Fuel Pressure Problems

[Mike]

I am having some serious problems with my fuel pressure. I have 99TJ so the electric pump should be building pressure as soon as the key is turned to the start position.

It does build to about 40PSI and then quickly bleeds off within 12 seconds. When the engine is running (if you can call what it is doing currently 'running'), the PSI stays steady at about 50PSI. But once the engine is off, it drops to nothing in about 12 seconds again.

I need to test the pressure using an adapter that connects to the fuel line and the fuel rail that has a 'T' connector in the middle for the fuel pressure guage. I can't find one that will work with the quick disconnects on the fuel line.

Does anyone have one of these that I could borrow for a day?

[aw12345]

If it chokes when first started up and smooths out after awhile you could have some leaking injectors, would explain the rapid bleed off. As long as it has adequate pressure when running and it prsurizes quickly when you cycle the key, I don't think the rapid bleed of is what causes it to run bad. Does it miss and choke badly when you first start it?
You could swing by my house on a week day afternoon don't mind taking a look at it. Ontario is not that far from RC

[Mike]

If it chokes when first started up and smooths out after awhile you could have some leaking injectors, would explain the rapid bleed off. As long as it has adequate pressure when running and it prsurizes quickly when you cycle the key, I don't think the rapid bleed of is what causes it to run bad. Does it miss and choke badly when you first start it?
You could swing by my house on a week day afternoon don't mind taking a look at it. Ontario is not that far from RC

Thanks for the offer Art, and I'd take you up on it if I thought the Jeep would actually make it to Ontario (yeah..., it's that bad).

The number one injector had some of the outside rubberized coating flaking off, so I replaced it when I replaced all the injector O-rings.

I made the adaptor that I was looking to borrow, but I am not sure that it is leak-proof. The threads for the connector are an odd mill, but I think that I have a snug fit.

When I used the adapter tonight, I found that the pump side of the engine still leaked as quickly as before, but the injector side leaked out as well but not nearly as quick. I hope that my home-made adapter has a leak and that I don't need both injectors and a new pump.

The annoying thing is that the pump seems to be operating properly, but some other aspect of the assembly (probably the fuel pressure regulator) is not working. The problem is that the fuel pump assembly comes a total unit. If the regulator goes out, you have to replace the whole pump! They're not cheap, the best price so far is $222.

But I agree with you Art, that it if the regulator is causing a pressure leak it is probably not the cause of my bad running conditions. If it didn't have the non-adjustable timing chain, I'd say that the timing was off. It runs rough at idle and all speeds. It backfires while accelerating. Most interestingly, these problems started all of a sudden.

I'll pull the plugs and do a compression check tomorrow to eliminate any cylinder, or head gasket problems. After that a full tune up check is in order.

I am open to any suggestions at this point. I need help on this one.

[aw12345]

Could be a timing chain, what is the idle vacuum, that is always a good starting point for engine diagnosis. If the fuel pressure is up to spec while running it should run ok. Some problems, that are possible leaking fuel pressure regulator, leaking injectors, they both cause very rough running and should somewhat clear out when it goes in closed loop.
a jumped timing chain would give low idle vacuum if it runs at all.Ignition timing retarded, no power low vacuum but runs fairly smooth. Clogged catalytic converter, poor running no power if it runs at all, but does not really miss, just runs poorly and sluggish if it runs at all. Low fuel pressure it will still run decent will hold back under full throttle, runs better when you ease up on the throttle a bit.
Prone to not starting and stalling when hot due to vapor lock. I think those are about the most common symptoms of poorly running engines.
Now if for some reason a rocker arm or push rod broke or failed it will have one cylinder not running if its the exhaust valve not opening you will get a lot of popping in the intake. For a none functioning intake valve, cylinder will not run will foul the plug with oil and higher oil consumption.
Any of these Symptoms ring true?

[Mike]

Several of these symptoms are happening.
How is the idle vacuum checked? I haven't done that check before.

The fuel pressure is up to spec while running, so I probably need to look for other issues. Even so, it has been hard to start since May 08. It usually takes three cranks to start.

The 'bogging' down and loss of power started recently. The rough idle and rough driving is very new. It runs rough, badly rough, at all speeds.

There are some new noises that I haven't identified completely, but popping in the intake does not seem right from what I can hear so far.

The only code that it has thrown so far is a misfire in the #1 cylinder. That could be many things.

I plan to check the plugs tomorrow, so I will share if the plugs are fouled. I will also check the regular tune-up stuff like cracked distributor and plug wire damage.

I welcome the input so far. Any help is greatly appreciated.

[dirtman13]

Mike, I think my Jeep got yours sick in Isham. For what it's worth check your exhaust connections for leaks. Especially where the monifold connects to the exhaust pipe. I had some of those same symptoms and found that my connector was loss. My 02 sensors are close to the connection and the fresh oxygen was giving false readings for short term fuel trim.

[aw12345]

To check idle vacuum you would need a vacuum gauge or a scanner and read map sensor voltage. It is always hard to diagnose from a distance, figuring out why cyl 1 misfires is a good starting point. Does it have coil pacs? you could swap number one to anther cyl see if the misfire travels same goes for the injector.
Backfiring in the intake is often related to ignition or the exhaust va;ve not opening. Ignition is far more likely. If the fuel pressure is good I would stop looking there, they all bleed of pressure, as long as the pressure comes up when cranking its good

[Mike]

To check idle vacuum you would need a vacuum gauge or a scanner and read map sensor voltage. It is always hard to diagnose from a distance, figuring out why cyl 1 misfires is a good starting point. Does it have coil pacs? you could swap number one to anther cyl see if the misfire travels same goes for the injector.
Backfiring in the intake is often related to ignition or the exhaust va;ve not opening. Ignition is far more likely. If the fuel pressure is good I would stop looking there, they all bleed of pressure, as long as the pressure comes up when cranking its good

I just checked the fuel pressure using my home-made adapter and I can rule out injectors. It held the pressure perfectly. The Fuel pressure leak is at the rear of the Jeep and is probably the regulator. I agree with you Art that I am looking in the wrong place.

Both your and Chuck's comments about exhaust issues may be part of the real issue. With someone else cranking the engine, I could tell that the small exhaust leak that I had seems to be a big leak now. I have headers and the two joints to the exhaust pipe (just before the O2 sensor) are both leaking pretty badly. I am going to the garage now to see if I can fix the leak. We'll see if that makes a difference before tackling the standard tune-up stuff.

[Mike]

Well, the exhaust leak is fixed, but the Jeep is still not running properly. Art, from your list of possibilities, I am sure that the injectors are not leaking. I think that the #1 injector was bad and I replaced it.

As for the other options, the symptoms of low fuel pressure that you described are there, but I doubt that the pressure is low. The idle pressure is 50 PSI and when the engine is revved, the PSI doesn't wiggle even a little bit.

I don't have a vaccuum gauge, but if you do, I think that I can make it to Ontario and back now. If not, I have AAA.

I still need to do the standard tune-up inspection. It could be as simple as a cracked distributor cap, but I doubt it.

I think the suggestion of vaccuum being the problem is a real possibility. Any suggestions as to where to start?

[aw12345]

If you don't work in the afternoons buzz by my house.
I can also borrow you a vacuum gauge, popping and spitting in the intake is generally more related to ignition especially since the fuel pressure is somewhere in the neighborhood of where it ought to be.
i would be more inclined to an ignition problem, an exhaust leak can cause a trick rich condition, which is not that hard to daignose simply unplug the oxygen sensor or sensors that are before the catalytic converter, then it runs in open loop but should run decent. Here is another question sis it go bad all of a sudden or got gradually worse?

[dirtman13]

I agree with Art about the popping and spitting. Sounds like an ignition problem. If you are looking for a vacuum leak pull your air intake off the throttle body and cover the opening with something like duct tape. Find a fitting on the intake manifold and pump some air in to it from your compressor. Not a lot maybe 5 psi. Use a squirt bottle with a soap and water solution and spay your intake manifold on all sealing points and all the vacuum fittings. I just did the same thing and found a leak on the fitting for the secondary air intake.

[Mike]

If you don't work in the afternoons buzz by my house.
I can also borrow you a vacuum gauge, popping and spitting in the intake is generally more related to ignition especially since the fuel pressure is somewhere in the neighborhood of where it ought to be.
i would be more inclined to an ignition problem, an exhaust leak can cause a trick rich condition, which is not that hard to daignose simply unplug the oxygen sensor or sensors that are before the catalytic converter, then it runs in open loop but should run decent. Here is another question sis it go bad all of a sudden or got gradually worse?

It started all of a sudden. Is it possible for a TJ to slip a tooth on the timing gear and get slightly off? It acts sort of like my old 74 Corvette when the timing was off.

As for checking the ignition system, I'll pull the distributor cap and plugs tonight and inspect them. I probably will not get home from work early enough to come by, but how late is too late?

[aw12345]

I go to work at about 6.15 pm, It is very well pssible it jumped the timing chain, if the engine has a timing marker set it on the marker then move the crank back and forth while watching the rotor if it takes more than 10 degrees of crank shaft rotation to get the rotor to move then its either ready to jump or has jumped already. I guess an other way to check is look at the rotor position when its at tdc number 1 cyl firing,

[Mike]

Sorry that I missed you Art. I just get home too late. Tonight I checked the plugs, the number one plug, looked a little fouled, but the rest were perfect. I checked the compression in all cylinders and for a Jeep with 140K miles, I was impressed that the compression was at the top of the scale on all cylinders.

I checked the plug wires, distributor cap, and rotor and all were in good condition. I moved the #1 plug to the #2 position and put everything back together.

I then tried to tighten all the bolts around the header and the intake manifold and all were tight. I checked all the bolts around the throttle body and they were tight. I also traced all the vacuum lines looking for any obvious problems and didn't find any.

After putting everything back together, I started the engine and the roughness and backfiring was still happening. I checked for any codes pending and a small evap leak and a misfire on the #1 cylinder were showing. I cleared those and revved the engine to see the reaction. It stumbled as fuel was added and then smoothed out some. Back at idle it was still pretty rough.

I got out to listen at various areas of the vehicle and it sounded like a steady mild backfire was happening near the intake and an occasional back fire at the exhaust. I also noticed that a fair amount of condensation was splattering from the tailpipe.

When I went back to the driver's seat, the engine light was on so I checked the codes again and I had a small evap leak and two pending misfires: one on #1 and one on #2.

I am not comfortable pulling the front of the engine apart and checking the timing chain for myself, so I think that I will be taking the Jeep to a mechanic to have them check it out.

I have used Expert Auto off Masy Ave. in Rancho Cucamonga in the past, but does anyone have another recommendation in the RC / Ontario area?

[RAT]

Mike and Art, I'll pull my front bumper off and we can put it on Mikes Jeep then I'll tow it to Art's house this weekend and we can gang up on it there. Whatcha think?