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How to achieve less cranking time?

9

90Pioneer

NAXJA Forum User
Location
USA
I have a 1990 XJ 4.0 AW4. It consistently takes between 1 and 3 seconds of cranking. Sometimes it'll crank for a couple seconds, and not "catch". I'll let off the ignition and try cranking again, and then it'll fire right up, almost instantly.

Lots of newer (and many older) vehicles start right up with just a small turn of the key. Why does my XJ not?

I've upgraded the battery cables, has a new starter, alternator, CPS, ignition switch, key cylinder, fuel pump, and battery. Yet it still takes a couple seconds of cranking to fire up. What's the problem? Well I wouldn't call it a problem, but more of an annoyance.


Basically I would like to have the Jeep start on the first try, every time, and with minimal cranking time.

Would a Mean Green starter and an Optima red top battery improve my situation? Would they get me to where I want to be?

What other possibilities should I look at? Or am I just asking too much?

Thanks
 
You upgraded the pump but are you holding the pressure? It is possible that one of the checkvalves is bad and your fuel is flowing back that's why it doesn't start immediately.
 
my thoery is, nothing is gonna help. Almost every cherokee/Gcherokee owneri have met, say the same thing. 1-3 secs aint too bad. Have you tried turning the ignition to "on" to prime thr fuel pump?
 
Turn the key on and then wait for the fuel pump to quit pumping, normally about 2-3 seconds Then crank it. The Renix computer requires about three revolutions of the motor to determine the correct timing from the sensors. No way to shorten that time, its normal.
 
I forgot to mention I replaced the fuel injectors and o rings about six months ago, with 19lbs Mustang injectors. I also have good fuel pressure, actually 1 pound higher than rated.

Priming the pump has no effect. I would let it sit in the run position all day long, and it'd still take 2 or 3 seconds to crank.

No way to get around this?
 
Nope, there's really no way around it. Like Tom said, the CPS needs several revolutions to give signal to the computer before it will start. The only thing I found with my Renix'd 89 was that it would start slightly faster if I turned the key to 'on' and let the fuel pump prime...but you've already tried that.
 
My '90 has taken between 2-5 seconds since I bought it new in '90. I wouldn't worry about it. I have heard though that there is a way to get the cps closer to the tone ring and this is supposed to shorten the start time.
 
I've got the Renix manual and it states that it will not fire until a certain number of pulses are sensed on the CPS and on the camshaft position sensor. Spacing is an old wives tale. The spacing spec on the CPS is is approximately .005" or the thickness of a sheet of typing paper. Want to try and adjust it closer, go ahead. Be ready to pick up the pieces.
 
old_man said:
I've got the Renix manual and it states that it will not fire until a certain number of pulses are sensed on the CPS and on the camshaft position sensor. Spacing is an old wives tale. The spacing spec on the CPS is is approximately .005" or the thickness of a sheet of typing paper. Want to try and adjust it closer, go ahead. Be ready to pick up the pieces.
Click to expand...

The Chryslers are quicker, but as far as I know, Renix models require 4 revolutions of the engine. Count them. If it's 4, you won't improve start time except by speeding up the starter.
 
I know this is a repeat thread! I have owned my 90 since new and it is slow. allowing the pump to reach preasure is what I do. My 92 is much faster but my habit is still there! I usually turn the key, buckle up, start the cranking.
 
90Pioneer said:
I have a 1990 XJ 4.0 AW4. It consistently takes between 1 and 3 seconds of cranking. Sometimes it'll crank for a couple seconds, and not "catch". I'll let off the ignition and try cranking again, and then it'll fire right up, almost instantly.

Lots of newer (and many older) vehicles start right up with just a small turn of the key. Why does my XJ not?

I've upgraded the battery cables, has a new starter, alternator, CPS, ignition switch, key cylinder, fuel pump, and battery. Yet it still takes a couple seconds of cranking to fire up. What's the problem? Well I wouldn't call it a problem, but more of an annoyance.


Basically I would like to have the Jeep start on the first try, every time, and with minimal cranking time.

Would a Mean Green starter and an Optima red top battery improve my situation? Would they get me to where I want to be?

What other possibilities should I look at? Or am I just asking too much?

Thanks
Click to expand...

I fought a long crank in my 89 a few years back, finally took it to the dealer and they just scratched their head.......go figger. I found a local guy (now known as "Gordy the Jeep God") who diagnosed the problem and fixed it for $80.00......IIRC, it was the distributor trigger not being in sync with the CPS......or something like that. Been starting quick for 4 years, 2.5 seconds or less.
 
I recall something about using a BMW check valve spliced into the fuel line, anyone recall that and the part number- I may try that for fun it it's not too pricey.
 
Sometimes it'll crank for a couple seconds, and not "catch". I'll let off the ignition and try cranking again, and then it'll fire right up, almost instantly.
Click to expand...
My '90 does the same thing when the inside of the throttle body gets crudded up. Disconnect the intake hose and spray the TB out real well with carb/throttle body cleaner. Make sure you get under the butterfly and in any ports. You may also want to use some compressed air to blow out the PCV tube while you're at it in order to keep the TB from getting cruddy as quickly.


:revolver
 
herreraxto said:
where is located the checkvalve mine is a 90 xj and i have the same problem
Click to expand...
This is a fix that I've heard works, but can't find the part number or where to put it.
 
If you're referring to a PCV check valve, there isn't one. There's a thin tube that runs from a grommet at the back of the valve cover to a vaccuum connection on the intake manifold. That's the PCV "valve." Fresh air is supposed to be provided by the thicker hose running from the front of the valve cover to the air cleaner box. The little line often gets plugged or the gromment in the valve cover gets plugged which causes the vaccuum to reverse, sucking oily air into the air cleaner box, fouling your air filter and crudding up the throttle body. That's why I recommend cleaning up the TB and blowing out the PCV line/grommet at the same time. I do it every 4-6 months.

:revolver
 
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