I recently did a ring, valve, and new oil pump "job" on a 1988 Bronco II with 2.9 engine. The top end of the engine had been disassembled before I got it. and piled in the back of the truck. I have re-installed the engine and it will run if I squirt gas in the intake but the fuel pump does not run and I don't think the injectors are firing. It appears that I may have a ground problem. I can't find any wires that are not connected however there is a non-stock large wire in the back of the truck that may have been an auxillary ground but I have no idea where it goes or if it is needed.

How can I identify the fuel pump relay (I assume it is one of the relays on the right fender)? Any trouble shooting suggestions will be appreciated.

 

Get a wiring diagram.
In addition to checking the fuel pump relay, check the EEC relay (which feeds power to the fuel pump relay).

 

I'm pretty sure the injectors won't fire if the fuel pump isn't running, and the inertia switch will shut that down as will a fuse. I think (never looked at mine) that the inertia switch (shuts off fuel if you have a wreck) is in a compartment on the wall behind the drivers seat, like the opposite of where the jack is stowed.

 

Thanks guys for the quick reply. I have wiring diagrams (Chilton, Haynes, and a factory Ford but for a 1986 instead of a 1988 but they appear the same in Chilton). The ECC relay (brown) seems to be working OK. It sends power (red wire) to the fuel pump relay. The fuel pump relay does not energize the pump. The yellow power wires on both the ECC and fuel pump relays are hot all the time as the wiring diagrams show they should be. The pumps run when I apply power to a wire at the inertia switch and the wire at the relay going to the pumps will then show 12 volts. If I jump the yellow wire at the fuel pump relay to the pump wires (at the relay) the pumps run. The wire going from the fuel pump relay to the computer shows a ground with the key off and 12 volts when the key is on. With the key on the red injector wires show 12 volts. The truck still will not start even if I jump the yellow wire to the fuel pump wire. I've considered grounding the wire going from the fuel pump relay to the computer but am concerned that it might damage the computer. It doesn't seem like the fuel pump relay is the problem because the truck will still not run even if the relay is jumped. I've checked the ground at the computer and it seems OK. I checked the resistance between the ground wire and the battery ground post and I even ran a temporary ground directly from the batter to the ground wire on the computer. The computer case is grounded to the body. Should it be? If I'm reading the wiring diagrams correctly the computer grounds the injectors and the fuel pump relay to energize them. Is this correct? If so does the computer cause a full 12 volts to be applied or is there resistance in the computer so something less that 12 volts is applied? What happens if I ground the wires going to the computer? According to the previous owner the truck ran fine but the heads were cracked causing antifreeze to be lost. The heads were cracked but were not leaking. The leak was from a pinhole in a freeze plug. The truck has been sitting for 2 years. Could corrosion at some of the terminals be causing the problem?

I'd appreciate any other trouble shooting suggestions. Thanks, Allan

 

You are correct, the computer acts as a ground side switch for the fuel injectors and the fuel pump relay. If you're worried about making your own ground for the fuel pump relay, one of the leads in the self-test connector is a test lead for the fuel pump/relay. It's the lead in the short end of the trapezoidal connector. Just ground that lead with the key on, and the pump should run. From what you describe, it sounds like the relay is bad.

As for the injectors, I didn't see it mentioned, do you have 12V to the injectors with the key on?

 

Thanks Mr. Shorty. I'll do the check for the fuel pump relay that you described. Yes, there is 12 volts on the red wire at the injectors. I hope the fuel pump relay is the problem.

 

Mr. Shorty (and all). Per your suggestions, I just grounded the terminal in the end of the trapezoidal connector. When turning on the key the fuel pump relay clicks, the pumps run, there is a lot of pressure in the fuel rail but the engine will not start. When I squirt gas in the intake the engine will start and run smoothly for a few seconds then die when the gas is gone. There is power in the small red wires at the injectors. What other tests can I run? Should I ground the colored leads on the injectors to see if I hear a click? If I hear a click should the truck start and run for a few seconds for the gas that would be injected by "manually" opening the injectors? I would not think all 6 injectors are stuck or malfunctioning but I'm a novice on fuel injection systems. I'm still driving an old flathead for my daily driver. It is hard for an old man to learn all this "new" stuff. I may need to stick with ignition points, mechnical fuel pump, and two barrel carb.
Thanks in advance for any help anyone can provide.
Allan

 

Can you hear the fuel injectors clicking while trying to start the engine? A stethoscope or equivalent would help. You can also get a "noid" light that plugs into the injectors and indicates if they are getting the electrical signal to open and close.

 

You have fuel pressure in the rail, and 12V on the injectors. It starts if you spray gas, so there is spark.

Wow. It seems like the injectors aren't being turned on and off by the computer. Is there a connector for the fuel injector cable bundle? But then the 12V would probably go through that connector too.

 

GREAT NEWS! I found the problem. I found a wire coming out of the harness that was under the air cleaner on the right fender with no connector (bare at the end). I grounded this wire and the fuel pump ran for a few seconds and clicked off as it should. The truck then started almost instantly when I "hit the starter". I can't find this wire in my wiring diagrams and do not know where it should go but perhaps it was originally attached to the battery ground cable at the battery terminal. The wire is black with a green stripe and appears to be 12 ga. Thanks to everyone for their input. The truck is running fine, engine sounds great. My initial attenpt to set the timing resulted in about 20 degrees advanced, speeding up the engine moves to about 30 degrees advanced. One of my manuals says timing should be 10 degrees but I hear no spark knock and no kick back on the starter. Does anyone have any suggestions, at this point I see no reason to change the timing.

 

The wiring diagram for my '87 shows a black/lt green wire as the main ground for the EEC ocmputer. I guess it never got mentioned specifically as an item to check, but if you the computer wasn't grounded, that would explain a lot.

As for the timing, are you checking base timing with the SPOUT unplugged? See ignition timing tests at www.dalidesign.com/hbook/eectest.html for the proper procedure for checking base timing and timing advance.

 

You are correct! I checked the timing with the SPOUT plugged in. I should have read the manual. The link you provided has great information!
My problem seemed like I had a ground problem but because the case of the computer showed a good ground as well as the ground wire at the computer (grounded to the door jam) I was lulled into thinking the computer was actually grounded. Obviouly it was not. Thanks again. I may have more questions later. It does not seem that the torque converter is locking up. The transmission works well but I can not feel (nor see on the tack) any drop in RPM other than from gear changes. I'll drive the truck some more (only have 8 miles on so far) and enter a new question if I need more help. I certainly appreciate this web site and everyone willing to assist me.