No Start After Bad Jump Start Attempt
My 1993 Jeep YJ 4.0L no longer starts. Starter cranks, and fuel pump primes, but Jeep does not fire up.
Jeep was in storage. Installed brand new Optima Red Top (AGM) battery. Jeep started and ran for one day until battery drained (alternator fuses were unknowingly bad).
Replaced both red 50A fuses in PDC and attempted to jump start, but didn't realize jumper cables were reversed on vehicle with good battery (my YJ was + to battery and - to engine ground, as it should be). Both 50A (alternator) fuses blew again as a result.
Replaced them with new ones and checked all other fuses with multimeter, both in PDC and interior fuse box. Now, when attempting to jump start, engine cranks and fuel pump primes but Jeep does not fire up."
Areas to Inspect / Test
Checked so far...
NOT (thoroughly) checked so far...
I have the factory service manual and I've also reviewed countless forum posts over the past several days, so I think I'm on the right track, but if anyone has any suggestions please share!
My goal is to post the solution to this problem once I can figure it out, as I haven't been able to find a lot of forum content covering an engine ignition failure due to a bad jump start.
Reverse Back feeding will almost always take out the pcm. You have power to the pcm because you can check codes. Does the fuel pump cycle when you turn the key to start? Do you have fuel pressure at the real when you push the valve on the fuel rail? Do you have spark?
My guess would be that the cam sensor or the CPS is bad resulting in the no spark condition.
I believe it's 8 volts to the cam & CPS sensors.
Excellent 8th post! This is what every help me post should look like. You are obviously trying to help yourself as well. :thumbsup:
You say that the fuel pump primes, have you checked the pressure at the rail via the Schrader valve? We'll know a bit more when you do a proper spark check too. Do you have anyone near you to temp swap sensors?
I reread the post. Sorry I asked for info you posted. Cam and crank are powered through regulated supplies inside the ECU. Not likely to have killed one if it was able to run before you jumped it. Power from the asd is getting where it needs to go or the ECU and fuel pump sequence wouldn't function. The cps will give you the symptoms you describe. Check power at the coil. If you have power at the coil with three key on then I am thinking you need to check your cps and see if anyone near by has an ECU you can try out.
Do you believe there could be a link to the miswired jump start and a failed sensor or merely coincidental? I am not a fan of coincidence although it most definitely exists.
If the battery was completely dead use a proper charger to recharge it before using it. You can kill an alternator quicker than you can spit if you let the car charge a dead battery.
The sensors are isolated. The ECU and electronics are designed to take a reverse feed. Load dumping its the killer for most yjs.
Update (more troubleshooting completed...)
Thank you everyone for your great comments! I did some more troubleshooting tonight and this is where things stand so far:
Checked so far... (note, items in BLUE are things I've checked this evening in addition to what I already checked previously...)
I also checked the following tonight, but I'm not 100% on the results:
Last bit of info for tonight...
The very last thing I did before I called it quits was to re-check my PCM codes after all of my diagnostic fun this evening... the PCM is now giving me additional codes, in the exact order that I started unplugging and testing connectors...
12 = battery was disconnected [Reason: I've been disconnecting the battery, so this is expected)
33 = a/c compressor relay [Reason: expected code… my YJ doesn't have a/c]
54 = No fuel sync (camshaft signal) detected during engine cranking [Reason: I unplugged it and was testing voltage at the connectors]
24 = Throttle position sensor (TPS) sensor or circuit (outside of max/min acceptable voltage) [Reason: I unplugged it and was testing voltage at the connectors]
11 = no ignition reference signal detected during cranking [Reason: I unplugged it and was testing voltage at the connectors]
55 = end of test
So it appears that my PCM is working, although I'm not ruling it out just yet.
This is by far the most difficult problem I've ever had to fix on my YJ. I can't help but keep thinking it's going to be something obvious, right in front of my face. The saga continues :mad:
Don't ever cross your jumper cables boys and girls. It's been 3 weeks of "fun" ever since :p
Clear the codes. Do a battery reset.
Good call Que89YJ. I didn't reset the computer properly last night to clear the codes and try to start again, to see which codes remain after the PCM reset.
Woke up determined this morning to get this resolved. Here's what I did quickly this morning:
1. Unplugged both battery cables (unplugging the negative terminal only is not enough to reset the computer) to reset the PCM
2. Checked the codes BEFORE trying to start the engine (12, 33, 55). These are all normal / expected / "clean" codes.
3. Checked the codes AFTER trying to start the engine. This is what I ended up with:
12, 33, 54, 55
54 should be the camshaft sync sensor. However, I thought it was the CPS (trying to remember the codes from memory as I didn't bring my FSM with me) but CPS should be code 11. So what I did was the following...
1. Checked for continuity on the CPS on my '99 XJ (that I know is working, as it's our every day vehicle). There was continuity on two of the pigtail connector pins, so this would lead me to believe electricity can pass into the sensor and come back out.
2. Did the same test of the CPS on my dead '93 YJ. I did not get continuity between ANY of the pigtail harness pins at all.
This makes me think the CPS is truly toast. It's a magnetic sensor so it would make sense (I think) that a reverse feed of electricity (from the bad jump start) would screw it up.
However, the engine code is still 54 (camshaft) and not 11 (cps).
SO... my next step is going to be:
1. Reset the PCM and unplug each sensor (camshaft & CPS) 1-by-1, check to see what code is "tripped" in the PCM, reset the PCM to fresh, and repeat the same step for the 2nd sensor to try and isolate exactly which sensor (when unplugged) is tripping the PCM. In theory, I guess should still get a matching code (no matter 11 or 54) when the CPS is plugged in AND when it's unplugged... since if it's really not moving electricity through its internal wiring anymore, the PCM should always think it's not getting a CPS signal in either case.
At least I'm getting closer. Trying to not to over think things, but don't want to start buying expensive parts until I'm sure I've narrowed something down. CPS isn't' cheap. Parts store quoted me ~$160 (I'll call around first if I decide to pick it up in the end).
QUESTION: Has anyone ever had a code 54 (which points to camshaft sensor) and not a code 11 (cps), but the root cause was actually a bad CPS and nothing to do with the camshaft sensor? It's really looking like a CPS failure based on what I just did.
Yes you will get 54 by itself. If that code is repeatable then you know you have a problem there.
Is this the $160 sensor in question?
No that is the crank position sensor for code 11. Correct me if I am wrong but I thought you had 54 cam fault. The crack sensor is the one on the back pod the engine and usually cost 60. The cam is in the distributor and you can buy it separate for about the same or if it is the cam fault get the entire distributor with it installed for 20 or so more.
Cleared PCM and did some more troubleshooting...
1. Checked that PCM reset, then tried to start engine with both cam and crank sensors disconnected: 12, 33, 11, 55
2. Checked that PCM reset, then tried to start engine with crank sensor plugged and cam disconnected: 12, 33, 54, 55
3. Checked that PCM reset, then tried to start engine with cam sensor plugged and crank disconnected: 12, 33, 11, 55
4. Checked that PCM reset, then tried to start engine with both sensors PLUGGED in: 12, 33, 54, 55
I have a distributor assembly on order from my local parts store ($93+tax). Will pickup tomorrow, install, and fingers crossed...
NOTE: Apparently you can't get just the camshaft sensor for model year 91-93 YJ's. I talked with three different parts stores (Napa, Lordco & West-Can) and they all told me the same thing.
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