Fuel injectors or EEC or other?

[tinman_72]

I have a '93 5 speed with '98 2.5L motor.

How do I test the fuel injectors and computer? I believe one or the other is bad. I get a puff of white, gas scented smoke on startup. I get horrible mileage and the engine bogs whenever taking off.
The injectors are factory Ford injectors with ~150K miles. I have read that they can stick open. I also know that on other Ford vehicles there is a somewhat common issue with the computer causing one or more injectors to hang open. I don't know if it is common with Rangers or not.
I did a fuel pressure test a few months back and I am getting proper pressure but it builds slowly and does not hold when the engine is turned off. This leads me to think that it is an injector sticking open by itself. But I had the same issue before I swapped in the 2.5 leading me to think that it might be the computer.
I already tested the new FPR that I installed during the swap so I know that is not suspect.

TL;DR
How can I test to find out whether my injectors or computer are bad. (Or something else?)

 

[adsm08]

Excessive pressure bleed off with the key off can be caused by an injector, an external leak, or a bad check valve in the pump. If you had an external leak you would probably know.

To test the injectors for a leak you need to pull the rail and injectors out of the manifold, secure the injectors to the rail if they aren't already, then cycle the key a few times to build pressure and look at the injectors. If one is leaking you will be able to see it.

If you find a leaking one unplug the electrical connector from it, if it continues to leak the injector itself has a problem. If it stops then you have a wiring or computer issue causing your problem.

If you find no leak suspect the fuel pump has an issue.

 

[RonD]

Like all Ford fuel injection systems I have seen the injectors are all given 12volts when key is turned on but computer controls the Ground for each injector.

This is better to prevent any blown fuse shorts for the 4 wires to computer, but if you do get a shorted wire then injector opens when key comes on, and stays open.

The Red wire on each injector is just daisy chained from one injector to the next, the other color will be the Ground to computer, you can test these other wires with OHM meter to ground, key off and key on, also move wiring harness around to see if there is a short to ground.

Computer should be setting codes with the MPG you describe and smell of gas at tail pipe, have you tested if CEL is working, i.e. unplug MAF sensor and start engine, CEL should come on fairly fast

 

[tinman_72]

Thanks. I will try this stuff out this weekend.

I am pretty sure my CEL is not trying to come on. It was lit up before I changed my EGR valve last year and I still had the same issues. But as you describe it is easy enough to test so I will give that a go just to be sure.

Hopefully I don't have any wiring issues. It is a twenty two year old truck but I have not had any other signs of electrical gremlins.