Problem Starting

[Jesse]

With great pleasure I bring you guys an update.

 

Went through some of the things you guys suggested. Cleaned grounds, replaced CPS... seemed to run a bit better but didn't really make it start any better.

 

 

 

Replaced injectors with these:

http://www.ebay.com/itm/Jeep-Comanche-87-92-4-0L-Bosch-Type-3-4-hole-upgrade-injectors-set-/251338454201?pt=Motors_Car_Truck_Parts_Accessories&fits=Make%3AJeep|Model%3AComanche|Engine+-+Liter_Display%3A4.0L&hash=item3a84f074b9&vxp=mtr

 

Holy cow what a difference. Starts right up, runs like a champ, more responsive. Thanks for all the help guys!

 

 

Hello,

 

I've had a problem with starting my Comanche since I've owned it, and the previous owner had the issue for quite some time.

 

Truck overview: 1989 4.0 I6 4x4 Manual Long Bed

 

It will not start without being cranked more than once. Almost always takes 2 tries, though starting it cold occasionally takes 3.

 

I have replaced the fuel filter, spark plugs, rotor, cap, and spark plug wires. I've measured my fuel pressure at the test port on the rail. 45 PSI with hose disconnected, 35 PSI connected. This is a little high but I've been told it should be good.

 

"Priming" before starting does not help. (Turning the key enough so the fuel pump kicks on, turning to the off position, and then turning it to start). Still takes two full tries, turning it until it cranks both times.

 

From searching around I've found a lot of information saying it would be the regulator or pump, however my pressure doesn't seem to line up with this. On one thread it mentioned that it could be an issue with the crankshaft position sensor, I don't know how much of a reach that is.

[Jeep Driver]

Hello,

 

I've had a problem with starting my Comanche since I've owned it, and the previous owner had the issue for quite some time.

 

Truck overview: 1989 4.0 I6 4x4 Manual Long Bed

 

It will not start without being cranked more than once. Almost always takes 2 tries, though starting it cold occasionally takes 3.

 

I have replaced the fuel filter, spark plugs, rotor, cap, and spark plug wires. I've measured my fuel pressure at the test port on the rail. 45 PSI with hose disconnected, 35 PSI connected. This is a little high but I've been told it should be good.

 

"Priming" before starting does not help. (Turning the key enough so the fuel pump kicks on, turning to the off position, and then turning it to start). Still takes two full tries, turning it until it cranks both times.

 

From searching around I've found a lot of information saying it would be the regulator or pump, however my pressure doesn't seem to line up with this. On one thread it mentioned that it could be an issue with the crankshaft position sensor, I don't know how much of a reach that is.

Pull it out and see if it's covered with muck......if so........clean it or replace it.

 

I don't think it's that far of a reach at all.

[cruiser54]

Hello,

 

I've had a problem with starting my Comanche since I've owned it, and the previous owner had the issue for quite some time.

 

Truck overview: 1989 4.0 I6 4x4 Manual Long Bed

 

It will not start without being cranked more than once. Almost always takes 2 tries, though starting it cold occasionally takes 3.

 

I have replaced the fuel filter, spark plugs, rotor, cap, and spark plug wires. I've measured my fuel pressure at the test port on the rail. 45 PSI with hose disconnected, 35 PSI connected. This is a little high but I've been told it should be good.

 

"Priming" before starting does not help. (Turning the key enough so the fuel pump kicks on, turning to the off position, and then turning it to start). Still takes two full tries, turning it until it cranks both times.

 

From searching around I've found a lot of information saying it would be the regulator or pump, however my pressure doesn't seem to line up with this. On one thread it mentioned that it could be an issue with the crankshaft position sensor, I don't know how much of a reach that is.

Test the CPS. Here's how. And if you click on the link in my signature, you'll find some things to do which address the issue you're describing. I recommend posts 1,3,4, and 5 for sure.

 

Also realize that your era of Jeep does not start instantly like you're used to with other vehicle. Usually a 3 to 5 second crank time is normal.

 

Renix CPS Testing and Adjusting

 

 

 

Renix CPSs have to put out a strong enough signal to the ECU so that it will provide spark. 

 

Most tests for the CPS suggest checking it for an ohms value. This is unreliable and can cause some wasted time and aggravation in your diagnosis of a no-start issue as the CPS will test good when in fact it is bad.

 

The problem with the ohms test is you can have the correct amount of resistance through the CPS but it isn’t generating enough voltage to trigger the ECU to provide spark. 

 

Unplug the harness connector from the CPS. Using your voltmeter set on AC volts and probing both wires in the connector going to the CPS, crank the engine over. It won’t start with the CPS disconnected. 

 

You should get a reading of  .5 AC volts. 

 

If you are down in the .35 AC volts range or lower on your meter reading, you can have intermittent crank/no-start conditions from your Renix Jeep. Some NEW CPSs  (from the big box parts stores) have registered only .2 AC volts while reading the proper resistance!!  That’s a definite no-start condition. Best to buy your CPS from Napa or the dealer.

 

Sometimes on a manual transmission equipped Renix Jeep there is an accumulation of debris on the tip of the CPS. It’s worn off clutch material and since the CPS is a magnet, the metal sticks to the tip of the CPS causing a reduced voltage signal. You MAY get by with cleaning the tip of the CPS off. 

 

A little trick for increasing the output of your CPS is to drill out the upper mounting hole to 3/8” from the stock 5/16”, or slot it so the CPS bracket rests on the bell housing when pushed down. Then, when mounting it, hold the CPS down as close to the flywheel as you can while tightening the bolts.

 

 

 

 

Revised 01-26-2013

[Oddmodman]

I back the CPS theory. Mine was hard starting and rough running till I pulled the CPS, cleaned it, and to boot I did Cruiser's CPS overbore trick. Mucho bettero now.

[cruiser54]

I back the CPS theory. Mine was hard starting and rough running till I pulled the CPS, cleaned it, and to boot I did Cruiser's CPS overbore trick. Mucho bettero now.

Yup. Normal stuff.

[Jesse]

With great pleasure I bring you guys an update.

 

Went through some of the things you guys suggested. Cleaned grounds, replaced CPS... seemed to run a bit better but didn't really make it start any better.

 

 

 

Replaced injectors with these:

http://www.ebay.com/itm/Jeep-Comanche-87-92-4-0L-Bosch-Type-3-4-hole-upgrade-injectors-set-/251338454201?pt=Motors_Car_Truck_Parts_Accessories&fits=Make%3AJeep|Model%3AComanche|Engine+-+Liter_Display%3A4.0L&hash=item3a84f074b9&vxp=mtr

 

Holy cow what a difference. Starts right up, runs like a champ, more responsive. Thanks for all the help guys!