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I am measuring the voltage at the plug connector at the battery about 4 or 5 inches from the negative battery terminal. I unplug the connector, put the volt meter probe in to the female connector and touch the negative battery post with the other probe.
One end of the wires goes to the computer, I'm checking at the other end.
With key off disconnect the ECM connector as well and repeat the measurement. If there's still voltage present you would have a short to voltage within the harness/wiring. If no voltage is present then yes, the ECM is putting out this voltage. Repeat the test with key on.
An expert is someone who knows each time more on each time less, until he finally knows absolutely everything about absolutely nothing.
J.S, here we go.
ECM unplugged, key off, no voltage
ECM unplugged, key on, no voltage
Now what?
After studying a wiring diagram, I find that these # 40 and #60 pins are called power grounds. I would think they should have power on them. If that is so, now I just need to know what the voltage should be, if any.
Thanks again very much, you all have been very helpful.
Connect the ecm connector again and cut the two wires that connect to terminals 40 and 60 a couple of inches away from the ecm. Take another measurement on the cut wires that emanate from the pcm pins, key on and off. If now you got voltage on these wires the ecm is faulty.
An expert is someone who knows each time more on each time less, until he finally knows absolutely everything about absolutely nothing.
Last edit: 3 years 10 months ago by juergen.scholl.
I cut the #40 and #60 wires. With ECM plugged in it show the 8+ volts on both wires. The wires going to negative bat post are now dead. It is coming from computer. This thing has so many problems , like cut and spliced wires all over the place. I think the fuel pressure reg. is bad ( it's the one you can barely see after blocking up a load of rubber hoses, and the screws go in from the bottom) The fuel tank selector is not functioning and maybe letting fuel leak back because it won't fire unless you turn the key on and off at least 3 times before trying to start.
I have never been one to give up but I'm almost 70 yrs. old and this isn't as easy as it used to be. My son owns the truck and he thinks he just want's me to go with a carburetor and it sounds pretty good especially when thinking about getting rid of all this crap. The 1988 model is the worst I have ever seen. You can't even see the valve covers unless you pry up the wires and hoses. I know all the issues with carbs and I don't miss them much especially in the winter but at least they run and when they don't it's usually just one of three things.
Well, the saga continues.
We rented every fuel pressure gauge in town (3) and none of the had the fitting for ford. I went to harbor freight and bought one and it has the correct fitting.
The pressure sometimes gets up to 30 psi engine off but most of the time it's only 21 psi. I'm almost deaf and can't hear the pumps so I bought a stethoscope and I find that both tank pumps are running. Talk about confusing a selector valve.
I also find more air than gas. Well , I 've got another mess to figure out.
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