jmrec100

Thanks. I'll check if Autozone rents them. I noticed that schrader valve when putting in a new exhaust manifold. I assume the tester works on the running engine. Next step is that. I did not put in the lower T-stat.
========================

TEST FUEL PRESSURE

Got that. What should the readings be?
The test plan.
1) Hook up the gauge
2) Turn the ignition on. Should hear/see fuel pressure go up
3) Start the engine, read the pressure.

Now what should it be for 1994 Cherokee, 4.0L Sport. Can't find those specs.
Thanks

jmrec100

I have to sum up what has happened because I'm going a little crazy trying to solve what is going on.

First pre-test, failed miserably. Put in a new Bosch O2 sensor. Still failed.
Searched around and found cracked exhaust manifold. I find out that is typical and No surprise with Jeeps. I didn't want to pull the whole thing apart so used a great ceramic bonding epoxy. And now I know it worked after I did replace with new exhaust manifold. I looked at the ceramic I put on and it was solid sealed. Where no ceramic epoxy, a new crack formed. So hindsight says, the problem was that it had way too many cracks. I did not know that at the time. And more would occur as I patched it up. Welded up another exhaust manifold but it also was bad. Each time I went to smog, it failed miserably. Decided a new Catalytic converter. (this was before the new manifold). Swapped back between new and old O2 Sensor and both still failed.
Pulled it apart and found that the original manifold still cracked so it failed.
This time, put in a new manifold. The old manifold with the ceramic epoxy actually worked. But I did not cover ALL the cracks - too many.
New manifold, new gasket and new donut gasket, previous new O2 Sensor (NTK/NGK). Still failed. I checked again for leaks. Put air line in tailpipe and felt for leaks and used a liquid leak detector. No leaks anywhere from the donut gasket to the exhaust manifold where it mounts. Checked at the cat and it leaked ! Thought it was at the joint but turns out the cat leaked itself where its pipe joint was. Shop I bought it at welded it. Ran an engine cleaner in it for the 50 mile drive to the shop. Thinking break-in for the manifold, O2 Sensor learning etc....
Came back and the welded sealed cat still failed. But I had forgotten to plug in the fan so it wasn't regulated.
Came back in the morning with cooler temps, tested and it failed but better and closer numbers. I'll post. . The cat wasn't burning hot before the test like want it to be because I was more worried about combustion temps. This time failed but closer. Tried to get temp reading of the cat inlet and outlet but it fluctuated a lot. Took temp at the pipe just before the cat and the pipe just after the cat. Not that consistent. Seemed get 60F hotter difference, then 100F, then cooler at outlet then hotter. I'm thinking maybe the cat is plain no good. And maybe with all this trouble with bad cat leak, cracked manifold, the O2 sensor is bad too now. And adding Seafoam may have damaged the cat, the O2 sensor?
So I am confused what I have.
Tonight, I'll check the fuel rail with a tester from Autozone to eliminate that possibility. then wire up the O2 Sensor leads to a multimeter and see if I can see the voltage change as it supposed to do. If it does, then good O2 sensor. I was going to run 2 wires from the O2 connector terminals up into the cab attached to my multimeter. Sound fair enough?
Sorry for the story but asking if I'm going the right path. With the comedy of errors from hole in the cat to me forgetting the fan connection, I want to get this beast passed.

===========
I did stop at a muffler shop near home and he couldn't be sure the cat was bad either using the temp test.

jmrec100

TEST FUEL PRESSURE

Got that. What should the readings be?
The test plan.
1) Hook up the gauge
2) Turn the ignition on. Should hear/see fuel pressure go up
3) Start the engine, read the pressure.

Now what should it be for 1994 Cherokee, 4.0L Sport. Can't find those specs.
Thanks

jmrec100

Found the specs.
http://www.lunghd.com/Tech_Articles/...iagnostics.htm
Says with vacuum line disconnected, 39psi
Connect Vacuum line, 31 psi

I went to test. Hook everything up. Start the Jeep, and fuel pours out of the gauge pressure relief line. Button stuck. Get it unstuck, restart but fuel still flows. Whoever used it last time BROKE it! I'm pissed. Seems everything just trying to pass smog goes wrong !!! Tomorrow, I'll say a few extra prayers, beg God to please make this easier for me and then go back to AutoZone to get another kit. Tomorrow is another day.

red4dr

sounds like you are about where i am, ready to dig a hole for the damn thing haha. keep your head up, you are bound to get it sooner or later.

jmrec100

Yep. Was last night. That's when you call it a night,.grab a beer and sit. And I don't drink. I'm rigging in a shutoff needle valve on the gauge so I can still use it. Then return it tomorrow.

jmrec100

Rigged in my own Needle valve so I can use the fuel Pressure tester.
Results:
With Vacuum hose attached 32 psi
With Vacuum hose not attached 40 psi
Test good. So looks like fuel regulator in the injector rail is good.
So back to checking the O2 sensor and then the catalytic converter again

Another question. I know combustion temps are very important. I'm wondering if a 'dirty' engine will cause some major issues. There was a oil leak due to that oil filter adapter. The inner oring dries out and then get crazy leak. This leaked like a oil gusher well before I fixed it. Splashed oil everywhere. So the engine IS dirty. How big of an effect is that. I will drain some water from the radiator and add antifreeze to it to increase the amount. There was not a lot. Are these issues worth worrying about?

salad

Fuel pressure should be approx 39 PSI. 32 with the vac hose attached is no bueno. Was it wet when you took it off?

Parsnip

Agreed, his pressures are almost perfectly backwards what they should be

jmrec100

It was not wet. I am confused. According to this test,

http://www.lunghd.com/Tech_Articles/...iagnostics.htm

jmrec100

Yes/No??? I think these fuel psi readings are within the good range.

jmrec100

Had to put the jeep off for a bit. Had disaster at home with water pressure regulator going south. Blew up my water heater and now my shut off valve is stuck.

But are my reading in fuel pressure in range!

jmrec100

Took care of the 'other' issues on the home front with minor flooding etc...
Back to working on the Jeep smog issue. Last test was fuel pressure and what I read, it's within range.
I'll check the catalytic converter and O2 sensor again. Have a gut feeling, the 'new' cat is bad.

F1Addict

Nope. Should be 32 at idle with vacuum line attached, 39-40 with it disconnected. You're good.

Mendax13

definitely make sure the 02 sensor is working ive heard some bosch o2 sensors have been known to come dead. Bosch in the blue box i believe. correct me if im wrong.

if its stuck saying its rich and leans out the mixture it would increase the cylinder temps. high cylinder temps creates NOx. if not...

maybe it could be a clogged injector(s). but that's just a thought/guess.