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No injectors or spark, cps strange voltages

WebDog

WebDog

NAXJA Forum User
Location
Center City, MN
We are in death valley and have a jeep with no start condition.

94 xj, no injectors or spark. The cps is ground good, 5v on one side and 7v on the other. Would this be a bad ecu?
 
I hope everybody is warm and safe? Please let us know where you're at if you need assistance? Have you checked your coil/wires, CPS, or your Dizzy?
 
Note from DJ
Look over this post for info o CPS
Crankshaft Position Sensor Connector (CPS/CKP) test for HO 1991 - 2001
Will turn over, but won't start?
http://www.naxja.org/forum/showthread.php?t=1062496
--------------------------------
Look over for how to check the CPS/CKP
99XJ How to Test the (CMP) Camshaft Position Sensor
NAXJA http://www.naxja.org/forum/showthread.php?t=1003757&page=2

Test procedure provided by Tim_MN in post # 17
--------------------------------

Checking Fuel Pump Procedure
No power to your fuel pump (check fuses and relays) or your fuel pump is shot.

I would first hot wire the fuel pump, there is an electrical connector on the drivers side near the gas tank, should have three wires to it, hopefully there is a smaller gauge wire on it like mine this is for the sender, so ignore it. Run a pair of long wires from battery to the connector, one to the + side of the battery and one to the - side of the battery (black preferably) to the black wire of connector, the other color to the probably orange wire of connector to positive side of battery.

On your 1994 Jeep Cherokee 2WD 4.0L MFI , the Fuel Filter is located: Under vehicle, driver side, below rear seating area, front of fuel tank, mounted on chassis in fuel line

FUEL DELIVERY
Power to fuel pump relay is supplied from ignition switch when in "ON" or "START" position, at which time the ECU supplies a ground for fuel pump relay. When relay contacts are closed, power is applied to fuel pump.
Fuel is drawn through one end of a roller-type electric fuel pump, compressed and forced out opposite end.
Pump capacity is greater than maximum engine consumption so that pressure in fuel system is always maintained.

From Go Jeep
http://jeepgarage.free.fr/OWN/fuel%20injection%20system%20multipoint.pdf

Fuel System Test
WARNING: Always relieve residual fuel pressure in fuel delivery system before opening system. To prevent chance of personal injury, cover fittings with shop towel while disconnecting fittings.

1) Remove cap from pressure test port located in fuel rail. See Fig. 3. Connect Fuel Pressure Gauge (J-34730-1) to pressure fitting.

2) Start vehicle. Pressure should be approximately 31 psi (2.1 kg/cm) with vacuum hose connected to pressure regulator and 39 psi (2.6 kg/cm) with vacuum hose removed from pressure regulator.

3) Check fuel pump flow rate by pinch off fuel return line. Run fuel pump by placing jumper wire between terminals "D1-5" and "D1-6" of diagnostic connector "D1". If fuel flow is less than one quart or (1L) in one minute, inspect fuel system for a plugged fuel filter or filter sock.
If above items check out OK fuel pump will need to be replaced.
 
WebDog said:
We are in death valley and have a jeep with no start condition.

94 xj, no injectors or spark. The cps is ground good, 5v on one side and 7v on the other. Would this be a bad ecu?
Click to expand...
which pins? 5 volts is the expected value for the power supply to the CPS but 7 volts shouldn't be anywhere near it. Since 5+7 = 12 I suspect some sort of weird wiring harness issue or grounding problem.
 
kastein said:
which pins? 5 volts is the expected value for the power supply to the CPS but 7 volts shouldn't be anywhere near it. Since 5+7 = 12 I suspect some sort of weird wiring harness issue or grounding problem.
Click to expand...

One of the links I posted below suggested that it could be more than 5 volts incoming.
"Verify that a 5 volt or greater signal is present at one of the two terminals."
 
There really shouldn't be, since it's a TTL-level component and (IIRC, checking FSM now) powered off the same rail as the MAP sensor and TPS, but I guess it could happen.

EDIT: on a 98 (can also check 91, 95, 96, and some others) it is powered by circuit K7 from the ECU, 5V supply voltage, and the CPS, CKP, and TPS all share the rail.
 
Hmm, I wonder if it might be a ground problem since he had 5 volts on the other side as well?
 
yeah, that's what I am thinking. Either a ground for the ECU or a ground for the CPS, not sure which, and I think the CPS may ground through the ECU anyways.
 
I agree, I think the CPS grounds through the ECU, that would be a smart one to check. Also at the battery. Starter may be grounded better than the other grounds at the battery.
 
Well hours of trouble shooting things only got stranger, after trying another ECU and still no go we put the original ECU in and now it would not crank. I tried jumping the starter manually and no go, maybe it burnt out from so many tries??

Anyway we got them on a flatbed this morning and hopefully AAA has them home by now.

Thanks for all the replies, Ill post up when I find whats wrong...
 
Not cranking has nothing to do with the ECU, so that sounds unrelated... unless the grounds are so horrible that the starter isn't grounding properly now.
 
Wife,s 98 had the "no crank"problem.....Replaced the NSS and it was good,,,
 
Bad ignition switch is also possible.
 
I guess a little more background on the jeep, he has had lots of issues with coils going bad and just had a new cps installed 2 weeks ago. I wonder if it is a grounding issue that is causing his issues.
 
kastein said:
which pins? 5 volts is the expected value for the power supply to the CPS but 7 volts shouldn't be anywhere near it. Since 5+7 = 12 I suspect some sort of weird wiring harness issue or grounding problem.
Click to expand...

on the cps connector the center is ground, the orange was 5V feed and the other side was supposed to be 0 was reading 7, I tested with CPS connected and disconnected and got the same reading.
 
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