Any TBI wizards?

[crapmanche4l]

Have a TBI 350 that wont run. It is a fuel issue. Has air, spark, and will run with fuel poured into throttle body ( or test light grounded injector from purple/white wire). NO injector pulse.

All started, tried to start it to get it on the trailer, something got left on, battery dead. replaced battery, runs for a few minutes, dies. crank but no start. get starter fluid, fires up, get it onto trailer drive 4 hours home.

Go to get it off trailer at home fires right up, get it to backyard. Next day, battery is weak-ish so charge it. Jeep starts for a minute, find voltage at 12.5 volts, no charge from alternator. rewire alternator, now gets 14.3v. Jeep starts drive it around the backyard, turn it off, clean up, put it all back together. Go to take kids for a ride, crank no start... grrr.

Go through fuel system, replace filter just in case, line pressure at 23 to the throttle body, no injector activation. after checking for spark, ECU power, pick up coil (825 ohms), blah blah, read on internet replace ICM. Get replacement part from Oreilly's, Jeep starts right up, idles for 10 minutes, purge coolant system, drive it down the road. Park it shut it off. wait 30 sec or so, start it back up x 2-3times. Put it all back together, go to take kids for a spin. Crank no start. no injector pulse.

I'm now on ICM #4, no way I get that many defectives right? so, how/what is causing me to keep burning up only the "injector side" of the ICM. Continue to have spark, will run all day if I manually feed fuel, just cant keep the injectors to stay involved. Also thought maybe its related to taking the kids for a spin, so sold the kids . Any one have a possible idea, experience ect.

In all the searching I can't find anyone with a scenario like this one. they all have a bad pick up coil, or distributor, or lose spark too, or.... Engine is unknown year and was told it was not in any vehicle, but was shipped to shop from GM on a pallet hooked to the 4l80 and 241. wired by automotive electronics program and has ran fine previously to my receiving vehicle.

 

[mbryson]

I'm assuming you're using the GM relay for fuel? I've bypassed that and just wired a switch directly to my fuel pump. I've also grounded the HELL out of my motor. I think there are three significant ground wires from my motor to the frame or battery. With it being intermittent, I've got to think something like a ground has worked it's way loose? Sometimes it's connected, sometimes not. (my last faux paus was not having the lead to the alternator tightened past finger tight---things would run fine, then it would just die. Sometimes sparking at the alternator post... )

 

[crapmanche4l]

Im not sure on the relay, im going to guess no (i didnt start this project and the wiring is a mess!) though and it is constantly running with key on 12v without the 2 sec run then wait for rpms. What does grounding the block like crazy achieve? Complications without? It does have a ground from head to firewall, i dont recall if there are more. Electronics are not my strong suit, im more a hard mechanical kinda guy lol. Im all up for learning, but seems ive hit a point I can diag past. Ill look for grounding when i get time and it isnt 108* outside. Thanks for the tip.

 

[mbryson]

On my swap, I have “over grounded” the block if there is such a thing. If you’re killing that many ECM, there has to be something doing it? TBI is SUPER simple.

 

[Jinx]

To find potential loose grounds I recommend the @TEAM FRED wiggle test.

Get the Jeep running. Opening the hood and systematically wiggle the wiring harness to see if you can get it to turn off. Where ever you wiggle and it shuts off start looking for loose bolts and or wires.

The next test I would recommend is a fuel pressure gauge on the manifold. Not 100% sure if a TBS system has the pressure valve, like a valve stem, but if you are over or under pressure that would show it.

I had similar issues once and it was a pinched return line that caused the the injectors to hydrolock and not fire from too much pressure.

Keep posting we should be able to help you through this. Mbryson is right these systems aren’t that hard.

 

[crapmanche4l]

Yeah when i first started trackkng this down first place i went was fuel system. Its all good though, its just whatever electrically keeps taking out the ICM (ignition control module) in the distributor that is keeping me from running. Which leads me to your wire test...lol, i cant get it to run so i cant wiggle it haha. The Last ICM swap i didnt even get it to stay fired, just a blurp and now have a replacement to put in but am hesitant to put it in as im tired of driving to the part store. I guess i can wiggle test it when i get home to see if by miracle that helps TO get it going . Thanks for ideas, keep them coming.

 

[crapmanche4l]

So, looked this morning, there is one ground (braided) from firewall to engine, but it is broken, so no ground to chassis from engine itself, would this kill the ignition control module in the distributer like I'm experiencing, or after I fix it and add more grounds am I still looking for as issue as to why the jeep eats through them even though all the trouble shooting points to everything else being good?

 

[mbryson]

I don't know the answer to that for sure. You did find a problem, I'd fix it. See what happens. I've not had the same problems as you've had. For something like this, I've found third gen.org (a Camaro website) to be a WEALTH of TBI/TPI knowledge. I've not spent a ton of time over there for at least a decade, so I don't know if it's gone the way of pirate4x4.com and become less tech oriented over the years? There's solid stuff there if it's still available

 

[Bart]

I was missing one ground when I put my motor in this spring, and did have another going from the tub to the head. Yes, it made a huge difference. They are very ground sensitive.