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7.4L tbi + fuel problems...injectors dump gas (full open delivery)

36762 Views 22 Replies 9 Participants Last post by  Napoleon Solo
7.4L 1992 GMC sierra 1ton
--Problems just started, i have to fully depress pedal to start
--injectors have been replaced, they pulse during ignition...when started, injectors spray constant, dumping fuel
--NO o2 sensors on the manifold

**NO engine codes, only code 12
**Can't figure out why injectors are not pulsing, idle revs up to 1,500
--ECM replacement? TPS and IAC need to be replaced?
--everything on the harness gets the correct Voltage.

I'm thinking that the ECM needs to be replaced, the IAC and possibly the fuel pressure regulator.
Very hard to maintain an idle now on the truck and the conical spray pattern is thick and constant when the truck is running.

No MAF sensor or O2 sensors on this TBI 454's a 1ton.
again, i replaced the injectors but it's not fixed yet.
Played with the idle screw to no avail as well. :grrrrrr:
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Your ignition control module sends out the signal to pulse the injectors. Have you replaced the stock distributor? If not, have the module tested. If so, put the stock distributor back in. If all that's good, you should check the harness from the module.
You don't have to worry about the crank sensor -- they didn't put them in until 1996. :)
If it's running that rich still, the only other thing I can think of is your oxygen sensor. Luckily, that's easy to change, and if you're really lucky, it's the 20-dollar one-wire unit. If it's stuck sending a lean signal, it can make your engine use a horrendous amount of gas.
Look about six inches in front of the catalytic converter. They weren't all on the manifold. It does have an O2 sensor. They've had them since the 80's.
Yeah, I've seen a few of them. You must have one of the weird ones. :3
Well, two other things I suppose you could try...
Replace the fuel pressure regulator diaphragm. That's pretty cheap and easy to get.
Try also, unplugging the vacuum hose from the EGR valve and block it off. See what happens. That's a long shot, though.
1 - 4 of 23 Posts
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