Renix issue?

[1990JEEPXJ]

and another thing thats weird is that when it does decide to buck and stall, then not start, after i let it sit then try to start it sometimes, it will start immediately after i turn the key back to run position after attempting to start the XJ. that leads me to something ignition related. hmmm

 

[BillDunn83]

ok guys check this out i have heard it is a big problem with xj's. there is a rubber hose that runs down into the gastank from the pump. The hose tends to crack which causes the pump to take a while longer to pressurize and suck the gas. it is something that is easy to check i will be doing it tomorrow on my rig I will take pics and show you guys what i am talking about..

 

[joe_peters]

and another thing thats weird is that when it does decide to buck and stall, then not start, after i let it sit then try to start it sometimes, it will start immediately after i turn the key back to run position after attempting to start the XJ. that leads me to something ignition related. hmmm

Almost sounds like no power to the fuel pump in the START position?

 

[jujuscisyn]

Guys, I am open to anything. Hell, I'll search the tank for pink bunnies with football helmets on, as long as it gets this thing going. I've heard of that cracked line before but it was on another forum and only once, so I didn't give it much thought. The check valve in the tank had also crossed my mind... just won't hold enough for throttle application but at idle it does the job. I don't know. If I find something out, count on a post.

 

[5-90]

5-90, are you still using the Bosch platinum single ground electrode plugs?

No - Autolites. I used the Bosch before the Autolites came out, but I don't like the fact that Bosch uses a "pin" electrode and shrouds it with porcelain. The Autolite electrode is "open" and does a better job of keeping itself clean.

I haven't used Champion plugs since I had a set explode in my Bug back in 1989. That was when they were still putting in a vacuum space around the centre conductor down the porcelain, which is probably why mine exploded (and took the plug wires out with them.) That was when I switched to Autolite - and the only time I've strayed was trying the Bosch plugs.

I get good reports from the field on Champions these days, but the only thing I can bring myself to use Champions in is small engines. Just can't bring myself to do it, that's all.

 

[5-90]

Guys, I am open to anything. Hell, I'll search the tank for pink bunnies with football helmets on, as long as it gets this thing going. I've heard of that cracked line before but it was on another forum and only once, so I didn't give it much thought. The check valve in the tank had also crossed my mind... just won't hold enough for throttle application but at idle it does the job. I don't know. If I find something out, count on a post.

The check valve is there to hold pressure while the pump is not running - it's not necessary when the pump is running.

However, if the vane shoes in your pump are wearing out, you could be not developing enough pressure to run the fuel system properly, and screwing things up. Have you checked fuel pressure? The Schrader valve on the rail answers to a standard GM dingus, making a check gage easy enough to find.

Dimensions for the manifold screws and studs are on my website, in the Tech section. I usually cut new studs out of brass threaded rod (since brass won't seize against iron or steel like steel will.) If you can't get brass or bronze screws for replacements, use SAE5 screws and replace them every time you take them out. (SAE5 will hold up under repeated heat-cycling better than SAE8 will - verified experimentally.)

 

[jujuscisyn]

The check valve is there to hold pressure while the pump is not running - it's not necessary when the pump is running.

However, if the vane shoes in your pump are wearing out, you could be not developing enough pressure to run the fuel system properly, and screwing things up. Have you checked fuel pressure? The Schrader valve on the rail answers to a standard GM dingus, making a check gage easy enough to find.

Dimensions for the manifold screws and studs are on my website, in the Tech section. I usually cut new studs out of brass threaded rod (since brass won't seize against iron or steel like steel will.) If you can't get brass or bronze screws for replacements, use SAE5 screws and replace them every time you take them out. (SAE5 will hold up under repeated heat-cycling better than SAE8 will - verified experimentally.)

That makes sense, but you can see just how many things I am trying. Even thought maybe a valve was floating. I have checked the fuel pressure but not for a while, when I first noticed the jeep doing this I checked and it was a little low, like 29 and almost 39 with the fpr disconnected and didn't figure that kinda of pressure would give these severe of symptoms. I gotta get my hands on a gauge to check again. A renix owner without a fuel pressure gauge or multimeter is just not gonna get very far when these things go south.

 

[joe_peters]

That makes sense, but you can see just how many things I am trying. Even thought maybe a valve was floating. I have checked the fuel pressure but not for a while, when I first noticed the jeep doing this I checked and it was a little low, like 29 and almost 39 with the fpr disconnected and didn't figure that kinda of pressure would give these severe of symptoms. I gotta get my hands on a gauge to check again. A renix owner without a fuel pressure gauge or multimeter is just not gonna get very far when these things go south.

29/39 should be about right for Renix, gotta give a little allowance for gauge variations and your eyesight!

 

[jujuscisyn]

knew it was pretty close to the 30 and 39. I didn't have a chance to do a leak down test or test it when it was acting up so as of right now I'm in the dark about the fuel system performance. I hope to rectify that situation soon.

 

[jujuscisyn]

I backprobed the camshaft position sensor today and found that I only have 2.25 volts. I cleaned the grounds (again) and have no resistance on the path to ground. but between a and c its low. The manual says 5 volts. Does anyone know how critical the 5 volts is? Seems to me that less than half isn't good and could it cause the symptoms I'm seeing?

 

[Ecomike]

I backprobed the camshaft position sensor today and found that I only have 2.25 volts. I cleaned the grounds (again) and have no resistance on the path to ground. but between a and c its low. The manual says 5 volts. Does anyone know how critical the 5 volts is? Seems to me that less than half isn't good and could it cause the symptoms I'm seeing?

Disconnect the harness connector, and probe the harness side to see if you have 5 V from the ECU, power on, engine off. If not, you have resistance or short losses in the wiring somewhere, or an ECU problem.

Correction, you should be reading between terminal B and C, according to my FSM. C should be a ground, B should be 5 volts.

 

[1990JEEPXJ]

so i replaced my plugs and wires the other and discovered the terminal on the distributor cap for cylinder #2 was completely corroded and blue. so i hit it with some steel wool and put dielectric grease on all the connections for the plugs and wires. so my random bucking problem at speed it gone, which i now assume was the horrible connection for cylinder #2. i also got the MAP vacuum line temporarily fixed. so i runs good now, but doesnt idle well at all when warm, probably 500-600 RPM. it stumbles and dies on occasion and sometimes fires right up, sometimes takes a few tries. but not nearly as bad as before when i would have to wait 15-20 minutes to retry. i broke the clip off the MAP sensor and that vacuum line needs to be replaced, both of which i am replacing next. im going to recheck my TPS voltage, which is new, and i thik i might have to replace the IAC. and when i was looking for vacuum leaks i noticed two manifold bolts were no more than finger tight. that also helped it out a bit. i also did a compression test and they were a little low but not bad, all within 120-130psi.

 

[Ecomike]

Sounds like you are making progress.

Have you considered that the corrosion on #2 in the cap might have been a sign of a crack in the cap? I have seen hairline cracks, nearly invisible, cause miss fires, only when the cap got hot enough.

so i replaced my plugs and wires the other and discovered the terminal on the distributor cap for cylinder #2 was completely corroded and blue. so i hit it with some steel wool and put dielectric grease on all the connections for the plugs and wires. so my random bucking problem at speed it gone, which i now assume was the horrible connection for cylinder #2. i also got the MAP vacuum line temporarily fixed. so i runs good now, but doesnt idle well at all when warm, probably 500-600 RPM. it stumbles and dies on occasion and sometimes fires right up, sometimes takes a few tries. but not nearly as bad as before when i would have to wait 15-20 minutes to retry. i broke the clip off the MAP sensor and that vacuum line needs to be replaced, both of which i am replacing next. im going to recheck my TPS voltage, which is new, and i thik i might have to replace the IAC. and when i was looking for vacuum leaks i noticed two manifold bolts were no more than finger tight. that also helped it out a bit. i also did a compression test and they were a little low but not bad, all within 120-130psi.

 

[1990JEEPXJ]

Sounds like you are making progress.

Have you considered that the corrosion on #2 in the cap might have been a sign of a crack in the cap? I have seen hairline cracks, nearly invisible, cause miss fires, only when the cap got hot enough.

i have not considered that but i do plan on replacing the cap and rotor soon as it more than likely was contributing to the misfire. it did seem very odd that only one was corroded like that. one question, is it ok to remove the vacuum lines from the little exhaust tube thing to the air box, and the two on the back side closest to the firewall that control the bimetal temp sensor? assuming i cap the leaks of course

 

[Ecomike]

i have not considered that but i do plan on replacing the cap and rotor soon as it more than likely was contributing to the misfire. it did seem very odd that only one was corroded like that. one question, is it ok to remove the vacuum lines from the little exhaust tube thing to the air box, and the two on the back side closest to the firewall that control the bimetal temp sensor? assuming i cap the leaks of course

Don't know, mine are all still there, stock.

 

[1990JEEPXJ]

Don't know, mine are all still there, stock.

mine are still there as well. just wasnt sure if they really affected anything.

 

[Shorty]

i have not considered that but i do plan on replacing the cap and rotor soon as it more than likely was contributing to the misfire. it did seem very odd that only one was corroded like that. one question, is it ok to remove the vacuum lines from the little exhaust tube thing to the air box, and the two on the back side closest to the firewall that control the bimetal temp sensor? assuming i cap the leaks of course

should not cause any problems-- the pre-heater only closes the butterfly during cold starts to let the engine receive heated air off the exhaust manifold. It's default position is open to fresh air and I don't think you see too many prolonged sub-zero days in S.D.

 

[jujuscisyn]

if you take the airbox out and look the pre heater doesn't close fresh air off completely just acts like a diverter. My tube to the manifold was gone when I got it and haven't noticed problems with it but my heep runs like crap but I don't think that has anything to do with it.
I think I made some head way today still waiting on the fuel pressure gauge but I think my problem is a delivery issue or at least part of it. Tried to go down the road and it was worse than ever. Had to limp home in L1 at 12mph. No power, stumbling, bucking and now surging. Just to check I jumped the ballast resistor. RPMs came back up throttle response was 90% better. Still backfired a bit but no where near as bad. Now I really need to get my hands on that pressure gauge. Pump sounds strong but I just don't think its getting there. It really went down hill the past week and the last time I checked pressure was over 6 months ago when this problem was mild and not nearly as frequent. I'm still working on it. If I get it figured out I'll let you know.

 

[Ecomike]

That sounds like your ballast resistor is toast, among other things.

 

[jujuscisyn]

I know folks have permanently bypassed the ballast resistor, does this affect the longevity of the pump at all or does it just quiet it down. Didn't know if I should bypass or replace.