Hello,

Im new to the forum! Im a auto tech... that is very confused. I work at a shop that works on everything and its been far to long since I have seen one of these trucks in my shop! Please help! :-)

I having a problem with a 1987 Ford Ranger 2.9L 4x4.

I have been beating my head against the wall, and I know Im missing something stupid. So I need some fine people to bounce some ideas off of.

The problem is, 3 of the injectors are not firing. They all have 12volts! This system kind of has pulled a fast one on me caues for the life of me, I cant figure out how it works.

2.9L engines use a Multi-Port injection system.

They have 6 injectors powered all by a common 12v source.
The other side of the injector, is tied up into 2 banks. Injectors 1,2,4 are together and 3,5,6 are tied together. Injectors are firing on 1,2,4 but not 3,5,6. The wires are connected, and one single wire goes to the ECU. The wire going from the injectors to the ECU is fine, the wires going from the wiring harnes to the injectors are fine. I have replaced the ECU, with no luck.

For one, I dont understand how the ecu gets the right injector to fire when they are all connected to one injector output! Im super busy at work and this is just pissing me off. I dont like not knowing the answer

I cant see how it can be anything but the ECU. I guess its possible, that I got another bunk ECU.

 

Welcome to FTE.

The fuel injectors will have 12 volts B+ to them at KOEO.
When the computer gets a signal from the cam sensor that the engine is rotating, it'll wake up & have the appropriate ground switching driver switch the injector on & when the computer gets the PIP signal from the distributor Hall efect sensor, that'll tell it the engine is rotating for a start & it's time for the ICM to make spark, to make er run.

SO, if half of the injectors aren't working, one thing that is common to those three is the B+ feed to them. If thats not ok, they won't work, as there isn't any load for them to switch. If you have B+ to the suspect injectors electrical connector at KOEO, then look to a wiring, connection, or computer ground switching driver problem. So maybe as you suspect the replacement computer has problems, but seems to me it would be kinda unusual for 3 injectors to be affected though.

 

At least it ought to be simple. All six injectors are grounded together - so if half of them work, the trouble is between the three bad ones and the computer.

Connection 58, or 59 from the ECA.

The injectors are in groups of three.

One notion I had was to switch the B+ wires and see if the opposite set fires.
Another might be to switch the injectors, but that would be a hassle.

My strongest suggest at this point is to break out an OHM meter and see if the injector harness for the bad set of three is somehow grounded or shorted out-

You would have to disconnect the injectors and read to the chassis or engine block, and the battery is best disconnected when you do this.

If the wires feeding that bank have gotten shorted to ground it will take down the signal to the injectors and could possibly trash one computer after another...

(I know, that would really suck)

 

Fixed.. thanx for the input!!

 

What was the problem???? I'am curious. Thanks.

 

Bad ECU driver, Short in the 3 wire plug! In the plug, right ... in the plug. Not in the connector, in the plug where u cant see. Sneaky...

It was actually the side of the injectors that were working that was shorted enough to take power from the side that wasnt working ....

Finally just rewired the whole thing haha. Should have done that to start and it would have saved me 2 hours haha.

 

Good find, fix, feedabck & to hear you got er fixed & on the road again.