Leeky fuel injector?

How can you tell if you have a leeky fuel inector?

Without taking them off? Pull the plug to each injector one at a time, canceling each cylinder one at a time, then put the plug back on. It will run on 5 cylinders, but noticeably worse. If an injector is leaking the affect on the engine caused by unplugging the injector will be less than the others. This is SOMETIMES the case. If you think one cyl is running rich, pull the spark plugs and look for sooty carbon buildup associated w/ a rich condition. If they look the same you would be running entirely rich, caused by an exhaust leak or sensor failing.

you will see fuel leaking from it

Staining on the intake manifold under the injector is a good indicator. Likewise, wet injector bodies after a short drive (before the engine heats up and the gas evaporates) can be a sign.

There's fuel on it?

Check the injector area for fuel - you might want to clean the area, dry it thoroly, and check it at idle as well.

It would help (as usual,) if we knew what year - here's the reason: The RENIX 4.0 (1987-1990) is known for injector leaks at the body seam, and if you do a search here for "Engine Bay Fires" or something similar, you'll find several RENIX burnouts caused by leaking fuel injectors (they sit right over the exhaust.)

The good news is that you can get a set of pulled Ford 5.0 injectors to replace them - just put new orings on them before you put them in. It's about an hour to change all six of them, and you should DEFINITELY not let this go too long (I'd say get it done no later than week's end - sooner, if you can swing it.) The OEMR injectors are spendy (and even the aftermarket ones specified for the 4.0) but the 19#-20# fuel injectors will serve for the XJ - all years. I'd consider 21# injectors a maximum for a stock 4.0, anything larger than that would probably cause you to run rich - or cause the ECM to overcompensate for the oversize injectors.

Oh - the rating in pounds (19#, 20#, 21#) refers to the amount of fuel the injector will deliver at rated pressure (usually about 39#) Too much fuel injector is like overcarburating an engine, too little will restrict power by not allowing enough fuel to be delivered.

5-90

Get your replacements from http://www.fiveomotorsport.com/Injector_SetsJEEP.asp - good service, pricing, and quick delivery.

Yucca-Man said:

Get your replacements from http://www.fiveomotorsport.com/Injector_SetsJEEP.asp - good service, pricing, and quick delivery.

Click to expand...

x2 that's where I bought mine

When I saw your question I thought you were asking how to tell when an injector leaks from the pintle seat or something, into the manifold. I also bought 19 lb injectors (for 95 4.0, seemed to run lean before, except in leaking 2 injectors) from the 50motorsports guy, years ago. Paid something like a hundred and change.