owellwhatever

So, I had an '87 XJ and sometimes it would crank for a seemingly long time before starting. I mean like 10 or 20 seconds. Not like a sensor was bad or anything. The '93 I had for 10 years never did that.

Just bought an '89 quite cheap, it needs a little love. Broke a bolt trying to take the cracked header off so I took it up to Olympic 4x4, they're supposed to be the best place for Jeep stuff and repairs north of Seattle.

Anyway, the mechanic I chatted with when dropping it off was a cool guy. This '89 is sometimes cranking for a very long time. But I think it's the CPS on this one, which I'll swap as soon as I get it back from getting the exhaust manifold done.

He was saying that the Renix models sometimes did crank longer than most vehicles, because the Renix computer is very slow, much like PC's were at the time.

So my question to all of you is: Is there an "upgrade" chip that is faster technology wise, not "performance" wise? Meaning: It's not some cheasy aftermarket performance chip. The chip itself is made with modern technology that is much faster than the original. Is there such a thing?

Cheers

posjeepxj

try throwing some jumper cables on it or a charger on start and see if it starts faster. if it does upgrade all of your wiring (should do anyway)

You can always tear the starter appart and clean/inspect it to

http://go.jeep-xj.info/HowtoStarterClean.htm

Do you turn the key forward and wait for the fuel pump or just try to start write away. I recomend turning the key forward and counting to 5 before starting any vehicle

darknezz

my 89 cranks longer than what I think is normal as well, I thought it was a jeep thing, or maybe fuel pressure or something. I've done a full regular tune up to it and it didnt make it start any faster. Is there something I should be looking for? Doesn't really bother me much but it would be nice for it to start right up.

I always turn the key and wait for the fuel to pressurize, on any vehicle

JeepingDan

My 89 cranks for awhile to. I thought about putting a New not rebuilt starter in it since I've never put one in it for the past 7 years. Maybe that will do it. I just put a good battery in it. Funny thing is my 88 fires right up lol

owellwhatever

Yeah, the guy at Olympic 4x4 said they have long cranks because the Renix system is slow and sometimes it takes a while to check each sensor, etc. before firing up. Just got me to thinking about the possibility of a "faster chip" I'm an IT guy so leave it to me to wonder about such things

redrunner

I have two 89s both crank longer than I would think is required. I read on here some thing about that process but can't remember the entire thread...old age....but after reading that, I understand the longer crank time. All Renix engines crank longer. My manchanic guy said it was normal as well. He told me not to be concerned unless it doesn't start. If you count it out or time it, it takes the same amount of time to start it each time I hit the key. So that is telling me nothing is wrong just the nature of the beast.

My375hp302

Mine does the same thing, I was wondering about that!

89Laredo

Its not really that the computer is slow, The Renix ecu has more parameters to meet before it will fire.
It must reach 300rpm and find TDC before it will send fuel and spark. It is normal for a Renix to take 5-10 seconds to start.

Here is a normal (actually faster than usual) start for my jeep:
http://www.youtube.com/watch?v=http:...?v=RuLBopSXRpY

COSXJFAN

It's normal, don't worry about it...

darknezz

Defiance665,

Mine definitely takes longer than that to start, I'd say a good 5 seconds. But if its normal I won't worry about it, it is about the same amount of time each start.

Why when I copy something bolded it wont unbold the rest of the post...

89Laredo

Yeah, mine usually takes a little longer than that. apparently it was in a good mood that day.

For the bold stuff:
Select all, and in the upper left corner theres two "A"s with an x through them, click that and it will go to standard text.

5-90

This is a known issue, and has to do with the way RENIX is programmed.

When cranking, the ECU does not fire the fuel injector or ignition drivers until it reads 300rpm at the CKP (crankshaft) and gets a valid SYNC signal (CMP - distributor.) It may start without the CMP signal by "guessing" (it will act like the timing is off, and then catch and run properly. I've tested this - drove around all day with the CMP disconnected - on purpose - once just to see. Started the engine with the CMP connected, then unplugged it. Also did various start cycles with the CMP disconnected to begin with for additional experimenting.)

If you want to reduce cranking times, the best way to go about it is to service/clean your mains connections (particularly your grounds!) and to consider upgrading your mains cables (OEM mains on RENIX are 6AWG, I offer kits in 4AWG and 1AWG. Even the 4AWG tends to show marked improvements, according to reports from the field.)

This has nothing to do with microprocessor speed - it's simply the way the beast is programmed. None of us have figured out enough yet to blow a new PROM to change that (say, reduce the firing threshhold to 150rpm or so?) and the going theory is that it was done to promote oil circulation and reduce dry starts. Considering that RENIX was built by Bendix/King, and B/K made their name in avionics, I consider this likely to be a valid theory (I've dealt with B/K avionics - I was a pilot for six years or so - and B/K stuff isn't known for breaking. I've only heard of three RENIX ECUs failing - I have two of them here.)

mike albo

I changed out my battery cables,put in a newer starter (out of an 89).Helped out alot.