vistacruiser

think you're onto something there. Great write up !! I'm not much on these earlier iterations of the 4.0, that's for sure. It's plainly obvious too, isn't it? ... lol.

Early in the thread she did say that she had checked the fuel pressure and I think she said it was 'fine'. Like you say, bet it was very likely a spritz check from the Schrader valve.

IMHO, I think the whole thing has been boiling down to a fuel issue too ... cuz we're right on the verge of eliminating virtually EVERYTHING else. .... this may be another clue: she also said earlier that the injectors 'sprayed a stream' ... I don't think that is right ... gotta' fog, don't they? ... could very well be pressure related ... filter, short little hose on the fuel pump, or otherwise pump related. Excellent, ZJ !!

So you can snake a fuel pump outa there without droppin the tank, eh? That's awesome ... I'm not worthy ...

ol"blue

Great tip indeed. The injectors won't have the correct cone pattern at a lower fuel pressure. And the back-firing could be caused by a lean condition from insufficient fuel pressure.

zjrog

I'm just surprised nobody was asking for the actual pressure. And yes, at least on the Renix XJs, the pump can be yanked without dropping the tank. Seriously, I friends kept saying check the fuel and I had fuel at the rail. But not enough pressure to keep it running. Try and advance the throttle and it backfired through the intake... There are a few threads about that here...

karen7

A guy at work explained to me what the cone fog pattern your talking about coming from the injectors looks like.

Answer-NO the injectors are not spraying fog like, its more like the stream setting if you are spraying window cleaner.

My moms husband chcked it and said it was good, I wasnt there so I was going off of what he said. They are getting 31 with vac line and 39 without.

He replaced the fuel filter and he said it sounds better. He is pulling the fuel pump to check the hose.

I apologize for the mix up in the beginning about the fuel pressure. When they said it tested good I never questioned what the pressure was. My moms husband has a 97 jeep so I assumed he knew what he was talking about.

So lets say this is fuel related, how do we fix it?

zjrog

If you have those pressures, I'm not sure pulling the pump will do you any good, other than maybe peace of mind and one more thing you have physically checked. Although it wouldn't hurt to check and make sure the hose in in good shape anyway. Also make sure there isn't debris clogging the bottom of the pump. It could still have good pressure, but very poor volume.

I am encouraged by the change of a fuel filter making it "sound better". By that does he mean it runs better too?

karen7

Yes it runs better at idle. when you give it throttle it backfires into the TB and dies. It will not stay running when you give it gas.

vistacruiser

ZJ ... they ran it out of gas during this ordeal. I had suggested a clogged sock earlier too ... but the f/p sounds normal, right? I also suggested an injector cleaning .. either off the car on a bench somewhere or with a strong solution of Seafoam in the tank.

I have all but begged for someone to look at the timing marks under the strobe light ... but there has been no report of that. If that could be done, that would just about eliminate everything but the fuel.

Do you not plan on having them check that at all, K ... or has it been done and just not been posted up .. or I missed it ... or what?

Or, ZJRog, would it not show anything anyway? Help me learn something here

zjrog

A pump can put out the right pressure but not enough volume. But there isn't an easy way, really, to check that that I know of. I don't recall exactly, but they did check the timing.

Ummm, I don't know if it would be an issue, but have you tried the TPS adjustment procedure? DO a search for TPS adjustment... I'm at work and lots of that stuff gets filtered.

Sounds like it is getting closer though.

And for the record, I am NOT a professional mechanic.

karen7

At 1 point they did check with the timing light and it seemed a bit advanced from what they said, personally idk what they were looking at so I couldn't say. The light stopped working when we tried to retest. I'll see if they can run the test again tomorrow.

Injectors are putting out too much gas so they aren't clogged, right? Are they just bad? Hes going to put the injectors from the other motor in it and see what happens. That will also be tomorrow. Plugs are black and sooty so also another indication of too much fuel???

No we haven't but I search that tonight.

vistacruiser

Doesn't work exactly like that ... suffice it to say that they must spray a mist or a fog in a cone like pattern .. GREAT idea to try the other injectors in there too. Gettin close ... Anxious to hear what is found in the fuel pump too.

Good deal with the light .. didn't mean to seem cranky either .. FrankZ would chew me out ... lol. If there is WAY too much advance at idle, then either the wires may still be off one hole on the cap or the dist may be off one tooth and a little twist too. Maybe just be a little twist. I'm just pluggin in the number of 0 to 10 degrees of advance at idle as a baseline ... maybe someone with a Renix will know the exact number or even take a look?? ... anyway, try to get them to experiment with that in mind ... it's gettin' down to the wire now.

I'm seein light at the end of the tunnel ... and it's gettin' brighter ....

karen7

fuel pump good, hose in good shape.

I updated my first post with all info I can think of so its all in 1 place. Thanks for the tip.

Thanks for the help so far everyone. i am feeling confident again that we can fix it.

vistacruiser

Cool ... these guys work late, don't they

ol"blue

This is really something.
It's weird that an 80,000 mile transplanted engine could cause this much trouble. Why did you change the head if the engine ran good before, and was guaranteed to run?

karen7

That was 1 more thing we were told by ppl that could be the problem. We had the other motor and knew the head was good. Sounded like a good idea to do so.
Also the head was not swapped until after we had tried many other things. The motor sounded like this when they swapped it, hooked up everything day 1 and tried to run it. We didn't just swap it for no reason.

vistacruiser

You said a mouthful there, Dan