QuestionQUESTION: Howard,
Point well taken. I should slow down a bit, I was just anxious to put things back together. I will pull the caliper and get that bleeder screw out and replace it if it takes all weekend. Also, thanks for the reference on brake lines, but I actually found straight lines with the correct fittings on the rack at local parts store for $4 each. Inserting a coat hanger wire allows bending by hand without kinks for a wonderful result. Another thing, you asked for a sketch of the return line issue on my fuel tanks, which I could probably illustrate well, but can't figure out my scanner. Any way, return fuel is flowing to the top through the line as it should, so I imagine all is well there. Until I am stumped again...
Thanks,
Michael
ANSWER: Sounds great on the brake line. As long as the return fuel is returning to the same tank that the car is running on everything is correct.
When drilling out the bleeder valve you only need to go to the bottom of the drilled hole already in the bleeder valve. don't drill any deeper so as not to damage the bleeder seat area. I usually just go in size steps a little at a time and when I get just into the threads you can usually use a pick to break the pieces of threaded parts of the bleeder out and you will usually find the end of the bleeder will just fall out thus not damaging the seat area.
Howard
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QUESTION: Howard,
Ok, "until I get stumped again" didn't take long. I worked to remove the bleeder screw tonight from the one rear caliper, and I'll just say I reached a point where I realized it would probably be more responsible for me to replace the rear calipers. I found a loaded, rebuilt pair at the same auto parts chain as the generic brake line for less than some outfits are charging for one. So, I decided to move on to my running issue. I cleaned out fuel lines, and dumped the fuel filter and blew it clear with compressed air. The engine ran fine until it began to heat up, then a pull of the throttle would result in a dive of RPM and backfire at the intake. I have about 30 PSI of fuel at the back of the fuel rail, about 40 without vacuum, and it drops to 25 or so when I pull the throttle. I shut the car off for 10 minutes or so, then cranked it back up, and it ran strong, but after about ten minutes of idle - same condition. It was running well before being parked to remove fuel tanks and brakes, so refresh me on what to check next. Is this sounding like a Cat converter getting hot? The first one is a non-issue, I can promise that. Thanks so much for taking your time to help!
Michael
ANSWER: Michael, you are jumping around at several issues. Why are you starting and running and stopping and running again so many times for?
Fuel pressure should be about 32 not 25 when running. A quick blip of the throttle should raise pressure Not drop, because vacuum drops when you open the throttle. Could be a fuel pump problem or a filter problem. You said you dumped the fuel out of the fuel filter and blew it out with air pressure. Did you blow it out backwards (out let towards inlet?) and did you see any trash?
Second item, If a CAT (Front CAT) is getting hot (turning red), that is normally a sign of either raw fuel going into the CAT (cylinder misfiring, injector stuck open, cold start valve stuck open, leak in the pressure regulator diaphragm or retarded Ignition timing)
CATs don't over heat for no reason. If it was running lean due to your low fuel pressure you will also see some higher exhaust gas temp but not usually enough to make a CAT over heat. In fact just sitting still running with no load it is difficult to get a CAT up to operating temp (600 deg F.)
Sometimes it is necessary to put a Ser III car in gear and hold the brake and run the RPM up to force it into a load condition to get a CAT to get hot enough to start operating when stuck in a line of cars waiting to get emission testing.
A melted CAT will usually cause an engine to idle ok but as you run the RPM and/or add load it will act as though there is no throttle opening and it will just bog but return to running ok at idle. The test for that is remove one of the exhaust manifold plugs and put a low pressure gauge in and run the RPM up and put a load on the engine and if the pressure exceeds 2 to 3 PSI, you have a stopped up CAT or muffler. That will not affect fuel pressure though.
Howard
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QUESTION: Howard,
I'm not jumping around by choice, actually, I decided to work on my leaky rear calipers as the car was up on stands while the fuel tanks were out anyway, and this has just developed two issues I am chasing. Brakes are all but done, calipers due in early next week. I wasn't starting and stopping the car for no reason. I started it, and when it began to idle rough, I shut it off and installed the gauge in the fuel line and ran it again, testing throttle, etc. That is where I was last night. Tonight I have tested 60 PSI of fuel at the pump, while a helper turned the ignition key, I have blown compressed air back through the filter and confirmed good air flow through filter with a gauge (compared with pressure at outlet, and with air hose direct to gauge). I have blown air back from the fuel rail to the trunk, and confirmed good pressure there, as well. I am now awaiting my battery charger to try a start again. Prior to that, on first start tonight, it ran for five minutes, showing a steady 30 PSI of fuel at the rail, then went to rough idle, gauge dropped to 15 PSI. Perhaps I have cleared out the last of any blockages in the lines and filter, I'll know once I get it to crank again.
I guess the only thing that still confuses me is how a fuel pressure problem can develop after several minutes of idle, if that does turn out to be the problem.
Thanks again,
Michael
AnswerOK, all that is understandable but you have a problem that you must correct before bothering with anything else and that is the low fuel pressure at the rail.
The series III XJ-6 used two different mounts for the pressure regulator. One is where the regulator is mounted off of the rail and the other has the regulator mounted directly on the front of the fuel rail. Either one controls the pressure on the rail at 32 PSI running and if you open the throttle (which drops vacuum) the pressure will raise.
If your hoses are not to dried and hardened take a pair of needle nose pliers and slip a short piece of hose over each of the two points of the pliers so as not to damage the fuel return hose off of the regulator. With a fuel pressure gauge on the fuel rail hose in a "T" so fuel can flow to the rail and on to the regulator.
Remove the air filter can and turn the ignition key to ignition (not start) and reach in the front of the air flow meter and open the flap with your finger.
The fuel pump should start running and show about 42 PSI on the gauge. While the pump is running Slowly pinch off the return flex line off of the regulator. You should be able to raise the fuel pressure higher than 42 PSI very easily. Don't let it go too high as you don't want to blow a weak hose in the system anywhere.
If you can't get it to raise higher instantly, you for sure have a fuel supply problem.
The pump has the capability of a high pressure and a high volume of fuel and the method the system uses to control the pressure is for the regulator to dump most of the fuel back to the same tank it is drawing from. The regulator when manifold vacuum is applied will not restrict the fuel returning to tank very much (32 PSI) but as soon as the throttle is opened, manifold vacuum drops and the regulator restricts the fuel returning to the tank thus raising the fuel pressure (40+ PSI) instantly to act as a accelerator pump used on a carburetor.
Howard
