kryptronic Posted September 22, 2017 Share Posted September 22, 2017 Hey guys. Here's the situation. My 91 HO Comanche has been running top notch, no issues. Today I ran back and forth to the comic book store this morning, 10 miles round trip, no problem. About an hour ago I tried to leave to go somewhere else and about a 1/8 mile from home the engine basically revved down to nothing then shut off. So I began my side of the road run-through. Electric looked good, no blown fuses, nothing fried within site, instrument cluster gauge read 12 volts. Belt was on, no blown hoses, etc. Air looked good, no obstructions. I uncapped the port on the fuel rail and verified there was fuel pressure. I tried to listen for the fuel pump pushing fuel, but no hum was present. I was pretty sure it was a fuel issue, but just in case voltage was off, I tried to I walked home, grabbed my JK and tried to jump the MJ with it. No dice. While at the house I grabbed a rubber mallet and I used that to bang various areas around the MJ fuel tank and sender. No dice. Then I completely evacuated all the fuel from the fuel rail using the port on the rail, my key and an old rag. Tried to start the MJ again, and she fired right up. I tried a couple of subsequent stops and starts, and she's running well. A little more vibration that usual, but she's shaken up a bit. I was cranking on the starter here or there for 30 seconds at a clip. Anyway, I'd say the MJ is good right now, but would love to know what the issue was/is. Air or obstruction in the fuel line? Are these the foreboding signs of my 230k fuel pump or sender going up? Bad gas? Something else? I haven't run into this one before. Usually it's a no start from the get-go. Thanks for the input. Link to comment Share on other sites More sharing options...
Pete M Posted September 22, 2017 Share Posted September 22, 2017 when was the last time the fuel filter was changed? Link to comment Share on other sites More sharing options...
kryptronic Posted September 22, 2017 Author Share Posted September 22, 2017 9 minutes ago, Pete M said: when was the last time the fuel filter was changed? No idea but it looks very new. PO swapped in a fresher engine about 1000 miles ago and it looks to have been changed at that time. Link to comment Share on other sites More sharing options...
Pete M Posted September 22, 2017 Share Posted September 22, 2017 well, as I usually say about weird issues that magically fix themselves; one occurrence is a glitch, twice becomes a trend, 3 times is a problem that needs a-fixin'. Link to comment Share on other sites More sharing options...
HOrnbrod Posted September 22, 2017 Share Posted September 22, 2017 I'd head to the Zone, rent a set of gauges and pressure test at the rail port just to be sure. ~40 w/o vacuum. 30 w. vacuum. My original pump died instantly at around 120K. It didn't fool around. Also check to make sure it's not throwing a fault code or two. Link to comment Share on other sites More sharing options...
kryptronic Posted September 22, 2017 Author Share Posted September 22, 2017 48 minutes ago, HOrnbrod said: I'd head to the Zone, rent a set of gauges and pressure test at the rail port just to be sure. ~40 w/o vacuum. 30 w. vacuum. My original pump died instantly at around 120K. It didn't fool around. Also check to make sure it's not throwing a fault code or two. I've got a fuel pressure tester here. Let me see what it says. Link to comment Share on other sites More sharing options...
gogmorgo Posted September 22, 2017 Share Posted September 22, 2017 X2 on checking for codes. I'd also take a look at the ballast resistor. If it happens bypass it and see what's up. Link to comment Share on other sites More sharing options...
kryptronic Posted September 22, 2017 Author Share Posted September 22, 2017 I didn't check codes, but there is no check engine light. Maybe somebody can verify, but I don't believe there will be any codes on an HO without a CEL. Here's how my last 20 minutes went: My son and I gathered up a fuel pressure gauge, and a vacuum gauge, went over to the MJ, popped open the hood, started it, and within the time it took me to walk around to the front, it died. The same exact way it died before, gently. The only thing to note is that just before it died, I heard a fairly audible low hum coming from the transmission area or rearward. Then it would not start. I verified there was no fuel in the fuel rail by attempting to extract it via the pressure test port. I figured for sure this is a fuel pump, or fuel sending unit issue. I fiddled for a minute, tried a couple of starts, then it started right up. I wasted no time getting gauges hooked up. Fuel pressure read 32 PSI with vacuum, 41 PSI without vacuum. Vacuum was 18 in-Hg. These are very similar numbers to those of my last tests, on 2017-06-19, about 200 miles ago. After the engine settled down from being stressed, I let it run for about five minutes. It ran nicely, without issue, the whole time. Towards the end, I stuck my ear near the gas tank, and I swear the fuel pump is whining at a high pitch. It's always whined a bit during operation, but this was subtly different. Higher pitched, a bit louder than what I've been told is normal. So, I'm thinking it's a fuel pump issue. I have an extra fuel pump in the garage that only has about 200 miles of use on it from a 95 YJ. I have to check whether that will work, it's an HO pump. Not sure if it's a fit for the sender, though. Does anybody think I'm barking up the wrong tree? Or should I run more tests before dropping the tank? Thanks. Link to comment Share on other sites More sharing options...
Jeep Driver Posted September 22, 2017 Share Posted September 22, 2017 Replace the fuel pump relay and see what happens. Link to comment Share on other sites More sharing options...
Pete M Posted September 23, 2017 Share Posted September 23, 2017 you don't necessarily need to drop the tank to pull the pump. access is on the side. I guess it's also possible that the sock is getting clogged from something in the tank. Link to comment Share on other sites More sharing options...
gogmorgo Posted September 23, 2017 Share Posted September 23, 2017 Pretty sure the fuel pump was the same for Renix and HO, just everything else back there was different. If your truck is a '91, it has a check engine light. Even if it hasn't been triggered (I.e. illuminated), there could be stored codes. All it takes is rocking the ignition key back and forth to check, don't need a fancy scanner or even to start the engine. Unless of course your CEL was illuminated for so long the bulb burnt out... or someone pulled it... But you may be on the right track with the fuel pump. Mine (in my '91) exhibited similar symptoms very occasionally for a year and like, 10,000 miles, before it started becoming painfully clear the pump was dying. But check codes and try to look at the ballast resistor before you shell out for a new pump. And if you do end up needing a new pump don't get the $#!&ty Delphi one... It doesn't fit in the holder and the adapter kit is garbage... I had no choice but to use one on a roadtrip (took me 1000 miles at no more than 2000rpm before I found any pump) and with some creative hose clamping I made it work... But within two weeks it obviously popped out of the holder cause now I run out of gas just below a half tank. Link to comment Share on other sites More sharing options...
HOrnbrod Posted September 23, 2017 Share Posted September 23, 2017 You normally don't get a CEL even with codes. Do check the codes first. https://comancheclub.com/forums/topic/28111-reading-obdi-91-and-92-mj-fault-codes/ FWIW, I think it's ignition. Sync sensor or CPS maybe......... Link to comment Share on other sites More sharing options...
kryptronic Posted September 23, 2017 Author Share Posted September 23, 2017 Thanks for all the tips. I'll run codes and check some things out. I'm used to the YJ where the tank does need to drop out to get to the pump. Thanks for pointing out thats not the case with the MJ. I should have thought before I typed. Link to comment Share on other sites More sharing options...
kryptronic Posted September 23, 2017 Author Share Posted September 23, 2017 Alright. Update here. Didn't try to start the MJ, but did run codes. I was unaware that fault codes (errors) could exist without a CEL (or more specifically, the CEL not being illuminated). Thank you for the information. Diagnostics produced codes 12 (battery disconnected in last 50 starts) and 55 (end of codes). So OBDI doesn't have anything to go on. 14 hours ago, HOrnbrod said: FWIW, I think it's ignition. Sync sensor or CPS maybe......... Please correct me if I'm wrong. This has happened twice with a cold engine. The engine was not at operating temperature either time it died and would not restart. It is my understanding that the computer is there to optimize engine performance, fuel economy and emissions at operating temperature (known as open loop). The computer functions in a very limited capacity prior to the engine reaching operating temperature (closed loop). During closed loop, no sensors are active or could contribute to a no-start situation, or the engine dying. So that would rule out basically all the sensors. Is this right, or wrong? So the list of things I'm going to look at today, in order: Fuel Pump Relay, Ballast Resistor, Fuel Pump, Ignition Link to comment Share on other sites More sharing options...
HOrnbrod Posted September 23, 2017 Share Posted September 23, 2017 The ignition system of course is involved in both closed and open loop operation. So failures of the sync sensor, CPS, and other ignition stuff will cause problems. Your codes do look fine. Do you have a spare ignition coil? Just for grins, stick it in there and try it. I've had three go bad over the years causing intermittent problems and they tested good with an ohmmeter. Link to comment Share on other sites More sharing options...
kryptronic Posted September 24, 2017 Author Share Posted September 24, 2017 I couldn't reproduce the issue today. I've got spares of just about every HO part that I might need. And I'll look at ignition. My experience with both the crankshaft and camshaft sensors is they only kick on in closed loop. Both contribute to poor idle when not functioning. Thanks for all the info. I'm actually thinking relay or ballast resistor based on symptoms. I'll post back if when I figure it out. Link to comment Share on other sites More sharing options...
kryptronic Posted October 6, 2017 Author Share Posted October 6, 2017 Update: I've driven about 60 miles since the incident and not a single issue. I'm an engineer by trade, so I don't believe in glitches - no offense, Pete. The plan is to replace all the parts that may have contributed to the failure. I've got a new relay, new ballast resistor and various fuel pump parts to refresh that, but I have not had luck getting a fuel pump. I ordered the Bosch from Amazon because it's really highly rated, but since they've sent two of them that were previously installed/used. So I need to order a fuel pump, should I persist and try to get a new Bosch? Link to comment Share on other sites More sharing options...
kryptronic Posted November 26, 2017 Author Share Posted November 26, 2017 SOLVED: Happy to report that I replaced the fuel pump with a Bosch unit from Napa, and the MJ is running proper again. The upper plastic piece provided with the pump to retrofit it to the MJ HO sending unit needed substantial modification to get a proper fit. I'll update my build thread with pics and specifics on the actual install. Thanks for all the help. Link to comment Share on other sites More sharing options...
gogmorgo Posted November 28, 2017 Share Posted November 28, 2017 Interesting. My local Napa said they couldn't order me the Bosch pump. Ended up getting it online. I paid a shop to replace it, or rather my insurance company paid, replaced the gas tank after mowing down a whitetail, got them to swap out the Delphi for the Bosch while they were in there. They didn't say anything about issues installing it, although you're not the first person who said they had to do some modifying to make things fit. I'm almost tempted to go pull the sending unit now just to see what the shop did. Link to comment Share on other sites More sharing options...
kryptronic Posted November 28, 2017 Author Share Posted November 28, 2017 This is what had to be done to it. 0.20" off the top, 0.20" off the top of the fins on the sides, 0.30" wide x 0.15" deep notches cut on either side of the opening. Link to comment Share on other sites More sharing options...
HOrnbrod Posted November 28, 2017 Share Posted November 28, 2017 On 11/26/2017 at 11:28 AM, kryptronic said: SOLVED: Happy to report that I replaced the fuel pump with a Bosch unit from Napa, and the MJ is running proper again. The upper plastic piece provided with the pump to retrofit it to the MJ HO sending unit needed substantial modification to get a proper fit. I'll update my build thread with pics and specifics on the actual install. Thanks for all the help. Which Bosch p/n did you get? Link to comment Share on other sites More sharing options...
kryptronic Posted November 29, 2017 Author Share Posted November 29, 2017 19 hours ago, HOrnbrod said: Which Bosch p/n did you get? #69302 Link to comment Share on other sites More sharing options...
Jeep Driver Posted November 29, 2017 Share Posted November 29, 2017 Yeah, the Bosch does not fit like it should, guess they figure it's up to you to make it work. Link to comment Share on other sites More sharing options...
HOrnbrod Posted November 29, 2017 Share Posted November 29, 2017 The Mopar p/n for the original long Bosch fuel pump was 4637192, long gone and superceded by p/n 68001826AA. This pump looks like the Bosch 69302 that most of us are now using. The Mopar 68001826AA looks to be a remanufactured unit and they are available. HERE's one on Ebay. I may give one of these a try for the next one... Link to comment Share on other sites More sharing options...
gogmorgo Posted November 30, 2017 Share Posted November 30, 2017 I saw stuff about refurb pumps when I was looking to replace my POS Delphi. I'm pretty sure that's the pump I saw, although I couldn't find any reference to them actually being done by/for Mopar. And any reviews I saw for reman units said they were cheap junk that either didn't work out of the box or else failed right away. I'll acknowledge that when a product just hits the shelf the only reviews will be the negative ones before the product's been stress tested in the field, and the users who had the product fail generally shout the loudest, but I still wasn't sure I wanted to take the chance. I got the Bosch 69302, but I've only put 50 miles on it, and like I said I have no idea how the install went... All I know is the truck runs and the new fuel pump box disappeared from my passenger seat. Link to comment Share on other sites More sharing options...
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