renix starting issues

I'm running an 89 waggy ltd with 4.0 and aw4. bone stock. Now I know the renix era 4.0's are known for long crank times before firing up, and i've gotten used to that. But in the last few days the time spent cranking seems to get longer with every start. Where should I start looking for a problem? Once again, the jeep knows when its payday . . .

Maybe there is a magic cure for this, but for me it always turned out to be a combination of things.
A good tuneup is a good place to start, plugs. cables and cap.
Tune up, a tired CPS, low fuel pressure and even slow cranking from a tired battery can individually or all together add up to longer crank times.
Other things that have helped me some are cleaning the grounds and checking the CPS circuit for resistance (corroded connectors). A TPS wiring resistance check (corroded connectors) and TPS adjustment also seemed to help some. Cleaning connectors and grounds always seems to be benenfitial.
A sticky IAC, will also give you grief. On occasion my IAC gets sticky and I have to crank it forever to get it going.
Mine pops off (normally) after about 5-6 revolutions. A lot better than it used to be, before I cleaned up all the connectors and grounds, replaced the CPS, adjusted the TPS, cleaned and oiled the IAC and other assorted maintenance items.

8Mud said:

Maybe there is a magic cure for this, but for me it always turned out to be a combination of things.
A good tuneup is a good place to start, plugs. cables and cap.
Tune up, a tired CPS, low fuel pressure and even slow cranking from a tired battery can individually or all together add up to longer crank times.
Other things that have helped me some are cleaning the grounds and checking the CPS circuit for resistance (corroded connectors). A TPS wiring resistance check (corroded connectors) and TPS adjustment also seemed to help some. Cleaning connectors and grounds always seems to be benenfitial.
A sticky IAC, will also give you grief. On occasion my IAC gets sticky and I have to crank it forever to get it going.
Mine pops off (normally) after about 5-6 revolutions. A lot better than it used to be, before I cleaned up all the connectors and grounds, replaced the CPS, adjusted the TPS, cleaned and oiled the IAC and other assorted maintenance items.

Click to expand...

It's got good plugs, wires, cap and rotor. They were replaced within the last 7k or so. Same with the TPS, IAC and battery. New alternator too, as of about a week ago. I'll give a look at the CPS, that was the one sensor I didnt test when I ran a multimeter diagnostic on everything I could. As for fuel pressure, I can't say. Never tested it, dont have the tool. But it does have a new fuel filter. So yeah, I'll get back to you on the results. Thanks for the tips.

The most common "issue" I hear of in relation to this is simple - old mains cables. You know, the heavy-duty ones that come right off your battery.

RENIX has a "long" crank time because it's looking for two valid sensor inputs (CPS and SYNC,) and because it looks for 300rpm at the crankshaft before it fires fuel injection and ignition.

Why mains? Because...
1) Better mains connection to the starter means it spins up faster.
2) Better main grounds (for the sensors) means cleaner signals, and the ECU reads them quicker.

I've heard of the mains cables being the closest thing to a "Magic Bullet" repair - but I've not noticed, because I'm fairly aggressive on maintenance anyhow. The next suspect would be the CPS (which, my local service techs tell me, has a service life of ~150kmiles.) RENIX will start and run without the SYNC, but it sounds like a "bad timing chain" getting progressively better when it's trying to start - that's from the ECU "guessing" which cylinder is coming up next. It runs just fine if you unplug it - since it already knows what's going on.

Try this - unplug the CPS connector, blow it out with some contact cleaner (NOT carburettor cleaner!) and reconnect. See if there's a difference in starting.

Move ahead to the SYNC sensor (3-wire connector off of distributor.) Same treatment here, but try to start it with the sensor disconnected after you clean it. I didn't tell you to try this with the CPS pulled because I already know what will happen - "damn thing won't start!"

Also, visually check your mains cables for any corrosion, mechanical wear, or other defects. If you need new ones (I'd not be surprised,) the link in my sig goes to my website, and I'm sure you'll be able to find out about what I made from people here (who have bought enough - but I would prefer not to "blow my own horn," as it were...)

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