Hey Guys,

I have a 99 Cherokee that I did a motor swap on and now I have a crank but no start situation. I have found that my issue is that I am not getting any voltage to my ignition coil. I have been using this youtube video to help diagnose . I have tested both the gray wire (Power Constant) and the Green/Orange wire (Signal) and I am getting squat. As far as I can tell my CAM sensor and Crank Sensor are good and have power. I did buy a new cam sensor from autozone because the wires were exposed on the original sensor. I have also just replaced my Ignition switch and no luck. I did check for continuity from the ECU all the way to the ignition coil connector and it is good. I believe the ASD relay is also good because I switched it with the starter relay.
Does anyone have any other suggestions as to why I am getting no power being delivered to the ignition coil?

Thank you

 

does the fuel pump prime for 3secs when ignition switched to "on" ?

does the ASD relay have 12V (from the ignition key) at one terminal ?

when the ASD relay recieves a signal from the PCM, it will perform the self test prime and close to provide 12V to the coil

descriptions of the circuit diagram and test procedures are outlined in FSM, Electrical; Ignition

 

Fuel pump does not seem to prime.

I got to step (4) and there is no voltage at terminal 86 when I crank the engine over. I did a continuity check from terminal 86 to the PCM which is a DB/Y wire and it is good. I am a bit unsure what to do next. It seems to direct me to the ignition switch in the FSM.

RELAY CIRCUIT TEST
(1) The relay common feed terminal cavity (30) is
connected to battery voltage and should be hot at all
times. If OK, go to Step 2. If not OK, repair the open
circuit to the fuse in the PDC as required.
(2) The relay normally closed terminal (87A) is
connected to terminal 30 in the de-energized position,
but is not used for this application. Go to Step 3.
(3) The relay normally open terminal (87) is connected
to the common feed terminal (30) in the energized
position. This terminal supplies battery voltage
to the starter solenoid field coils. There should be
continuity between the cavity for relay terminal 87
and the starter solenoid terminal at all times. If OK,
go to Step 4. If not OK, repair the open circuit to the
starter solenoid as required.
(4) The coil battery terminal (86) is connected to
the electromagnet in the relay. It is energized when
the ignition switch is held in the Start position. On
vehicles with a manual transmission, the clutch
pedal must be fully depressed for this test. Check for
battery voltage at the cavity for relay terminal 86
with the ignition switch in the Start position, and no
voltage when the ignition switch is released to the
On position.

 

you could most probably stimulate pin 86 with 12V by slipping a thin 5A wire into the socket, plug relay back in, turn ignition to "on" and jump that to the battery, see what happens

I do not have my FSM in front of me, there is a very specific test procedure outlined for this issue in the Chapter I mentioned

unfortunately one of only several possible outcomes is the PCM is failed

 

So I jumped power from the battery to terminal 86 and that did really seem to do much. When I did this there was a single click but still no power to ignition coil wire.

I am trying to follow the FSM but I am not seeing the specific procedure you are referencing. The rest of step (4) is below that says to go to 8D but when I went there it basically refenced me to the wiring diagrams. I will try to look a bit more closely at this after work today.

Also here is the link I used to download the FSM http://cruiser54.com/?page_id=365


(4) The coil battery terminal (86) is connected to
the electromagnet in the relay. It is energized when
the ignition switch is held in the Start position. On
vehicles with a manual transmission, the clutch
pedal must be fully depressed for this test. Check for
battery voltage at the cavity for relay terminal 86
with the ignition switch in the Start position, and no
voltage when the ignition switch is released to the
On position. If OK, go to Step 5. If not OK with an
automatic transmission, check for an open or short
circuit to the ignition switch and repair, if required.
If the circuit to the ignition switch is OK, refer to
Ignition Switch and Key Lock Cylinder in the
Diagnosis and Testing section of Group 8D - Ignition
System for testing of the ignition switch.

 

If I do have a bad cam sensor will that also cause me to fail test number (4)?

 

I do not believe so.

The ASD relay is connected to the PCM both input and output, if the PCM does not sense 12V output from the ASD relay, it will not activate anything else, such as fuel pump

have a look at the circuit diagrams and diagnostics section from both sections 8 and 14..(I have a '96)

you activated the ASD relay with 12V, which should have sent 12V down the line, but you noted no change

To my knowledge, there is 3 likely causes for the issue; bad Crank sensor, bad (wiring/connectors/fuse), bad PCM

 

ASD relay seems like a good place to start. Also verify that you have the correct flexplate for a 99, the crank sensor is connected and not damaged. It's easy to wing it doing an engine swap if you didn't remove it from the bellhousing first.

 

Lawsoncl so I did not remove the crank sensor when doing the swap. So are you saying I could have damaged it while installing the new motor? Is there a way I can verify that is the problem before I go and buy another sensor?

Also to clarify on my earlier post I made an error and I was testing the ASD relay when that diagnosis was for the starter relay. I redid the tests on the starter relay and it was good.

I also jumped the fuel pump relay from pin 30 to 87 and I here the pump kicked on.

I did find that fuse 21 was blown. I replaced it and symptoms did not change.

 

The end of the sensor sticks into the bellhousing, so it it possible to clip it with the flexplate when doing the engine swap. I believe a 99 should still prime the fuel pump for a few seconds when the ignition is initially turned out, and again if it sees the crank turning. Here's a writeup on testing the sensor with a volt-meter https://troubleshootmyvehicle.com/je...crank-sensor-1 It has you turn the engine slowly by hand and watch for the 5-volt d/c signal to flip on/off as the crank turns. You could also set the meter for a/c and crank with the starter. Is it the correct flexplate for a 99, right?

 

Why make it complicated, if you believe it’s as simple as no power to the coil then take a piece of wire and supply the coil with power from the battery and see if it starts

if so, now you can concentrate on one problem and not worrying with any other possibilities.

its not going to tear anything up to bypass all that safety equipment for just testing .

preaching to the choir possibly, but it may help raise morale lol

 

So I have gone through and verified the 5 volt test and it passes. There was another test where I measured the resistance across terminals B and C and it passed that test as well so I believed I have a good crank sensor. Could the sensor still be damaged but would pass those tests? The flexplate is the original from the original engine which ran fine until it overheated. I'm not sure how I would verify if it is the correct flexplate.

 

So I tried your advice and supplied power to the grey wire on the ignition coil from the battery. I noticed fuel pump doesn't kick on so I jumped 87 to 30 to force it to turn on. Still nothing. I still need to go through the diagnosis of the fuel pump as AWG suggested earlier.

Could a bad fuel pump trigger the ASD Relay to disable power to the ignition coil?

 

[QUOTE=jdill;3623408]So I tried your advice and supplied power to the grey wire on the ignition coil from the battery. I noticed fuel pump doesn't kick on so I jumped 87 to 30 to force it to turn on. Still nothing. I still need to go through the diagnosis of the fuel pump as AWG suggested earlier.

Could a bad fuel pump trigger the ASD Relay to disable power to the ignition coil?[/QUOTE

no

the system isn’t that smart

start at basics like this

how sure are you that the fuel pump itself is good? Supply it with a straight source of +12v and a good ground.

I admit I have not read the entire thread,I’m going to try that now and catch myself up to speed.

 

what is protected by fuse 21? It’s obviously shorted in some way that is probably going to end up being your tell tale sign of where to find this problem.

i think I would start here by removing the battery positive terminal and checking continuity from the + terminal itself to my asd, fuel pump Relays (terminal 30 on both) , and ignition coil 12v wire.

there are only (2) wires going to the ignition coil that is a +12v straight from the battery (many splices along the way though) and the one you said you checked for continuity which is from the pcm to the coil ....that one is ground ...

so check the ground to the pcm and the coil.

reverse the process, take the negative battery terminal off and go to your pcm and make sure you have continuity to pin d3 in the pcm plug.

if you need diagrams by all means ask I have an alldata subscription that needs to be used more.