seww

Hey guys,

I need your assistance once again.
My Jeep XJ 1990 has been acting up since september. Just one day it wouldn't start, it cranked and cranked and then there'd be like a slap-sound and it would stop cranking for a second and then start over. And then a slap! and start cranking again.

Eventually it would start like normal. At first, it died on me backing out. But started right up again. Drove fine for a few days until it wouldn't start again. Same procedure again.
Then I went under the hood and cleaned off all electrical contacts and the Jeep would be fine for a few weeks.

Did plenty of research and I thought it was probably the CPS acting up so I ordered a new one just in case.
End of september, it happened again so I did replace the CPS.
Since then, she's started every single time, like normal, until this week.

Drove to work, and just when I come into the parking lot, she died on me, and wouldn't start again. Just cranking and not really starting. Once she almost started. We let her stand for a few hours, and she has started fine every time since then.

Now to my question, could it be the CPS? Like a faulty one from the box? I know the resistance was in range before I replaced the old one, I did measure it.
Other culprits?
I have had problems before with starting and after I cleaned the starter relay it was fine, could it be a bad starter relay?

Sorry for the long post, just want to get out clear information that should make it easier for you experts to help out a fellow jeep brother across the pond

BlueRidgeMark

I have read that afermarket CPSs are very unreliable. Did you get yours from a Jeep dealer or aftermarket?

cruiser54

Could be a faulty CPS. Test it. Post # 7 in my pink link below.

Could also be a weak and dying fuel pump or a split hose to the pump inside the tank.

Double check the spade connectors to the fuel pump ballast resistor also. If they're loose/corroded the fuel pump gets really low voltage.

seww

I cannot say what brand it is, bought it from a store online, but it never stated what brand of CPS it was.
Most likely an aftermarket but it did cost almost $100. (In Sweden, so everything's expensive as hell and then taxes on that!)

Gonna test the Ohm's on it today...

cruiser54

Do NOT bother with the ohms test. Do the VOLTAGE test. Post 7.

seww

I'm gonna test the CPS tonight or at least this weekend, need to solve this issue.

If it's inside the tank, that doesn't sound fun to check out...
The fuel pump or whatever it is that comes on when I turn the key, comes on every time. So it seems to work as usual.

Gonna check out those connectors, I know I had to clean them pretty good last time I was in there so another check is in order.

cruiser54

The fuel pump priming noise does not guarantee that you have correct fuel pressure at the fuel injector rail. That pressure can be lost through the hose I mentioned or due to a faulty pump.

seww

Ok I'll skip the Ohm-test

Ah fuel primer, that's the word I was looking for.
Ok I see now how it works. I'll get back when I've tested the CPS correctly, thanks cruiser.

seww

So i just got home and tested the CPS, it reads .05 volts and correct Ohms.
Should mean we can leave that behind right?

cruiser54

.5 AC volts.....Pretty much yes, you can consider the CPS good enough.

seww

.5 is what I meant
Ok so later ill be checking that double connector.

BlueRidgeMark

Exactly. You must test the pressure at the fuel rail to be sure. Perhaps you can rent a gauge? I just bought one on Amazon for $45, which was a steal. I used it just last Saturday to make sure I pulled out a few more hairs. I was suspecting a fuel pump problem but mine checked out just fine. But at least now I know.

Somewhere here on the forum is the proper test procedure for the fuel pump. You need to test not only how much pressure you have, but how long it holds the pressure with the key off.

Anybody got a link to the test procedure?

seww

Ok I haven't really looked at the Jeep yet, been busy shifting bedrooms in the house.

What about the fuel filter? Don't know how old the one installed now is, could that be somewhat clogged and cause these issues?

Gotta see if I can get a hold of some sort of fuel pressure tester, maybe a buddy of mine has one...

fwak1234

I had an issue similar to this one when I first got my xj to finally find that my coil was cracked on the bottom side and would arc and cuz it to sputter or no start depending on temp and humidity.

cruiser54

Always a good idea to do maintenence first.