have to pump gas for it to drive...

ok, so the heep is running, finally,

but in order to get it to go you have to make long strokes on th gas pedal and pump it.

ideas?

clog in the line somewhere. put in a bottle of Lucas fuel treatment and fill her up with good detergent gas

I had a problem very close to what you are describing... Turned out to be my IAC (idle air control valve). Check that out and clean the TB.

I would start with replacing fuel filter if your XJ is not a newer one (post 96 I believe) with the filter in the tank. It helps to post the year of your Jeep as for something like this, there are differences.

Check fuel pressure on the schrader valve on the fuel rail. Compare your pressure reading to spec. You could have a bad fuel pump.

JoeOffRoad said:

I had a problem very close to what you are describing... Turned out to be my IAC (idle air control valve). Check that out and clean the TB.

Click to expand...

It's likely the IAC, but the vacuum line to the MAP sensor coming loose (or plugged in the wrong hole at the TB), a CPS going bad or a bad MAP sensor can do pretty much the same thing.
IAC can usually be driven, but requires a subtle touch on the throttle. A MAP or a CPS often can't hardly be driven, getting any sort of RPM out of the motor is often difficult.
A stuck open EGR, will hardly idle and needs RPM's. It will eventually smooth out with enough RPM's. But idles poorly and may stall a lot (much like a stuck closed IAC).

ok the HEEP in question is my project '89

located here:

http://naxja.org/forum/showthread.php?t=938039

I need to update the thread, but we have replaced the fuel pump, and filter.

hard wired the pump assembly to the battery with an interupter switch due to a bad harness. the previous owner was a bit trigger happy with the wire cutters.

we have taken off the iac and cleaned it with carb cleaner,

removed the map censor from the firewall, so the vac lines would reach. engine dies with the map disconnected, so i assume it works right?

took apart the fuel rail and cleaned all the injectors, new O rings all the way around. still a pesky gas leak at the return line. but its intermitant and dripping

new wires

new plugs.

all the vac lines have been checked and connected to there proper place.

and my pressure tester was faulty so i returned it to napa

dumped about 7 gallons all over the conoco because the lock ring was not in the gas tank...

its been fun, just stumped at the moment.

There is probably no short cut or easy way to do it, like most new to me XJ's you have to figure out what you have and then fix it. I usually do a compression test first, just to avoid wasting a lot of time.
Sounds like a fuel problem or an air problem, fuel air mix or whatever with maybe some timing thrown in. Let a little oil dribble behind the piston on the IAC, when they stick it can be internal as well as external.
A combination of the TPS and the MAP sets the baseline fuel mix and timing. With some input from the cam position sensor (which is actually fairly subtle in my experience). Cam position sensor is usually well down on my list, but is actually a good place to test the 5 volt sensor circuit.
I'd check the TPS grounds, both sides. Adjust the TPS on the ECU side and make sure it is near the .08 ideal, though this isn't as critical as getting the TCU side of the TPS, as close as possible.
Check and make sure the front fuel rail harness, where it goes down the front of the block isn't cooking on the manifold. And then test the O2 sensor heater circuit. make sure the engine temp. sensor is hooked up and the harness isn't cooked onto the exhaust manifold.
You'll likely have to test all the sensors eventually, it's nice to have a plan.
It actually took me years to really fix my 88. I got the major bugs worked out fairly quickly, the subtle stuff took a lot longer. I eventually found a loose splice that was causing a variable ground in the TPS circuit.
I tend to check the basics first, like initial timing, compression, vacuum and fuel pressure. If your compression is much below 105 you don't really stand a chance of getting it to run anywhere near good. Vacuum, the needle should be fairly stable and not take wild swings, the vacuum reading itself is less important. TDC piston "1"compression, with the timing marks aligned to "0" the rotor should be near the number one spark plug lug on the cap (usually marked with a "1"). Fuel pressure between 30 with the regulator connected and 40 with the regulator disconnected. Near the higher number during cranking.
Block off the vacuum line to the EGR and tap the EGR a few times with a screwdriver handle. If they hang open it can cause all sorts of grief until the RPM's get up some.
You've probably already checked much of this stuff, but sometimes it's better to start over and have a plan, just in case something simple was overlooked.

No easy fixes? Amen brother. I got this one beat today, not but a few hours ago on a hunch.

Most of the problems suggested here were ruled out. The first "guess" we put in was plugs, wires, and a fuel filter. The fuel pump was replaced based on the low fuel pressure at the rail, and the fuel pump relay bypassed via a switch and wires run directly to the sender due to insufficient voltage readings at the sender. This could have been the cause of the low pressure in the first place, but the pump I took out of the Heep (an aftermarket replacement pump) had no sock on it, so was probably not going to be long for this world anyway. The TPS checked out, the IAC was clean and the port clean (recently replaced in fact). MAP sensor had the correct input voltage, the EGR valve had long since been blocked off, and we have white hot spark. The distributor appeared suspicous, and the firing order is different from the factory specification, so a timing issue would have been a good place to suspect.

Still, I felt based off of some experience and a bit of a hunch the the issue was in the MAP sensor - also making it a bit of a timing issue in a sense as well. So pulling the MAP sensor from Tlowery04's totaled jeep, I walked resolutely over to the Heep but then remembered an important point. During our initial diagnostic tests I had taken the connector off of the MAP sensor and tested it with a multimeter to see if it was recieving the correct voltage from the computer. At that moment, I had the epiphany.

At some point, your's truly, Captain Retard here had reconnected the MAP sensor BACKWARDS.

So I won a mixed victory, as the Heep now runs very well overall (still a few minor loose ends to tie up), but I was at the same time humbled by my inability to figure the correct orientation on the MAP sensor connector.

In my defense, it is a small consolation that the original owners had broken the clasp on the connector quite cleanly, which made it difficult to really figure the correct orientation once the connector was removed for that first round of diagnostics.

That concludes my long winded story. Maybe some day somebody will search the forums and find they made the same stupid error I made, which would make me feel a whole lot better about myself, frankly. )

LOL good endings, sigh. I'm all warm and fuzzy. Good job.

Glad you had a happy ending, when I first got my 88 it had a bent pin in the same connector.