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1999 5.2 Magnum, what generates the tach signal? #3202147 01/04/24 09:31 AM 01/04/24 09:31 AM
Joined: Jan 2003 Posts: 179 Confusion D Dodger440 OP member
Dodger440 OP member D Joined: Jan 2003 Posts: 179 Confusion	I am having a intermittent issue with my 99 Dodge pickup where the engine will shut off. It starts back up again, sometimes it takes a minute or so before it will restart. If this happens while I am on the highway or going fast enough that the torque converter is locked, the engine will keep spinning even though it is dead. When this happens the tachometer still reads the accurate engine rpm. I know it's loosing spark and I am pretty sure it's either the crank sensor or the distributor pickup. Does anyone know for sure which one of those 2 parts provides the signal for the tach? If I knew the answer to that I would replace the other part. Thanks

Re: 1999 5.2 Magnum, what generates the tach signal? [Re: Dodger440] #3202260 01/04/24 06:55 PM 01/04/24 06:55 PM
Joined: Dec 2014 Posts: 5,812 ohio R ruderunner master
ruderunner master R Joined: Dec 2014 Posts: 5,812 ohio	Pretty sure the crank sensor is the tach source. But, this is also used for the ignition. The cam sensor is for fuel timing and that's the one in the distributor. Are you certain it's losing spark and not fuel? How did you determine that? Angry white pureblood male

Re: 1999 5.2 Magnum, what generates the tach signal? [Re: ruderunner] #3202268 01/04/24 07:29 PM 01/04/24 07:29 PM
Joined: Jan 2003 Posts: 179 Confusion D Dodger440 OP member
Dodger440 OP member D Joined: Jan 2003 Posts: 179 Confusion	Thanks for the reply! I'm pretty sure it's spark. When it dies it's like the key is shut off, no sputtering it just instantly shuts off. When I go to restart it it will crank and crank with no sign of wanting to start, and then it will just fire right up and run perfectly. When it happens cruising down the highway with the converter locked up, it will die and then 20-30 seconds later it restarts itself. It didn't happen at all today. Yesterday it did it 3 times within about 5 minutes and then ran perfectly the rest of the way home. It doesn't throw any codes, I checked.

Re: 1999 5.2 Magnum, what generates the tach signal? [Re: Dodger440] #3202288 01/04/24 08:55 PM 01/04/24 08:55 PM
Joined: Jan 2003 Posts: 32,929 Grand Prairie,Texas stumpy I Win
stumpy I Win Joined: Jan 2003 Posts: 32,929 Grand Prairie,Texas	You do understand that if you lose the fuel injector signal it will shut off without sputtering.

Re: 1999 5.2 Magnum, what generates the tach signal? [Re: Dodger440] #3202321 01/04/24 10:47 PM 01/04/24 10:47 PM
Joined: Jan 2003 Posts: 18,415 UPPER MICHIGAN, MARQUETTE COUN... N NITROUSN I Live Here
NITROUSN I Live Here N Joined: Jan 2003 Posts: 18,415 UPPER MICHIGAN, MARQUETTE COUN...	You should get a scanner that shows live sensor data. There are some out there that are not real expensive.

Re: 1999 5.2 Magnum, what generates the tach signal? [Re: Dodger440] #3202364 01/05/24 07:57 AM 01/05/24 07:57 AM
Joined: Jan 2006 Posts: 8,162 USA 3 360view Moparts resident spammer
360view Moparts resident spammer 3 Joined: Jan 2006 Posts: 8,162 USA	Very similar thing starting happening to my Ram, and like you I first suspected the ignition system and replaced the coil. But it kept happening and “the root cause” was that the “sock filter” at the bottom of the submerged in tank fuel pump assembly was so plugged with crud that it created a near vacuum at the suction entrance to the fuel pump. This creates “cavitation bubbles” at the pump suction and stops fuel flow. When the gasoline cools down a few degrees it will run for awhile again, then die suddenly. The “crud” restricting the sock filter could come from unclean fuel, but others suspect it may be from an unusually hardy Algae that can survive in 90% gasoline living on the alcohol and water in today’s E10 or E15 mixture fuel. Tilting the bed to get at the fuel pump after removing half the Cargo Box frame bolts and loosening the other half was surprisingly easy compared to dropping the tank - but if you drop the tank spend the time and money now to replace the hidden by tank brake line section that is prone to rust and suddenly blow out. “Cargo Box” is Dodge’s official name for what we customers call a “Truck Bed.” Last edited by 360view; 01/05/24 08:22 AM.

Re: 1999 5.2 Magnum, what generates the tach signal? [Re: 360view] #3202391 01/05/24 10:14 AM 01/05/24 10:14 AM
Joined: Jan 2003 Posts: 179 Confusion D Dodger440 OP member
Dodger440 OP member D Joined: Jan 2003 Posts: 179 Confusion	Thanks for all the replies! I have my scan tool in the truck so I can try to view live data the next time it happens. I also have my fuel pressure tester, but i can't really drive with that hooked up and be able to watch it. The problem is most of the time it fixes itself quickly so I don't have a lot of time to see whats happening. I will post an update when I have more information or find the problem.

Re: 1999 5.2 Magnum, what generates the tach signal? [Re: 360view] #3202403 01/05/24 10:57 AM 01/05/24 10:57 AM
Joined: Jan 2003 Posts: 18,415 UPPER MICHIGAN, MARQUETTE COUN... N NITROUSN I Live Here
NITROUSN I Live Here N Joined: Jan 2003 Posts: 18,415 UPPER MICHIGAN, MARQUETTE COUN...	Originally Posted by 360view Very similar thing starting happening to my Ram, and like you I first suspected the ignition system and replaced the coil. But it kept happening and “the root cause” was that the “sock filter” at the bottom of the submerged in tank fuel pump assembly was so plugged with crud that it created a near vacuum at the suction entrance to the fuel pump. This creates “cavitation bubbles” at the pump suction and stops fuel flow. When the gasoline cools down a few degrees it will run for awhile again, then die suddenly. The “crud” restricting the sock filter could come from unclean fuel, but others suspect it may be from an unusually hardy Algae that can survive in 90% gasoline living on the alcohol and water in today’s E10 or E15 mixture fuel. Tilting the bed to get at the fuel pump after removing half the Cargo Box frame bolts and loosening the other half was surprisingly easy compared to dropping the tank - but if you drop the tank spend the time and money now to replace the hidden by tank brake line section that is prone to rust and suddenly blow out. “Cargo Box” is Dodge’s official name for what we customers call a “Truck Bed.” Low or dropping fuel pressure does not cause an abrupt cut off. Poster claims it just shuts off.

Re: 1999 5.2 Magnum, what generates the tach signal? [Re: NITROUSN] #3202423 01/05/24 12:33 PM 01/05/24 12:33 PM
Joined: Jan 2003 Posts: 25,786 Rio Linda, CA John_Kunkel Too Many Posts
John_Kunkel Too Many Posts Joined: Jan 2003 Posts: 25,786 Rio Linda, CA	Originally Posted by NITROUSN You should get a scanner that shows live sensor data. There are some out there that are not real expensive. Shotgunning parts is the wrong way. The INTERNET, the MISinformation superhighway

Re: 1999 5.2 Magnum, what generates the tach signal? [Re: John_Kunkel] #3202677 01/06/24 11:33 AM 01/06/24 11:33 AM
Joined: Jan 2021 Posts: 983 rust belt M Moparite super stock
Moparite super stock M Joined: Jan 2021 Posts: 983 rust belt	Quote You should get a scanner that shows live sensor data. There are some out there that are not real expensive. Well do some research before you buy one. I looked for a scanner that would show cam/crank signal and most do not. This is not mentioned as what it WILL do. This is what they say "Live Data Stream : Show the information of continuous data stream from a vehicle in a live graphic (waveform) display." They say "and more" but don't give details on what they(more) are. You have to contact the manufacture for that info. I am looking for a windows based software that WILL show cam/crank output(graph style) and only found one. Some have it available as a "upgrade" to add it. If any of you have any good sources please post. The scanners i looked at where in the $100-150 range, Not sure what you consider "real expensive".

Re: 1999 5.2 Magnum, what generates the tach signal? [Re: Moparite] #3202679 01/06/24 11:39 AM 01/06/24 11:39 AM
Joined: Jan 2008 Posts: 2,232 ILLINOIS V volaredon top fuel
volaredon top fuel V Joined: Jan 2008 Posts: 2,232 ILLINOIS	And on my snap on vs the ships OTC and newer autel I can do most of the same stuff with them but the different companies bury the info in different places in their machines. I find the snap on easiest on mopars and the OTC seems to be easier to use if working on a GM the autel? Seems like I can do the least with

Re: 1999 5.2 Magnum, what generates the tach signal? [Re: volaredon] #3202795 01/06/24 04:55 PM 01/06/24 04:55 PM
Joined: Dec 2014 Posts: 5,812 ohio R ruderunner master
ruderunner master R Joined: Dec 2014 Posts: 5,812 ohio	Injector pulse can be checked with a test light. I've used a 194 bulb and socket and some wire to rig a test light on the dash for checking such stuff. Angry white pureblood male

Re: 1999 5.2 Magnum, what generates the tach signal? [Re: Dodger440] #3202889 01/07/24 07:49 AM 01/07/24 07:49 AM
Joined: Jan 2006 Posts: 8,162 USA 3 360view Moparts resident spammer
360view Moparts resident spammer 3 Joined: Jan 2006 Posts: 8,162 USA	Originally Posted by Dodger440 Thanks for all the replies! I have my scan tool in the truck so I can try to view live data the next time it happens. I also have my fuel pressure tester, but i can't really drive with that hooked up and be able to watch it. The problem is most of the time it fixes itself quickly so I don't have a lot of time to see whats happening. I will post an update when I have more information or find the problem. Previous Ram owners who have had this problem have commented about all the “jury rigging” involved in hooking up a pressure gauge that finally pinpoints the problem. The engine dies suddenly - and I certainly thought it was a bad wire connection or electrical component that only misbehaved when hot or vibrating. I had a Mopar Performance PCM which I swapped in but that did not fix it. Cavitation at the pump suction sock filter depends on fuel flow, fuel temperature, and also altitude/air pressure. The first time it happened to my Ram I was climbing a steep hill in the Smokey Mountains in hot weather. My ScanTool OBD-I scanner gave me all kinds of engine data such as fuel injector duty cycle, voltages and so forth but was ultimately no help. When I finally changed out the fuel pump assembly I was alone in Florida outside during Tropical Storm Ernesto during 40 mph wind gusts, with the Cargo box tilted. Biggest problem was getting the “Rollover Valve” off the old pump assembly which took a couple hours and detailed grinding with a Dremel Tool. I would recommend a new pump assembly that has a new roll over valve already attached.

Re: 1999 5.2 Magnum, what generates the tach signal? [Re: 360view] #3202964 01/07/24 12:40 PM 01/07/24 12:40 PM
Joined: Jan 2021 Posts: 983 rust belt M Moparite super stock
Moparite super stock M Joined: Jan 2021 Posts: 983 rust belt	Check your coil resistance, If it's out of speck that could be your issue also. I am leaning towards the crank sensor. I had the problem too but would only cut out for split second. Most of the time the engine would stay running but if you where stopped it would stall.

Re: 1999 5.2 Magnum, what generates the tach signal? [Re: Moparite] #3203337 01/08/24 11:35 PM 01/08/24 11:35 PM
Joined: Mar 2007 Posts: 858 Southeast Pa. SALEM1912 super stock
SALEM1912 super stock Joined: Mar 2007 Posts: 858 Southeast Pa.	If you can't get to a scanner quick enough,you can look at the dash tach. It's hard to see but if there is no movement while cranking it's a good chance the crank sensor is the problem.

Re: 1999 5.2 Magnum, what generates the tach signal? [Re: SALEM1912] #3203362 01/09/24 07:00 AM 01/09/24 07:00 AM
Joined: Dec 2014 Posts: 5,812 ohio R ruderunner master
ruderunner master R Joined: Dec 2014 Posts: 5,812 ohio	He noted that the tach still works if the engine shuts down at speed. I'm guessing he's losing the injectors Angry white pureblood male

Re: 1999 5.2 Magnum, what generates the tach signal? [Re: 360view] #3203529 01/10/24 07:16 AM 01/10/24 07:16 AM
Joined: Jan 2006 Posts: 8,162 USA 3 360view Moparts resident spammer
360view Moparts resident spammer 3 Joined: Jan 2006 Posts: 8,162 USA	A cold snap is coming for many parts of the country. Cavitation will not happen in very cold weather so in low temperatures do a test safely climbing hills on lesser travelled roads. Sudden shut down should not happen when very cold. Maybe add weight to the cargo box to increase engine load. Then when it is warm redo the test over the same route. Troubleshoot every other possibility because it is a lot of work to remove the submerged pump assembly, and I bet it now costs way more than the $280 I paid. Last edited by 360view; 01/10/24 07:17 AM.

Re: 1999 5.2 Magnum, what generates the tach signal? [Re: 360view] #3203731 01/10/24 11:25 PM 01/10/24 11:25 PM
Joined: Jan 2004 Posts: 8,251 fredericksburg,va C cudaman1969 master
cudaman1969 master C Joined: Jan 2004 Posts: 8,251 fredericksburg,va	Crank sensor is bad, get the factory one. The rest are junk, I got a cheap one at the parts store, chased my tail for two years then on a wimm I got a used one at the picapart, dirty but the engine ran great after that. Before Engine would buck-jump for no reason going up slight grade.

Re: 1999 5.2 Magnum, what generates the tach signal? [Re: cudaman1969] #3203786 01/11/24 10:10 AM 01/11/24 10:10 AM
Joined: Jan 2003 Posts: 179 Confusion D Dodger440 OP member
Dodger440 OP member D Joined: Jan 2003 Posts: 179 Confusion	Just an update. The problem only happened 1 time this week while on the highway (I drive the truck every day). I had the scan tool hooked up, but by the time I picked it up and started looking at it the engine was running again. It was probably dead for about 10-15 seconds. I did pull the coil off and checked primarily and secondary resistance like someone suggested, but both were in spec (1.1 ohms primarily and 12,400 ohms secondary). I ordered a oem Mopar crank sensor, I plan to replace that when it arrives. I don't like just throwing parts at it, but it's really hard to troubleshoot a problem that is only there for seconds. I appreciate everyone taking the time to help! I will post again if I have more information.

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