1988 YJ Wrangler 2.5L TBI Won't Start or Run Right—What Now?

[jpjeep26]

Hi Moses, my UK based 1988 YJ 2.5l 4cyl just won't fire up.

Huge list of parts bought since Jan, you name it, pretty much I've imported it and yet she just won't fire up.

Cranks fine, fuel pressure fine, refurbed ECU, all sensors, cylinder pressure good, she turns over but just won't start and then floods everytime. Injector seems fine, plugs all firing, she almost starts with my foot buried in the floor but never does. She's only fired up a few times over the months and then runs rough as heck and black smoke pouring out the exhaust and misfiring all the time. Have to shut her down as the neighbours complain. Any help would be gratefully accepted. ( new fuel pump and filter, tank cleaned and 3 gallons new fuel put in there last week) thanks from the UK.

[Moses Ludel]

jpjeep26...You have justified frustration, as do the neighbors!  Here are some quick suggestions:

1) Have you checked the return line to the fuel tank for a restriction?  Fuel must flow freely through the return line and into the fuel tank.

2) What is the TBI pressure reading?  Does pressure increase during this starting/cranking effort?  The pressure regulator can work fine, but if there is a restriction in return flow to the tank or excessive incoming fuel pump pressure, the regulator can be overwhelmed.  Fuel pressure would spike way up and cause flooding.

3) Is the fuel pump correct for your 2.5L TBI engine?  Use of a similar looking fuel pump for a multi-point EFI model will put out too much pressure.  This excess pressure can overwhelm the TBI's pressure regulator and create excessive fuel flow.  The result can be a severe enrichment situation.  Check the fuel pump's rating and make sure the pressure matches (does not exceed!) TBI requirements.

4) Are the spark plugs building up carbon?  This is a clear sign of an overly rich mixture.  Wet plugs are another story, usually the inability to fire/ignite.

Start with troubleshooting these issues...

Moses