Replaced the fuelpump on my 1999 4 Door, just a cheapo one from ultrapower so i can spin it around to get Code enforcement off my back about it having no license plate currently. Its got good pressure at the rail and consistent pressure when cranking, It took a good few tries after installing, about 15 seconds of cranking total before it finally caught. It idled at about 750rpm after the temp needle got off the peg so i tried giving it a quick rev test to make sure it wasnt going to stall. it kept pulsing up by about 200rpm or so until 1500 where it stalled out, like a lean stumble. Now it wont restart. The only fuel related issue i think it could be would be the vent checkvalve on the front end of the tank is wide open instead of going back to the evap filter. the pump is brand new and i dont have time to wait for an RMA return so any help would be appreciated.

edit: mulling over it i had a thought, Could their still have been gas in the injectors from 3 or so years ago? its an MFI system on an 01 block.

 

Upper intake was off today, checked each injector hose and all was clean, not a fun 9 hours of labor. now im thinking TPS or IAC issue.

 

got it all together, tried starting fluid, no dice so that rules out fuel. no coolant blowoff and a compression test was done by an ASE cert mechanic before it was shelved and it read 160+. Pulled dipstick as i've been checking for flooding constantly and there is a smell of gasoline now so its definitely poor ignition. so im in for an oil change (again, just did one 0 miles and 2 minutes of total idle time ago). It doesnt end does it.

 

Tested the rail from the switch up to the fusebox, and then from the fusebox up to the rail at the ICM and the Coil connector, all reads 12.50 key on and 10.20 key start, no voltage cutout. im really at a loss here.

 

did yet even more testing today, made an improvised spark tester by taking an old plug wire - was only replaced as for some reason the boot was missing - and ziptied it to the throttle cable so it sat about 6mm above an alligator clip on the alternator, cranked it and got a couple of arcs but that was it over a good few seconds of just cranking. Not a conclusive method but at this point i've poured over wiring diagrams and nothing else is unchecked, the only possible thing outside of coil/ICM could be the knock sensor module under the ECU giving up the ghost and feeding garbage into the ECU making it play ****y with the spark timing. The knock sensor on this truck has been unbolted and just laying on the passenger side head for many many years now even before i owned it and it was running well. i dont want to and cant give up on it yet but im out of options.

 

Big Vacuum leak, me and a buddy got together today and put our heads together, he thought to block off the throttle body and idle air bypass and sure as **** she runs. never said i was the sharpest pencil in the toolbox now did i .

 

Looks like someone watched the short Tuesday SMA video!

In the case of a large vacuum leak, it should run fairly well with the MAF sensor unplugged which should be unplugged if you are attempting to run the engine without the intake duct work installed anyway. If the PCM doesn't see all of the air entering the engine also going through the MAF sensor, it does some pretty wacky things, but if it doesn't see the MAF sensor, it defaults to MAP sensor data and another table for fuel/spark control.

As far as the source of the leak, I would take a look at the EGR valve after doing the easy visual inspection on the vacuum lines under the hood and trying to plug off all of the lines (including the large one to the vacuum booster and to the PCV valve) and re-running your blocked throttle body test.

You can test the booster for leaks with a hand vacuum pump.

The PCV valve could be one of two types, an actual valve or an orifice type. The valve type will rattle when shaken. The orifice type will not, but will have a fairly high resistance when blown through.

 

The buddy in question just got out of jail yesterday so i dont know about the video part of that lol

As for the leak, the EGR actuator/valve is new, the PCV is a valve type and does plenty of rattling, but i also dont think it could produce a big enough leak to completely lean-stall the motor. the maf i believe was left plugged in although i was inside the truck doing the cranking so i didn't see, either way this should confirm its getting air from somewhere it shouldn't. i believe the plenum is to blame since when i had it off i noticed its gasket was very flat so its probably not sealing at all, just wasnt able to replace it at the time and it was already no-start to begin with. the vacuum lines up until they go into the drivers side fender are new.

 

New gaskets in, the new upper intake gasket was much thicker then the old one, which didnt even come up above the groove it seats into, now she starts but man does it hate running, takes lots of cranking to get it going still but it restarts now. i believe its due to the brake booster hose but even after swapping a new seal onto that, and then blocking off the port (admittedly with an old sparkplug wire as i dont have any vacuum caps on hand) its still a bear.

 

rebuilt the top end again in order to reseat the injection spider, now she starts very consistently. but is a stone cold b%&$ if left to sit for a few minutes, as figured earlier this truck has MPFI injectors and it doesnt flood itself from sitting as far as i can tell - atleast no "hard" starts where it feels like its hammering the bearings.