No start, no 5v power to cam sensor, about to give up….

[Dborns]

I’ve been dealing with this for awhile now and am at the end of what I can figure out. I need a second set of eyes and suggestions on what to do…

So just to recap in case I've missed anything or if anyone has any other suggestions before I lose my mind-

'84 Jeep CJ7
'96 4.0/ AX-15 with engine harness tied into a CJ-7 harness. Only a few connections are being used from the CJ harness, mostly interior stuff. Exterior inline E2000 FUEL PUMP
Last summer while driving for awhile with no issues, it would stall out on me and I could pop it out of 2nd gear to jumpstart it while rolling. It stalled on me numerous times but I was able to get home. Another time after that, same thing, hot summer, long drive, and it just died on me. I let it sei and after cooling down it started right up. Same thing happened again, with same outcome. So this was happening when the motor was getting warm.
After researching symptoms, stalling, dying after the motor is warmed-up, starts again after cooling down, I zeroed in on the crankshaft position sensor. I replaced that and no change. I get the motor to crank, but it won't start.

I've checked all fuses on the CJ interior harness, which should have nothing to do with ignition issues, all good.
All fuses in the '96 PCM are good. I've changed the fuel pump and ASD relay out with new. No change.
I have power to both the ASD and fuel pump relay.
I replaced the camshaft position sensor and cleaned the metal parts on the inside of the distributor; the dis looks new and I may have put a new one in when I built this a couple years ago.
Tried to run the OBD2 codes and it showed it couldn’t communicate. I know I’ve run the codes on this before so this is new. I probed terminals 4/16 and 5/16 on the OBD2 connector and have 12v at each.
I removed and bench tested the coil, and have spark. I've tested the coil with a MM and have the correct ohms on primary and secondary.
I DO NOT have spark on the plug when I pulled one, and tested it by grounding it to the block. No spark at all while the motor is turning over.
I probed the camshaft position sensor 5v terminal while cranking and DO NOT have 5v.

At some point through all the tests, I noticed I lost the prime that happens shortly on the fuel pump when the key is turned to ON. It wouldn't prime at all. So then I thought I burned the pump up so I bought a new one, and just to be sure, ran dedicated power and ground lines to it. I now have the pump running constant, not just priming when the key is turned to ON.

So again, no idea what to do now. I have power to the ASD and fuel relay, no spark at the coil, and the fuel pump running, it'll crank, but it won't start. I'm still thinking there is something not allowing the ASD relay to ground so that I get spark, but I'm way in over my head. I'd have a mechanic look at it, but I don't know any that would have a clue on how the 4.0 motor/ harness/ CJ7 harness/ frankenstein fuel system works when I put all this together. I've been using this as a DD for the past four plus years now with no issues, so it's something that just started.
Another issue I vaguely remember is when I was building this, I couldn't get the thing to start up at all until I found a write-up that mentioned the tach wire on the '96 harness had to be connected to something on the CJ harness, but I don't remember the specifics on that now.
Please bear with me if you explain something or tell me how to test something as the electric part of this is confusing to me.

HELP please!

 

[Anak]

So you have power to the ASD relay, but is the relay getting triggered properly?

What happens if you take out the relay and put a jumper in its place?

 

[Dborns]

So you have power to the ASD relay, but is the relay getting triggered properly?

What happens if you take out the relay and put a jumper in its place?

I’ve tried switching relays but not running a jumper. What “terminals” on the relay should I run a jumper from and to? Sorry the electrical was the hardest part of this build because I’m not great at auto wiring so please bear with me. I can’t post a pic, so if I’m looking at the spot where the 5 pin relay goes, there are three vertical slots, and two horizontal slots under those. Which should I jump?

 

[Anak]

I would have to go hunting through schematics to figure that out.

Rumor has it you can access the Factory Service Manual (FSM) online. That should tell you which wire needs jumped to.

Actually, probably simpler, would be to find the schematic for the relay itself. The Bosch style relays which used to be the standard configuration tended to have the schematic printed on the top. I have not noticed that on any of these newer, smaller relays. I don't even know what they call these newer relays.

If you look up a Bosch style relay you will see that the terminals have numbers associated with them. Number 30 is the power coming in. Numbers 87 and 87A are the terminals being fed (one when open, the other when closed). Numbers 85 and 86 are the two sides of the coil (the coil is what flips the switch back and forth).

It sounds like you have determined which terminal is the equivalent of number 30 as that would be the one you have found is power coming in. If you have good continuity to ground on one of the other terminals that is probably the equivalent of number 85 or 86. That should account for two of the five. That leaves three to figure out.

Or, another thought...They make manually controlled diagnostic relays, such as these: Diagnostic Relays

Looking at those, I think (make your own comparison with actual parts in hand) the lower left hand corner relay is equivalent to the ones in an XJ PDC. Given it appears to have only two terminals that would make them numbers 30 and 87. Those would be the two to jump.

That is the best I can come up with short of digging through the FSM.

 

[Dborns]

Ok, I’ve got a FSM that I can look through to see if it shows any info on that. I’ll probe the ASD wires to see what is what and hopefully maybe get some more answers tomorrow.

 

[Dborns]

I would have to go hunting through schematics to figure that out.

Rumor has it you can access the Factory Service Manual (FSM) online. That should tell you which wire needs jumped to.

Actually, probably simpler, would be to find the schematic for the relay itself. The Bosch style relays which used to be the standard configuration tended to have the schematic printed on the top. I have not noticed that on any of these newer, smaller relays. I don't even know what they call these newer relays.

If you look up a Bosch style relay you will see that the terminals have numbers associated with them. Number 30 is the power coming in. Numbers 87 and 87A are the terminals being fed (one when open, the other when closed). Numbers 85 and 86 are the two sides of the coil (the coil is what flips the switch back and forth).

It sounds like you have determined which terminal is the equivalent of number 30 as that would be the one you have found is power coming in. If you have good continuity to ground on one of the other terminals that is probably the equivalent of number 85 or 86. That should account for two of the five. That leaves three to figure out.

Or, another thought...They make manually controlled diagnostic relays, such as these: Diagnostic Relays

Looking at those, I think (make your own comparison with actual parts in hand) the lower left hand corner relay is equivalent to the ones in an XJ PDC. Given it appears to have only two terminals that would make them numbers 30 and 87. Those would be the two to jump.

That is the best I can come up with short of digging through the FSM.

The FSM shows a red/blk going into the ASD with a broken line that would close on a dk/ grn org, so I’d say the wires to jump would be red to dark green/ orange?

 

[Anak]

Assuming the red wire shows 12V power, then that is the one to jump from, and if it is closing on dark green/orange then yes, that is where I would start.

If jumping that combination works then you need to figure out what is supposed to be tripping that switch (oil pressure sending unit?) and figure out why it isn't doing its job.

If jumping that combination does not work I would be inclined to go after grounds. This was my go around with a grounding issue: Intermittent Stalling

 

[Dborns]

I jumped the red and green and no go. I was afraid you would mention the dirty G word…. I’ll start chasing down grounds and I’m going to test a few other plugs that should have 5v on them. There are quite a few so I guessing I can narrow things down more by doing that.
I’ll also work on finding and cleaning grounds too.

 

[Dborns]

Found that I don’t have 5v to the crankshaft sensor either. There’s quite a bit of grease and grime on the ground bolt at the back of the motor passenger side, so I sprayed that with degreaser and will let it sit. Then disconnect and check all the grounds on it.

 

[Dborns]

I worked on some grounds today. Two on the passenger side of the engine. I disconnected them and wire brushed the terminals and checked wires. No change. I also disconnected the fuel line at the rail and I have good fuel flow.
Turns over but doesn’t fire.

 

[Dborns]

I’ve been doing research most of the day and kept coming back to the ASD relay ad the crank position sensor. I just went out and retested the new crank position sensor and may have found what I missed.
I tested the B and C pin on the sensor with my analog MM set at 10k ohms(?), and the meter read right at 25. From what I understand, the meter shouldn’t read at all indicating infinite resistance.
Does that sound correct? My new sensor could have been bad? It’s not OEM.

 

[Dborns]

Assuming the red wire shows 12V power, then that is the one to jump from, and if it is closing on dark green/orange then yes, that is where I would start.

If jumping that combination works then you need to figure out what is supposed to be tripping that switch (oil pressure sending unit?) and figure out why it isn't doing its job.

If jumping that combination does not work I would be inclined to go after grounds. This was my go around with a grounding issue: Intermittent Stalling

What do you think about both crank position sensors reading the same? They’re supposed to have infinite resistance and they both read around the same at 25 when I tested the sensor pins. I have another one coming and I’ll test it also before installing.

 

[Anak]

I have not gone down that particular rabbit hole, but someone else may have a good answer.

Another thing to check is the wiring for the O2 sensors. If you ground out an O2 sensor it is a good as a kill switch. I think the most likely culprit on that front is a harness getting too close to the exhaust, but an abrasion situation would work as well.

 

[Dborns]

I have not gone down that particular rabbit hole, but someone else may have a good answer.

Another thing to check is the wiring for the O2 sensors. If you ground out an O2 sensor it is a good as a kill switch. I think the most likely culprit on that front is a harness getting too close to the exhaust, but an abrasion situation would work as well.

I’ve seen that mentioned too. I plan on crawling underneath tonight and I’ll check the sensor wiring.

 

[Dborns]

I had time to look underneath the Jeep tonight for the O2 sensors, and I found one but couldn’t find the other. Keep in mind the exhaust is a custom set up from the collector(?) out to the tailpipe. I swear I had two bungs installed for an up and downstream sensor, but couldn’t find a second one. I also don’t have a cat installed just the muffler so I need to look for the second plug for an 02 sensor or maybe I just missed it all together. Would the motor even run with only one O2 sensor installed?

 

[Anak]

The upstream sensor is the important one. That is the one that tells the confuser what is going on with the fuel mixture so the confuser can make adjustments. Without that sensor there will be problems.

The downstream sensor comes after the catalytic converter. As far as I know, all it does it tell the confuser whether or not the catalytic converter is doing its job. Those who delete the cat generally replace the downstream O2 with a dummy to keep the computer from throwing a code. The dummy does not attach to the exhaust. It could be zip tied in place just about anywhere. I don't know for certain, but it is possible if there were a problem with the dummy or its wiring it might kill things just as well as the upstream O2 sensor.

So yes, the motor would run with only the one (upstream) sensor installed, but the computer would throw a code if the downstream sensor were missing. The computer would also throw a code if the cat were missing. If the cat is missing and computer is not throwing a code something has been done to cope with that. Either a dummy is hiding somewhere or the computer was re-programmed.

If you used to have a catalytic converter in place the missing bung was part of the catalytic converter. It would have been on the very back end, oriented to the top. I would start by looking for your wiring somewhere in that area, and work forward from there.

 

[Dborns]

Ok if the upstream isn’t in the exhaust manifold, then I probably only have the one. The cat was removed when the exhaust was installed. I’ll look for the wiring for the downstream sensor to make sure it’s not been damaged. The wiring for the upstream one looks good

 

[Anak]

I don't know what has been done for your conversion, but the original configuration of a '96 H.O. motor did place the upstream O2 sensor in the exhaust manifold (or header).

The ideal location for the O2 sensor is as close to the head as possible, once the exhaust gases from all the cylinders have come together.

 

[Dborns]

I don't know what has been done for your conversion, but the original configuration of a '96 H.O. motor did place the upstream O2 sensor in the exhaust manifold (or header).

The ideal location for the O2 sensor is as close to the head as possible, once the exhaust gases from all the cylinders have come together.

Ok I’ll be able to look today when it’s not dark. I swore I had two sensors and everything is original from the motor down to the collector(?). They then cut the pipe a few inches past that and installed a long pipe down to the muffler.
I appreciate all your help so far. Hopefully I’ll find the first sensor grounded out. If not I have a second CPS coming and I’ll try that.

 

[Dborns]

I took a look in the engine compartment and underneath, and see just one O2 sensor, and it does look like the upstream. It is just past the connection from the manifold to the pipe going to the muffler. Unfortunately I don't see any other sensors, or even the wiring and plug for the downstream sensor. I've looked for a plug that looks like the gray upstream one, but I see nothing. There's no way I would have cut that off, so it's got to be there somewhere. If I can find that, I can follow that wiring up and check it for damage, or see if maybe the plug itself has damage.
I googled O2 sensor wiring location for a '96 and I'm not able to find where the sensor for that downstream wire comes off the motor or where it's at in the harness. Does anyone have any pics of that you could send me?