Crank time on renix

I'm new to this forum, but I have searched, and can not find a sollution to my problem. (maybe I'm misspelling something when searching? To my defence; I'm Norwegian and English is not my native language...)

My Xj is a 88 renix, and everytime I try to start it i have to run it close to 3 seconds on the starter before it starts.

I suspect (but may be wrong) the reason is loss of fuel pressure in the injector rail. When i push the valve on the rail when the engine is running i get a good spray of gas, but one minute after the car is stopped, and I push the valve, I get one drop of gas at most.

I do not suspect any of my injectors of leaking (runs nice and with no smoke when starting), and I have not been abel to detect any leaks in the lines.

One answer, i realize, is a possible faulty pressure regulator causing the gas to leak through to the return line, but before investing in a new regulator I would like to have the following question answered:

Could the reason be that the gas is leaking back through the supply line and pump? Has anybody experienced this? Is there a seperate non-return valve by/in the pump, or would I have to replace my entire pump assembly if this it the problem?

OR is there another reason that I haven't thought of?

(the reason I worry about this is: 1) My starter will wear out 3 times as fast as normal. 2) I'm going to install a remote start system on the car, and this will let the starter run for maximum 2 seconds, which might not be enough, especially when the temperature falls below zero.)

My buddy had a renix, all tuned up and running well... always needed 3 seconds to get fired. I've read threads on other message boards and this is normal for renix Jeeps.

I agree, I have heard this is normal. My '87 renix does the same thing.

Don

I too have heard this is normal, but I also believe i read somewhere that they were not like that from factory... So I guess few people have bothered to try to find out what is wrong, as it is only vaguely annoying.

AND I also read read the procedure for testing the regulator in some service manual, and it stated that a pressure gauge should be fitted, engine started and turned of, and after this the pressure should remain constant for 30 minutes. (if memory serves me...) (I don't have a gauge that fit the connection at the injector rail.)

I think I will have a buddy put a clamp on the fuel supply hose just as I stop the engine, and see it the pressure still disappears.... If it does, it should be the regulator, and if the regulator is leaking, it's also possible that it don't regulate properly. (could I be suffering from a loss of HP because of this?? I wonder)

3 senconds isn't anything on what my old 89 took to crank. It would just sit there and turn and turn and turn, finally cranking after a solid 8-10 seconds. It was not a good getaway vehicle.

My father in law's 89 takes a few seconds to catch...

leave it that way, mine takes about 30 sec. minimum...........

The good news is I fixed mine, the bad news is I really don't know exactly what I did. It is fixable. Mine starts twice as fast now, after sitting for a couple of weeks, than it used to sitting over night.
My hot start (random high RPM starts on a hot motor also stopped), it appears that's also fixable and seems to be related with the long crank times.
Up the percentage on your TPS adjustment (or lower it on the ECU side of the TPS) and make sure your TPS ground has as low a resistance as possible, shake the harness and check the ground splices.
Check the contacts between the coil and ignition module (Renix). I also have low resistance (solid core coil) plug wires, but a stock coil to cap wire.
I really don't know exactly what fixed it, the IAC function and strong battery also play a roll.
It may just be a collection of small faults that adds up.
I've gotten in the habit over the years, of turning the key to run and waiting a second for the fuel rail to prime, before I start.

8Mud said:

I've gotten in the habit over the years, of turning the key to run and waiting a second for the fuel rail to prime, before I start.

Click to expand...

X2...that's the ticket!!

As I understand it, owing to the dynamic setting of timing, the computer has to read the output of the crank position sensor for 4 revolutions, before it will initiate a spark on a cold start. If you have a healthy Renix Jeep, you can confirm this, I think. If it takes more than 4 complete engine revolutions to start, some other problem is being added, such as a leaky check valve in the fuel system, or a weak CPS.

My ex wife bought a new 88 XJ back in 88, and I remember I was surprised that it always took a few cranks before it fired up. My 87 did the same, but when everything was in good tune, it always fired after four revolutions. How long that takes depends on how happy your battery and starter are, but see if you can count the revs. "nya-nya-nya-nya-vroom" is as good as you'll get.

I've been digging around quite a bit, and I've got some possible solutions for you:

1) Make sure your battery and starter are up to scratch. You'll know why in a minute.
2) Make sure the fuel rail is pressurised before you crank (the fuel system doesn't always hold pressure overnight, and this can effect starting times.)
3) Make sure all of your main grounds are up to scratch (particularly the cylinder head-firewall connection - sand the contact spot on the firewall down to BARE METAL and apply corrosion inhibitor) and consider adding a chassis ground directly from the battery to the fender liner (same treatment - bare metal, then corrosion inhibitor.)

Why do I pick out the battery and starter? Because the RENIX system is programmed to get timing information for fuel injection and ignition from the CPS and and SYNC sensor (in the distributor) before it starts to fire anything - AND it wants to see a minimum 300rpm before it fires anything as well (give the oil a chance to circulate, methinks. And, since it won't fire fuel injection until a certain threshhold, it's probably done to keep starting HC and CO emissions low, by preventing drastically rich starts. Take that with a suitable grain of salt...)

The firewall ground strap gets picked on because it is the only ground path for the chassis, which means it provides the ground reference for the ECU and the associated sensors and reference voltages. If this gets dirty, it can wreak havoc with the vehicle electronics - at least, the part that keeps the engine running. This is why adding the secondary ground directly from the battery to the chassis is a good idea - having a secondary ground reference can't hurt anything, and can actually help in quite a few cases!

Considering you're dealing with a twenty-year-old vehicle, your mains cables are probably getting old anyhow. I'd probably start with checking/cleaning/replacing those as needed, checking/cleaning all the grounds, and treating the chassis contact points as described. This should have a positive effect on your starting times (most of the people with RENIX rigs who have gotten upgraded mains from me have reported a shortening of cranking times - meaning the engine gets up to speed more quickly - and more positive starting - meaning the signals from the sensors are probably "cleaner" by virtue of the improved mains cables and the installation of the extra chassis ground.)

I'd be willing to ship to Norway, but you may find the cost prohibitive. If you check my website, you can find measurements for your cables there - and either make your own, or source something locally (it's not that I don't want to ship, but shipping will probably be close to the cost of the cabling, and I do want for you to save some money fixing this thing...)

Good luck! If that doesn't do it, continue the post and we'll see what else we can come up with for you.

Thanks for the input so far. I realize it could be that this is how the 'nix should operate, but I don't want to give up yet.

After going over the wiring yesterday I don't think the problem is electrical. At least not related to bad grounds or connectors. Starter engine is fairly new, and runs good and with plenty of power from battery. But I still think it could be the loss of pressure in the injector rail. Turning the ignition on and waiting does not help, even when repeated. Could be because of air trapped in injector/rail? (how this hypothetical air would get into the system i dont know... :roll: )

The FSM states that fuel pressure drop after shut down could be caused by leaky "fuel tank residual pressure valve". Anyone know if this can be changed, if it's integrated into the fuel pump, or where it would be if it's not part of the pump?

If you turn the key on and cycle it a couple of times, and it does not make any difference, I think you can rule out the residual pressure valve. Air in the system is not likely, because the system is self purging: once the fuel rail is up to pressure, additional fuel is sent back to the tank.

My sisters as always done this...

No Big...

collkid said:

My sisters as always done this...

No Big...

Click to expand...

Indeed, it's an easy habit to learn, and cheaper than replacing the fuel pump. I've been doing it on my 95 for the last hundred thousand miles or more.

5 seconds on mostly original parts 180k mile 88, reliable as heck.

My start times improved when I added additional, larger gauge ground cables.
Not only do the grounds get corroded, but the original cables never had enough current carrying capacity to begin with.
5-90 is correct when he discusses the conditions required for starting, some delay is built into the Renix rigs.