Bronco won't start

[Bronco Brian]

RJM Wire Harness with a 5.8 (351)

Loaded the Bronco up to take a trip to the coast pulled it in front of the house took a shower go to leave and she would not start.

Always before would turn the key and the fuel pump would run for a few Sec. and stop. Now it just runs till you turn key to start let key off to run and no pump. 42 Lb of fuel presure have spark (will run with a shot of starting fluid but won't stay running) Checked for a injector pules and am not getting one. Checked all the relays and they are good even swaped in a few new one to make sure. anyone got any ideas

Brian

[1968u15]

Re: Bronco won't start

Just a thought, does the ecu have an aftermarket chip installed? I have seen dirty connections at the j3 port cause this. Otherwise check your ecu grounds, there is likely more than one. What year is the ecu?{ note,this is my first reply, just trying to help.}

[Bronco Brian]

Re: Bronco won't start

Just a thought, does the ecu have an aftermarket chip installed? I have seen dirty connections at the j3 port cause this. Otherwise check your ecu grounds, there is likely more than one. What year is the ecu?{ note,this is my first reply, just trying to help.}

No chip, Grounds should be good but I will check them

[Daddy4zack]

Re: Bronco won't start

Power to the pumps? sounds like just start , and not constant 12V. Hot wire it?? Just for trouble shooting..

[crawlin68]

Re: Bronco won't start

I would run the trouble codes from the ECU first. You could guess all day long and never find the problem. Let the ECU do the thinking for you.

[1968u15]

Re: Bronco won't start

It is normal for the pump to turn on for a few seconds then turn off if the key is not set to crank, this action helps to prime the lines so there will be adequate pressure for the injectors at start up. The ecu keeps the fuel pump relay energized while the engine is running, it needs to receive a signal from the distributor to do this. This signal also allows the ecu to control the injectors. Will the car self test? I believe there should be grounds for pins 20,40,60 on the ecu. Double check your manual/harness instructions.

[tim]

Re: Bronco won't start

try pulling the spout plug/wire at the distributor and seeing if it starts.

[NorcalKD]

Re: Bronco won't start

Check the 4 fuses right next to the relays near the battery tray. I believe one is for the fuel pump. I have had a ground out and had similar issues. I believe its one of the 20 amp fuses the was blown. I fixed where it ground out and replace the fuse. It was good to go.

[Bronco Brian]

Re: Bronco won't start

power and grounds at the computer are good, with key on ecm has source voltage and while cranking. the injectors have 12 volts with key on, but the computer is not pulsing them. it has spark. the tps has power signal return and ground, all check out fine. the fuel pump runs constant with key on will not turn off, once i start cranking the fuel pump stops running, but sometimes it will run during cranking. tried unplugging the ect"coolant temp sensor" still no injector pulse.

[DirtDonk]

Re: Bronco won't start

I'm sure there are plenty of checks (did you check for codes?), but maybe try swapping in a new or other known-good TFI module.
Since the ECU gets it's cranking signal from the TFI, perhaps it just failed?
I don't really think that would cause the pump to stay running, but it's a direction to go next anyway. And besides, even though I don't like throwing money at a problem without first doing tests, having a spare TFI in the truck should be SOP anyway.

Good luck.
Sorry 'bout the lost trip.

Paul

[1968u15]

Re: Bronco won't start

Any luck yet? If not here are a few things you might want to check. Your grounds should be on pins 16,20,40,and 60 of the ecu. If those are ok and your power wires are ok, pins1,5, 37,57, then I would check for codes. If ok(code11 or 111depending on the year) Then you may want to check your crank sensor/speed signal. No codes returned and your ecu may be damaged. Your crankshaft position signal is on pin 56. Voltage between this wire and pin 16 should be between 3 and 6 volts while cranking. If you have a small scope you can check the wave , it should be a square wave. No voltage and the wiring has failed or the tfi has failed. High voltage, check for a short to power. A proper signal means your ecu is likely damaged. The tfi module will run the coil without the ecu. It only needs the ecu to modify timing, thats why you have spark. I hope this helps. Good Luck.

[Bronco Brian]

Re: Bronco won't start

Any luck yet? No work has gotten in the way The tfi module will run the coil without the ecu. It only needs the ecu to modify timing, thats why you have spark. I hope this helps. Good Luck.

Would the spark be weak?

[welndmn]

Re: Bronco won't start

It's either the TFI or the PIP, it your injectors are. It firing, those are the most common.

[Bronco Brian]

Re: Bronco won't start

Pulled the ECM pin #1 stayed in the Wiring Harnesses looks like it melted off. Also found my Tach wire uncaped and bouncing around

[1968u15]

Re: Bronco won't start

Pin 1 is for keep alive power. This is the computers adaptive memory power and must be hot all the time. This should also be dedicated power, nothing else on that circuit. This is a low load circuit but it must have clean power. If memory serves me correctly there will be no start if this is disconnected. Did you ever get a chance to run codes?