fuel pressure q, 4.0

Stinking rough idle will not go away but I think I've found the problem with the miss after heat-soak. There is a TSB for putting insulation around the #3 fuel injector.

Anyhoo..

- Fuel pressure, no run, 33psi

- Fuel pressure, run, 33 psi

- Giving it the gas I notice the pressure does fluctuate quite a bit but returns to steady with engine rpm. Might be the pump having a hard time keeping up with surges?

- Take the vac line off the fuel rail pressure regulator, run, 40psi

- Engine off after run, 30psi then.... The fuel pressure gauge creeped up from 30psi to 36psi and vaporbubbles come out the drain hose when I dumped it.... Boiling fuel. :(

Guess I could wrap the injectors with insulation and insulate the fuel rail.

Does leave me wondering if this is "normal" to have some buildup after a shutdown.

To top it off, the only place around here I could find a good fuel pressure tester with release drain was Sears.. OW. Oh well, the tester should last a good long time and it qualifies as a new toy. :)

Haven't left the gauge on and put it under boost, the hose isn't long enough to reach where it can be seen.

My thoughts are now circling around both a week pump and one or several faulty injectors, plus heat soak.

Feeling a shotgun solution coming up. :) Any suggestions on pumps or should I swallow the lump and go OEM? Otherwise it would probably be NAPA.

Reply to
DougW
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Reply to
L.W.(ßill) Hughes III

Hmmm, my '97 FSM says 39 psi at the rail. :)

Jerry

Reply to
Jerry Bransford

Jerry Bransford did pass the time by typing:

32 is what my FSM says, but I've come across several references to a newer, higher pressure pump refit. Sometimes I wish this thing had a carb. Carbs I can rebuild. Fuel injectors I can just look at and scratch my ass. :/

Gonna throw some fiberglass insulation and high temp tape around the injectors and rail.

Or punch a few dozen louvers in the hood. :)

Reply to
DougW

L.W. ("ßill") Hughes III did pass the time by typing:

I like that last page.

14-13, installation, (3) .."Tighten fuel rail mounting bolts and nuts to 11N.m (100 ft.lbs) torque.

Yowsa! 100 ft.lbs on a 10mm nut into the intake manifold? yea... ooookay.

Try 10 n.m == 8 ft.lbs

Reply to
DougW

The 2000 TJ FSM calls for 49.2 plus or minus 5 psi at the test port on the fuel rail.

If the pressure is below 44.2psi, check for k>Hi Doug,

Reply to
Matt Osborn

Whoops, I meant to say 49 PSI for my '97, not 39 PSI... fat fingered it!

Jerry

Reply to
Jerry Bransford

Reply to
L.W.(ßill) Hughes III

Well, the Jeep is back from Sooner Auto where they did a compression check, leak down, and checked the injectors. All within spec. (forgot to get a copy with the numbers) :/

Anyhoo, that has it down to one last possible problem area that I didn't want to mess with.

Way back when I did the exhaust header the gasket may have gotten sqooshed improperly or had a fault and some exhaust is getting back into the intake. (basically acting like a stuck EGR valve would)

BAH!

Oh well, looks like I'll have something to do this winter cause for right now I'm done farking with it. :) The Jeep runs and I'm going to go play in the mud.

Reply to
DougW

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