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1990 4.0 no start

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Old 05-21-2012, 10:14 PM   #1
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Default 1990 4.0 no start

it will not start up i checked the fuel rail for fuel it checked out good. i checked the spark plugs they are good. it will start and run for a few seconds on brake clean. is there a fuse or some thing i can check next?
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Old 05-21-2012, 10:42 PM   #2
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CPS.
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Old 05-21-2012, 10:51 PM   #3
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x2 on CPS. did it act up quickly?
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Old 05-22-2012, 12:09 AM   #4
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yes drove fine to work and back then i whent to move it and it stalled out and would not refire
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Old 05-22-2012, 02:38 AM   #5
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There in my signature is a thing on checking your CPS. Power to your fuel pump goes out the rear of the ceramic ballast resistor on the inner fender by your air cleaner. Connections there get funky. Do you hear the pump run for a couple secs when you turn the key?
When you depress the little deal on the Schrader valve on your fuel rail, does a little fuel spurt out onto the rag?
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Old 05-22-2012, 06:38 AM   #6
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If it starts and runs for a while ONLY when you introduce brake kleen or starting fluid, the problem is not spark or the crank sensor; it is fuel delivery.

Turn the key to the ON position. By design, the fuel pump should energize and run for approximately 2 seconds and then turn off. Listen for it. Does yours do that?

As DFlintstone mentioned, the ceramic ballast resistor can cause problems but usually with that, the engine will start on its own but die quickly as the ballast resistor is out of circuit with the key in the full ON position so some fuel is introduced, but the ballast resistor is back in circuit as soon as you let go of the key and it returns to the RUN position and at that point, no more fuel so the engine dies. The ballast resistor can be jumpered to rule it in or out when troubleshooting. Jumpering is not a problem as the resistor is only there to reduce noise on the fuel pump circuit; later models don't even have this resistor.

I suspect that if you can only get it to run when you introduce a flammable into the intake, you have a problem either with the fuel pump itself, OR with the control electronics for the fuel pump (relay, etc).

Last edited by tjwalker; 05-22-2012 at 06:42 AM.
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Old 05-24-2012, 10:59 PM   #7
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do you know which relay is the fuel pump and where it is located
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Old 05-24-2012, 11:16 PM   #8
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Under the hood, passenger, side, second one back out of the 4 there.

I'm sure, at least one diagram out there is wrong.
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Old 05-24-2012, 11:25 PM   #9
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when i first checked the fuel rail when it first happened i had full pressure. today when i checked the resistor i also checked the fuel rail again and there was no fuel. dang it this sucks. I am going to refresh the grounding points this week end and bring home my volt meter and test power to the pump.
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Old 05-25-2012, 01:03 AM   #10
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My Jeep doesn't pump fuel unless I'm cranking the motor not wen the key is just on
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Old 05-25-2012, 01:04 AM   #11
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Have u checked your cps
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Old 05-25-2012, 01:10 AM   #12
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Please check the CPS, I had the same problem. Replaced my coil packs, fuel pump.... Nothing. Replaced the CPS and bam my jeep ran like a jewel
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Old 05-25-2012, 08:37 AM   #13
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Quote:
Originally Posted by stev-o View Post
My Jeep doesn't pump fuel unless I'm cranking the motor not wen the key is just on
It pumps when it's running. Re-read tjwalker's post above.
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Old 05-26-2012, 01:00 AM   #14
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ok i dug a little deeper today after work. trouble shot the fuel pump relay. I found the main power to the relay was bad. i cut out a bad spot from the batter to the in line fuse link it was melted in half. i jumped the relay and the pump would not turn on. I also checked the cps with my meter on ac volts and cranking over the engine i only had about .37 volts. i ordered a new pump and cps will install it tomorrow when it come in at the store. I will let you know how it turns out.
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Old 05-26-2012, 02:30 AM   #15
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Quote:
Originally Posted by DFlintstone View Post
Power to your fuel pump goes out the rear of the ceramic ballast resistor on the inner fender by your air cleaner.
You should have power there^^, to the pump for a couple seconds after you turn the key on, then cranking and running. Of course if you don't have power there a new pump won't help....

Stevo has some other issue going on. IIRC he's also posted before his only powers up cranking and running. Maybe an ECU issue? Idk. Anyway his is the only one I've seen here that does that.

3.7 is defiantly iffy. Mine actually worked a little below that, then soon crapped out, then with the new seemed to run smoother and start better than it had in a long time. Idk your $ situation, but myself I'd make darn sure the old pump wasn't working with power and a good ground before I bought a new one.

Again...that's tough. My NEW Cps tested at .4 right after I put it in. I happened to check it again a few days later and got a .5. If your pump is indeed dead, that might be all you need at this moment. You might take a good look at the wiring back there. I wonder if a shorting wire isn't what blew your fusable link? Maybe all you need is more wire!

This link here has some pretty good diagrams,(just don't get messed up looking at the 2.5 like I did!)>> http://www.scribd.com/justin-goldber...-Cherokee-1989 You'll ger'r!

Last edited by DFlintstone; 05-26-2012 at 02:43 AM.
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