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
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Joined: Dec 2014
Posts: 5,812 ohio
ruderunner
master
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master
Joined: Dec 2014
Posts: 5,812
ohio
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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
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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
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Joined: Jan 2006
Posts: 8,162 USA
360view
Moparts resident spammer
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Moparts resident spammer
Joined: Jan 2006
Posts: 8,162
USA
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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.
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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
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Joined: Jan 2003
Posts: 18,416 UPPER MICHIGAN, MARQUETTE COUN...
NITROUSN
I Live Here
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I Live Here
Joined: Jan 2003
Posts: 18,416
UPPER MICHIGAN, MARQUETTE COUN...
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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.
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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
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Joined: Jan 2003
Posts: 25,786 Rio Linda, CA
John_Kunkel
Too Many Posts
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Too Many Posts
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Posts: 25,786
Rio Linda, CA
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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
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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
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Joined: Jan 2021
Posts: 983 rust belt
Moparite
super stock
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super stock
Joined: Jan 2021
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rust belt
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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".
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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
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Joined: Dec 2014
Posts: 5,812 ohio
ruderunner
master
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master
Joined: Dec 2014
Posts: 5,812
ohio
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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
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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
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Joined: Jan 2006
Posts: 8,162 USA
360view
Moparts resident spammer
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Moparts resident spammer
Joined: Jan 2006
Posts: 8,162
USA
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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.
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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
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Joined: Dec 2014
Posts: 5,812 ohio
ruderunner
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master
Joined: Dec 2014
Posts: 5,812
ohio
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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
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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
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Joined: Jan 2006
Posts: 8,162 USA
360view
Moparts resident spammer
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Moparts resident spammer
Joined: Jan 2006
Posts: 8,162
USA
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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.
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