Very hard starting ,sometimes

[88AMComanche]

..Hello ....What would make a renix 4.0 sit there and crank over & over & over for like 30 seconds stright & never fire up? I know the fuel pump is kicking in & pumping up. I can hear it, plus its only a few months old. It always starts after about 5 seconds of cranking over. Yet TWICE now in the last few weeks it has sat there & will crank over forever till I let off the key. So I shut the key off & turn it back on & it fires right up ???????

This is so random. but just enough to stress me out & not be confident that maybe somethings going bad maybe. anyone else ever have this issue??

 

its like ......it will start within 5 seconds 100 times in a row, but one time it will not fire up at all,almost as if the coil is unplugged or something. yet turn the key off & back on then it fores right up.

 

W I E R D

[CGross]

Check your fuel pressure.

[Pete M]

crankshaft position sensor (CPS) will do just that.

[STERLING STINGER]

Holy crap i was just going to ask the same question.

Thanks !!!

[ricracer]

Mine did the same thing and it turned out to be two things. First the battery which was in it was too small and when cranking it alot it got down to 8 volts . The second was the crank sensor wire was rubbing the exhaust manifold when I wire tied it out of the way it started fine . I also had a problem with the wire harness that ran ontop of the intake to the injectors , you could move it and get some of the injectors to not fire. hope that helps

[88AMComanche]

wow, thanx.........will give that a try.

 

Mine did the same thing and it turned out to be two things. First the battery which was in it was too small and when cranking it alot it got down to 8 volts . The second was the crank sensor wire was rubbing the exhaust manifold when I wire tied it out of the way it started fine . I also had a problem with the wire harness that ran ontop of the intake to the injectors , you could move it and get some of the injectors to not fire. hope that helps

[88AMComanche]

3 times now in the last week .Ive went out to get in the truck,hit the key & it will sit and crank over seems like forever. Just to a point where you should stop otherwise the battery will start to lug down. .So I popped the hood & randomly moved the wiring harness back n forth & several other stray wires & just touched them so theyd move. silly I know....but,when your stranded,anything is worth a try.

I get in & it started up this time. ----What I don't know is....Was it a wire? causing the issue?

OR was it the Sitting fo9r a few minutes after i cranked it over for a while? that made it correct itself & finally start up?

 

 

 

SO DA*M IRRITATING!! .....grrrrr!!!!!!!!!

[88AMComanche]

PS- When i turn the key ON,i wait tioll i no longer hear the fuel pump (about 2-3 sec) TEHN i TRY to start it. Once when it wouldnt start after 40 seconds straight cranking...I popped the hood, & pressed the fuel rail pressure relase valve and had excellent pressure. so Id assume it can't be a fuel problem, or what? any ideas?

[Pete M]

CPS or its wire harness.

 

 

[carnuck]

My fuel pump relay had moisture inside it. Swapped for my AC one and it's been fine

[cruiser54]

3 times now in the last week .Ive went out to get in the truck,hit the key & it will sit and crank over seems like forever. Just to a point where you should stop otherwise the battery will start to lug down. .So I popped the hood & randomly moved the wiring harness back n forth & several other stray wires & just touched them so theyd move. silly I know....but,when your stranded,anything is worth a try.

I get in & it started up this time. ----What I don't know is....Was it a wire? causing the issue?

OR was it the Sitting fo9r a few minutes after i cranked it over for a while? that made it correct itself & finally start up?

 

 

 

SO DA*M IRRITATING!! .....grrrrr!!!!!!!!!

 

 

Good possibility the CPS signal is weak. Sometimes unplugging the CPS and plugging it back in will temporarily solve the problem.

 

For you guys with 87 and 88s the C101 connector neads to be cleaned to eliminate the resistance it has developed between your CPS and the ECU. See the info below.

 

Renix CPS Testing and Adjusting

 

 

 

Renix TPSs 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.

 

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 3.5 range 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 it’s mounting holes with the first drill bit that just won’t fit through the original holes. Then, when mounting it, hold the CPS down as close to the flywheel as you can while tightening the bolts.

 

 

Renix Jeep C101 Connector Refreshing

 

 

The C101 connector on 1987 and 1987 Renix Jeeps was a source of electrical resistance when the vehicles were new. So much so that the factory eliminated this connector in the 1989 and 1990 models. The factory recommended cleaning this connector to insure the proper voltage and ground signals between the ECU and the fuel injection sensors. We can only imagine how this connector has become a larger source of voltage loss and resistance increase over a period of almost 25 years.

 

Almost every critical signal between the engine sensors, injectors, and the ECU travel the path through the C101.

 

The C101 is located on the driver’s side firewall above and behind the brake booster. It is held together with a single bolt in it’s center. To get the connectors apart, simply remove the bolt and pull the halves apart. You will find the connector is packed with a black tar like substance which has hardened over time.

Take a pocket screwdriver or the like and scrape out all the tar crap you can. Follow up by spraying out both connector halves with brake cleaner and then swabbing out the remainder of the tar. Repeat this procedure until the tar is totally removed. This may require 3 or more repetitions. Wipe out the connectors after spraying with a soft cloth.

 

If you have a small pick or dental tool tweak the female connectors on the one side so they grab the pins on the opposite side a bit tighter. Apply a true dielectric grease to the connection and bolt it back together.