2000 TJ 4.0L fuel injectors

While I am also interested in the expected life expectancy of the injectors is it worthwhile to incur the expense of changing them before failure?

There was a post several days ago where someone was unable to find the grounds in his engine compartment. While I was down photographing them I decided, for some reason, to check the pressure in my fuel rail. As I hooked up the gauge I got no leakage so I am assuming that all the pressure had leaked down. I turned on the key for a few seconds and then turned the ignition off and removed the key. The pressure gauge was now set on 50 psi and stayed there for the duration of the photography and removal of leaves/needles from the cowling and inspection of the wiper blades. When I removed the gauge, still at 50 psi, I did get fuel spillage.

How long will the fuel rail hold pressure? I know for sure I drove the Cherokee Sunday but I think it may have sat several days since then.

Matt Osborn did pass the time by typing:

A set of injectors will last as long as the engine if you maintain the filter and use good fuel.

Pressure drop in the fuel rail is one of three things. - fuel pressure regulator - fuel pump backflow valve - fuel injectors

And injectors are bloody expensive. A system called MotorVac can be used to clean the whole thing from intake to cat. about $100.

First thing to get is a fuel rail pressure gauge. The good ones have a little hose for dumping fuel. Measure the rail then measure how fast it drains. Failed check valve in the pump will drop pressure very quick, failed regulator will give you a low 20-30psi reading rather than the stock 32 (double check with the dealer to make sure 32 is standard it was in 93) and your pressure gauge will also drop quickly.

A leaky injector will drop pressure very slowly.

If you want to, you can remove the rail, leave the injectors attached. Let the pump run and the rail pressurise, then look for drips.

If you do remove/clean/replace the injectors, use new O rings and lube them with a bit of motor oil so they slide in easily and don't tear. (and don't loose the clips)

Billy Ray did pass the time by typing:

On a new engine, days. Test threshold is less than a 20psi drop in 30min. Mine still has about 10psi in it after sitting all night and that's a 93

Jerry, that's the first time anyone has mentioned that valve being a seperate unit but it rings a bell. I've replaced several pumps in different vehicles over the past few years (comes with kids doing their own repairs - "Hey, Dad...") and it got me to thinking. Best I can recall, every single one I replaced had that valve in the piece of hose between the pump and the mount! I just looked and I have 3-4 of them in a junk box - some even have the flow direction indicated. Looks like a 50 cent part - wonder who sells them? It's just a ball with a spring to seat it until pump pressure pushes it open. I haven't had the opportunity (yet) to look at the newer pumps with the integral regualtor so that may require a whole pump assy but dollars to donuts you are onto something for the older ones with the external regualtors.

With my luck all my pump problems so far have been total, undeniable pump failures but this is a good th> Matt, my guess is that your problem isn't from leaky injectors at all,

Will Honea did pass the time by typing:

You can put an external check valve in the line between the fuel pump and filter. It's loads cheaper than a new pump.

I'd check race and marine stores, but NAPA should have them.

You of course can always add an anti-drainback valve anywhere in the feed line, which would be as good of a fix as replacing the OE anti-drainback valve would be. As said already, I'd bet big $$$ your problem is nothing more than a leaky antidrainback valve.

Jerry

Will H> Jerry, that's the first time anyone has mentioned that valve being a

Thanks, everyone.

The injectors are due for cleaning, so I'll have that done. The anti-drainback valve Jerry mentioned sounds like something I can live with until the fuel pump fails.

Again, thanks for help!

-- msosborn at msosborn dot com

Matt, I really doubt you're having ANY fuel injector problems and I even more strongly doubt they need cleaning. Today's injectors with todays fuels that ALL contain fuel injector cleaners keep them pretty darned clean. They just don't wear out this quickly, 110,000 miles is not a lot of miles at all. Mine have 160K miles on them and I know plenty with over 220K miles on them. Just trying to save you a bit of $$$ and time.

Jerry

Matt Osborn wrote:

philthy did pass the time by typing:

Interesting note. There are at least two different types of injector designs out there. The older ones use fairly high current to keep the injector valve open. Others use a higher current pulse to open the injector and a lower current to keep them open. That type uses a much finer coil and is more suceptable to overheating and shorting out.

philthy did pass the time by typing:

Sounds like they got a bad shipment of injectors or are just using bad products.

Delphi (and many airlines and other manufacturers) are going down because management made deals with their unions for unsustainable benefit packages.

We now face the specter of our government subsidizing both. Not only are these companies going to be let off the hook for their disastrous union contracts, but we are actually going to pick up the tab for the union members as well.

As one who has provided for his own retirement, I find the above appalling. If union members are to have a publicly financed retirement aside from SSI, why shouldn't everyone else?

-- msosborn at msosborn dot com

Delphi is shipping water because their business model -- and the big GM teat that it suckles on, didn't adapt to change. GM wasn't under any union obligation to pack their dealer's lots with Escalades at 13MPG while ignoring that there's a shooting war in the oil-rich middle east, they did that all by their lonesome, thinking that they'd make big cars with big profit margins today instead of having a plan for half a decade down the road. Was GM going to maintain their market share forever? No, but they -- and the unions -- clearly thought that they would.

Those were contracts that were written when both sides of the table figured that the gravy train would continue to roll. You could, depending on your bias, lay the blame at any number of other parties: GM for underfunding their pension plan by some $31 billion[1], stock buyers for not only encouraging such madness but rewarding the company for doing so, the federal government for failing to prevent companies from underfunding pensions, the medical system for being so efficient at keeping retirees from dying early, other companies for making cars that outsold GM's, and so on.

As it is, Delphi isn't on the hook for the whole nut: "As as part of the [1999] spin-off deal, GM agreed to back the pension, life insurance and retiree health benefits of its former workers at Delphi." [2]

I recall when Lee Iacocca slyly suggested that it might be in the country's best interest if the federal government just "forgave" that bailout loan that they got. Fortunately it wasn't.

Well, just to play the Devil's Advocate, you -- and I -- are going to pay either way. Either we pay for the retirement of past employees out of current company profits -- that means paid for by consumers, or we pay for out of tax revenue, and that means paid for by workers, or GM and Delphi collapse and we pay for it in lost investment. In any case, if the Pension Benefit Guaranty Corporation does have to take over a plan it caps the benefits at $43,977 a year. For a lot of professionals that's half of what they had planned on having for their service to their employer. Do I want to pay for it out of taxes? Hell, no, but at least there's a cap.

Oh, and poor Delphi? Their Board of Directors are getting between $120,000 and $200,000 a year in cash after managing the company into the ground, their new CEO got a $3 million signing bonus and 600 of their executives stand to get a average of 2/3 of a million dollars each if they don't jump ship. [4] It's good work if you can get it, I guess. Who is bleeding the company white?

All of those manufacturers and their unions have known for forty years that they were killing their golden goose. They are both responsible for their problems. Those Escalades you mention amount only to a minor irritant in the scheme of things. It is the retirement benefits that are bringing down both of them.

I'm not taking sides. Both parties are responsible for the failure.

I'm not limiting my argument to Delphi or even auto manufacturers. As it is, all organizations, from auto makers to airlines, that allowed their unions to steamroll them (yes, the manufacturers are just as guilty as the unions) are currently collapsing.

I'm afraid the consumers have already opted out of the 'reward the foolish' program. Toyota, Honda, et. al. have been eating their lunch for years.

Real companies, with real products and real jobs have been locked out of the market for 70 years due to this unrealistic business model. We've already lost our investment, now it is simply a matter of throwing good money after bad.

Only half what they expected? Oh, those poor workers, only $44,000 dollars a year above and beyond what the rest of us receive. How will they ever survive?

Sorry, they get no sympathy from me. All involved, from management to floor sweepers are responsible for the failure.

Let them go under now, right along with their employees,investors and fraudulent business practices. Just break them up and sell the pieces.

There are future generations that need jobs, and there are investment monies that will provide them if we sweep these corrupt, bankrupt organizations out of the way.

-- msosborn at msosborn dot com