to be on the safe side, i went to pull a part and picked up 4 computers. all 4 trucks were 5.0's, manual, and 2wd. none of them were supercabs like mine. hopefully it doesn't matter. one computer had the same AJA code number (mine origionally was AJB but according to cardone, they are the same). the others were different, but from what i've read, the truck should still start. with all 5 computers (including the reman one i bought) the check engine light came on very dim. all the other bulbs are nice and bright. unless all of those computers are bad, i'm guessing i still have another issue, lol. so i got to thinking, that the body may not be grounding correctly, since i changed the cables, and put the negative on the alternator bolt. so i added another ground cable in the stock location (on the frame), and also added another smaller 14ga ground from the body to the battery just in case. the origional ground strap from the body to frame is still intact, and looks really good (no corrosion, or rust). still nothing.

i also checked one of the grounds on the computer connector. i took the cover off the connector, and saw where one black wire went from the computer plug to body (not into the big fat bundle of wires). it hooked up to a bare ground wire with no sheathing, just bare wire, but that checked out fine. i didn't have the pic of the computer connector that some one posted earlier, so i'll be checking the rest of them tomorrow.

lastly, i unpluged the big fat round connector next to the computer plug, that has like 100 wires going thru it, just to see if any of the pins looked corroded, or melted, but nothing, all looked well.


If all else fails, i'm just gonna have to rip all the EFI stuff off, and go with a carb. i guess i could always toss a megasquirt ECU in there too

 

You're gonna kill me for this, but are we sure that we are getting spark out of the coil wire? If so, then the RPM signal from the dist is getting to the ECA and the injectors should fire. Were you able to confirm that the injectors were actually getting the ground from the ECA to fire ? You were going to do this with the peanut lite.

The other side of this problem could be a possible short in the wiring to the ECA.
Since I don't what kind of diagnostic /test equip you have to work with, you can try this; unplug any sensors that you can see ,all of them, then watch what happens when you turn on the key. Either the check engine lite will come on and stay on at full illumination or a possible short may have destroyed all the ECAs.
If you do have a shorted sensor and the light does come on as it should connecting them one at a time should tell which one is the problem.
There are no shortcuts for finding a problem like this and you need to be persistent
, but the pay-off is nice.

 

That would suck if i burned out the computers, lol. I know i'm getting spark because when i spray starting fluid in the intake, it starts and idles pefrctly untill the starting fluid runs out. but the fuel pumps aren't comming on (no pressure, and the relay isn't grounding. its getting power in the right places, just isn't grounding via the computer. and if i bypass the relay with a piece of wire, i get about 45 psi to the rail, and if i try to crank it with the relay bypassed, and good pressure it still doesn't even try to catch, so this tells me the injectors aren't firing. i'm about to go out now and start tesing every last wire on the computer connector and see if each one is making contact with each respective sensor.

Also not sure if this is relavent or not, but between the computer, and the fuel pump relays, where all those random connectors are leaning on the wheel well, there's one connector there, that has nothing plugged into it. its grey, about 3/4'' wide, an inch long, and about 1/4'' fat, and has 2 wires going to it. the two wires are either both green, both blue, or one was green and one was blue (i saw it yesterday, but it was getting dark, so i couldn't tell). didn't see any corresponding plugs for it, so i'm not sure if it even goes anywhere (maybe some kind of test point?).

And one more thing that shouldn't matter, but i might was well mention, the two wires on the A/C clutch on top of the compressor seems to have been cut or chewed thru by rats. i'm guessing that shouldn't cause the truck not to start tho, lol. i haven't seen any wires anywhere else on the truck that are chewed or cut, so it might have been from the PO working on it, or me. or a lazy rat that chewed those two wires, then gave up, XD

i'm off to start the tedious task of first tracing every ground for continuity to the negative on the battery, then resistance, then testing every wire going to the sensors. wish me luck, lol.

 

In looking at the first page of the wiring diagram, you will notice that it shows the check engine light.
According to that diagram,the light gets its voltage from the ign switch run circuit. That needs to be confirmed to be 12 volts.
Then it gets its ground from the ECA. With the ECA unplugged if you ground the correct wire terminal in the diagnostic plug that lite should glow properly , does it?

 

minor victory today, lol. i started checking all of the wires on the harness. when i came to the two main ground wires #40 and #60, i wasn't getting a very strong continuity. when i checked ohms, it was over 200K ohms. so I spliced in another wire to each ground wire, and grounded them to a random bolt on the body. now the check engine light comes on fully lit up, and the fuel pumps now come on for a second and cut off like they should.

But now i have another problem, which was actually the problem i faced years ago. it still wouldn't start, and i kept checking the pressure, and less and less gas kept dribbling out of the test port, till eventually nothing came out. so i figured the fuel filter may be clogged. so i took the filter off, and turned the key and no gas came out. so i umped the relay so the pumps would stay on, and the rear tank pump was on, but still no gas comming out of the lines????? how is that possible? the tank has over 10 gallons of gas in it, and the truck is level, not at a crazy angle. and i can hear the pumps. how can no gas be comming out of the lines? i was thinking the strainer may have gotten clogged, but i doubt it, because when i changed the pump years ago before it sat, i had cleaned the tank, and still had this issue even with a new strainer. any ideas?

are those big round diapham things that connect all the lines together, known for going bad? thanks yall for all the help so far

-Mike

 

Do you by any chance have two fuel tanks on this truck? If not,
Can you disconnect the line coming from the tank to the fuel reservoir (that diaphragm thing)?
It's touchy because when you turn the key on it is going to shoot fuel out with the line disconnected. If you get fuel , then you need to try the other side and see fuel comes through.
If you don't get fuel in either case , The pump is suspect.

 

yes, two tanks.

 

the tank i've been using is the rear tank, as thats the one i replaced the fuel pump and strainer in, and cleaned out.

 

On the F series the shuttle valve is in the fuel pump assy and if it is stuck open your fuel has been getting pumped to the other tank and your rear tank is empty !
Add some fuel to that rear tank and maybe you will get enough up to the other pump and the engine will now start.

I hate to tell you this , but if those pumps have been running dry long enough, you could be in the market for new pumps.

 

rear tank is still full. both tanks are actually. both intank pumps are working. i just went out to it, and tried it again, and fuel started to come out, slow down, and stop. it seems that if you give it about 30 minutes, some gas will come out, then stop. almost like a clogged filter or something, but again, the rear tank has a new strainer. but i hit the switch for one tank, it came out hard, hit the switch again, monmentary pause, then hard, then started to trickle down, to almost nothing, then flipped the switch again, and still a trickle and then nothing. its as if theres a filter between the regular filter, and the two pumps, clogging, not like both pumps clogging differently, if that makes sense.

anyhoo, what exactly is the shuttle valve? are you talking about the big round thing with 6 lines (4 on one side, and 2 on the other)? if so, mine is on the frame rail. or is there another piece to this overly complex fuel system i'm not aware of,

i think i'll go disconnect all 4 lines off it (the ones comming from the tanks), and see if gas comes out of both pumps with out stopping. if thats the case, the i guess the problem is with that big round thing, no?