96 Country, auto, engine mostly stock, fuel injectors upgraded 4 years ago, exhaust manifold change out 11 years ago, 289K miles. Never been inside the engine. Have used Mobile High Miles 10-40 for 150K (rear main leak). Change oil about every 5K (over the 5K jeep leaks/consumes out about 1.5 quarts - mostly leaks). Went to the Wix filters in last year (didn't know how ****ty Fram was). Oil used to stay light (or lighter) for 3,500 to 4K. Suddenly it blackens in 1200 miles. Replaced original stock fuel pump a month ago. Did not do anything with the fuel pressure relief valve. Great oil pressure and engine remains strong. I live in Reno and do a lot of mountain driving with cruise control. I did the tranny controller mods and normally drive on the highway with TCM shut off and the torque converter forced into lockup with another switch (about 160K doing this with no problems with TC). This achieves a no-downshift situation and, if light load on board, engine will torque up almost all mountain grades.

I think we can all start with suspecting the new fuel pump pressuring up somewhat higher and either creating a rich situation when running (o-ring leaking) or the injectors letting high pressure fuel by the o-rings after shutdown.

I'll check the fuel rail pressure to make sure the pump is not way too high. If pressure is in spec, will probably start with changing out the injector o-rings. Maybe overhaul injectors? What does it take?

Thanks to all in advance.
Larry

 

Hnmmm. I don't *think* oil leaking past the piston rings will make the oil black. Sounds like you are running rich.

Any codes?

Injector o-rings are no big deal.

 

I've had an intermittent check engine light for as long as I've had the revised TCM wiring. After it comes on, it resolves itself after a few starts - light is off 95% of the time. No change in that condition or behavior. Can't remember what the code is/was - next time it comes on, I'll check the code and report back.

Regarding a greater quantity of gasoline in the oil, that would break down the oil much quicker than the alternative. I believe that's the reason with use 195* thermostats - the extra heat boils off the chemicals that break down the oil - primarily gasoline.

 

What oil smell like ?

 

Send off an oil sample to Blackstone to find out what's actually in it. They'll send you the sample collection kit for free and charge you $28 for the analysis, which they'll send back to you via email. If you include a note with the oil slip explaining your concern, they'll address it directly in their little write-up that comes with the analysis. They also respond to email and answer their phones if you have additional questions.

I send off samples at every oil change for all my vehicles. It's cheap peace of mind to know how the motors are wearing and how the oil is performing. Also, I always ship my samples in a padded envelope via UPS ground to avoid delays with the US Postal Service.

 

what's your air filter look like ? clean and no leaks behind it?

 

you can use the XP filters from Wix to get better cleaning of the oil , and does the oil smell like gas and how old is your O2 sensor ?

 

I probably won't get to checking out this problem until the weekend. O2 sensor is 5 or 6 years old - easily over 100K on it.

 

The DTC is P0420 - catalytic converter not performing to specs. Could be converter or O2 sensor(s) or could be running rich.

Check fuel rail pressure. Got some interesting results. Jeep had sat for about 45 minutes and when the hose was attached I got some gasoline spray and pressure relief. That was encouraging but hard to really judge internal pressure from that at the end of the 45 minutes.
1. Started engine and pressure went quickly to 50 psi and stayed there with increased throttle and also when it went back to idle.
2. After shutting off, pressure dropped to 10 psi within 10 minutes. 17 psi in about 3 minutes.
3. Restarted engine and it took 2 minutes for pressure to get back to 50 psi. But Jeep ran good during the 2 minutes - weird!

It's my understanding that if all is right, the system should hold the pressure somewhere near the 50 psi. Is that right?

 

You could have one or more injectors that are not closing completely when de-energized.

Pissing fuel with the engine off.....

 

I've bought an injector kit off of ebay - should arrive Sat. In the rebuild process, I'll pressure up before re-installation into the manifold and see what kind of leakage I get. Will also check elec resistance.

I tried the identical gauge test yesterday and it looks like the gauge may be faulty. Have changed it out but will do no further testing until injectors are rebuilt and tested.

What should happen to the fuel pressure after engine is shut off????? If it should hold (and I'm fairly sure mine does not) then it seems like it's got to be either the injectors or the check valve, which is in the fuel tank.

 

I believe the fuel pressure is supposed to hold after the engine is off.