doughtyjeep

Gentlemen, me again with the 89 Cherokee. Couldn’t get it to crank. When it did, it blew back tons of oil and gas. I drained about 4 gallons of mixed gas and oil. Changed fuel pressure sensor, injectors, plugs and wires, MAP sensor. Will run with correct amount of oil, imagine that, but now gas still getting in oil. Is fuel bar supposed to keep pressure after engine is turned off? Because it doesn’t. Checked injector wires and positive wire flashes and negative shows ground. About to change TPS. Or is it ECM??

Veeb0rg

My guess would be a stuck injector. Would explain the lack of pressure when turned off and gas in the oil.

doughtyjeep

I agree so I changed them. It’s possible I got a bad one with the new ones. Is there a way to identify the culprit?

MrTodd

Watch this video. It may help you ID if there is a bad injector.

Todd

MtnGoat

First find out if the new injectors solved the problem. Then run a compression test to see if youve bent a rod. Turning or firing a Hydro-locked cylinder will mess an engine very easily. If you've ever watched those old piston aircraft doing a cold start, they'll hand turn the engine before starting to avoid this this problem.

lawsoncl

The other possibility is the diaphragm in the fuel pressure regulator has failed. Pull the vac line off and see if it's leaking fuel into the vacuum line.

doughtyjeep

Update
compression test shows all pistons in the 120 range. #3 piston had 130
The part # for the injectors I installed end in 5710. I was told to get the ones that end in 5746 so I have those on the way.

if you’ve ever heard someone with sleep apnea catch their breath once they quit breathing, you’ve got an idea what it sounds like when I crank it with the air breather off. Which is what I have to do to get a cold start. When I rev it up and then let off, sometimes it dies.

tech

Also make sure the the injector wiring is not shorted . the computer runs the ground side to the injector if the positive side was shorted you would blow a fuse so check to see if any injector wiring is shorted to ground

doughtyjeep

I connected the test light to the positive battery post and touched the ground wire to the injector. I got a bright light. I then touched the positive wire to the injector and got a dim light. Is that what you’re talking about?

tech

Did all the injector grounds like up or was it 1 or 2 of them ? and did you do it with all the injectors plugged in or were they all disconnected ?

lawsoncl

He's got an 1989. The Renix era setup controlled the +12-volts to each injector and they shared a common ground.

tech

Ok that backwards to almost all other cars but if that the way it is OK .

lawsoncl

Yeah, the Renix fuel injection was a bit backwards in a few other ways. TPS sensor voltages are backwards too. Crank sensor was a different type, etc.d

doughtyjeep

Ok gentlemen, I took out the spark plugs after it was sitting over night. #2 and #4 spark plugs were wet with gas. Swapped both injectors with and regained pressure on the fuel rail.NO MORE GAS IN OIL!!! The bad injectors were new out of the box. Cranked and runs like a champ. Also, unknown to me, the computer allowed the Jeep to crank the first time and drive down the road. The guy who owned it before me had a spare comp laying on the back seat so I plugged it in and started fine. Put the old computer back in and won’t crank. So first computer went bad and wouldn’t let it crank. Trying to start it was dumping fuel in the oil. Bad injectors was the second cause of fuel in the oil.
Thanks guys for all the advice. You guys are great!!

Rogue4x4

Awesome!

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