theangler

Okay, so I'm still new to jeeps but I'm trying to figure this out. I have a nasty slow start which seems to kind of go away if I turn the key to on a few times and let it prime the injectors or whatever it's doing. Also, i'm getting a hesitation when I try to take off on the gas. When I first picked the jeep up a month or so ago, It was hardly idling, but I plugged the vaccume line to the EGR and it smoothed it out 100%. I dont know if this matters or not. I see someone has messed with the vaccume lines before. It's an 89 pioneer so I'm guessing that it has the renix system. Anyone got any ideas where to start? TPS or something like that?

Thanks a bunch

jpdocdave

if priming the fuel system with the key helps then you need to go there first. check for leaky pressure regulator, or pump on the way out. might want to replace the fuel filter first.

okcjeeper

My guess is fuel pump...similar syptoms as mine...Mine is slowly getting worse and I know the pump is on its way out...I plan on replacing the whole assembly, sending unit, pump and so forth...May even replace the gas tank as well..I think it's leaking..

BlueXJ

Yes it is a Renix Jeep. What exactly did you plug and is it still plugged?If so unplug it and hook it back up. Take i apart and inspect it. The diaphram may be bad or the spring.
To test it with the engine running, take a screwdriver and open the valve (pull the rod away from the engine). The engine RPM's should drop and engine should sound like it's running like garbage (may even stall out). Release the valve and it should return to normal. If not, it's getting stuck. Mine passed these tests, but I guess it wasn't closing all the way and you really can't tell if it is or not. I even took mine off and cleaned it/checked for operation while off the vehicle. I had to replace mine. As far as the transducer goes, you can open that up with a screwdriver (the plastic pieces are just snapped together). Like I said, the rubber diaphragm was real beat in mine and the spring was pretty much non existent as it was rusted to nothing. I'm not sure what affect the transducer has on the system, but it comes with the new valve. Remember to get a new EGR Valve gasket if you replace yours.
Also check the coolant temp sensor located on the drivers side of the block just above the pan. It sends a signal to broaden on narrow the injectors pulse width. And can be affected by the EGR solinoid as well and vice-versa.
HTH
Blue

theangler

Yeah it's still plugged. I plugged the line going from what I think is the EGR valve on the back right of the firewall to the front right junction block? (a few different vaccume lines, two big rings on top abs black plastic).

Also on the passenger side under the hood near the relay junction block, a few vaccume lines have been tapped up. I believe an orange-ish line as well as one that wraps around to the front near the headlights etc. (didn't trace it all the way). I'm not good with vaccume lines. Are there a lot on my XJ? I have a haynes manual with the diagrams, but they're greek to me.

Thanks

theangler

Also, is it alright to bypass the EGR? The guts have also been taken out of the CAT. We don't have strict emissions laws in this part of maine yet, so I can get away with it.

theangler

Okay, I'll check into the egr / coolant temp sensor (the gauges read correctly). Any other emissions stuff that could be bothering? I'll definitely check the fuel pressure on the rail. Where is the fuel pressure regulator located?

BlueXJ

Fuel pressure regultor is the round (about 1") shiney thing at the front of the fuel rail and has a vacuum line coming into the valvecover side of the regulator.
Yes there are several vacuum lines on a Renix engine.
Can you snap a pic and opost it of what you described on the firewall. Because it sounds like you have plugged the MAP sensor.

BlueXJ

The MAP sensor has only a couple of duties but can definitly affect the hesitation you described. It compares ambient barometric pressure during start-up (cranking) to engine load while engine is running. The ECU computes that information and adjusts the air-fuel mixture accordingly, thus it changes the rice vs lean mixture thus hesitation.

theangler

Hmm, I may have. I'll wont be able to snap a few pics for a little bit because the jeep is a few hours away. I'll be getting it down here this weekend or early in the week. I'm sure the MAP (master absolute pressure I believe) is pretty critical. I'll be sure to get some pictures of what I plugged as well as the hacked up lines on the other side.

Thanks

If I have the map plugged, will it run for the few hour trip? or is it risky?

When I plugged whatever I did, it would actually Idle smooth for the most part like it should. Before it was hardly idling. It was hesitating before as well though, worse then now. Could the map be bad? I also have my check emissions light on the dash, but that's no surprise to me

BlueXJ

Yeah angler but take it easy on your way home with it. The plugged MAP sensor will cost you more fuel but may cause it to hesitate or even bog when you accelerate.
BTW- MAP stands for Manifold Absolute Pressure. It takes a reading straight from the intake manifold.

theangler

Alright, Blue, I've finally got the inspection all taken care of so now I'll be paying more attention to this hesitation / start issue. So where do you think is the best place to start? I'm thinking first check the fuel pressure on the rail (check pump pressure / fuel pressure regulator). Then go to the vaccume issues I've had. TPS sensor, MAP sensor, EGR (which I don't plan on replacing unless I really have to), etc.

What do ya think?

BlueXJ

Sounds like a plan to me. Take a reading on the O2 sensor too as it also has an effect on the ECU changing the mixture of rich vs lean too.
To test, using an ohmmeter, disconnect the O2 sensor connector. Connect the ohmmeter test leads to connector terminals A and B of the sensor connector. Resistance should be between 5 and 7 ohms. Replace the sensor is the ohmmeter displays and infinite reading. I don't know about you, but this test is pretty vague. They say it should be between 5 and 7 ohms, but infinite is bad. What if you get a reading of 13 ohms or 100 for that matter? I wasn't too fond of this test as I found it is a test of the O2 sensor heating element!. One other thing you can do with the O2 sensor is hook up the voltmeter to terminals B and C (I can't remember if those are the right letters, but you want to get the sensor wire (believe it was blue) and the ground wire, or just ground to something else) with the connector hooked up and the engine on, warm, and idling. You should notice the voltage jumping up and down in about 2 second or less intervals. If it doesn't jump up and down considerably or takes longer than 2 seconds to do so, change it.

theangler

Sounds good, easy enough test. I agree about the ohm measurement. At least I'll know if it's in the "good" range. I suppose you know where the oxy sensor is mounted? I'm lazy haha, could look it up.

theangler

All signs are pointing to the fuel pump... no pressure at the rail. what do you think Blue? I put in a new fuel filter earlier and still nothing. Thing just bogs out when I hit the gas. The pressure regulator looks like quite a job, and I'm assuming these don't go as frequently as a fuel pump. 180k on the jeep, so I wouldn't be surprised. I do hear the pump priming, but what do you think? I've been reading the haynes manual and all the diagnostics are pointing to this. I also see that you don't need to drop the tank to get the pump! ...