Hey fellas,

As the description states, I replaced my fuel filter today after noticing a very bad leak when I started the ole Waggie this morning (the 3'' piece of fuel tubing had cracked). Anyway, the change over was easy and went as expected. After doing the requisite three on/off (without starts) of the ignition I turned the key and it started up, after a bit of additional cranking - which I expected after draining the fuel pressure.

Well, I expected that additional cranking to dissipate, but it seems that it's decided to stay.

Could I have an air bubble or something up in the rail? Would I purge the air bubble by turning the ignition on and then pushing in the schrader valve?

1987 Jeep Wagoneer 4.0L - 146,000 miles.

*edit* In second post I also describe sluggish 4.0 questions!

Thanks for any help!

S/F,

-Matt

 

What's the fuel pressure in psi?

 

Did a bit of looking and intend to rent the tool and test it today at lunch or this evening if I don't have time.

It actually started up just fine this morning, so perhaps if there was an air bubble or something it worked itself out overnight.

The reason I'm still wanting to check the fuel pressure is that this Jeep (new to me) sure feels awful sluggish compared to the others I've owned, granted, this is my first 4-door, automatic and non-HO.

That said, my little '97 two-door with the 5-speed and HO 4.0 felt like a drag car compared to this thing (and I'm not just having fond memories, my parents still have the Jeep and I just drove it a couple of weeks ago). I'd say it's more akin (in speed) to my 2.5L two-door that I had.

I'm not expecting a speed demon or anything, but something definitely feels "off" with the acceleration of this truck...

Will report back with the fuel pressure.

 

Alright, unfortunately I got busy today at work and didn't get the chance to test the fuel pressure. That said, when I was driving home I noticed that I have a switch for my transmission that states "power" or "comfort". I flipped it on and at first nothing happened. Then I flipped it on/off a couple more times and the amber light came on. After it came on *blamo* all the power I expected to be there was just there. After doing some research I have found that most people just leave it in "power" mode, and that is what I shall do!

I still think I need to bleed the fuel system of air though, it's doing the slow start/long cranking thing again.

 

Long crank time seems to be normal on Renix 4.0s.

 

Well, I got the fuel pressure tester from Autozone today. We'll see what the pressure shows tonight.

I've made another *ridiculous* discovery that also brought back in some ummph...I checked the air pressure in the tires. Not to make stupid excuses, but since I'll be replacing these tires very soon I didn't give them much attention. But when I was walking out of the Autozone I noticed that one of the rear tires seemed a little low. At the gas station I was amazed to see that one was at 18.5 psi, another at 22.5 psi, another at 24 psi, and the last at 20 psi. Man o man, putting the right about are air in them certainly helped a lot.

 

HI..The "comfort" switch just changes the shift point a bit. It will downshift sooner in "power". (just giving it more throttle will do the same).

The fuel pump circulates the fuel in a loop through the rail, pressure controlled by the regulator. One would hope/assume air would be worked out soon enough.

Side story. For wholly different reasons I ran a couple tanks of Chevron Premium with that "techron" additive. (waz a mileage experiment, and yes the Renix got more, but I haven't "crunched" the # for economy) Anyway, unexpectedly the long crank went away, now my "new" (white) 90, starts as fast as my way older Brown 90. ~ 3-4 seconds. Injectors? Check valve? Idk, but that did indeed happen.

Edit. If/when you do hook up that pressure tester, do see how the pressure drops after you turn it off. Renix, running, is around 29# with the vacuum line off the regulator, and around 10 more with it on, IIRC. Someone else might have the drop-off spec. With it off. Around a pound a minute maybe...

 

The "power" setting also has the transmission delay upshift points. It also shifts crisper, rather than just sliding into gear.

It kind of feels like a shift kit was added to a regular transmission.

 

Flintstone,

Believe it or not, your Chevron experience is not just anecdotal. I actually work in the industry (though not in that part of it) and the chemists/engineers in my company have told me that the best two additive packages offered by the supermajors are V-Power by Shell and Techron by Chevron. From what I've been told, the Shell V-Power is the superior additive package (marginally) *however* they vary the amount injected into their supply based on the fuel grade (ie, you're only getting the full dose when you ante up for the Premium). Chevron injects the same concentration of Techron regardless of the grade so your $$$ goes a bit further for a comparably good additive package.

When I had my Ram Cummins I ran only Shell diesel when I was able as I got considerably better (2-3mpg) mileage with the Shell diesel vs other brands. That said, I've not noticed and appreciable difference using their *regular grade* gasoline. I just recently (haven't even had a chance to fill up yet) found about Chevron injecting at the same concentration regardless of grade. I'll be filling up with Chevron soon and conducting own little experiment!

I'm going to adjust my TPS cable this weekend as well as test the fuel pressure. It's getting better, but still pretty doggish when accelerating on the freeway!

S/F,

-Matt

 

My 4.0's are normally pretty strong. I rarely use allot of throttle even with a trailer or a load. (I often just floorboard my 2.5, often in 3 rd, on the other hand)


Interesting! Well I left out something that didn't seem to make sense. My "new to me White" 90, (as opposed to my 90 since 02), the white's long crank went away with the Techron. BUT GET THIS. When I went back to the Indian gas (40c less a gal), long crank came back. Right now I'm confused.

The throttle position sensor is supper crucial and needs to be adjusted with a digital meter. The "kickdown" cable, I just use a button on my housing to set the cable with about no, or less than a dime of slack.

YOu can also see your sensor ground resistance from the TPS, in Cruisers tips....

 

well I won't pretend to know why it went back to starting slower, but you could look on Indian's website and see if they rate their fuel as "Top Tier". Top Tier is a rating that assures that their supply meets certain quality and detergent specifications. Perhaps it's simply lower grade fuel.

And I agree with your assessment of the 4.0...in my experience it's a peppy little guy. I think mine is sick, or at the very least under the weather. I've only had it a couple of weeks though so I've got time to figure it out. I'll definitely have some time this weekend to do some diagnostics and check compression, etc. to whittle down some of the problems.

Aside from fuel pressure, my top thoughts are:

1. TPS issue
2. Low compression on one or more cylinders
3. Misfire/ignition issue
4. Transmission kick down needs adjusment

Any other thoughts?

 

Well, sounds like you know your way around. Yea clean and gap the plugs. .035 Since it's free to borrow the gauge, the pressure bleed down as well as the pressure with the vac line on, and off the regulator.

Technically it's not a "kick-down" , but no tension and no slop seems to work for me.

If I did a compression check (happens I haven't done one in a coon's age), the wet/dry test is cool. You first take 6 numbers, then (maybe with a long vinyl tube), blow a couple of tablespoon of oil in the hole and take a second set of numbers. If a low comes up, it's rings, if not, it's a valve or something up above. (always have the throttle open) UTube or Google "wet dry compression" I normally go 5/7 strokes, but others do it different.

Again, cruisers stuff is golden. Making sure your sensor grounds are A1 could be considered first in any attempt to diagnose problems. On mine, there on the stud that secures the dipstick is my ECU, TCU, the injectors and sensor grounds. > https://www.cherokeeforum.com/f51/cru...x-tips-153657/

 

Obvious suggestion, but did you verify there are no leaks at the new fuel filter?