dogkatcher

long start on older xjs

is there an answer?

my 90 renix was hit or miss .. somtimes really long, sometimes right on turn of key .. but usually long

this 93 i just got .. long start sometimes is really long .. even priming 1/2 turn of key .. sometimes fires right up sitting all night

any solution yet ?

JSchmitz

Are you talking about long cranking time before the engine fires? I just bought an '87 Cherokee recently. This is my first Jeep. It takes a long time to fire. I replaced the fuel filter, cleaned the throttle body, ran injector cleaner etc. It runs and idles great. I was wondering why it takes so long to fire.

dogkatcher

10-4

ive tried everyhitng laymans style ... fuel pump relay, fuel filter, pressure regs, charge fuel pump every time

Even priming fuel pump (1/2 key turn) doesnt work all the time .. maybe just the only flaw to a kick butt engine ?

89cherokee2gtmudy

Renix era jeeps always take a bit to fire. Coil won't fire till it receives signal from the ECM but that has to receive a signal from the CPS first.

dogkatcher

I got used to it .. this 93 fires right up .. or takes quite a few cranks

new cps needed ? wouldnt mind changing that before it breaks / stranded .. i dont know this jeeps history .. it could be bad

DFlintstone

Renix needs to see 300 rpm. (ECU sees that from the cps), before it will fire.

But try this, (poor mans prime). When you first turn the key on the fuel pump will run for a couple seconds, then stop. If doing that a few times first cuts your crank time you have a problem, often the check valve in the pump. No big deal, I'd just live with it. (might help a non Renix also)

The 87-90 renix always takes an extra second anyway. Guess the 91 on OBDI &II (with a PCM), are not like that.

That said, the Renix CPS is supper easy to check with a DVM. Just unplug it and check it for .35 plus, AC volts while you are cranking. Around there and lower might add to crank time. In my signature is a writeup Crusier did on that, as well as wire testing....

It's more involved actually checking the 96 CPS, but there is a simple resistance test, I think.

Rockville

I had leaking fuel regulator (inside fuel tank)

DFlintstone

Yea, the earlier have the regulator up front, that and the injectors, (as well as the lines), are the other places. I DID have some injectors leak and a longer crank time, but flooding might have been a issue.

I jusss the check valve is generally more common than the injectors, but the stock Renix injectors, (Decca Simmons), really are crap...and a fire hazard! (they leak out too)

dogkatcher

on this '93 gremlin machine

I wire-brush scrubbed the battery cable terminals (clamps) until super shiny inside, fresh anti-corrode gel .. battery is a true Interstate (nascar green), less than a yr old

Then cleaned ground wires off engine block and sandpaper'd their connectors til shiny .. took wire brush to the attaching bolt on block

1/2 turn of key, fuel pump is way louder priming .. starts way faster



grounds didnt look dirty at all from above .. glad I did that

Roblaza

Can you do a how to for all the grounds?? A lot of people might benefit from knowing exactly where all the grounds go and from where...me being one lol

dogkatcher

there is a ground screw just behind oil-dipstick tube .. my '93 has 3 wires attached there

mine had a 13mm nut holding wire terminals on .. people say: check if that screw in block has any play in it .. mine was solid

my '90 had the 4awg ground cable from battery attached there also, this '93 I have now, does not .. Im about to scope the large cables out for quality, see where they go.

good idea to clean / tighten the fuel pump reg terminals too .. plastic / clay looking piece in engine compart (w/ a wire on each end) ... over drivers side front fender

Im sure if you search forums, you'll find what all is controlled by that ground behind dipstick .. curious to see where my battery cables go, thought it was odd the battery ground wasnt strait to it, like my other jeep

cruiser54

Renix Ground Refreshing
The Renix era XJs and MJs were built with an under-engineered grounding system for the engine/transmission electronics. One problem in particular involves the multiple ground connection at the engine dipstick tube stud. A poor ground here can cause a multitude of driveabililty issues, wasted time, and wasted money replacing unnecessary components.
The components grounding at the dipstick tube stud are:
Distributor Sync Sensor, TCU main ground, TCU "Shift Point Logic", Ignition control Module, Injectors, ECU main ground which other engine sensors ground through, Oxygen sensor, Knock Sensor, Cruise Control, and Transmission Sync signal. All extremely important stuff.
The factory was aware of the issues with this ground point and addressed it by suggesting the following:
Remove the nut holding the wire terminals to the stud. Verify that the stud is indeed tightened securely into the block. Scrape any and all paint from the stud’s mounting surface where the wires will attach. Must be clean, shiny and free of any oil, grease, or paint.
Inspect the wire terminals. Check to see that none of the terminals are crimped over wire insulation instead of bare wire. Be sure the crimps are tight. It wouldn’t hurt to re-crimp them just as a matter of course. Sand and polish the wire terminals until clean and shiny on both sides. Reinstall all the wires to the stud and tighten the nut down securely.
While you’re in that general area, locate the battery negative cable which is fastened to the engine block just forward of the dipstick stud. Remove the bolt, scrape the block to bare metal, clean and polish the cable terminal, and reattach securely.
Another area where the grounding system on Renix era Jeeps was lacking is the engine to chassis ground. There is a braided cable from the back of the cylinder head that also attaches to the driver’s side of the firewall. This cable is undersized for it’s intended use and subject to corrosion and poor connections at each end.
First off, remove the cable end from the firewall using a 15mm wrench or socket. Scrape the paint off down to bare metal and clean the wire terminal. Reattach securely.
Remove the other end of the cable from the rear of the head using a 3’4" socket. Clean all the oil, paint and crud from the stud. Clean the wire terminal of the cable and reattach securely.
A suggestion regarding the braided cable:
I prefer to add a #4 Gauge cable from the firewall to a bolt on the rear of the intake manifold, either to a heat shield bolt or fuel rail bolt. A cable about 18" long with a 3/8" lug on each end works great and you can get one at any parts store already made up. Napa has them as part number 781116.
A further improvement to the grounding system can be made using a #4 cable, about 10" long with 3/8" terminals at each end. Attach one end of this cable to the negative battery bolt and the other end under the closest 10mm headed bolt on the radiator support just forward of the battery. Napa part number 781115.
　
　
If you want to upgrade your grounds and battery cables in general, contact Jon at www.kelleyswip.com. He makes an incredible cable upgrade for a very reasonable price.
　
Revised 11-28-2011

wjnfirearms

If the XJ has been sitting for a while, could only be a short time, and takes time to start up and will fire more quickly if it has just recently been shut down, it could be a faulty check valve. This is a common issue.

I had this issue with the '98. Installation of the inline SUR&R check valve (part #CKV5) corrected this problem. Easy fix.

The best way to see if this is the problem with your XJ is to use a fuel pressure tester on the fuel rail Schraeder valve. If the pressure is acceptable with the fuel pump active and drops quickly after the engine is shut down, this is the likely problem. Acceptable pressure should be in the 40 lb. range.

cruiser54

Where did you install the check valve?

Vincenza V

My 99's did the same thing. I swapped injectors to the rebuilt 4 port ones from a member of the forum. Never did it again.