85 S-10 ECM/Fuel pump problems

[shifterknob]

I have a 1985 S-10 4 Extended cab pickup with a '93 2.8 liter V-6. Been having intermittant problems starting it over the last year or so. Once in maybe every twenty starts, it would not want to fire. It would turn over just fine, but would not catch. However, if I rolled it and popped the clutch, it would start and run just fine.

Then, it started to be one in every fifteen starts, then one in ten, then every other start. Finally, even pop-starting it couldn't get it to fire.

I replaced the cap and rotor, the plug wires and spark plugs, checked all fuses. Checked the fuel pump, it ran fine when I ran a hot wire to it. Got no check engine light when I turned the key on, and no trouble codes or any signal at all from the ALDL.

Finally, in desperation, I spliced a toggle switch running from a constant hot source into the fuel pump hot wire, so I could manually turn the pump on and off. This worked... sort of. I would hit the toggle, the fuel pump would come on, and I could start it. I could then turn the toggle off, and the fuel pump would still keep running just fine.

It gets better, folks. After a couple of weeks, I noticed that if I turned the toggle switch off, it would kill the engine. Now I'm scratching my head. Why would it work at first, then not work?

We weren't getting any signal from the ECM to the fuel pump relay, so we decided we had a bad ECM. Went to a junkyard, and bought another ECM that matched up. Still not getting any voltage or signal to the fuel pump relay, to the ALDL, or a check engine light.

At this point I am seriously considering C-4 or TNT as a solution, if you get my drift.

I realize it is entirely possible we ended up with another bad ECM, but that seem a bit of a stretch that it would be doing exactly the same thing as the other ECM. Or maybe not. Are we missing something here? Perhaps a short that is causing the ECM to mess up, or a sensor that is messed up telling the ECM not to turn the fuel pump relay on? And why no signal to the ALDL? Why no check engine light with the key on?

Any assistance with this nightmare would be nice, before I come totally unglued and start using this truck as target practice for one of my high-powered rifles...

[bigreave]

you might have a bad conector in your relay and who hadnt got a bad part from a junkyard

[shifterknob]

Actually, after three days, two computers, and a lot of head-scratching we finally solved the problem.

What we couldn't understand was when we put either a used computer from a junkyard or a new reman from an auto parts store, we weren't gettng any signal from the computer to the relay, nor any signal to the ALDL.

Finally, we figured it out. There are two power leads going into the computer: one direct, and one that feeds through the ignition switch. We found the direct wire from the battery to the computer had been severed back behind the exhaust manifold, due to extreme heat melting a soldered connection.

Re-connected the line, everything worked perfectly. Even have a signal to the ALDL.

Now, does anyone know how to defuse a large, home-built bomb?

[dugie6551]

You might want to try a large open field, lawn chairs and a bag of marshmallows for the home-built bomb !!!!!!!!