this is an 89 ford ranger automatic 2wd with a multi point fuel injection 2.9l v6

so far i have confirmed compression, fuel pressure, injector pulse and and spark at plug.
this is what i was told about how the truck died

the owner says that they drove it to the post office one day and they shut it off and when they came back out to leave they couldn't get it started again. once they had gotten it home they tried starting it with starting fluid and it back fired and blew a few vacuum hoses off. they put the vacuum hoses back on and then it sat for a few years.

so the first thing i thought of was a sloppy timing chain that skipped a tooth, but first i checked the spark and fuel and they were food and i tried starting it and i could hear it backfiring so i ordered a new timing chain kit. i then started replacing the timing chain, but when i pulled the timing cover off the chain was good and in time. since i was already there and the deflection of the old chain was barley in specs i decided i would change it anyway. once i got everything back together again other than the coolant and belts i tried starting it and it was still doing the exact same thing (no surprise). so then i decided to check the compression (i even got to the passenger side rear plug) and all but one cylinder were at 125 psi and the #2 cylinder was at 100 psi. so i dont think its a head gasket or compression problem.

so i am thinking the ignition timing has gotten fudged up somehow. i am dreading it but i am thinking about pulling the disty cap and checking it out. what should i be looking for? is there a sensor that could be causing this? could the back fire caused another issue, like a burned out map sensor? what is the next step in diagnosing this problem?

also i have evacuated the old fuel, replaced with fresh gas, flushed fuel lines and replaced the fuel filter

 

5 at 125psi and 1 at 100psi is a 20% difference which is bad, you make have an intake valve that is not closing all the way, causing the back fire.

1989 2.9l will have a TFI system for spark.

This is a self contained system, it "talks with" computer but doesn't need the computer.

The distributor is like any other distributor system, it needs to be manually setup by you at 10deg Before TDC or it will be out of time.
Inside the distributor is a sensor in place of "points", the sensor tells the TFI module when the rotor is pointed to a spark plug wire on the cap, same as points did.
If this sensor was bad then you would have no spark so no backfire.

To correctly time the spark you need a timing light and to find the SPOUT connector, this is a Jumper that needs to be removed to prevent computer from advancing the timing while you are setting it;

Google: SPOUT connector image
To see what it looks like
It will be by the distributor on a 2.9l usually passenger side above intake manifold

Picture here: spout002.jpg Photo by gertsdsbs | Photobucket

You pull out Gray plastic piece to time spark, this disconnects TFI from computer, put it back after setting base timing.

First, double check firing order on cap, look here, about 1/2 way down page: Ford Ranger/Bronco II 2.9 liter Engines
Then remove distributor cap so you can see the rotor
Mark #1 wire placement on distributor so you know where that is for rotor position
Rotate crank manually untill rotor is close to #1, then put crank TDC mark at 10deg Before TDC, look at rotor, if it is not pointed at the mark then loosen distributor and adjust it so it is.
Snug up distributor
Put cap back on
Hook up timing light
Start engine

Time to 10 deg Before TDC, some like 12 deg better, your choice