm not seeing any fuel when I pull the return fuel line. ?? Could the fuel pressure regulator be stuck shut or something?

Update: I took a closer look inside the AFM, and sure enough I had a couple of connections that had broken the solder joints. I tried to reflow them, but now it runs a little longer before choking out. I still get codes for the air flow meter and intake temp sensor, so I'm assuming the AFM is toast and just not telling the ECU what to do..

 

[IBFJ62]

Well hell. Installed a new AFM today, and same damn thing. Starts up, runs for a few seconds, then sputters to a die out..

The codes I was getting are gone, now just a kinda rapid steady flash.

A little pissed off, but what next? Cold start timer switch? Fuel pressure regulator?