On an 1988 D150, w/3.9, auto,smec. The truck seems to not have enough
fuel. No fault codes except 12 and I noticed only one injector seems to
put out fuel. Now if I switch the injector wires then the other one
works.Should fuel be at both injectors or just one until more fuel is
12 is the one that tells you your battery have been disconected
Thanks in advance
When you switch wires does the other one quit? Yes it does. I've had
the harneses out before. Is that the only reason one wouldn't squirt.
Because I beleave I had the same voltage at both sides, but I'll have
to check again.
The computer or SMEC (single module engine controller) has two outputs for
the injectors. One (wire 18 WT) is pin 2-9 at the computer, the other (wire
18 TN) is 2-10. The color stays the same all the way to the injector plug.
On the injector plug, the outside wires are the grounds, both 16 gauge black
wires. The center two are the drive signals. There is a connector (right
fender) that they pass thru. Use a test lamp. Don't use a digital meter to
troubleshoot this or you will get lots of confusing readings. 18 TN is an 18
gauge tan wire, the other is 18 gauge white. Just look at the colors at the
injector plug to be sure.
BTW: I do not have a wiring diagram for an 88, this info is from an 89
manual. I believe they are the same. If the signal is at the computer
terminals, and you can't find the break in the wiring, just "jump" the wire
from the computer to the injector connector. In a pinch, you could
disconnect the dead wire and jump the good wire to both injectors. My 89
manual says the SMEC is in the center of the dash panel.
Hope this helps, good luck,
On that engine, you get 12v supply to both injectors from the autoshutdown
relay. First make sure you have 12v to both injectors via the Dk GN/ BK
tracer when you turn the key on. You'll have voltage for about three seconds
when you firest turn the key or when cranking the engine over. The smec
fires the injectors by grounding the white and tan wires. You can check
continuity from the white wire on #1 injector to the 14 pin connector at the
smec position #9. The tan wire goes to position #10 in the connector. If you
have voltage to the injectors and continuity from the injectors to the 14
way connector you probably have a bad smec.
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