jeep wont start sometimes...help please!

lyleorszulak807 · 08-25-2008, 03:02 PM

Have a 89 jeep renix 4.0L. Gotten most of the bugs worked out but one! Occasionally the jeep wont start, seems that removing/swapping the two relays (Passenger side, power latch relay and fuel pump relay??) closest to the front of the vehicle solve the problem for a while. Ive looked at various diagrams and there seems to be some variation on the order of relays. I have already replaced one relay a month ago.

Question: Is it possible that something along that wiring path is causing the relay to stop working intermittently? I do not believe this is the case because one night the jeep started fine and the next morning without moving the vehicle the jeep didn't start. Has anyone else had this problem? When the jeep wont start it does have good fuel pressure (strong squirt out of the schrader valve) and spark is good too. The only other thing I can think of is something grounding or shorting those two circuits or possibly the Cam Position Sensor? Already replaced the Crank Position Sensor among other sensors...

Any help would be great as this is a daily driver.

**balloo93** · 08-25-2008, 04:59 PM

You have a big C101 plug on the firewall. Disco that and make sure it is clean. Then reseat it and make sure the connection is solid.

Could be the pump is on it's way out or working too hard. Have you changed the fuel filter on it lately?

lyleorszulak807 · 08-26-2008, 12:53 PM

Ive already replaced the fuel pump and fuel filter about a month ago. Drove the jeep yesterday and stated right up numerous times without hesitation.

C101......i just looked up some pictures for this plug. They say it is on the driver side upper firewall. I never noticed it before, I will check tonight when I get home. Thanks!

PS: How would I know if the pump was working too hard? Less or more voltage at the resistor? I don't think this is the case since I always seem to have fuel and spark when it doesn't start. That's why I believe it to be a wiring/sensor/plug issue on the same circuit as those two relays. Maybe it is the C101 plug!

**balloo93** · 08-26-2008, 02:23 PM

If you replaced the pump and filter, I wouldn't worry about the pump.

DBALL · 08-26-2008, 09:50 PM

I have the same problem and its driving me crazy. My 89 stalls occassionally, no warning no sputter, just dead. Now I have a new problem, sometimes when I try to restart it I get nothing, no click no crank, just silence. Then after sitting for a while it will start right up, but still have the stalling problem. Some peiople have suggested the Neutral safety switch, others say starter and solenoid. Im going crazy.

lyleorszulak807 · 08-27-2008, 12:05 PM

Well I looked for the C101 plug but seems to be missing from driver side firewall. Ive read on couple of forum's that alot of people hard wire it in I will have to trace the whole wire harness it seems.

My problem is not cranking but starting, cranks all the time just doesn't start. In your case it could be the NSS switch, have you checked to see if you have reverse lights? They say that is one way to tell that the NSS needs cleaning/replacing. Also try pushing the auto stick forward while attempting to crank, heard that this helps sometime too.

As an update on my case, It died last night and by removing the power and switching out the relay's the jeep started right up. This morning it died on me twice...lol Kind of totally clueless on what is going on, without being able to perform some test while it doesn't start. Never wants to start when I have to be some where, especially work.

Question:
If the CPS (crankshaft position sensor) is not working properly will there still be fuel and spark?

If the CPS (camshaft position sensor) is not working properly there should be spark and fuel just out of whack spark timing?

**balloo93** · 08-27-2008, 07:00 PM

If the crank postion sensor is acting up, there will be fuel pressure, but no fuel or spark delivery. It could very well be a flaky Crank Postion Snesor that is going out.

Could also be a bad Can Postion Sensor (hall effect). If it is bad it would mimick the bad Crank postion sensor.

tangofox007 · 08-27-2008, 07:32 PM

I had a good crank/no spark/no start problem. It turned out to be the CPS connector. (CPS was fairly new.) Tightening up the female connectors seems to have solved the problem. It generally would be a problem when the engine was hot, like after a short stop.

lyleorszulak807 · 08-29-2008, 02:18 PM

Found out last night that the fuel injector wire harness is dry rotted and VERY loose on the fuel injectors. Brushing my hand against the wire caused the fuel injector to stop working.......found this on three fuel injectors. Probably the cause of my problem or one of many problems. Going to the bone yard to pull some injectors and wire harness today/tomorrow which should solve that problem. Are we having fun yet?

08-27-2008, 07:32 PM	#8
tangofox007 Web Wheeler Join Date: May 2005 Location: GA Posts: 5,933 Profile Gallery Classifieds My Jeeps	I had a good crank/no spark/no start problem. It turned out to be the CPS connector. (CPS was fairly new.) Tightening up the female connectors seems to have solved the problem. It generally would be a problem when the engine was hot, like after a short stop.