1992 mighty max getting too much fuel?

i have a 1992 mighty max bought it a week ago and it was sitting for 4 years the guy I bought it from said that he thought the head needed to be rebuit, I took the head off that was just on it and the original was in the back I cleaned it up and put it on. it started up but it has a bad miss and idles roughly. I just put new plugs in and they are already black, when I have the battery hooked up the fuel pump doesn't stop running, im wondering if it would be because the relay switch is stuck or the cut off is. I pulled the fuel line that goes into the fuel rail off and held it as hard as possible and pressure just kept building up and the fuel pump didn't shut off.

forgot to put in, while its idling and you unplug the fuel pump the idle smoothes out like how its supposed to be, then starts to die

Chances are the MPFI relay is messed up (passenger kick panel). Check the grounds under there as well. There are 2.

If the truck has been sitting, it probably has shit fuel in it, and changing spark plugs is only 25% of the ignition. The rest has been sitting just as long, and is just as worn/old. Do a full tune-up, replace the fuel filter, PCV valve, clean the TB and IM, use a fuel system cleaner, and put some fresh gas in it. You can't do a small portion of the job and expect 100%.

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Originally Posted by Merrill

Chances are the MPFI relay is messed up (passenger kick panel). Check the grounds under there as well. There are 2.

If the truck has been sitting, it probably has shit fuel in it, and changing spark plugs is only 25% of the ignition. The rest has been sitting just as long, and is just as worn/old. Do a full tune-up, replace the fuel filter, PCV valve, clean the TB and IM, use a fuel system cleaner, and put some fresh gas in it. You can't do a small portion of the job and expect 100%.

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I have changed the gas, the spark plugs, the fuel rail and the regulator, set the timing, I dropped the tank today and checked if the pump was hot wired, it wasn't from what I could tell and the return from the fuel rail was clogged I unclogged it and started it after I hooked everything back up. still does the same thing, im going to check the grounds on the relay tomorrow and if they are good im going to replace the computer, relay, o2 sensor and hope it works, and what is the IM?

Chase that problem with money, Eventually you may find it and afterwards probably kick yourself for something you find that turns out to be just a simple fix. Try not to break your bank, hang in there.
Check your basics...
is it electrical
is it fuel related
is it mechanical
Perform the test on troubleshooting in repair manuals.
I know your going through everything because I have done it to, but if you can determine what it is not might help.
Usually the engine will run better as it leans out then dies from lack of fuel. Ever heard anyone say it was running great just before she blew up, lol.

You still didn't do all the work if that's all you did.
Plugs are 25% of the ignition. You also need wires, cap, and rotor.
The injectors are probably trashed from sitting, especially if the regulator and related were clogged up. The fuel filter also needs to be replaced. You can almost bet it is trashed.

Just because it "runs" doesn't mean it is good to go. It's only going to run for so long that way, and probably isn't close to what it should be. You identified the main problem (been sitting/clogged up with shit fuel), so why start shot gunning everything else?

Do the whole job, then start troubleshooting. The MPFI relay pretty much controls everything. If it is getting stuck, it is most likely the problem.

i'm a 1st gen guy (so maybe this will not apply). i had some of what u described missfire/stalling on initial startup, black smoke pouring out, & rough idling til warmed up. took some time to figure out the stock carb & i'm still learning but it turned out to be choke adjustment by removing bracket (2 philips head) & moving the tiny plastic sprocket on the larger metal sprocket 1 tooth so the choke would open sooner (chokes are over-rated) only baffling thing to me was it appeared no-one had been in there. i also advanced timing slighty. no longer stalls & no black smoke.

We have replaced the plugs, Wires, cap and rotor, Dropped the tank cleaned it replaced it with fresh gas and some injector cleaner heet , Replaced the fuel filter, Had a used fuel rail and regulator, and 4 different injectors from a pick n pull motor, checked the timing, The motor is getting stuffed for of fuel, We will be checking the fuel relay and computer next However we are waiting on the Manual to arrive from ebay so we know how to check it, Any suggestions on how to check the relay or other computer components. Thanks for all the help !

so here is the latest and to recap and whats been done, 1st we have changed all the plugs, wires, rotor and cap, timed, Dropped the tank and cleaned it and put in fresh fuel, and looked over the fuel pump which appears to be fine, we have replaced the fuel regulator and fuel rail, injectors, ( from another motor which we had from pick n pull, pulled the computer and examined it but could not see any problems, also pulled the fuel pump relay and did not see any thing wrong , checked the 2 grounds, located at the bottom of the computer, still getting to much fuel and the pump never shuts off, so much fuel it drips out the exhaust, we have ordered the manuals and are waiting for them to arrive, any other suggestions

You did know we have the manuals you can down load. You need to ohm check the MAS air flow. They have a tendency to go off voltage and need to be readjusted.

Caps on the ecm can dry out and die, and not show leakage - 22 years is a long time for electrolytic caps.