So here goes the back story. 88 Cherokee, 4.0. Ran great, no issues Had a fuel injector start leaking. Looked like an oring on the the rail. Injectors were stock, 1 hole injectors. Tore apart, new orings, put it back together. This is where the trouble started. Took forever to get it running again. When it did run, heavy smoke, miss, heavy rich and overfueling. It would start but run terrible. Still a fuel leak on the injector, turns out it was the housing leaking. Ordered a set of Bosch 4 hole injectors. Tore it back apart, replaced everything. Now it won't start at all. Doesn't try to fire. Pulled the plugs, soaked in fuel. Checked spark-it was good. Heavy fuel in cylinders. Enough that as it cranked around it would shoot fuel out and across the engine bay. Went through wiring to injectors. Correct wires in order. Replaced vac hose to map since it cracked. All other seem ok. Fuel to rail good, fuel out through regulator looked good. If I just crank it will not start or try to fire. If I mash the pedal and put the injectors into the pulse cutout mode, it will eventually sputter and fire enough to barely run. Seems to be a fuel delivery problem with the computer thinking it should be giving the most fuel it can. Still super heavy smoke. Extremely rich. Missing and very loud through the exhaust. Any ideas or direction would be appreciated.

 

Sounds like it's still; flooded. Lot's of fuel in the exhaust too.

On the back of the starter relay, there are 2 green wires. One comes from the ignition switch, the other goes to the starter solenoid. When you turn the key to START, you apply 12v from the green from the ign switch to the green to the solenoid to engage the starter, The solenoid is the one next to the large post with all the other wires attached. If you run a jumper from the battery + (you can use that large post too) to this lead, you'll crank the starter without having to turn the key (so key OFF). Key off ensures no power to any other system (ign and fuel). Pull the plugs and crank the engine over to flush excess fuel from the cylinders. Make sure the plugs are clean and dry.

Be wary that excess fuel may have washed any oil off the cylinders so don't crank too much. Fuel may have seeped into the oil pan and thinned your oil out.. Be careful you don't run the battery too low. Make sure you do this in a well ventilated area (like outdoors). Then let it sit (plugs still out) to allow any residual fuel to evaporate. While you wait. pull the dipstick out and smell for fuel. Change your oil if needed before you resume daily driving.

 

2 questions.

Which injectors did you get?

Did the line from the throttle body to MAP sensor get messed up in the process?

 

They were Bosch 4 hole injectors. Bought on ebay. It is doing the same thing with those as it was with the stock 1 hole injectors. And the line did get messed up but I replaced it with a new hose

 

MAP sensor could be bad also.

 

Could the mapp sensor just go bad out of the blue?

 

It's electronic...... Test it.

 

definitely will. Gonna do some troubleshooting today. Thanks

 

Alright so pulled it apart. Holes were dry, plugs were dry. Did the tests for the map sensor. 5 volts in. 4.2 on input. Vac on hose lowers the input. I cycled the keys a few times when I was doing the tests. So for giggles I cranked the motor over again without the key by the solenoid. Had some fuel in the cylinders again. Enough to make it easily noticeable while cranking. So what is letting the fuel get in there? Do the injectors dump some in on a key cycle ?

 

You need to test the fuel pressure with a gauge.