I have spark and fuel pressure but no power to the injectors. Any suggestions? 1989 5.8L F150

 

this may not help because i have a 4.9 i6 but the wiring for my injectors lay in the back by fire wall right next to the pipe that goes from the exaust manifold to the egr or did this happen after a bump or pothole could be the auto gas shut off switch lose wire connection? i am guessing at this point maybe the 4.9 engine forum can help?

 

Check to see if you have battery voltage at the TAB,TAD, AND EGR solenoids. From what I can see the power for these and your injectors run in the same bundle and there is a wiring connector to supply this bunch which I think is on the drivers side of the engine near the power steering pump.

 

Thanks, I'll check those out too. I bouight "noid lights" to double check the injectors. I'll see what voltage is going to the solenoids.

 

Here is a print of your engine wiring, as you can see the power for the injectors is the same as the power for the coil of the fuel pump relay, so if you have fuel you should have power to the injectors.

Here is the print:
http://www.autozone.com/images/cds/g...3d800a3a44.gif

 

How are you measuring the voltage at the injectors?

 

Well, I tried my digital volt meter but nothing. I bought some noid lights that plug into the fuel injector wires and they are supposed to flash when I crank the engine. I haven't had a chance to try these yet. This truck has been sitting for a while and the guy who tried to get it going before said that he plugged in the noid lights and no power.

 

I don't see how a meter can measure injector voltage properly being that the injectors are pulsed. A noid light should, but I don't know how accurate they are.
Another question, when the key is turned over to the "ON" position (but not start), do you year the fuel pump turn on for a second and then go off?

 

The fuel pump does turn on and there is good pressure. It isn't turning off though. I don't know if that would cause a problem but there's no fuel getting to the cylinders.

 

If the fuel pump does not shut off then it is a good sign that the EEC is bad.

This tells you that the EEC power relay is good and you should have power on all the red wires from the EEC power relay.

 

I have a 1990 5.O engine that is completely intact and running on a engine stand. If the the key is in the on position and the engine not running I have battery voltage at the red wires at the injectors, and also battery voltage at the TAD,TAB, and EGR solenoids. There is wire harness bundle on the drivers that feeds the engine. On this model it has 4 different coloured connectors. Tan,White, Black, and Grey. If I disconnect the Black connector I don't have power to the above components. My thought was if you didnt have power to other areas including the fuel injectors it could be a problem at the wiring connector. The fact that the fuel pump is on all the time opens up some other issues. I have never had this happen so I can't advise you on that one. From what I have read on this site , I would also suspect that the culprit may be the EEC as Subford has posted. Does the wiring look stock or is there signs that it has been cut ,taped or butchered.

 

It is possible that the ECU is bad being that the pump runs all the time with the key on (engine off). I suggest you scan/check for codes.

 

The fuel injectors get power from the EEC relay, right?

 

I am no expert by any means but enjoy learning about these trucks and how they work.From what I can see from the wiring diagram that I have, the injectors get there power from the eec relay. Other components are also supplied power from the same source. I have discovered on my spare engine that you can still have power through to the fuel pump and not to the actual injectors by disconnecting the black electrical connector. The IAC motor is also fed by the same black connector. I have checked it a couple of times so I am pretty sure that is what is going on.

 

Another thought. This is more of a question. If the tan/lt green ( your colours may be different) wire that goes from the fuel pump relay that gets grounded at the computer and also goes to the self test connector was shorted to ground somewhere else would the pump run all of the time when the key was in the on position?